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The Project Gutenberg eBook of The Cambridge natural
history, Vol. 04 (of 10)
This eBook is for the use of anyone anywhere in the United States and
most other parts of the world at no cost and with almost no restrictions
whatsoever. You may copy it, give it away or re-use it under the terms
of the Project Gutenberg License included with this eBook or online at
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will have to check the laws of the country where you are located
before using this eBook.
Title: The Cambridge natural history, Vol. 04 (of 10)
Editor: S. F. Harmer
Author: Geoffrey Smith
D'Arcy Wentworth Thompson
Cecil Warburton
Walter Frank Raphael Weldon
Henry Woods
Editor: Sir A. E. Shipley
Release date: November 26, 2023 [eBook #72233]
Language: English
Original publication: London: Macmillan and Co., 1909
Other information and formats: www.gutenberg.org/ebooks/72233
Credits: Richard Tonsing, Peter Becker, and the Online Distributed
Proofreading Team at https://www.pgdp.net (This file was
produced from images generously made available by The
Internet Archive)
history, Vol. 04 (of 10)
This eBook is for the use of anyone anywhere in the United States and
most other parts of the world at no cost and with almost no restrictions
whatsoever. You may copy it, give it away or re-use it under the terms
of the Project Gutenberg License included with this eBook or online at
www.gutenberg.org. If you are not located in the United States, you
will have to check the laws of the country where you are located
before using this eBook.
Title: The Cambridge natural history, Vol. 04 (of 10)
Editor: S. F. Harmer
Author: Geoffrey Smith
D'Arcy Wentworth Thompson
Cecil Warburton
Walter Frank Raphael Weldon
Henry Woods
Editor: Sir A. E. Shipley
Release date: November 26, 2023 [eBook #72233]
Language: English
Original publication: London: Macmillan and Co., 1909
Other information and formats: www.gutenberg.org/ebooks/72233
Credits: Richard Tonsing, Peter Becker, and the Online Distributed
Proofreading Team at https://www.pgdp.net (This file was
produced from images generously made available by The
Internet Archive)
Page 4
*** START OF THE PROJECT GUTENBERG EBOOK THE
CAMBRIDGE NATURAL HISTORY, VOL. 04 (OF 10) ***
Transcriber’s Note:
New original cover art included with this eBook is
granted to the public domain.
CAMBRIDGE NATURAL HISTORY, VOL. 04 (OF 10) ***
Transcriber’s Note:
New original cover art included with this eBook is
granted to the public domain.
Page 5
THE
CAMBRIDGE NATURAL HISTORY
EDITED BY
S. F. HARMER, Sc.D., F.R.S., Fellow of King’s College,
Cambridge; Keeper of the Department of Zoology in the British
Museum (Natural History)
AND
A. E. SHIPLEY, M.A., Fellow and Tutor of Christ’s College,
Cambridge; Reader in Zoology in the University
VOLUME IV
CAMBRIDGE NATURAL HISTORY
EDITED BY
S. F. HARMER, Sc.D., F.R.S., Fellow of King’s College,
Cambridge; Keeper of the Department of Zoology in the British
Museum (Natural History)
AND
A. E. SHIPLEY, M.A., Fellow and Tutor of Christ’s College,
Cambridge; Reader in Zoology in the University
VOLUME IV
Page 6
MACMILLAN AND CO., Limited
LONDON · BOMBAY · CALCUTTA
MELBOURNE
THE MACMILLAN COMPANY
NEW YORK · BOSTON · CHICAGO
ATLANTA · SAN FRANCISCO
THE MACMILLAN CO. OF CANADA, Ltd.
TORONTO
CRUSTACEA
By Geoffrey Smith, M.A. (Oxon.), Fellow of New College, Oxford; and the late W. F. R.
Weldon, M.A. (D.Sc., Oxon.), formerly Fellow of St. John’s College, Cambridge, and Linacre
Professor of Human and Comparative Anatomy, Oxford
TRILOBITES
By Henry Woods, M.A., St. John’s College, Cambridge; University Lecturer in Palaeozoology
INTRODUCTION TO ARACHNIDA, AND KING-CRABS
By A. E. Shipley, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in
Zoology
EURYPTERIDA
By Henry Woods, M.A., St. John’s College, Cambridge; University Lecturer in Palaeozoology
LONDON · BOMBAY · CALCUTTA
MELBOURNE
THE MACMILLAN COMPANY
NEW YORK · BOSTON · CHICAGO
ATLANTA · SAN FRANCISCO
THE MACMILLAN CO. OF CANADA, Ltd.
TORONTO
CRUSTACEA
By Geoffrey Smith, M.A. (Oxon.), Fellow of New College, Oxford; and the late W. F. R.
Weldon, M.A. (D.Sc., Oxon.), formerly Fellow of St. John’s College, Cambridge, and Linacre
Professor of Human and Comparative Anatomy, Oxford
TRILOBITES
By Henry Woods, M.A., St. John’s College, Cambridge; University Lecturer in Palaeozoology
INTRODUCTION TO ARACHNIDA, AND KING-CRABS
By A. E. Shipley, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in
Zoology
EURYPTERIDA
By Henry Woods, M.A., St. John’s College, Cambridge; University Lecturer in Palaeozoology
Page 7
SCORPIONS, SPIDERS, MITES, TICKS, ETC.
By Cecil Warburton, M.A., Christ’s College, Cambridge; Zoologist to the Royal Agricultural
Society
TARDIGRADA (WATER-BEARS)
By A. E. Shipley, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in
Zoology
PENTASTOMIDA
By A. E. Shipley, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in
Zoology
PYCNOGONIDA
By D’Arcy W. Thompson, C.B., M.A., Trinity College, Cambridge; Professor of Natural
History in University College, Dundee
MACMILLAN AND CO., LIMITED
ST. MARTIN’S STREET, LONDON
1909
All the ingenious men, and all the scientific men, and all the fanciful
men, in the world, with all the old German bogypainters into the bargain,
could never invent ... anything so curious, and so ridiculous, as a lobster.
Charles Kingsley, The Water-Babies.
For, Spider, thou art like the poet poor,
Whom thou hast help’d in song.
Both busily, our needful food to win,
By Cecil Warburton, M.A., Christ’s College, Cambridge; Zoologist to the Royal Agricultural
Society
TARDIGRADA (WATER-BEARS)
By A. E. Shipley, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in
Zoology
PENTASTOMIDA
By A. E. Shipley, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge; Reader in
Zoology
PYCNOGONIDA
By D’Arcy W. Thompson, C.B., M.A., Trinity College, Cambridge; Professor of Natural
History in University College, Dundee
MACMILLAN AND CO., LIMITED
ST. MARTIN’S STREET, LONDON
1909
All the ingenious men, and all the scientific men, and all the fanciful
men, in the world, with all the old German bogypainters into the bargain,
could never invent ... anything so curious, and so ridiculous, as a lobster.
Charles Kingsley, The Water-Babies.
For, Spider, thou art like the poet poor,
Whom thou hast help’d in song.
Both busily, our needful food to win,
Page 8
We work, as Nature taught, with ceaseless pains,
Thy bowels thou dost spin,
I spin my brains.
Southey, To a Spider.
Last o’er the field the Mite enormous swims,
Swells his red heart, and writhes his giant limbs.
Erasmus Darwin, The Temple of Nature.
Thy bowels thou dost spin,
I spin my brains.
Southey, To a Spider.
Last o’er the field the Mite enormous swims,
Swells his red heart, and writhes his giant limbs.
Erasmus Darwin, The Temple of Nature.
Page 9
PREFACE
The Editors feel that they owe an apology and some explanation to the
readers of The Cambridge Natural History for the delay which has occurred
in the issue of this, the fourth in proper order, but the last to appear of the
ten volumes which compose the work. The delay has been due principally
to the untimely death of Professor W. F. E. Weldon, who had undertaken to
write the Section on the Crustacea. The Chapter on the Branchiopoda is all
he actually left ready for publication, but it gives an indication of the
thorough way in which he had intended to treat his subject. He had,
however, superintended the preparation of a number of beautiful
illustrations, which show that he had determined to use, in the main, first-
hand knowledge. Many of these figures have been incorporated in the
article by Mr. Geoffrey Smith, to whom the Editors wish to express their
thanks for taking up, almost at a moment’s notice, the task which had
dropped from his teacher’s hand.
A further apology is due to the other contributors to this volume. Their
contributions have been in type for many years, and owing to the inevitable
delays indicated above they have been called upon to make old articles new,
ever an ungrateful labour.
The appearance of this volume completes the work the Editors embarked
on some sixteen years ago. It coincides with the cessation of an almost daily
intercourse since the time when they “came up” to Cambridge as freshmen
in 1880.
S. F. Harmer.
A. E. Shipley.
March 1909.
The Editors feel that they owe an apology and some explanation to the
readers of The Cambridge Natural History for the delay which has occurred
in the issue of this, the fourth in proper order, but the last to appear of the
ten volumes which compose the work. The delay has been due principally
to the untimely death of Professor W. F. E. Weldon, who had undertaken to
write the Section on the Crustacea. The Chapter on the Branchiopoda is all
he actually left ready for publication, but it gives an indication of the
thorough way in which he had intended to treat his subject. He had,
however, superintended the preparation of a number of beautiful
illustrations, which show that he had determined to use, in the main, first-
hand knowledge. Many of these figures have been incorporated in the
article by Mr. Geoffrey Smith, to whom the Editors wish to express their
thanks for taking up, almost at a moment’s notice, the task which had
dropped from his teacher’s hand.
A further apology is due to the other contributors to this volume. Their
contributions have been in type for many years, and owing to the inevitable
delays indicated above they have been called upon to make old articles new,
ever an ungrateful labour.
The appearance of this volume completes the work the Editors embarked
on some sixteen years ago. It coincides with the cessation of an almost daily
intercourse since the time when they “came up” to Cambridge as freshmen
in 1880.
S. F. Harmer.
A. E. Shipley.
March 1909.
Page 10
CONTENTS
Page 11
PAGE
Scheme of the Classification adopted in this Volume xi
CRUSTACEA
CHAPTER I
CRUSTACEA
General Organisation 3
CHAPTER II
CRUSTACEA (continued)
Entomostraca—Branchiopoda—Phyllopoda—Cladocera—Water-fleas 18
CHAPTER III
CRUSTACEA ENTOMOSTRACA (continued)
Copepoda 55
CHAPTER IV
CRUSTACEA ENTOMOSTRACA (continued)
Cirripedia—Phenomena of Growth and Sex—Ostracoda 79
CHAPTER V
CRUSTACEA (continued)
Scheme of the Classification adopted in this Volume xi
CRUSTACEA
CHAPTER I
CRUSTACEA
General Organisation 3
CHAPTER II
CRUSTACEA (continued)
Entomostraca—Branchiopoda—Phyllopoda—Cladocera—Water-fleas 18
CHAPTER III
CRUSTACEA ENTOMOSTRACA (continued)
Copepoda 55
CHAPTER IV
CRUSTACEA ENTOMOSTRACA (continued)
Cirripedia—Phenomena of Growth and Sex—Ostracoda 79
CHAPTER V
CRUSTACEA (continued)
Page 12
Malacostraca: Leptostraca—Phyllocarida: Eumalacostraca: Syncarida—
Anaspidacea: Peracarida—Mysidacea—Cumacea—Isopoda—Amphipoda:
Hoplocarida—Stomatopoda 110
CHAPTER VI
CRUSTACEA MALACOSTRACA (continued)
Eumalacostraca (CONTINUED): Eucarida—Euphausiacea—Compound Eyes—
Decapoda 144
CHAPTER VII
CRUSTACEA (continued)
Remarks on the Distribution of Marine and Fresh-water Crustacea 197
CHAPTER VIII
CRUSTACEA (continued)
Trilobita 221
ARACHNIDA
CHAPTER IX
Arachnida—Introduction 255
CHAPTER X
ARACHNIDA (continued)
Delobranchiata = Merostomata—Xiphosura 259
Anaspidacea: Peracarida—Mysidacea—Cumacea—Isopoda—Amphipoda:
Hoplocarida—Stomatopoda 110
CHAPTER VI
CRUSTACEA MALACOSTRACA (continued)
Eumalacostraca (CONTINUED): Eucarida—Euphausiacea—Compound Eyes—
Decapoda 144
CHAPTER VII
CRUSTACEA (continued)
Remarks on the Distribution of Marine and Fresh-water Crustacea 197
CHAPTER VIII
CRUSTACEA (continued)
Trilobita 221
ARACHNIDA
CHAPTER IX
Arachnida—Introduction 255
CHAPTER X
ARACHNIDA (continued)
Delobranchiata = Merostomata—Xiphosura 259
Page 13
CHAPTER XI
ARACHNIDA DELOBRANCHIATA (continued)
Eurypterida = Gigantostraca 283
CHAPTER XII
ARACHNIDA (continued)
Embolobranchiata—Scorpionidea—Pedipalpi 297
CHAPTER XIII
ARACHNIDA EMBOLOBRANCHIATA (continued)
Araneae—External Structure—Internal Structure 314
CHAPTER XIV
ARACHNIDA EMBOLOBRANCHIATA (continued)
Araneae (CONTINUED)—Habits—Ecdysis—Treatment of Young—Migration—
Webs—Nests—Egg-cocoons—Poison—Fertility—Enemies—Protective
Coloration—Mimicry—Senses—Intelligence—Mating Habits—Fossil Spiders 338
CHAPTER XV
ARACHNIDA EMBOLOBRANCHIATA (continued)
Araneae (CONTINUED)—Classification 384
CHAPTER XVI
ARACHNIDA EMBOLOBRANCHIATA (continued)
ARACHNIDA DELOBRANCHIATA (continued)
Eurypterida = Gigantostraca 283
CHAPTER XII
ARACHNIDA (continued)
Embolobranchiata—Scorpionidea—Pedipalpi 297
CHAPTER XIII
ARACHNIDA EMBOLOBRANCHIATA (continued)
Araneae—External Structure—Internal Structure 314
CHAPTER XIV
ARACHNIDA EMBOLOBRANCHIATA (continued)
Araneae (CONTINUED)—Habits—Ecdysis—Treatment of Young—Migration—
Webs—Nests—Egg-cocoons—Poison—Fertility—Enemies—Protective
Coloration—Mimicry—Senses—Intelligence—Mating Habits—Fossil Spiders 338
CHAPTER XV
ARACHNIDA EMBOLOBRANCHIATA (continued)
Araneae (CONTINUED)—Classification 384
CHAPTER XVI
ARACHNIDA EMBOLOBRANCHIATA (continued)
Page 14
Palpigradi—Solifugae = Solpugae—Chernetidea = Pseudoscorpiones 422
CHAPTER XVII
ARACHNIDA EMBOLOBRANCHIATA (continued)
Podogona = Ricinulei—Phalangidea = Opiliones—Habits—Structure—
Classification 439
CHAPTER XVIII
ARACHNIDA EMBOLOBRANCHIATA (continued)
Acarina—Harvest-Bugs—Parasitic Mites—Ticks—Spinning Mites—Structure—
Metamorphosis—Classification 454
CHAPTER XIX
ARACHNIDA (APPENDIX I)
Tardigrada—Occurrence—Ecdysis—Structure—Development—Affinities—
Biology—Desiccation—Parasites—Systematic 477
CHAPTER XX
ARACHNIDA (APPENDIX II)
Pentastomida—Occurrence—Economic Importance—Structure—Development
and Life-History—Systematic 488
PYCNOGONIDA
CHAPTER XXI
Pycnogonida 501
CHAPTER XVII
ARACHNIDA EMBOLOBRANCHIATA (continued)
Podogona = Ricinulei—Phalangidea = Opiliones—Habits—Structure—
Classification 439
CHAPTER XVIII
ARACHNIDA EMBOLOBRANCHIATA (continued)
Acarina—Harvest-Bugs—Parasitic Mites—Ticks—Spinning Mites—Structure—
Metamorphosis—Classification 454
CHAPTER XIX
ARACHNIDA (APPENDIX I)
Tardigrada—Occurrence—Ecdysis—Structure—Development—Affinities—
Biology—Desiccation—Parasites—Systematic 477
CHAPTER XX
ARACHNIDA (APPENDIX II)
Pentastomida—Occurrence—Economic Importance—Structure—Development
and Life-History—Systematic 488
PYCNOGONIDA
CHAPTER XXI
Pycnogonida 501
Page 15
INDEX 543
Page 16
SCHEME OF THE CLASSIFICATION
ADOPTED IN THIS VOLUME
The names of extinct groups are printed in italics.
ADOPTED IN THIS VOLUME
The names of extinct groups are printed in italics.
Page 17
CRUSTACEA (p. 3).
ENTOMOSTRACA (p. 18).
Divisions. Orders. Sub-Orders. Tribes. Families.
Branchipodidae (pp. 19,
35).
Phyllopoda (pp. 19, 35)
Apodidae (pp. 19, 36).
Limnadiidae (pp. 20, 36).
Sididae (p. 51).
Ctenopoda (p. 51)
Holopediidae (p. 51).
Branchiopoda
Daphniidae (p. 51).
(p. 18) Calyptomera
(pp. 38, 51) Bosminidae (p. 53).
Cladocera
Anomopoda (p. 51) Lyncodaphniidae (p. 53).
(p. 37)
Lynceidae = Chydoridae
(p. 53).
Polyphemidae (p. 54).
Gymnomera (pp. 38, 54)
Leptodoridae (p. 54).
Divisions. Orders. Sub-Orders. Tribes. Families.
Amphascandria
Calanidae (p. 57).
(p. 57)
Gymnoplea
Centropagidae (p. 58).
(p. 57) Heterarthrandria
Candacidae (p. 60).
(p. 58)
Pontellidae (p. 60).
Cyclopidae (pp. 61, 62).
Harpacticidae (pp. 61, 62).
Peltiidae (p. 63).
Ampharthrandria
Monstrillidae (p. 63).
(p. 61)
Ascidicolidae (p. 66).
Asterocheridae (p. 67).
Dichelestiidae (p. 68).
Eucopepoda
Copepoda Oncaeidae (p. 69).
(p. 57)
(p. 55) Corycaeidae (p. 69).
Lichomolgidae (p. 70).
Podoplea (p. 61)
Ergasilidae (p. 71).
Bomolochidae (p. 71).
Chondracanthidae (p. 72).
Isokerandria (p. 69) Philichthyidae (p. 73).
Nereicolidae (p. 73).
Hersiliidae (p. 73).
Caligidae (p. 73).
Lernaeidae (p. 74).
Lernaeopodidae (p. 75).
Choniostomatidae (p. 76).
Branchiura (P. 76) Argulidae (p. 76).
Cirripedia (p. 79) Polyaspidae (p. 84).
Pentaspidae (p. 87).
Pedunculata (p. 84)
Tetraspidae (p. 88).
Anaspidae (p. 89).
Verrucidae (p. 91).
Octomeridae (p. 91).
Operculata (p. 89)
Hexameridae (p. 91).
Tetrameridae (p. 92).
Acrothoracica (p. 92).
ENTOMOSTRACA (p. 18).
Divisions. Orders. Sub-Orders. Tribes. Families.
Branchipodidae (pp. 19,
35).
Phyllopoda (pp. 19, 35)
Apodidae (pp. 19, 36).
Limnadiidae (pp. 20, 36).
Sididae (p. 51).
Ctenopoda (p. 51)
Holopediidae (p. 51).
Branchiopoda
Daphniidae (p. 51).
(p. 18) Calyptomera
(pp. 38, 51) Bosminidae (p. 53).
Cladocera
Anomopoda (p. 51) Lyncodaphniidae (p. 53).
(p. 37)
Lynceidae = Chydoridae
(p. 53).
Polyphemidae (p. 54).
Gymnomera (pp. 38, 54)
Leptodoridae (p. 54).
Divisions. Orders. Sub-Orders. Tribes. Families.
Amphascandria
Calanidae (p. 57).
(p. 57)
Gymnoplea
Centropagidae (p. 58).
(p. 57) Heterarthrandria
Candacidae (p. 60).
(p. 58)
Pontellidae (p. 60).
Cyclopidae (pp. 61, 62).
Harpacticidae (pp. 61, 62).
Peltiidae (p. 63).
Ampharthrandria
Monstrillidae (p. 63).
(p. 61)
Ascidicolidae (p. 66).
Asterocheridae (p. 67).
Dichelestiidae (p. 68).
Eucopepoda
Copepoda Oncaeidae (p. 69).
(p. 57)
(p. 55) Corycaeidae (p. 69).
Lichomolgidae (p. 70).
Podoplea (p. 61)
Ergasilidae (p. 71).
Bomolochidae (p. 71).
Chondracanthidae (p. 72).
Isokerandria (p. 69) Philichthyidae (p. 73).
Nereicolidae (p. 73).
Hersiliidae (p. 73).
Caligidae (p. 73).
Lernaeidae (p. 74).
Lernaeopodidae (p. 75).
Choniostomatidae (p. 76).
Branchiura (P. 76) Argulidae (p. 76).
Cirripedia (p. 79) Polyaspidae (p. 84).
Pentaspidae (p. 87).
Pedunculata (p. 84)
Tetraspidae (p. 88).
Anaspidae (p. 89).
Verrucidae (p. 91).
Octomeridae (p. 91).
Operculata (p. 89)
Hexameridae (p. 91).
Tetrameridae (p. 92).
Acrothoracica (p. 92).
Page 18
Ascothoracica (p. 93).
Apoda (p. 94).
Rhizocephala (p. 95).
Cypridae (p. 107).
Cytheridae (p. 107).
Halocypridae (p. 108).
Ostracoda (p. 107)
Cypridinidae (p. 108).
Polycopidae (p. 109).
Cytherellidae (p. 109).
MALACOSTRACA (p. 110).
LEPTOSTRACA (p. 111)
Phyllocarida (p. 111).
Divisions. Orders. Sub-Orders. Tribes Families.
EUMALACOSTRACA (p. 112).
Syncarida Anaspididae (p. 115).
Anaspidacea (p. 115)
(p. 114) Koonungidae (p. 117).
Peracarida Eucopiidae (p. 118).
(p. 118) Mysidacea (p. 118) Lophogastridae (p. 119).
Mysidae (p. 119).
Cumidae (p. 121).
Lampropidae (p. 121).
Cumacea (p. 120) Leuconidae (p. 121).
Diastylidae (p. 121).
Pseudocumidae (p. 121).
Apseudidae (p. 122).
Chelifera (p. 122)
Tanaidae (p. 122).
Anthuridae (p. 124).
Gnathiidae (p. 124).
Cymothoidae (p. 126).
Flabellifera (p. 124)
Cirolanidae (p. 126).
Serolidae (p. 126).
Sphaeromidae (p. 126).
Idotheidae (p. 127).
Valvifera (p. 127)
Arcturidae (p. 127).
Asellidae (p. 128).
Asellota (p. 127)
Munnopsidae (p. 128).
Oniscoida (p. 128).
Isopoda (p. 121)
Microniscidae (p. 130).
Cryptoniscidae (p. 130).
Liriopsidae (p. 130).
Cryptoniscina (pp. 129, 130) Hemioniscidae (p. 130).
Cabiropsidae (p. 130).
Epicarida Podasconidae (p. 130).
(p. 129) Asconiscidae (p. 130).
Dajidae (p. 130).
Phryxidae (p. 130).
Bopyrina (pp. 129, 130, 132) Bopyridae (pp. 130, 133).
Entoniscidae (pp. 130,
134).
Phreatoicidea (p. 136) Phreatoicidae (p. 136)
Apoda (p. 94).
Rhizocephala (p. 95).
Cypridae (p. 107).
Cytheridae (p. 107).
Halocypridae (p. 108).
Ostracoda (p. 107)
Cypridinidae (p. 108).
Polycopidae (p. 109).
Cytherellidae (p. 109).
MALACOSTRACA (p. 110).
LEPTOSTRACA (p. 111)
Phyllocarida (p. 111).
Divisions. Orders. Sub-Orders. Tribes Families.
EUMALACOSTRACA (p. 112).
Syncarida Anaspididae (p. 115).
Anaspidacea (p. 115)
(p. 114) Koonungidae (p. 117).
Peracarida Eucopiidae (p. 118).
(p. 118) Mysidacea (p. 118) Lophogastridae (p. 119).
Mysidae (p. 119).
Cumidae (p. 121).
Lampropidae (p. 121).
Cumacea (p. 120) Leuconidae (p. 121).
Diastylidae (p. 121).
Pseudocumidae (p. 121).
Apseudidae (p. 122).
Chelifera (p. 122)
Tanaidae (p. 122).
Anthuridae (p. 124).
Gnathiidae (p. 124).
Cymothoidae (p. 126).
Flabellifera (p. 124)
Cirolanidae (p. 126).
Serolidae (p. 126).
Sphaeromidae (p. 126).
Idotheidae (p. 127).
Valvifera (p. 127)
Arcturidae (p. 127).
Asellidae (p. 128).
Asellota (p. 127)
Munnopsidae (p. 128).
Oniscoida (p. 128).
Isopoda (p. 121)
Microniscidae (p. 130).
Cryptoniscidae (p. 130).
Liriopsidae (p. 130).
Cryptoniscina (pp. 129, 130) Hemioniscidae (p. 130).
Cabiropsidae (p. 130).
Epicarida Podasconidae (p. 130).
(p. 129) Asconiscidae (p. 130).
Dajidae (p. 130).
Phryxidae (p. 130).
Bopyrina (pp. 129, 130, 132) Bopyridae (pp. 130, 133).
Entoniscidae (pp. 130,
134).
Phreatoicidea (p. 136) Phreatoicidae (p. 136)
Page 19
Lysianassidae (p. 137).
Haustoriidae (p. 137).
Crevettina (p. 137) Gammaridae (p. 138).
Amphipoda Talitridae (p. 139).
(p. 136) Corophiidae (p. 139).
Caprellidae (p. 139).
Laemodipoda (p. 139)
Cyamidae (p. 140).
Hyperina (p. 140).
Hoplocarida
Stomatopoda (p. 141) Squillidae (p. 143).
(p. 141)
Eucarida Euphausiacea (p. 144) Euphausiidae (p. 144).
(p. 144) Decapoda Nephropsidae (p. 154).
(p. 152) Nephropsidea (p. 154) Astacidae (p. 157).
Parastacidae (p. 157).
Eryonidea (p. 157) Eryonidae (p. 158).
Peneidae (p. 162).
Peneidea (pp. 158, 162) Sergestidae (p. 162).
Stenopodidae (p. 162).
Pasiphaeidae (p. 163).
Acanthephyridae (p. 163).
Atyidae (p. 163).
Macrura
(p. 153) Alpheidae (p. 163).
Psalidopodidae (p.164).
Caridea (pp. 158, 163) Pandalidae (p. 164).
Hippolytidae (p. 164).
Palaemonidae (p. 164).
Glyphocrangonidae
(p. 164).
Crangonidae (p. 164).
Palinuridae (p. 167).
Loricata (p. 165)
Scyllaridae (p. 167).
Thalassinidea (p. 167) Callianassidae (p. 167).
Aegleidae (p. 169).
Galatheidea (p. 168) Galatheidae (p. 169).
Porcellanidae (p. 170).
Albuneidae (p. 171).
Hippidea (p. 170)
Hippidae (p. 171).
Pylochelidae (p. 180).
Anomura
(p. 167) Paguridae (p. 180).
Eupagurinae (p. 180).
Pagurinae (p. 180).
Paguridea (p. 171)
Coenobitidae (p. 181).
Lithodidae (p. 181).
Hapalogastorinae (p. 181).
Lithodinae (p. 181).
Brachyura Dromiidae (p. 184).
(p. 181) Dromiacea (p. 183) Dynomenidae (p. 184).
Homolidae (p. 184).
Calappidae (p. 187).
Leucosiidae (p. 188).
Oxystomata (p. 185)
Dorippidae (p. 188).
Raninidae (p. 188).
Cyclometopa (p. 188) Corystidae (p. 190).
Atelecyclidae (p. 190).
Cancridae (p. 191).
Portunidae (p. 191).
Haustoriidae (p. 137).
Crevettina (p. 137) Gammaridae (p. 138).
Amphipoda Talitridae (p. 139).
(p. 136) Corophiidae (p. 139).
Caprellidae (p. 139).
Laemodipoda (p. 139)
Cyamidae (p. 140).
Hyperina (p. 140).
Hoplocarida
Stomatopoda (p. 141) Squillidae (p. 143).
(p. 141)
Eucarida Euphausiacea (p. 144) Euphausiidae (p. 144).
(p. 144) Decapoda Nephropsidae (p. 154).
(p. 152) Nephropsidea (p. 154) Astacidae (p. 157).
Parastacidae (p. 157).
Eryonidea (p. 157) Eryonidae (p. 158).
Peneidae (p. 162).
Peneidea (pp. 158, 162) Sergestidae (p. 162).
Stenopodidae (p. 162).
Pasiphaeidae (p. 163).
Acanthephyridae (p. 163).
Atyidae (p. 163).
Macrura
(p. 153) Alpheidae (p. 163).
Psalidopodidae (p.164).
Caridea (pp. 158, 163) Pandalidae (p. 164).
Hippolytidae (p. 164).
Palaemonidae (p. 164).
Glyphocrangonidae
(p. 164).
Crangonidae (p. 164).
Palinuridae (p. 167).
Loricata (p. 165)
Scyllaridae (p. 167).
Thalassinidea (p. 167) Callianassidae (p. 167).
Aegleidae (p. 169).
Galatheidea (p. 168) Galatheidae (p. 169).
Porcellanidae (p. 170).
Albuneidae (p. 171).
Hippidea (p. 170)
Hippidae (p. 171).
Pylochelidae (p. 180).
Anomura
(p. 167) Paguridae (p. 180).
Eupagurinae (p. 180).
Pagurinae (p. 180).
Paguridea (p. 171)
Coenobitidae (p. 181).
Lithodidae (p. 181).
Hapalogastorinae (p. 181).
Lithodinae (p. 181).
Brachyura Dromiidae (p. 184).
(p. 181) Dromiacea (p. 183) Dynomenidae (p. 184).
Homolidae (p. 184).
Calappidae (p. 187).
Leucosiidae (p. 188).
Oxystomata (p. 185)
Dorippidae (p. 188).
Raninidae (p. 188).
Cyclometopa (p. 188) Corystidae (p. 190).
Atelecyclidae (p. 190).
Cancridae (p. 191).
Portunidae (p. 191).
Page 20
Xanthidae (p. 191).
Thelphusidae =
Potamonidae (p. 191).
Maiidae (p. 193).
Parthenopidae (p. 193).
Oxyrhyncha (p. 191)
Hymenosomatidae
(p. 193).
Carcinoplacidae (p. 195).
Gonoplacidae (p. 195).
Pinnotheridae (p. 195).
Catometopa (p. 193)
Grapsidae (p. 196).
Gecarcinidae (p. 196).
Ocypodidae (p. 196).
TRILOBITA (p. 221).
Families
Agnostidae (p. 244).
Shumardiidae (p. 245).
Trinucleidae (p. 245).
Harpedidae (p. 245).
Paradoxidae (p. 246).
Conocephalidae = Conocoryphidae (p. 247).
Olenidae (p. 247).
Calymenidae (p. 247).
Asaphidae (p. 249).
Bronteidae (p. 249).
Phacopidae (p. 249).
Cheiruridae (p. 250).
Proëtidae (p. 251).
Encrinuridae (p. 251).
Acidaspidae (p. 251).
Lichadidae (p. 252).
Thelphusidae =
Potamonidae (p. 191).
Maiidae (p. 193).
Parthenopidae (p. 193).
Oxyrhyncha (p. 191)
Hymenosomatidae
(p. 193).
Carcinoplacidae (p. 195).
Gonoplacidae (p. 195).
Pinnotheridae (p. 195).
Catometopa (p. 193)
Grapsidae (p. 196).
Gecarcinidae (p. 196).
Ocypodidae (p. 196).
TRILOBITA (p. 221).
Families
Agnostidae (p. 244).
Shumardiidae (p. 245).
Trinucleidae (p. 245).
Harpedidae (p. 245).
Paradoxidae (p. 246).
Conocephalidae = Conocoryphidae (p. 247).
Olenidae (p. 247).
Calymenidae (p. 247).
Asaphidae (p. 249).
Bronteidae (p. 249).
Phacopidae (p. 249).
Cheiruridae (p. 250).
Proëtidae (p. 251).
Encrinuridae (p. 251).
Acidaspidae (p. 251).
Lichadidae (p. 252).
Page 21
ARACHNIDA (p. 255).
DELOBRANCHIATA = MEROSTOMATA (pp. 258, 259).
Orders. Sub-Orders. Families. Sub-Families.
Xiphosurinae (p. 276).
Xiphosura (pp. 258, 259, 276) Xiphosuridae (p. 276)
Tachypleinae (p. 276).
Eurypterida = Gigantostraca (pp. 258, 283) Eurypteridae (p. 290).
EMBOLOBRANCHIATA (pp. 258, 297).
Buthinae (p. 306).
Buthidae (p. 306)
Centrurinae (p. 306).
Diplocentrinae (p. 307).
Urodacinae (p. 307).
Scorpionidae (p. 306) Scorpioninae (p. 307).
Hemiscorpioninae (p. 307).
Scorpionidea (pp. 258, 297) Ischnurinae (p. 307).
Chaerilidae (p. 307).
Megacorminae (p. 308).
Chactidae (p. 307) Euscorpiinae (p. 308).
Chactinae (p. 308).
Vejovidae (p. 308).
Bothriuridae (p. 308).
Thelyphonidae (p. 312).
Schizonotidae = Tartaridae (p. 312).
Pedipalpi (pp. 258, 308) Tarantulinae (p. 313).
Tarantulidae =
Phrynichinae (p. 313).
Phrynidae (p. 312)
Charontinae (p. 313).
Araneae (pp. 258, 314) Liphistiidae (p. 386).
Paratropidinae (p. 387).
Actinopodinae (p. 387).
Miginae (p. 387).
Aviculariidae =
Ctenizinae (p. 388).
Mygalidae (p. 386)
Barychelinae (p. 389).
Aviculariinae (p. 389).
Diplurinae (p. 390).
Atypidae (p. 390).
Filistatidae (p. 391).
Oecobiidae = Urocteidae (p. 392).
Sicariidae = Scytodidae (p. 393).
Hypochilidae (p. 393).
Leptonetidae (p. 393).
Oonopidae (p. 393).
Hadrotarsidae (p. 394).
Dysderinae (p. 394).
Dysderidae (p. 394)
Segestriinae (p. 395).
Caponiidae (p. 395).
Prodidomidae (p. 395).
Drassinae (p. 396).
Clubioninae (p. 397).
Drassidae (p. 396)
Liocraninae (p. 397).
Micariinae (p. 397).
Palpimanidae (p. 398).
Eresidae (p. 398).
Dictynidae (p. 398).
DELOBRANCHIATA = MEROSTOMATA (pp. 258, 259).
Orders. Sub-Orders. Families. Sub-Families.
Xiphosurinae (p. 276).
Xiphosura (pp. 258, 259, 276) Xiphosuridae (p. 276)
Tachypleinae (p. 276).
Eurypterida = Gigantostraca (pp. 258, 283) Eurypteridae (p. 290).
EMBOLOBRANCHIATA (pp. 258, 297).
Buthinae (p. 306).
Buthidae (p. 306)
Centrurinae (p. 306).
Diplocentrinae (p. 307).
Urodacinae (p. 307).
Scorpionidae (p. 306) Scorpioninae (p. 307).
Hemiscorpioninae (p. 307).
Scorpionidea (pp. 258, 297) Ischnurinae (p. 307).
Chaerilidae (p. 307).
Megacorminae (p. 308).
Chactidae (p. 307) Euscorpiinae (p. 308).
Chactinae (p. 308).
Vejovidae (p. 308).
Bothriuridae (p. 308).
Thelyphonidae (p. 312).
Schizonotidae = Tartaridae (p. 312).
Pedipalpi (pp. 258, 308) Tarantulinae (p. 313).
Tarantulidae =
Phrynichinae (p. 313).
Phrynidae (p. 312)
Charontinae (p. 313).
Araneae (pp. 258, 314) Liphistiidae (p. 386).
Paratropidinae (p. 387).
Actinopodinae (p. 387).
Miginae (p. 387).
Aviculariidae =
Ctenizinae (p. 388).
Mygalidae (p. 386)
Barychelinae (p. 389).
Aviculariinae (p. 389).
Diplurinae (p. 390).
Atypidae (p. 390).
Filistatidae (p. 391).
Oecobiidae = Urocteidae (p. 392).
Sicariidae = Scytodidae (p. 393).
Hypochilidae (p. 393).
Leptonetidae (p. 393).
Oonopidae (p. 393).
Hadrotarsidae (p. 394).
Dysderinae (p. 394).
Dysderidae (p. 394)
Segestriinae (p. 395).
Caponiidae (p. 395).
Prodidomidae (p. 395).
Drassinae (p. 396).
Clubioninae (p. 397).
Drassidae (p. 396)
Liocraninae (p. 397).
Micariinae (p. 397).
Palpimanidae (p. 398).
Eresidae (p. 398).
Dictynidae (p. 398).
Page 22
Psechridae (p. 399).
Zodariidae = Enyoidae (p. 399).
Hersiliidae (p. 400).
Pholcidae (p. 401).
Argyrodinae (p. 402).
Episininae (p. 402).
Theridioninae (p. 403).
Theridiidae (p. 401) Phoroncidiinae (p. 404).
Erigoninae (p. 404).
Formicinae (p. 405).
Linyphiinae (p. 405).
Theridiosomatinae (p. 407).
Tetragnathinae (p. 407).
Argiopinae (p. 408).
Nephilinae (p. 408).
Epeiridae (p. 406)
Epeirinae (p. 408).
Gasteracanthinae (p. 409).
Poltyinae (p. 410).
Arcyinae (p. 410).
Dinopinae (p. 410).
Uloboridae (p. 410) Uloborinae (p. 410).
Miagrammopinae (p. 411).
Archeidae (p. 411).
Mimetidae (p. 411).
Thomisinae =
Misumeninae (p. 412).
Philodrominae (p. 413).
Thomisidae (p. 412) Sparassinae (p. 414).
Aphantochilinae (p. 414).
Stephanopsinae (p. 414).
Selenopinae (p. 414).
Zoropsidae (p. 415).
Platoridae (p. 415).
Cybaeinae (p. 415).
Ageleninae (p. 416).
Agelenidae (p. 415)
Hahniinae (p. 416).
Nicodaminae (p. 416).
Pisauridae (p.416).
Lycosidae (p. 417).
Ctenidae (p. 418).
Senoculidae (p. 418).
Oxyopidae (p. 419).
Attidae = Salticidae (p. 419).
Palpigradi (pp. 258, 422).
Galeodidae (p. 428).
Rhagodinae (p. 429).
Solpuginae (p. 429).
Solifugae = Solpugae (pp. 258, 423) Solpugidae (p. 429) Daesiinae (p. 429).
Eremobatinae (p. 429).
Karshiinae (p. 429).
Hexisopodidae (p. 429).
Cheliferidae (p. 436)
Chernetidea = Chernetes =
Cheliferinae (p. 436). Garypinae (pp. 436, 437).
Pseudoscorpiones (pp. 258, 430)
Obisiinae (pp. 436, 437).
Podogona = Ricinulei (pp. 258, 439) Cryptosteinmatidae (p.440).
Phalangidea = Opiliones (pp. 258, 440) Cyphophthalmi (p. 447) Sironidae (p. 448).
Zodariidae = Enyoidae (p. 399).
Hersiliidae (p. 400).
Pholcidae (p. 401).
Argyrodinae (p. 402).
Episininae (p. 402).
Theridioninae (p. 403).
Theridiidae (p. 401) Phoroncidiinae (p. 404).
Erigoninae (p. 404).
Formicinae (p. 405).
Linyphiinae (p. 405).
Theridiosomatinae (p. 407).
Tetragnathinae (p. 407).
Argiopinae (p. 408).
Nephilinae (p. 408).
Epeiridae (p. 406)
Epeirinae (p. 408).
Gasteracanthinae (p. 409).
Poltyinae (p. 410).
Arcyinae (p. 410).
Dinopinae (p. 410).
Uloboridae (p. 410) Uloborinae (p. 410).
Miagrammopinae (p. 411).
Archeidae (p. 411).
Mimetidae (p. 411).
Thomisinae =
Misumeninae (p. 412).
Philodrominae (p. 413).
Thomisidae (p. 412) Sparassinae (p. 414).
Aphantochilinae (p. 414).
Stephanopsinae (p. 414).
Selenopinae (p. 414).
Zoropsidae (p. 415).
Platoridae (p. 415).
Cybaeinae (p. 415).
Ageleninae (p. 416).
Agelenidae (p. 415)
Hahniinae (p. 416).
Nicodaminae (p. 416).
Pisauridae (p.416).
Lycosidae (p. 417).
Ctenidae (p. 418).
Senoculidae (p. 418).
Oxyopidae (p. 419).
Attidae = Salticidae (p. 419).
Palpigradi (pp. 258, 422).
Galeodidae (p. 428).
Rhagodinae (p. 429).
Solpuginae (p. 429).
Solifugae = Solpugae (pp. 258, 423) Solpugidae (p. 429) Daesiinae (p. 429).
Eremobatinae (p. 429).
Karshiinae (p. 429).
Hexisopodidae (p. 429).
Cheliferidae (p. 436)
Chernetidea = Chernetes =
Cheliferinae (p. 436). Garypinae (pp. 436, 437).
Pseudoscorpiones (pp. 258, 430)
Obisiinae (pp. 436, 437).
Podogona = Ricinulei (pp. 258, 439) Cryptosteinmatidae (p.440).
Phalangidea = Opiliones (pp. 258, 440) Cyphophthalmi (p. 447) Sironidae (p. 448).
Page 23
Phalangodidae (p. 448).
Mecostethi = Laniatores
Cosmetidae (p. 449).
(p. 448)
Gonyleptidae (p. 449).
Sclerosomatinac (p.449).
Phalangiidae (p. 449)
Phalangiinae (p. 450).
Plagiostethi =
Ischyropsalidae (p. 451).
Palpatores (p. 449)
Nemastomatidae (p. 451).
Trogulidae (p. 452).
Eriophyidae = Phytoptidae (p. 464).
Vermiformia (p. 464)
Demodicidae (p. 465).
Sarcoptinae (p. 466).
Astigmata (p. 465) Sarcoptidae (p. 466) Analgesinae (p. 466).
Tyroglyphinae (p. 466).
Oribatidae (p. 467).
Argasidae (p. 469).
Ixodoidea (p. 468)
Metastigmata (p. 467) Ixodidae (p. 469).
Gamasinae (p. 470).
Gamasidae (p. 470)
Dermanyssinae (p. 471).
Acarina = Acari = Acaridea (pp. 258,
Heterostigmata (p. 471) Tarsonemidae (p. 471).
454)
Bdellidae (p. 471).
Halacaridae (p. 472).
Hydrachnidae (p. 472).
Limnocharinae (p. 472).
Prostigmata (p. 471) Caeculinae (p. 472).
Tetranychinae (p. 472).
Trombidiidae (p. 472)
Cheyletinae (p. 473).
Erythraeinae (p. 473).
Trombidiinae (p. 473).
Notostigmata (p. 473) Opilioacaridae (p. 473).
Orders.
TARDIGRADA (pp. 258, 477).
PENTASTOMIDA (pp. 258, 488).
PYCNOGONIDA = PODOSOMATA = PANTOPODA (p. 501).
Families.
Decolopodidae (p. 531).
Colossendeidae = Pasithoidae (p. 532).
Eurycididae = Ascorhynchidae (p. 533).
Ammotheidae (p. 534).
Rhynchothoracidae (p. 535)
Nymphonidae (p. 536).
Pallenidae (p. 537).
Phoxichilidiidae (p. 538).
Phoxichilidae (p. 539).
Pycnogonidae (p. 539).
Mecostethi = Laniatores
Cosmetidae (p. 449).
(p. 448)
Gonyleptidae (p. 449).
Sclerosomatinac (p.449).
Phalangiidae (p. 449)
Phalangiinae (p. 450).
Plagiostethi =
Ischyropsalidae (p. 451).
Palpatores (p. 449)
Nemastomatidae (p. 451).
Trogulidae (p. 452).
Eriophyidae = Phytoptidae (p. 464).
Vermiformia (p. 464)
Demodicidae (p. 465).
Sarcoptinae (p. 466).
Astigmata (p. 465) Sarcoptidae (p. 466) Analgesinae (p. 466).
Tyroglyphinae (p. 466).
Oribatidae (p. 467).
Argasidae (p. 469).
Ixodoidea (p. 468)
Metastigmata (p. 467) Ixodidae (p. 469).
Gamasinae (p. 470).
Gamasidae (p. 470)
Dermanyssinae (p. 471).
Acarina = Acari = Acaridea (pp. 258,
Heterostigmata (p. 471) Tarsonemidae (p. 471).
454)
Bdellidae (p. 471).
Halacaridae (p. 472).
Hydrachnidae (p. 472).
Limnocharinae (p. 472).
Prostigmata (p. 471) Caeculinae (p. 472).
Tetranychinae (p. 472).
Trombidiidae (p. 472)
Cheyletinae (p. 473).
Erythraeinae (p. 473).
Trombidiinae (p. 473).
Notostigmata (p. 473) Opilioacaridae (p. 473).
Orders.
TARDIGRADA (pp. 258, 477).
PENTASTOMIDA (pp. 258, 488).
PYCNOGONIDA = PODOSOMATA = PANTOPODA (p. 501).
Families.
Decolopodidae (p. 531).
Colossendeidae = Pasithoidae (p. 532).
Eurycididae = Ascorhynchidae (p. 533).
Ammotheidae (p. 534).
Rhynchothoracidae (p. 535)
Nymphonidae (p. 536).
Pallenidae (p. 537).
Phoxichilidiidae (p. 538).
Phoxichilidae (p. 539).
Pycnogonidae (p. 539).
Page 24
CRUSTACEA
CHAPTERS I and III-VII
BY
GEOFFREY SMITH, M.A. (Oxon.)
Fellow of New College, Oxford
CHAPTER II
BY
The Late W. F. R. WELDON, M.A. (D.Sc. Oxon.)
Formerly Fellow of St. John’s College, Cambridge, and Linacre Professor of Human and
Comparative Anatomy, Oxford
CHAPTERS I and III-VII
BY
GEOFFREY SMITH, M.A. (Oxon.)
Fellow of New College, Oxford
CHAPTER II
BY
The Late W. F. R. WELDON, M.A. (D.Sc. Oxon.)
Formerly Fellow of St. John’s College, Cambridge, and Linacre Professor of Human and
Comparative Anatomy, Oxford
Page 25
CHAPTER I
CRUSTACEA—GENERAL ORGANISATION
The Crustacea are almost exclusively aquatic animals, and they play a
part in the waters of the world closely parallel to that which insects play on
land. The majority are free-living, and gain their sustenance either as
vegetable-feeders or by preying upon other animals, but a great number are
scavengers, picking clean the carcasses and refuse that litter the ocean, just
as maggots and other insects rid the land of its dead cumber. Similar to
insects also is the great abundance of individuals which represent many of
the species, especially in the colder seas, and the naturalist in the Arctic or
Antarctic oceans has learnt to hang the carcasses of bears and seals over the
side of the boat for a few days in order to have them picked absolutely clean
by shoals of small Amphipods. It is said that these creatures, when crowded
sufficiently, will even attack living fishes, and by sheer press of numbers
impede their escape and devour them alive. Equally surprising are the
shoals of minute Copepods which may discolour the ocean for many miles,
an appearance well known to fishermen, who take profitable toll of the
fishes that follow in their wake. Despite this massing together we look in
vain for any elaborate social economy, or for the development of complex
instincts among Crustacea, such as excite our admiration in many insects,
and though many a crab or lobster is sufficiently uncanny in appearance to
suggest unearthly wisdom, he keeps his intelligence rigidly to himself,
encased in the impenetrable reserve of his armour and vindicated by the
most powerful of pincers. It is chiefly in the variety of structure and in the
multifarious phases of life-history that the interest of the Crustacea lies.
Before entering into an examination of these matters, it will be well to take
a general survey of Crustacean organisation, to consider the plan on which
these animals are built, and the probable relation of this plan to others met
with in the animal kingdom.
The Crustacea, to begin with, are a Class of the enormous Phylum
Arthropoda, animals with metamerically segmented bodies and usually with
CRUSTACEA—GENERAL ORGANISATION
The Crustacea are almost exclusively aquatic animals, and they play a
part in the waters of the world closely parallel to that which insects play on
land. The majority are free-living, and gain their sustenance either as
vegetable-feeders or by preying upon other animals, but a great number are
scavengers, picking clean the carcasses and refuse that litter the ocean, just
as maggots and other insects rid the land of its dead cumber. Similar to
insects also is the great abundance of individuals which represent many of
the species, especially in the colder seas, and the naturalist in the Arctic or
Antarctic oceans has learnt to hang the carcasses of bears and seals over the
side of the boat for a few days in order to have them picked absolutely clean
by shoals of small Amphipods. It is said that these creatures, when crowded
sufficiently, will even attack living fishes, and by sheer press of numbers
impede their escape and devour them alive. Equally surprising are the
shoals of minute Copepods which may discolour the ocean for many miles,
an appearance well known to fishermen, who take profitable toll of the
fishes that follow in their wake. Despite this massing together we look in
vain for any elaborate social economy, or for the development of complex
instincts among Crustacea, such as excite our admiration in many insects,
and though many a crab or lobster is sufficiently uncanny in appearance to
suggest unearthly wisdom, he keeps his intelligence rigidly to himself,
encased in the impenetrable reserve of his armour and vindicated by the
most powerful of pincers. It is chiefly in the variety of structure and in the
multifarious phases of life-history that the interest of the Crustacea lies.
Before entering into an examination of these matters, it will be well to take
a general survey of Crustacean organisation, to consider the plan on which
these animals are built, and the probable relation of this plan to others met
with in the animal kingdom.
The Crustacea, to begin with, are a Class of the enormous Phylum
Arthropoda, animals with metamerically segmented bodies and usually with
Page 26
externally jointed limbs. Their bodies are thus composed of a series of
repeated segments, which are on the whole similar to one another, though
particular segments may be differentiated in various respects for the
performance of different functions. This segmentation is apparent
externally, the surface of a Crustacean being divided typically into a number
of hard chitinous rings, some of which may be fused rigidly together, as in
the carapace of the crabs, or else articulated loosely.
Each segment bears typically a pair of jointed limbs, and though they
vary greatly in accordance with the special functions for which they are
employed, and may even be absent from certain segments, they may yet be
reduced to a common plan and were, no doubt, originally present on all the
segments.
Passing from the exterior to the interior of the body we find, generally
speaking, that the chief system of organs which exhibits a similar repetition,
or metameric segmentation, is the nervous system. This system is composed
ideally of a nervous ganglion situated in each segment and giving off
peripheral nerves, the several ganglia being connected together by a
longitudinal cord. This ideal arrangement, though apparent during the
embryonic development, becomes obscured to some extent in the adult
owing to the concentration or fusion of ganglia in various parts of the body.
The other internal organs do not show any clear signs of segmentation,
either in the embryo or in the adult; the alimentary canal and its various
diverticula lie in an unsegmented body-cavity, and are bathed in the blood
which courses through a system of narrow canals and irregular spaces
which surround all the organs of the body. A single pair, or at most two
pairs of kidneys are present.
The type of segmentation exhibited by the Crustacea is thus of a limited
character, concerning merely the external skin with its appendages, and the
nervous system, and not touching any of the other internal organs.[1] In this
respect the Crustacea agree with all the other Arthropods, in the adults of
which the segmentation is confined to the exterior and to the nervous
system, and does not extend to the body-cavity and its contained organs;
and for the same reason they differ essentially from all other metamerically
segmented animals, e.g. Annelids, in which the segmentation not only
affects the exterior and the nervous system, but especially applies to the
body-cavity, the musculature, the renal, and often the generative organs.
repeated segments, which are on the whole similar to one another, though
particular segments may be differentiated in various respects for the
performance of different functions. This segmentation is apparent
externally, the surface of a Crustacean being divided typically into a number
of hard chitinous rings, some of which may be fused rigidly together, as in
the carapace of the crabs, or else articulated loosely.
Each segment bears typically a pair of jointed limbs, and though they
vary greatly in accordance with the special functions for which they are
employed, and may even be absent from certain segments, they may yet be
reduced to a common plan and were, no doubt, originally present on all the
segments.
Passing from the exterior to the interior of the body we find, generally
speaking, that the chief system of organs which exhibits a similar repetition,
or metameric segmentation, is the nervous system. This system is composed
ideally of a nervous ganglion situated in each segment and giving off
peripheral nerves, the several ganglia being connected together by a
longitudinal cord. This ideal arrangement, though apparent during the
embryonic development, becomes obscured to some extent in the adult
owing to the concentration or fusion of ganglia in various parts of the body.
The other internal organs do not show any clear signs of segmentation,
either in the embryo or in the adult; the alimentary canal and its various
diverticula lie in an unsegmented body-cavity, and are bathed in the blood
which courses through a system of narrow canals and irregular spaces
which surround all the organs of the body. A single pair, or at most two
pairs of kidneys are present.
The type of segmentation exhibited by the Crustacea is thus of a limited
character, concerning merely the external skin with its appendages, and the
nervous system, and not touching any of the other internal organs.[1] In this
respect the Crustacea agree with all the other Arthropods, in the adults of
which the segmentation is confined to the exterior and to the nervous
system, and does not extend to the body-cavity and its contained organs;
and for the same reason they differ essentially from all other metamerically
segmented animals, e.g. Annelids, in which the segmentation not only
affects the exterior and the nervous system, but especially applies to the
body-cavity, the musculature, the renal, and often the generative organs.
Page 27
The Crustacea also resemble the other Arthropoda in the fact that the body-
cavity contains blood, and is therefore a “haemocoel,” while in the Annelids
and Vertebrates the segmented body-cavity is distinct from the vascular
system, and constitutes a true “coelom.” To this important distinction, and
to its especial application to the Crustacea, we will return, but first we may
consider more narrowly the segmentation of the Crustacea and its main
types of variation within the group. In order to determine the number of
segments which compose any particular Crustacean we have clearly two
criteria: first, the rings or somites of which the body is composed, and to
each of which a pair of limbs must be originally ascribed; and, second, the
nervous ganglia.
Around and behind the region of the mouth there is very little difficulty
in determining the segments of the body, if we allow embryology to assist
anatomy, but in front of the mouth the matter is not so easy.
In the Crustacea the moot point is whether we consider the paired eyes
and first pair of antennae as true appendages belonging to two true
segments, or whether they are structures sui generis, not homologous to the
other limbs. With regard to the first antennae we are probably safe in
assigning them to a true body-segment, since in some of the Entomostraca,
e.g. Apus, the nerves which supply them spring, not from the brain as in
more highly specialised forms, but from the commissures which pass round
the oesophagus to connect the dorsally lying brain to the ventral nerve-cord.
The paired eyes are always innervated from the brain, but the brain, or at
least part of it, is very probably formed of paired trunk-ganglia which have
fused into a common cerebral mass; and the fact that under certain
circumstances the stalked eye of Decapods when excised with its peripheral
ganglion[2] can regenerate in the form of an antenna, is perhaps evidence
that the lateral eyes are borne on what were once a pair of true appendages.
Now, with regard to the segmentation of the body, the Crustacea fall into
three categories: the Entomostraca, in which the number of segments is
indefinite; the Malacostraca, in which we may count nineteen segments,
exclusive of the terminal piece or telson and omitting the lateral eyes; and
the Leptostraca, including the single recent genus Nebalia, in which the
segmentation of head and thorax agrees exactly with that of the
Malacostraca, but in the abdomen there are two additional segments.
cavity contains blood, and is therefore a “haemocoel,” while in the Annelids
and Vertebrates the segmented body-cavity is distinct from the vascular
system, and constitutes a true “coelom.” To this important distinction, and
to its especial application to the Crustacea, we will return, but first we may
consider more narrowly the segmentation of the Crustacea and its main
types of variation within the group. In order to determine the number of
segments which compose any particular Crustacean we have clearly two
criteria: first, the rings or somites of which the body is composed, and to
each of which a pair of limbs must be originally ascribed; and, second, the
nervous ganglia.
Around and behind the region of the mouth there is very little difficulty
in determining the segments of the body, if we allow embryology to assist
anatomy, but in front of the mouth the matter is not so easy.
In the Crustacea the moot point is whether we consider the paired eyes
and first pair of antennae as true appendages belonging to two true
segments, or whether they are structures sui generis, not homologous to the
other limbs. With regard to the first antennae we are probably safe in
assigning them to a true body-segment, since in some of the Entomostraca,
e.g. Apus, the nerves which supply them spring, not from the brain as in
more highly specialised forms, but from the commissures which pass round
the oesophagus to connect the dorsally lying brain to the ventral nerve-cord.
The paired eyes are always innervated from the brain, but the brain, or at
least part of it, is very probably formed of paired trunk-ganglia which have
fused into a common cerebral mass; and the fact that under certain
circumstances the stalked eye of Decapods when excised with its peripheral
ganglion[2] can regenerate in the form of an antenna, is perhaps evidence
that the lateral eyes are borne on what were once a pair of true appendages.
Now, with regard to the segmentation of the body, the Crustacea fall into
three categories: the Entomostraca, in which the number of segments is
indefinite; the Malacostraca, in which we may count nineteen segments,
exclusive of the terminal piece or telson and omitting the lateral eyes; and
the Leptostraca, including the single recent genus Nebalia, in which the
segmentation of head and thorax agrees exactly with that of the
Malacostraca, but in the abdomen there are two additional segments.
Page 28
It has been usually held that the indefinite number of segments
characteristic of the Entomostraca, and especially the indefinitely large
number of segments characteristic of such Phyllopods as Apus, preserves
the ancestral condition from which the definite number found in the
Malacostraca has been derived; but recently it has been clearly pointed out
by Professor Carpenter[3] that the number of segments found in the
Malacostraca and Leptostraca corresponds with extraordinary exactitude to
the number determined as typical in all the other orders of Arthropoda. This
remarkable correspondence (it can hardly be coincidence) seems to point to
a common Arthropodan plan of segmentation, lying at the very root of the
phyletic tree; and if this is so, we are forced to the conclusion that the
Malacostraca have retained the primitive type of segmentation in far greater
perfection than the Entomostraca, in some of which many segments have
been added, e.g. Phyllopoda, while in others segments have been
suppressed, e.g. Cladocera, Ostracoda. It may be objected to this view of
the primitive condition of segmentation in the Crustacea that the Trilobites,
which for various reasons are regarded as related to the ancestral
Crustaceans, exhibit an indefinite and often very high number of segments;
but, as Professor Carpenter has pointed out, the oldest and most primitive of
Trilobites, such as Olenellus, possessed few segments which increase as we
pass from Cambrian to Carboniferous genera.
The following table shows the segmentation of the body in the
Malacostraca, as compared with that of Limulus (cf. p. 263), Insecta, the
primitive Myriapod Scolopendrella, and Peripatus. It will be seen that the
correspondence, though not exact, is very close, especially in the first four
columns, the number of segments in Peripatus being very variable in the
different species.
characteristic of the Entomostraca, and especially the indefinitely large
number of segments characteristic of such Phyllopods as Apus, preserves
the ancestral condition from which the definite number found in the
Malacostraca has been derived; but recently it has been clearly pointed out
by Professor Carpenter[3] that the number of segments found in the
Malacostraca and Leptostraca corresponds with extraordinary exactitude to
the number determined as typical in all the other orders of Arthropoda. This
remarkable correspondence (it can hardly be coincidence) seems to point to
a common Arthropodan plan of segmentation, lying at the very root of the
phyletic tree; and if this is so, we are forced to the conclusion that the
Malacostraca have retained the primitive type of segmentation in far greater
perfection than the Entomostraca, in some of which many segments have
been added, e.g. Phyllopoda, while in others segments have been
suppressed, e.g. Cladocera, Ostracoda. It may be objected to this view of
the primitive condition of segmentation in the Crustacea that the Trilobites,
which for various reasons are regarded as related to the ancestral
Crustaceans, exhibit an indefinite and often very high number of segments;
but, as Professor Carpenter has pointed out, the oldest and most primitive of
Trilobites, such as Olenellus, possessed few segments which increase as we
pass from Cambrian to Carboniferous genera.
The following table shows the segmentation of the body in the
Malacostraca, as compared with that of Limulus (cf. p. 263), Insecta, the
primitive Myriapod Scolopendrella, and Peripatus. It will be seen that the
correspondence, though not exact, is very close, especially in the first four
columns, the number of segments in Peripatus being very variable in the
different species.
Page 29
Table showing the Segmentation of various Arthropods
Malacostraca. Limulus. Insecta. Myriapoda. Peripatus.
(Scolopendrella).
1 Eyes Median eyes Eyes
2 1st antennae Rostrum Antennae Feelers Feelers
3 2nd antennae Chelicerae Intercalary
segment
4 Mandibles Pedipalpi Mandibles Mandibles Mandibles
5 1st maxillae 1st walking Maxillulae Maxillulae 1st jaw-
legs claw
6 2nd maxillae 2nd „ „ 1st maxillae 1st maxillae 2nd jaw-
claw
7 1st maxillipede 3rd „ „ 2nd maxillae 2nd maxillae 1st leg
8 2nd 4th „ „ 1st leg 1st leg 2nd „
maxillipede
9 3rd Chilaria 2nd „ 2nd „ 3rd „
maxillipede
10 1st ambulatory Genital 3rd „ 3rd „ 4th „
operculum
11 2nd „ 1st gill-book 1st abdominal 4th „ 5th „
12 3rd „ 2nd „ 2nd „ 6th „ 6th „
13 4th „ 3rd „ 3rd „ 6th „ 7th „
14 5th „ 4th „ 4th „ 7th „ 8th „
15 1st abdominal 5th „ 5th „ 8th „ 9th „
16 2nd „ No 6th „ 9th „ 10th „
appendages
17 3rd „ „ 7th „ 10th „ 11th „
18 4th „ „ 8th „ 11th „ 12th „
19 5th „ „ 9th „ 12th „ 13th „
20 6th „ „ 10th „ Reduced limbs 14th „
21 [4] „ Cercopods [5]
Telson Telson Telson Telson Telson
The appendages of the Crustacea exhibit a wonderful variety of
structure, but these variations can be reduced to at most two, and possibly to
one fundamental plan. In a typical Crustacean, besides the paired eyes,
which may be borne on stalks, possibly homologous to highly modified
limbs, there are present, first, two pairs of rod-like or filamentous antennae,
which in the adult are usually specialised for sensory purposes, but
frequently retain their primitive function as locomotory limbs even in the
adult, e.g. Ostracoda; while in the Nauplius larva, found in almost all the
chief subdivisions of the Crustacea, the two pairs of antennae invariably aid
in locomotion, and the base of the second antennae is usually furnished with
sharp biting spines which assist mastication. Following the antennae is a
Malacostraca. Limulus. Insecta. Myriapoda. Peripatus.
(Scolopendrella).
1 Eyes Median eyes Eyes
2 1st antennae Rostrum Antennae Feelers Feelers
3 2nd antennae Chelicerae Intercalary
segment
4 Mandibles Pedipalpi Mandibles Mandibles Mandibles
5 1st maxillae 1st walking Maxillulae Maxillulae 1st jaw-
legs claw
6 2nd maxillae 2nd „ „ 1st maxillae 1st maxillae 2nd jaw-
claw
7 1st maxillipede 3rd „ „ 2nd maxillae 2nd maxillae 1st leg
8 2nd 4th „ „ 1st leg 1st leg 2nd „
maxillipede
9 3rd Chilaria 2nd „ 2nd „ 3rd „
maxillipede
10 1st ambulatory Genital 3rd „ 3rd „ 4th „
operculum
11 2nd „ 1st gill-book 1st abdominal 4th „ 5th „
12 3rd „ 2nd „ 2nd „ 6th „ 6th „
13 4th „ 3rd „ 3rd „ 6th „ 7th „
14 5th „ 4th „ 4th „ 7th „ 8th „
15 1st abdominal 5th „ 5th „ 8th „ 9th „
16 2nd „ No 6th „ 9th „ 10th „
appendages
17 3rd „ „ 7th „ 10th „ 11th „
18 4th „ „ 8th „ 11th „ 12th „
19 5th „ „ 9th „ 12th „ 13th „
20 6th „ „ 10th „ Reduced limbs 14th „
21 [4] „ Cercopods [5]
Telson Telson Telson Telson Telson
The appendages of the Crustacea exhibit a wonderful variety of
structure, but these variations can be reduced to at most two, and possibly to
one fundamental plan. In a typical Crustacean, besides the paired eyes,
which may be borne on stalks, possibly homologous to highly modified
limbs, there are present, first, two pairs of rod-like or filamentous antennae,
which in the adult are usually specialised for sensory purposes, but
frequently retain their primitive function as locomotory limbs even in the
adult, e.g. Ostracoda; while in the Nauplius larva, found in almost all the
chief subdivisions of the Crustacea, the two pairs of antennae invariably aid
in locomotion, and the base of the second antennae is usually furnished with
sharp biting spines which assist mastication. Following the antennae is a
Page 30
pair of mandibles which are fashioned for biting the food or for piercing the
prey, and posterior to these are two pairs of maxillae, biting organs more
slightly built than the mandibles, whose function it is to lacerate the food
and prepare it for the more drastic action of the mandibles. So far, with
comparatively few exceptions, the order of specialisation is invariable; but
behind the maxillae the trunk-appendages vary greatly both in structure and
function in the different groups.
As a general rule, the first or first few thoracic limbs are turned forwards
toward the mouth, and are subsidiary to mastication; they are then called
maxillipedes; this happens usually in the Malacostraca, but to a much less
extent in the Entomostraca; and in any case these appendages immediately
behind the maxillae never depart to any great extent from a limb-like
structure, and they may graduate insensibly into the ordinary trunk-
appendages. The latter show great diversity in the different Crustacean
groups, according as the animals lead a natatory, creeping, or parasitic
method of life; they may be foliaceous, as in the Branchiopoda, or
biramous, as in the swimming thoracic and abdominal appendages of the
Mysidae, or simply uniramous, as in the walking legs of the higher
Decapoda, and the clinging legs of various parasitic forms.
Without going into detailed deviations of structure, many of which will
be described under the headings of special groups, it is clear from the
foregoing description and from Fig. 1 (p. 10), that three main types of
appendage can be distinguished: first, the foliaceous or multiramous;
second, the biramous; and, third, the uniramous.
We may dismiss the uniramous type with a few words: it is obviously
secondarily derived from the biramous type; this can be proved in detail in
nearly every case. Thus, the uniramous second antennae of some adult
forms are during the Nauplius stage invariably biramous, a condition which
is retained in the adult Cladocera. Similarly the uniramous walking legs of
many Decapoda pass through a biramous stage during development, the
outer branches or exopodites of the limbs being suppressed subsequently,
while the primitively biramous condition of the thoracic limbs is retained in
the adults of the Schizopoda, which doubtless own a common ancestry with
the Decapoda. The only Crustacean limb which appears to be constantly
uniramous both in larval and adult life is the first pair of antennae.
prey, and posterior to these are two pairs of maxillae, biting organs more
slightly built than the mandibles, whose function it is to lacerate the food
and prepare it for the more drastic action of the mandibles. So far, with
comparatively few exceptions, the order of specialisation is invariable; but
behind the maxillae the trunk-appendages vary greatly both in structure and
function in the different groups.
As a general rule, the first or first few thoracic limbs are turned forwards
toward the mouth, and are subsidiary to mastication; they are then called
maxillipedes; this happens usually in the Malacostraca, but to a much less
extent in the Entomostraca; and in any case these appendages immediately
behind the maxillae never depart to any great extent from a limb-like
structure, and they may graduate insensibly into the ordinary trunk-
appendages. The latter show great diversity in the different Crustacean
groups, according as the animals lead a natatory, creeping, or parasitic
method of life; they may be foliaceous, as in the Branchiopoda, or
biramous, as in the swimming thoracic and abdominal appendages of the
Mysidae, or simply uniramous, as in the walking legs of the higher
Decapoda, and the clinging legs of various parasitic forms.
Without going into detailed deviations of structure, many of which will
be described under the headings of special groups, it is clear from the
foregoing description and from Fig. 1 (p. 10), that three main types of
appendage can be distinguished: first, the foliaceous or multiramous;
second, the biramous; and, third, the uniramous.
We may dismiss the uniramous type with a few words: it is obviously
secondarily derived from the biramous type; this can be proved in detail in
nearly every case. Thus, the uniramous second antennae of some adult
forms are during the Nauplius stage invariably biramous, a condition which
is retained in the adult Cladocera. Similarly the uniramous walking legs of
many Decapoda pass through a biramous stage during development, the
outer branches or exopodites of the limbs being suppressed subsequently,
while the primitively biramous condition of the thoracic limbs is retained in
the adults of the Schizopoda, which doubtless own a common ancestry with
the Decapoda. The only Crustacean limb which appears to be constantly
uniramous both in larval and adult life is the first pair of antennae.
Page 31
We are reduced, therefore, to two types—the foliaceous and biramous.
Sir E. Ray Lankester,[6] in one of his most incisive morphological essays,
has explained how these two types are really fundamentally the same. He
compares, for instance, the foliaceous first maxillipede (Fig. 1, A), or the
second maxilla (Fig. 1, B) of a Decapod, e.g. Astacus, with the foliaceous
thoracic limb of Branchipus (Fig. 1, D), and with the typically biramous
first maxillipede of a Schizopod (Fig. 1, F).
In each case there is present, on the outer edge of the limb, one or more
projections or epipodites which are generally specialised for respiratory
purposes, and may carry the gills. The 6th and 5th “endites” in the
foliaceous limb (Fig. 1, D) are compared with the exopodite and endopodite
respectively of the biramous limb, while the endites 4–1 of the foliaceous
limb are found in the basal joints of the biramous limb. Lankester presumes
that the biramous type of limb throughout has been derived from the
foliaceous type by the suppression of the endites 1–4, as discrete rami, and
the exaggerated development of the endites 5 and 6, as above indicated.
Sir E. Ray Lankester,[6] in one of his most incisive morphological essays,
has explained how these two types are really fundamentally the same. He
compares, for instance, the foliaceous first maxillipede (Fig. 1, A), or the
second maxilla (Fig. 1, B) of a Decapod, e.g. Astacus, with the foliaceous
thoracic limb of Branchipus (Fig. 1, D), and with the typically biramous
first maxillipede of a Schizopod (Fig. 1, F).
In each case there is present, on the outer edge of the limb, one or more
projections or epipodites which are generally specialised for respiratory
purposes, and may carry the gills. The 6th and 5th “endites” in the
foliaceous limb (Fig. 1, D) are compared with the exopodite and endopodite
respectively of the biramous limb, while the endites 4–1 of the foliaceous
limb are found in the basal joints of the biramous limb. Lankester presumes
that the biramous type of limb throughout has been derived from the
foliaceous type by the suppression of the endites 1–4, as discrete rami, and
the exaggerated development of the endites 5 and 6, as above indicated.
Page 32
Fig. 1.—Appendages of Crustacea (A-G) and
Trilobita (H). A, First maxillipede of Astacus; B,
second maxilla of Astacus; C, second walking leg
of Astacus; D, thoracic limb of Branchipus; E,
first maxillipede of Mysis; F, first maxillipede of
Gnathophausia; G, thoracic limb of Nebalia; H,
thoracic limb of Triarthrus. bp, basipodite; br,
bract; cp, carpopodite; cxp, coxopodite; cx.s,
coxopoditic setae; dp, dactylopodite; end,
endopodite; ep, epipodite; ex, exopodite; ip,
ischiopodite; mp, meropodite; pp, propodite; 1–6,
the six endites.
The essential fact that the two types of limb are built on the same plan
may be considered as established; but it may be urged that the biramous
type represents this common plan more nearly than the foliaceous. It is, at
any rate, certain that in the maxillipedes of the Decapoda we witness the
conversion of the biramous type into the foliaceous by the expansion of the
basal joints concomitantly with the assumption by the maxillipedes of
masticatory functions. Thus in the Decapoda the first maxillipede is
decidedly foliaceous owing to the expanded “gnathobases” (Fig. 1, A, bp,
cxp), and the second maxillipedes are flattened, with their basal joints
somewhat expanded and furnished with biting hairs; but in the
“Schizopoda” (e.g. Mysis) the first maxillipede is a typical biramous limb,
Trilobita (H). A, First maxillipede of Astacus; B,
second maxilla of Astacus; C, second walking leg
of Astacus; D, thoracic limb of Branchipus; E,
first maxillipede of Mysis; F, first maxillipede of
Gnathophausia; G, thoracic limb of Nebalia; H,
thoracic limb of Triarthrus. bp, basipodite; br,
bract; cp, carpopodite; cxp, coxopodite; cx.s,
coxopoditic setae; dp, dactylopodite; end,
endopodite; ep, epipodite; ex, exopodite; ip,
ischiopodite; mp, meropodite; pp, propodite; 1–6,
the six endites.
The essential fact that the two types of limb are built on the same plan
may be considered as established; but it may be urged that the biramous
type represents this common plan more nearly than the foliaceous. It is, at
any rate, certain that in the maxillipedes of the Decapoda we witness the
conversion of the biramous type into the foliaceous by the expansion of the
basal joints concomitantly with the assumption by the maxillipedes of
masticatory functions. Thus in the Decapoda the first maxillipede is
decidedly foliaceous owing to the expanded “gnathobases” (Fig. 1, A, bp,
cxp), and the second maxillipedes are flattened, with their basal joints
somewhat expanded and furnished with biting hairs; but in the
“Schizopoda” (e.g. Mysis) the first maxillipede is a typical biramous limb,
Page 33
though the expanded gnathobases in some forms are beginning to project
(Fig. 1, E), while the limb following, which corresponds to the second
maxillipede of Decapods, is simply a biramous swimming leg. Besides this
obvious conversion of a biramous into a foliaceous limb, further evidence
of the fundamental character of the biramous type is found, first, in its
invariable occurrence in the Nauplius stage, which does not necessarily
mean that the ancestors of the Crustacea possessed this type of limb in the
adult, but which does imply that this type of limb was possessed at some
period of life by the common ancestral Crustacean; and, second, the limbs
of the Trilobita, a group which probably stands near the origin of the
Crustacea, have been shown by Beecher to conform to the biramous type
(Fig. 1, H). Furthermore, the thoracic limbs of Nebalia, an animal which
combines many of the characteristics of Entomostraca and Malacostraca,
and is therefore considered as a primitive type, despite their flattened
character, are really built upon a biramous plan (Fig. 1, G).
In conclusion, we may point out that this view of the Crustacean limb, as
essentially a biramous structure, agrees with the conclusion derived from
our consideration of the segmentation of the body, and points less to the
Branchiopoda as primitive Crustacea and more to some generalised
Malacostracan type.
So far we have shortly dealt with those systems of organs which are
clearly affected by the metameric segmentation of the body; we must now
expose the condition of the body-cavity to a similar scrutiny. If we remove
the external integument of a Crustacean, we find that the internal organs do
not lie in a spacious and discrete body-cavity, as is the case in the Annelids
and Vertebrates, but that they are packed together in an irregular system of
spaces (“haemocoel”) in communication with the vascular system and
containing blood. In the Entomostraca and smaller forms generally, a
definite vascular system hardly exists, though a central heart and artery may
serve to propel the blood through the irregular lacunae of the body-cavity;
but in the larger Malacostraca a complicated system of arteries may be
present which pour the blood into fairly definitely arranged spaces
surrounding the chief organs. These spaces return the blood to the
pericardium, and so to the heart again through the apertures or ostia which
pierce its walls.
(Fig. 1, E), while the limb following, which corresponds to the second
maxillipede of Decapods, is simply a biramous swimming leg. Besides this
obvious conversion of a biramous into a foliaceous limb, further evidence
of the fundamental character of the biramous type is found, first, in its
invariable occurrence in the Nauplius stage, which does not necessarily
mean that the ancestors of the Crustacea possessed this type of limb in the
adult, but which does imply that this type of limb was possessed at some
period of life by the common ancestral Crustacean; and, second, the limbs
of the Trilobita, a group which probably stands near the origin of the
Crustacea, have been shown by Beecher to conform to the biramous type
(Fig. 1, H). Furthermore, the thoracic limbs of Nebalia, an animal which
combines many of the characteristics of Entomostraca and Malacostraca,
and is therefore considered as a primitive type, despite their flattened
character, are really built upon a biramous plan (Fig. 1, G).
In conclusion, we may point out that this view of the Crustacean limb, as
essentially a biramous structure, agrees with the conclusion derived from
our consideration of the segmentation of the body, and points less to the
Branchiopoda as primitive Crustacea and more to some generalised
Malacostracan type.
So far we have shortly dealt with those systems of organs which are
clearly affected by the metameric segmentation of the body; we must now
expose the condition of the body-cavity to a similar scrutiny. If we remove
the external integument of a Crustacean, we find that the internal organs do
not lie in a spacious and discrete body-cavity, as is the case in the Annelids
and Vertebrates, but that they are packed together in an irregular system of
spaces (“haemocoel”) in communication with the vascular system and
containing blood. In the Entomostraca and smaller forms generally, a
definite vascular system hardly exists, though a central heart and artery may
serve to propel the blood through the irregular lacunae of the body-cavity;
but in the larger Malacostraca a complicated system of arteries may be
present which pour the blood into fairly definitely arranged spaces
surrounding the chief organs. These spaces return the blood to the
pericardium, and so to the heart again through the apertures or ostia which
pierce its walls.
Page 34
This condition of the body-cavity or haemocoel is reproduced in the
adults of all Arthropods, but in some of them by following the development
we can trace the steps by which the true coelom is replaced by the
haemocoel. In the embryos of all Arthropods except the Crustacea, a true
closed metamerically segmented coelom is formed as a split in the
mesodermal embryonic layer of cells, distinct from the vascular system.
During the course of development the segmented coelomic spaces and their
walls give rise to the reproductive organs and to certain renal organs in
Peripatus, Myriapoda, and Arachnida (nephridia and coxal glands), but the
general body-cavity is formed as an extension of the vascular system, which
is laid down outside the coelom by a canaliculisation of the extra-coelomic
mesoderm. In the embryos of the Crustacea, however, there is never at any
time a closed segmented coelom, and in this respect the Crustacea differ
from all other Arthropods. The only clear instance in which metamerically
repeated mesodermal cavities have been seen in the embryo Crustacean is
that of Astacus; here Reichenbach[7] states that in the abdomen segmental
cavities are formed which subsequently break down; but even in this
instance no connexion has been shown to subsist between these embryonic
cavities and the reproductive and excretory organs of the adult.
Since the connexion between the coelom and the excretory organs is
always a very close one throughout the animal kingdom, interest naturally
centres upon the renal organs in Crustacea, and it has been suggested that
these organs in Crustacea represent the sole remains, with the possible
exception of the gonads, of the coelom. Since, at any rate, a part of the
kidneys appears to be developed as a closed sac in the mesoderm, and since
they possess a possible segmental value, this suggestion is plausible; but, on
the other hand, since there are never more than two pairs of kidneys, and
since they are totally unconnected with the gonads or with any other
indication of a segmented coelom, the suggestion remains purely
hypothetical.
The renal organs of the Crustacea, excluding the Malpighian tubes
present in some Amphipods which open into the alimentary canal, and
resemble the Malpighian tubes of Insects, consist of two pairs—the
antennary gland, opening at the base of the second antenna, and the
maxillary gland, opening on the second maxilla. These two pairs of glands
rarely subsist together in the adult condition, though this is said to be the
case in Nebalia and possibly Mysis; the antennary glands are characteristic
adults of all Arthropods, but in some of them by following the development
we can trace the steps by which the true coelom is replaced by the
haemocoel. In the embryos of all Arthropods except the Crustacea, a true
closed metamerically segmented coelom is formed as a split in the
mesodermal embryonic layer of cells, distinct from the vascular system.
During the course of development the segmented coelomic spaces and their
walls give rise to the reproductive organs and to certain renal organs in
Peripatus, Myriapoda, and Arachnida (nephridia and coxal glands), but the
general body-cavity is formed as an extension of the vascular system, which
is laid down outside the coelom by a canaliculisation of the extra-coelomic
mesoderm. In the embryos of the Crustacea, however, there is never at any
time a closed segmented coelom, and in this respect the Crustacea differ
from all other Arthropods. The only clear instance in which metamerically
repeated mesodermal cavities have been seen in the embryo Crustacean is
that of Astacus; here Reichenbach[7] states that in the abdomen segmental
cavities are formed which subsequently break down; but even in this
instance no connexion has been shown to subsist between these embryonic
cavities and the reproductive and excretory organs of the adult.
Since the connexion between the coelom and the excretory organs is
always a very close one throughout the animal kingdom, interest naturally
centres upon the renal organs in Crustacea, and it has been suggested that
these organs in Crustacea represent the sole remains, with the possible
exception of the gonads, of the coelom. Since, at any rate, a part of the
kidneys appears to be developed as a closed sac in the mesoderm, and since
they possess a possible segmental value, this suggestion is plausible; but, on
the other hand, since there are never more than two pairs of kidneys, and
since they are totally unconnected with the gonads or with any other
indication of a segmented coelom, the suggestion remains purely
hypothetical.
The renal organs of the Crustacea, excluding the Malpighian tubes
present in some Amphipods which open into the alimentary canal, and
resemble the Malpighian tubes of Insects, consist of two pairs—the
antennary gland, opening at the base of the second antenna, and the
maxillary gland, opening on the second maxilla. These two pairs of glands
rarely subsist together in the adult condition, though this is said to be the
case in Nebalia and possibly Mysis; the antennary glands are characteristic
Page 35
of adult Malacostraca[8] and the larvae of the Entomostraca, while the
maxillary glands (“shell-glands”) are present in adult Entomostraca and
larval Malacostraca, that is to say, the one pair replaces the other in the two
great subdivisions of the Crustacea. The shell-gland of the Entomostraca is
a simple structure consisting of a coiled tube opening to the exterior on the
external branch of the second maxilla, and ending blindly in a dilated
vesicle, the end-sac. The antennary gland of the Malacostraca is usually
more complicated: these complications have been studied especially by
Weldon,[9] Allen, and Marchal[10] in the Decapoda. In a number of forms we
have a tube opening to the exterior at the base of the second antenna, and
expanding within to form a spacious bladder into which the coiled tubular
part of the kidney opens, while at the extremity of this coiled portion is the
vesicle called the end-sac. This arrangement may be modified; thus in
Palaemon Weldon described the two glands as fusing together above and
below the oesophagus, the dorsal commissure expanding into a huge sac
stretching dorsally down the length of the body. This closed sac with
excretory functions thus comes to resemble a coelomic cavity, and the view
that it is really coelomic has indeed been upheld.
A modified form of this view is that of Vejdovský, who describes a
funnel-apparatus leading from the coiled tube into the end-sac of the
antennary gland of Amphipods; he regards the end-sac alone as representing
the coelom, while the funnel and coiled tube represent the kidney opening
into it.
Not very much is known of the development of these various structures.
Some authors have considered that both antennary and maxillary glands are
developed in the embryo from ectodermal inpushings, but the more recent
observations of Waite[11] on Homarus americanus indicate that the
antennary gland at any rate is a composite structure, formed by an
ectodermal ingrowth which meets a mesodermal strand, and from the latter
are produced the end-sac and perhaps the tubular excretory portions of the
gland with their derivatives.
With regard to the possible metameric repetition of the renal organs, it is
of interest to note that by feeding Mysis and Nebalia on carmine, excretory
glands of a simple character were observed by Metschnikoff situated at the
bases of the thoracic limbs.
maxillary glands (“shell-glands”) are present in adult Entomostraca and
larval Malacostraca, that is to say, the one pair replaces the other in the two
great subdivisions of the Crustacea. The shell-gland of the Entomostraca is
a simple structure consisting of a coiled tube opening to the exterior on the
external branch of the second maxilla, and ending blindly in a dilated
vesicle, the end-sac. The antennary gland of the Malacostraca is usually
more complicated: these complications have been studied especially by
Weldon,[9] Allen, and Marchal[10] in the Decapoda. In a number of forms we
have a tube opening to the exterior at the base of the second antenna, and
expanding within to form a spacious bladder into which the coiled tubular
part of the kidney opens, while at the extremity of this coiled portion is the
vesicle called the end-sac. This arrangement may be modified; thus in
Palaemon Weldon described the two glands as fusing together above and
below the oesophagus, the dorsal commissure expanding into a huge sac
stretching dorsally down the length of the body. This closed sac with
excretory functions thus comes to resemble a coelomic cavity, and the view
that it is really coelomic has indeed been upheld.
A modified form of this view is that of Vejdovský, who describes a
funnel-apparatus leading from the coiled tube into the end-sac of the
antennary gland of Amphipods; he regards the end-sac alone as representing
the coelom, while the funnel and coiled tube represent the kidney opening
into it.
Not very much is known of the development of these various structures.
Some authors have considered that both antennary and maxillary glands are
developed in the embryo from ectodermal inpushings, but the more recent
observations of Waite[11] on Homarus americanus indicate that the
antennary gland at any rate is a composite structure, formed by an
ectodermal ingrowth which meets a mesodermal strand, and from the latter
are produced the end-sac and perhaps the tubular excretory portions of the
gland with their derivatives.
With regard to the possible metameric repetition of the renal organs, it is
of interest to note that by feeding Mysis and Nebalia on carmine, excretory
glands of a simple character were observed by Metschnikoff situated at the
bases of the thoracic limbs.
Page 36
The alimentary canal of the Crustacea is a straight tube composed of
three parts—a mid-gut derived from the endoderm of the embryo, and a
fore- and hind-gut formed by ectodermal invaginations in the embryo which
push into and fuse with the endodermal canal. The regions of the fore- and
hind-gut can be recognised in the adult by the fact of their being lined with
the chitinous investment which is continued over the external surface of the
body forming the hard exoskeleton, while the mid-gut is naked. The
chitinous lining of fore- and hind-gut is shed whenever the animal moults.
In the Malacostraca, in which a complicated “gastric mill” may be present,
the chitinous lining of this part of the gut is thrown into ridges bearing
teeth, and this stomach in the crabs and lobsters reaches a high degree of
complication and materially assists the mastication of the food. The gut is
furnished with a number of secretory and metabolic glands; the so-called
liver, which is probably a hepatopancreas, opening into the anterior end of
the mid-gut, is directed forwards in most Entomostraca and backwards in
the Malacostraca, in the Decapoda developing into a complicated branching
organ which fills a large part of the thorax. In the Decapoda peculiar
vermiform caeca of doubtful function are present, a pair of which open into
the gut anteriorly where fore-passes into mid-gut, and a single
asymmetrically placed caecum opens posteriorly into the alimentary tract
where mid- passes into hind-gut.
The disposition of these caeca, marking as they do the morphological
position of fore-, mid-, and hind-gut, is of peculiar interest owing to the
variations exhibited. From some unpublished drawings of Mr. E. H.
Schuster, which he kindly lent me, it appears that in certain Decapods, e.g.
Callianassa subterranea, the length of the mid-gut between the anterior and
posterior caeca is very long; in Carcinus maenas it is considerable; in Maia
squinado it is greatly reduced, the caeca being closely approximated; while
in Galathea strigosa the caeca are greatly reduced, and the mid-gut as a
separate entity has almost disappeared. The relation of these variations to
the habits of the different crabs and to their modes of development is
unknown.
The reproductive organs usually make their appearance as a small
paired group of mesodermal cells in the thorax comparatively late in life;
and neither in their early development nor in the adult condition do they
show any clear signs of segmentation or any connexion with a coelomic
cavity. The sexes are usually separate, but hermaphroditism occurs
three parts—a mid-gut derived from the endoderm of the embryo, and a
fore- and hind-gut formed by ectodermal invaginations in the embryo which
push into and fuse with the endodermal canal. The regions of the fore- and
hind-gut can be recognised in the adult by the fact of their being lined with
the chitinous investment which is continued over the external surface of the
body forming the hard exoskeleton, while the mid-gut is naked. The
chitinous lining of fore- and hind-gut is shed whenever the animal moults.
In the Malacostraca, in which a complicated “gastric mill” may be present,
the chitinous lining of this part of the gut is thrown into ridges bearing
teeth, and this stomach in the crabs and lobsters reaches a high degree of
complication and materially assists the mastication of the food. The gut is
furnished with a number of secretory and metabolic glands; the so-called
liver, which is probably a hepatopancreas, opening into the anterior end of
the mid-gut, is directed forwards in most Entomostraca and backwards in
the Malacostraca, in the Decapoda developing into a complicated branching
organ which fills a large part of the thorax. In the Decapoda peculiar
vermiform caeca of doubtful function are present, a pair of which open into
the gut anteriorly where fore-passes into mid-gut, and a single
asymmetrically placed caecum opens posteriorly into the alimentary tract
where mid- passes into hind-gut.
The disposition of these caeca, marking as they do the morphological
position of fore-, mid-, and hind-gut, is of peculiar interest owing to the
variations exhibited. From some unpublished drawings of Mr. E. H.
Schuster, which he kindly lent me, it appears that in certain Decapods, e.g.
Callianassa subterranea, the length of the mid-gut between the anterior and
posterior caeca is very long; in Carcinus maenas it is considerable; in Maia
squinado it is greatly reduced, the caeca being closely approximated; while
in Galathea strigosa the caeca are greatly reduced, and the mid-gut as a
separate entity has almost disappeared. The relation of these variations to
the habits of the different crabs and to their modes of development is
unknown.
The reproductive organs usually make their appearance as a small
paired group of mesodermal cells in the thorax comparatively late in life;
and neither in their early development nor in the adult condition do they
show any clear signs of segmentation or any connexion with a coelomic
cavity. The sexes are usually separate, but hermaphroditism occurs
Page 37
sporadically in many forms, and as a normal condition in some parasitic
groups (see pp. 105–107). The adult gonads are generally simple paired
tubes, from the walls of which the germ-cells are produced, and as these
grow and come to maturity they fill up the cavities of the tubes; special
nutrient cells are rarely differentiated, though in some cases (e.g.
Cladocera) a few ova nourish themselves by devouring their sister-cells (see
p. 44). The oviducts and vasa deferentia are formed as simple outgrowths
from the gonadial tubes, which acquire an opening to the exterior; they are
usually poorly supplied with accessory glands, the epithelium of the canals
often supplying albuminous secretions for cementing the eggs together,
while the lining of the vasa deferentia may be instrumental in the formation
of spermatophores for transferring large packets of spermatozoa to the
female. In the vast majority of Crustacea copulation takes place, the male
passing spermatophores or free spermatozoa into special receptacles
(spermathecae), or into the oviducts of the female. The spermatophores are
hollow chitinous structures in which the spermatozoa are packed; they are
often very large and assume characteristic shapes, especially in the
Decapoda.
The spermatozoa show a great variety of structure, but they conform to
two chief types—the filiform, which are provided with a long whip-like
flagellum; and the amoeboid, which are furnished with radiating
pseudopodia, and are much slower in their movements. The amoeboid
spermatozoa of some of the Decapoda contain in the cell-body a peculiar
chitinous capsule, and Koltzoff[12] has observed that when the spermatozoon
has settled upon the surface of the egg the chitinous capsule becomes
suddenly exceedingly hygroscopic, swells up, and explodes, driving the
head of the spermatozoon into the egg. We cannot enter here into a
description of the embryological changes by which the egg is converted into
the adult form. Crustacean eggs as a whole contain a large quantity of yolk,
but in some forms total segmentation occurs in the early stages, which is
converted later into the pyramidal type, i.e. the blastomeres are arranged
round the edge, and the yolk in the centre is only partly segmented to
correspond with them. The eggs during the early stages of development are
in almost all cases (except Branchiura, p. 77, and Anaspides, p. 116) carried
about by the female either in a brood-pouch (Branchiopoda, Ostracoda,
Cirripedia, Phyllocarida, Peracarida), or agglutinated to the hind legs or
some other part of the body (Copepoda, Eucarida), or in a chamber formed
groups (see pp. 105–107). The adult gonads are generally simple paired
tubes, from the walls of which the germ-cells are produced, and as these
grow and come to maturity they fill up the cavities of the tubes; special
nutrient cells are rarely differentiated, though in some cases (e.g.
Cladocera) a few ova nourish themselves by devouring their sister-cells (see
p. 44). The oviducts and vasa deferentia are formed as simple outgrowths
from the gonadial tubes, which acquire an opening to the exterior; they are
usually poorly supplied with accessory glands, the epithelium of the canals
often supplying albuminous secretions for cementing the eggs together,
while the lining of the vasa deferentia may be instrumental in the formation
of spermatophores for transferring large packets of spermatozoa to the
female. In the vast majority of Crustacea copulation takes place, the male
passing spermatophores or free spermatozoa into special receptacles
(spermathecae), or into the oviducts of the female. The spermatophores are
hollow chitinous structures in which the spermatozoa are packed; they are
often very large and assume characteristic shapes, especially in the
Decapoda.
The spermatozoa show a great variety of structure, but they conform to
two chief types—the filiform, which are provided with a long whip-like
flagellum; and the amoeboid, which are furnished with radiating
pseudopodia, and are much slower in their movements. The amoeboid
spermatozoa of some of the Decapoda contain in the cell-body a peculiar
chitinous capsule, and Koltzoff[12] has observed that when the spermatozoon
has settled upon the surface of the egg the chitinous capsule becomes
suddenly exceedingly hygroscopic, swells up, and explodes, driving the
head of the spermatozoon into the egg. We cannot enter here into a
description of the embryological changes by which the egg is converted into
the adult form. Crustacean eggs as a whole contain a large quantity of yolk,
but in some forms total segmentation occurs in the early stages, which is
converted later into the pyramidal type, i.e. the blastomeres are arranged
round the edge, and the yolk in the centre is only partly segmented to
correspond with them. The eggs during the early stages of development are
in almost all cases (except Branchiura, p. 77, and Anaspides, p. 116) carried
about by the female either in a brood-pouch (Branchiopoda, Ostracoda,
Cirripedia, Phyllocarida, Peracarida), or agglutinated to the hind legs or
some other part of the body (Copepoda, Eucarida), or in a chamber formed
Page 38
from the maxillipedes (Stomatopoda). Development may be direct, without
a complicated metamorphosis, or indirect, the larva hatching out in a form
totally different to the adult state, and attaining the latter by a series of
transformations and moults. The various larval forms will be described
under the headings of the several orders.
The respiratory organs are typically branchiae, i.e. branched
filamentous or foliaceous processes of the body-surface through which the
blood circulates, and is brought into close relation with the oxygen
dissolved in the water. In most of the smaller Entomostraca no special
branchiae are present, the interchange of gases taking place over the whole
body-surface; but in the Malacostraca the gills may reach a high degree of
specialisation. They are usually attached to the bases of the thoracic limbs
(“podobranchiae”), to the body-wall at the bases of these limbs, often in
two series (“arthrobranchiae”), and to the body-wall some way above the
limb-articulations (“pleurobranchiae”). In an ideal scheme each thoracic
appendage beginning with the first maxillipede would possess a
podobranch, two arthrobranchs, and a pleurobranch, but the full
complement of gills is never present, various members of the series being
suppressed in the various orders, and thus giving rise to “branchial
formulae” typical of the different groups.
After this brief survey of Crustacean organisation we may be able to form
an opinion upon the position of the Crustacea relative to other Arthropoda,
and upon the question debated some time ago in the pages of Natural
Science[13] whether the Arthropoda constitute a natural group. The Crustacea
plainly agree with all the other Arthropoda in the possession of a rigid
exoskeleton segmented into a number of somites, in the possession of
jointed appendages metamerically repeated, some of which are modified to
act as jaws; they further agree in the general correspondence of the number
of segments of which the body is primitively composed; the condition of
the body-cavity or haemocoel is also similar in the adult state. An
apparently fundamental difference is found in the entire absence during
development of a segmented coelom, but since this organ breaks down and
is much reduced in all adult Arthropods, it is not difficult to believe that its
actual formation in the embryo as a distinct structure might have been
secondarily suppressed in Crustacea.
a complicated metamorphosis, or indirect, the larva hatching out in a form
totally different to the adult state, and attaining the latter by a series of
transformations and moults. The various larval forms will be described
under the headings of the several orders.
The respiratory organs are typically branchiae, i.e. branched
filamentous or foliaceous processes of the body-surface through which the
blood circulates, and is brought into close relation with the oxygen
dissolved in the water. In most of the smaller Entomostraca no special
branchiae are present, the interchange of gases taking place over the whole
body-surface; but in the Malacostraca the gills may reach a high degree of
specialisation. They are usually attached to the bases of the thoracic limbs
(“podobranchiae”), to the body-wall at the bases of these limbs, often in
two series (“arthrobranchiae”), and to the body-wall some way above the
limb-articulations (“pleurobranchiae”). In an ideal scheme each thoracic
appendage beginning with the first maxillipede would possess a
podobranch, two arthrobranchs, and a pleurobranch, but the full
complement of gills is never present, various members of the series being
suppressed in the various orders, and thus giving rise to “branchial
formulae” typical of the different groups.
After this brief survey of Crustacean organisation we may be able to form
an opinion upon the position of the Crustacea relative to other Arthropoda,
and upon the question debated some time ago in the pages of Natural
Science[13] whether the Arthropoda constitute a natural group. The Crustacea
plainly agree with all the other Arthropoda in the possession of a rigid
exoskeleton segmented into a number of somites, in the possession of
jointed appendages metamerically repeated, some of which are modified to
act as jaws; they further agree in the general correspondence of the number
of segments of which the body is primitively composed; the condition of
the body-cavity or haemocoel is also similar in the adult state. An
apparently fundamental difference is found in the entire absence during
development of a segmented coelom, but since this organ breaks down and
is much reduced in all adult Arthropods, it is not difficult to believe that its
actual formation in the embryo as a distinct structure might have been
secondarily suppressed in Crustacea.
Page 39
The method of breathing by gills is paralleled by the respiratory
structures found in Limulus and Scorpions; the transition, if it occurred,
from branchiae to tracheae cannot, it is true, be traced, but the separation of
Arthropods into phyletically distinct groups of Tracheata and Branchiata on
this single characteristic is inadmissible. On the whole the Crustacea may
be considered as Arthropods whose progenitors are to be sought for among
the Trilobita, from whose near relations also probably sprang Limulus and
the Arachnids.
structures found in Limulus and Scorpions; the transition, if it occurred,
from branchiae to tracheae cannot, it is true, be traced, but the separation of
Arthropods into phyletically distinct groups of Tracheata and Branchiata on
this single characteristic is inadmissible. On the whole the Crustacea may
be considered as Arthropods whose progenitors are to be sought for among
the Trilobita, from whose near relations also probably sprang Limulus and
the Arachnids.
Page 40
CHAPTER II
CRUSTACEA (CONTINUED): ENTOMOSTRACA—
BRANCHIOPODA—PHYLLOPODA—CLADOCERA—
WATER-FLEAS
SUB-CLASS I.—ENTOMOSTRACA.
The Entomostraca are mostly small Crustacea in which the segmentation
of the body behind the head is very variable, both in regard to the number
of segments and the kind of differentiation exhibited by those segments and
their appendages. An unpaired simple eye, known as the Nauplius eye from
its universal presence in that larval form, often persists in the adult, and
though lateral compound eyes may be present they are rarely borne on
movable stalks. In the adult the excretory gland (“shell-gland”) opens on
the second maxillary segment, but in the larval state or early stages of
development a second antennary gland may also be present, which
disappears in the adult. The liver usually points forwards, and is simple and
saccular in structure, and the stomach is not complicated by the formation
of a gastric mill. With the exception of most Cladocera and Ostracoda the
young hatch out in the Nauplius state.
Order I. Branchiopoda.[14]
The Branchiopods are of small or moderate size, with flattened and
lobate post-cephalic limbs, and with functional gnathobases. Median and
lateral eyes are nearly always present. The labrum is large, and the second
maxillae are small or absent in the adult.
Branchiopods are found in every part of the world; a few are marine, but
the great majority are confined to inland lakes and ponds, or to slowly-
moving streams. The fresh waters, from the smallest pools to the largest
lakes, often swarm with them, as do those streams which flow so slowly
CRUSTACEA (CONTINUED): ENTOMOSTRACA—
BRANCHIOPODA—PHYLLOPODA—CLADOCERA—
WATER-FLEAS
SUB-CLASS I.—ENTOMOSTRACA.
The Entomostraca are mostly small Crustacea in which the segmentation
of the body behind the head is very variable, both in regard to the number
of segments and the kind of differentiation exhibited by those segments and
their appendages. An unpaired simple eye, known as the Nauplius eye from
its universal presence in that larval form, often persists in the adult, and
though lateral compound eyes may be present they are rarely borne on
movable stalks. In the adult the excretory gland (“shell-gland”) opens on
the second maxillary segment, but in the larval state or early stages of
development a second antennary gland may also be present, which
disappears in the adult. The liver usually points forwards, and is simple and
saccular in structure, and the stomach is not complicated by the formation
of a gastric mill. With the exception of most Cladocera and Ostracoda the
young hatch out in the Nauplius state.
Order I. Branchiopoda.[14]
The Branchiopods are of small or moderate size, with flattened and
lobate post-cephalic limbs, and with functional gnathobases. Median and
lateral eyes are nearly always present. The labrum is large, and the second
maxillae are small or absent in the adult.
Branchiopods are found in every part of the world; a few are marine, but
the great majority are confined to inland lakes and ponds, or to slowly-
moving streams. The fresh waters, from the smallest pools to the largest
lakes, often swarm with them, as do those streams which flow so slowly
Page 41
that the creatures can obtain occasional shelter among vegetation along the
sides and bottom without being swept away, while even rivers of
considerable swiftness contain some Cladocera. Several Branchiopods are
found in the brackish waters of estuaries, and some occur in lakes and pools
so salt that no other Crustacea, and few other animals of any kind, can live
in them. The great majority swim about with the back downwards,
collecting food in the ventral groove between their post-oral limbs, and
driving it forwards, towards the mouth, by movements of the gnathobases
(p. 10). The food collected in this way consists largely of suspended organic
mud, together with Diatoms and other Algae, and Infusoria; the larger
kinds, however, are capable of gnawing objects of considerable size, Apus
being said to nibble the softer insect larvae, and even tadpoles. Many
Cladocera (e.g. Daphnia, Simocephalus) may be seen to sink to the bottom
of an aquarium, with the ventral surface downwards, and to collect mud, or
even to devour the dead bodies of their fellows, while Leptodora is said to
feed upon living Copepods, which it catches by means of its antennae.
The Branchiopoda fall naturally into two Sub-orders, the Phyllopoda
including a series of long-bodied forms, with at least ten pairs of post-
cephalic limbs, and the Cladocera with shorter bodies and not more than
six pairs of post-cephalic limbs.
Sub-Order 1. Phyllopoda.
The Phyllopoda include a series of genera which differ greatly in
appearance, owing to differences in the development of the carapace, which
are curiously correlated with differences in the position of the eyes. Except
in these points, the three families which the sub-order contains are so much
alike that they may conveniently be described together.
In the Branchipodidae the carapace is practically absent, being
represented only by the slight backward projection on each side of the head
which contains the kidney (Fig. 2); the paired eyes are supported on mobile
stalks, and project freely, one on either side of the head.
In the Apodidae[15] the head is broad and depressed, the ventral side being
nearly flat, the dorsal surface convex; the hinder margin of the head is
indicated dorsally by a transverse cervical ridge, bounded by two grooves,
behind which the carapace projects backwards as a great shield, covering at
sides and bottom without being swept away, while even rivers of
considerable swiftness contain some Cladocera. Several Branchiopods are
found in the brackish waters of estuaries, and some occur in lakes and pools
so salt that no other Crustacea, and few other animals of any kind, can live
in them. The great majority swim about with the back downwards,
collecting food in the ventral groove between their post-oral limbs, and
driving it forwards, towards the mouth, by movements of the gnathobases
(p. 10). The food collected in this way consists largely of suspended organic
mud, together with Diatoms and other Algae, and Infusoria; the larger
kinds, however, are capable of gnawing objects of considerable size, Apus
being said to nibble the softer insect larvae, and even tadpoles. Many
Cladocera (e.g. Daphnia, Simocephalus) may be seen to sink to the bottom
of an aquarium, with the ventral surface downwards, and to collect mud, or
even to devour the dead bodies of their fellows, while Leptodora is said to
feed upon living Copepods, which it catches by means of its antennae.
The Branchiopoda fall naturally into two Sub-orders, the Phyllopoda
including a series of long-bodied forms, with at least ten pairs of post-
cephalic limbs, and the Cladocera with shorter bodies and not more than
six pairs of post-cephalic limbs.
Sub-Order 1. Phyllopoda.
The Phyllopoda include a series of genera which differ greatly in
appearance, owing to differences in the development of the carapace, which
are curiously correlated with differences in the position of the eyes. Except
in these points, the three families which the sub-order contains are so much
alike that they may conveniently be described together.
In the Branchipodidae the carapace is practically absent, being
represented only by the slight backward projection on each side of the head
which contains the kidney (Fig. 2); the paired eyes are supported on mobile
stalks, and project freely, one on either side of the head.
In the Apodidae[15] the head is broad and depressed, the ventral side being
nearly flat, the dorsal surface convex; the hinder margin of the head is
indicated dorsally by a transverse cervical ridge, bounded by two grooves,
behind which the carapace projects backwards as a great shield, covering at
Page 42
least half the body, but attached only to the back of the head. In Lepidurus
productus the head and carapace together form an oval expansion, deeply
emarginate at the hinder, narrower end, the sides of the emargination being
toothed. The carapace has a strong median keel. The kidneys project into
the space between the folds of skin which form the carapace, and their coils
can be seen on each side, the terminal part of each kidney-tube entering the
head to open at the base of the second maxilla. In all Branchiopoda with a
well-developed carapace the kidney is enclosed in it in this way, whence the
older anatomists speak of it as the “shell-gland.”
Fig. 2.—Chirocephalus diaphanus, female, × 5, Sussex. D.O, Dorsal organ; H,
heart; Ov, ovary; U, uterus; V, external generative opening.
Associated with the development of the carapace, in this and in the next
family, is a remarkable condition of the lateral eyes, which are sessile on the
dorsal surface of the head, and near the middle line, the median eye being
slightly in front of them. During embryonic life a fold of skin grows over all
three eyes, so that a chamber is formed over them, which communicates
with the exterior by a small pore in front.
In the Limnadiidae the body is laterally compressed, and the carapace is
so large that at least the post-cephalic part of the body, and generally the
head also, can be enclosed within it.
In Limnetis (Fig. 3) the dorsal surface of the head is bent downwards and
is much compressed, the carapace being attached to it only for a short
distance near the dorsal middle line. The sides of the carapace are bent
downwards, and their margins can be pulled together by a transverse
adductor muscle, so that the whole structure forms an ovoid or spheroidal
case, from which the head projects in front, while the rest of the body is
entirely contained within it. When the adductor muscle is relaxed the edges
productus the head and carapace together form an oval expansion, deeply
emarginate at the hinder, narrower end, the sides of the emargination being
toothed. The carapace has a strong median keel. The kidneys project into
the space between the folds of skin which form the carapace, and their coils
can be seen on each side, the terminal part of each kidney-tube entering the
head to open at the base of the second maxilla. In all Branchiopoda with a
well-developed carapace the kidney is enclosed in it in this way, whence the
older anatomists speak of it as the “shell-gland.”
Fig. 2.—Chirocephalus diaphanus, female, × 5, Sussex. D.O, Dorsal organ; H,
heart; Ov, ovary; U, uterus; V, external generative opening.
Associated with the development of the carapace, in this and in the next
family, is a remarkable condition of the lateral eyes, which are sessile on the
dorsal surface of the head, and near the middle line, the median eye being
slightly in front of them. During embryonic life a fold of skin grows over all
three eyes, so that a chamber is formed over them, which communicates
with the exterior by a small pore in front.
In the Limnadiidae the body is laterally compressed, and the carapace is
so large that at least the post-cephalic part of the body, and generally the
head also, can be enclosed within it.
In Limnetis (Fig. 3) the dorsal surface of the head is bent downwards and
is much compressed, the carapace being attached to it only for a short
distance near the dorsal middle line. The sides of the carapace are bent
downwards, and their margins can be pulled together by a transverse
adductor muscle, so that the whole structure forms an ovoid or spheroidal
case, from which the head projects in front, while the rest of the body is
entirely contained within it. When the adductor muscle is relaxed the edges
Page 43
of the carapace gape slightly, like the
valves of a Lamellibranch shell, and
food-particles are drawn through the
opening thus formed into the ventral
groove by the movements of the
thoracic feet, locomotion being
chiefly effected by the rowing action
of the second antennae, as in the
Cladocera, to which all the
Limnadiidae present strong
resemblances in their method of
locomotion, in the condition of the Fig. 3.—Limnetis brachyura, × 15. (After G. O.
carapace, and in the form of the Sars.)
telson.
In Limnadia and Estheria the carapace projects not only backwards from
the point of attachment to the head, but also forwards, so that the head can
be enclosed by it, together with the rest of the body.
In all these genera the carapace is flexible along the middle dorsal line; in
Estheria especially the softening of the dorsal cuticle goes so far that a
definite hinge-line is formed, and this, together with the deposition of the
lateral cuticle in lines concentrically arranged round a projecting umbo,
gives the carapace a strong superficial likeness to a Lamellibranch shell, for
which it is said to be frequently mistaken by collectors.
The eyes of the Limnadiidae are enclosed in a chamber formed by a
growth of skin over them, as in Apodidae, but the pore by which this
chamber communicates with the exterior is even more minute than in Apus.
The paired eyes are so close together that they may touch (Limnadia,
Estheria) or fuse (Limnetis); they are farther back than in the Apodidae,
while the ventral curvature of the head causes the median eye to lie below
them. In all these points the eyes of the Limnadiidae are intermediate
between those of Apus and those of the Cladocera.
Dorsal Organ.—A structure very characteristic of adult Phyllopods is
the “dorsal organ” (Figs. 2, 5, D.O), whose function is in many cases
obscure. It is always a patch of modified cephalic ectoderm, supplied by a
nerve from the anterior ventral lobe of the brain on each side; but its
characters, and apparent function, differ in different forms. In the
valves of a Lamellibranch shell, and
food-particles are drawn through the
opening thus formed into the ventral
groove by the movements of the
thoracic feet, locomotion being
chiefly effected by the rowing action
of the second antennae, as in the
Cladocera, to which all the
Limnadiidae present strong
resemblances in their method of
locomotion, in the condition of the Fig. 3.—Limnetis brachyura, × 15. (After G. O.
carapace, and in the form of the Sars.)
telson.
In Limnadia and Estheria the carapace projects not only backwards from
the point of attachment to the head, but also forwards, so that the head can
be enclosed by it, together with the rest of the body.
In all these genera the carapace is flexible along the middle dorsal line; in
Estheria especially the softening of the dorsal cuticle goes so far that a
definite hinge-line is formed, and this, together with the deposition of the
lateral cuticle in lines concentrically arranged round a projecting umbo,
gives the carapace a strong superficial likeness to a Lamellibranch shell, for
which it is said to be frequently mistaken by collectors.
The eyes of the Limnadiidae are enclosed in a chamber formed by a
growth of skin over them, as in Apodidae, but the pore by which this
chamber communicates with the exterior is even more minute than in Apus.
The paired eyes are so close together that they may touch (Limnadia,
Estheria) or fuse (Limnetis); they are farther back than in the Apodidae,
while the ventral curvature of the head causes the median eye to lie below
them. In all these points the eyes of the Limnadiidae are intermediate
between those of Apus and those of the Cladocera.
Dorsal Organ.—A structure very characteristic of adult Phyllopods is
the “dorsal organ” (Figs. 2, 5, D.O), whose function is in many cases
obscure. It is always a patch of modified cephalic ectoderm, supplied by a
nerve from the anterior ventral lobe of the brain on each side; but its
characters, and apparent function, differ in different forms. In the
Page 44
Branchipodidae the dorsal organ is a circular patch, far forward on the
surface of the head (Figs. 2, 5, D.O). Its cells are arranged in groups, which
remind one of the retinulae in a compound eye; each cell contains a solid
concretion, and the concretions of a group may be so placed as to look like
a badly-formed rhabdom. Claus,[16] who first called attention to this
structure in the Branchipodidae, regarded it as a sense-organ. In Apodidae
the dorsal organ is an oval patch of columnar ectoderm, immediately behind
the eyes; it is slightly raised above the surrounding skin, and is covered by a
very delicate cuticle (with an opening to the exterior?), and below it is a
mass of connective tissue permeated by blood; Bernard has suggested that it
is an excretory organ.
Most Limnadiidae resemble the Cladocera in the possession of a “dorsal
organ” quite distinct from the above; in Limnetis and Estheria it has the
form of a small pit, lined by an apparently glandular ectoderm, and this is
its condition in many Cladocera; in Limnadia lenticularis it is a patch of
glandular epithelium on a raised papilla. Limnadia has been observed to
anchor itself to foreign objects by pressing its dorsal organ against them,
and many Cladocera do the same thing; Sida crystallina, for example, will
remain for hours attached by its dorsal organ to a waterweed or to the side
of an aquarium. Structures resembling a dorsal organ occur in the larvae of
many other Crustacea, but the presence of this organ in the adult is confined
to Branchiopods, and indeed in many Cladocera it disappears before
maturity. It is certain that the sensory and adhesive types of dorsal organ are
not homologous, especially as rudimentary sense-organs may exist on the
head of Cladocera together with the adhesive organ.
The telson differs considerably in the different genera. In the
Branchipodidae[17] the anus opens directly backwards; and the telson carries
two flattened backwardly directed plates, one on each side of the anus, the
margins of each plate being fringed with plumose setae. In Artemia the anal
plates are rarely as large as in Branchipus, and never have their margins
completely fringed with setae; in A. salina from Western Europe, and in A.
fertilis (Fig. 4, A) from the Great Salt Lake of Utah, there is a variable
number of setae round the apical half of each lobe, but in specimens of A.
salina from Western Siberia the number of setae may be very small, or they
may be absent; in the closely allied A. urmiana from Persia the anal lobes
are well developed in the male, each lobe bearing a single terminal hair, but
they are altogether absent in the female. Schmankewitch and Bateson have
surface of the head (Figs. 2, 5, D.O). Its cells are arranged in groups, which
remind one of the retinulae in a compound eye; each cell contains a solid
concretion, and the concretions of a group may be so placed as to look like
a badly-formed rhabdom. Claus,[16] who first called attention to this
structure in the Branchipodidae, regarded it as a sense-organ. In Apodidae
the dorsal organ is an oval patch of columnar ectoderm, immediately behind
the eyes; it is slightly raised above the surrounding skin, and is covered by a
very delicate cuticle (with an opening to the exterior?), and below it is a
mass of connective tissue permeated by blood; Bernard has suggested that it
is an excretory organ.
Most Limnadiidae resemble the Cladocera in the possession of a “dorsal
organ” quite distinct from the above; in Limnetis and Estheria it has the
form of a small pit, lined by an apparently glandular ectoderm, and this is
its condition in many Cladocera; in Limnadia lenticularis it is a patch of
glandular epithelium on a raised papilla. Limnadia has been observed to
anchor itself to foreign objects by pressing its dorsal organ against them,
and many Cladocera do the same thing; Sida crystallina, for example, will
remain for hours attached by its dorsal organ to a waterweed or to the side
of an aquarium. Structures resembling a dorsal organ occur in the larvae of
many other Crustacea, but the presence of this organ in the adult is confined
to Branchiopods, and indeed in many Cladocera it disappears before
maturity. It is certain that the sensory and adhesive types of dorsal organ are
not homologous, especially as rudimentary sense-organs may exist on the
head of Cladocera together with the adhesive organ.
The telson differs considerably in the different genera. In the
Branchipodidae[17] the anus opens directly backwards; and the telson carries
two flattened backwardly directed plates, one on each side of the anus, the
margins of each plate being fringed with plumose setae. In Artemia the anal
plates are rarely as large as in Branchipus, and never have their margins
completely fringed with setae; in A. salina from Western Europe, and in A.
fertilis (Fig. 4, A) from the Great Salt Lake of Utah, there is a variable
number of setae round the apical half of each lobe, but in specimens of A.
salina from Western Siberia the number of setae may be very small, or they
may be absent; in the closely allied A. urmiana from Persia the anal lobes
are well developed in the male, each lobe bearing a single terminal hair, but
they are altogether absent in the female. Schmankewitch and Bateson have
Page 45
shown that there is a certain relation between the salinity of the water in
which Artemia salina occurs and the condition of the anal lobes, specimens
from denser waters having on the whole fewer setae; the relation is,
however, evidently very complex, and further evidence is wanted before
any more definite statements can be made.
Fig. 4.—A, Ventral view of the anal region in Artemia fertilis, from the Great
Salt Lake; B, ventral view of the telson and neighbouring parts of Lepidurus
productus; C, side view of the telson and left anal lobe of Estheria (sp.?).
In the Apodidae the anal lobes have the form of two-jointed cirri, often of
considerable length; in Apus the anus is terminal, but in Lepidurus (Fig. 4,
B) the dorsal part of the telson is prolonged backwards, so as to form a
plate, on the ventral face of which the anus opens, much as in the
Malacostraca.
In the Limnadiidae (Fig. 4, C) the telson is laterally compressed and
produced, on each side of the anus, into a flattened, upwardly curved
process, sharply pointed posteriorly, and often serrate; the anal lobes are
represented by two stout curved spines, while in place of the dorsal
prolongation of Lepidurus we find two long plumose setae above the anus.
In the characters of the telson and anal lobes, as in those of the head, the
Limnadiidae approximate to the Cladocera. In Limnetis brachyura the
ventral face of the telson is produced into a plate projecting backwards
below the anus, in a manner which has no exact parallel among other
Crustacea.
The appendages of the Phyllopoda are fairly uniform in character, except
those affected by the sexual dimorphism, which is usually great.
which Artemia salina occurs and the condition of the anal lobes, specimens
from denser waters having on the whole fewer setae; the relation is,
however, evidently very complex, and further evidence is wanted before
any more definite statements can be made.
Fig. 4.—A, Ventral view of the anal region in Artemia fertilis, from the Great
Salt Lake; B, ventral view of the telson and neighbouring parts of Lepidurus
productus; C, side view of the telson and left anal lobe of Estheria (sp.?).
In the Apodidae the anal lobes have the form of two-jointed cirri, often of
considerable length; in Apus the anus is terminal, but in Lepidurus (Fig. 4,
B) the dorsal part of the telson is prolonged backwards, so as to form a
plate, on the ventral face of which the anus opens, much as in the
Malacostraca.
In the Limnadiidae (Fig. 4, C) the telson is laterally compressed and
produced, on each side of the anus, into a flattened, upwardly curved
process, sharply pointed posteriorly, and often serrate; the anal lobes are
represented by two stout curved spines, while in place of the dorsal
prolongation of Lepidurus we find two long plumose setae above the anus.
In the characters of the telson and anal lobes, as in those of the head, the
Limnadiidae approximate to the Cladocera. In Limnetis brachyura the
ventral face of the telson is produced into a plate projecting backwards
below the anus, in a manner which has no exact parallel among other
Crustacea.
The appendages of the Phyllopoda are fairly uniform in character, except
those affected by the sexual dimorphism, which is usually great.
Page 46
Fig. 5.—Chirocephalus diaphanus, male. Side view of head, showing the large
second antenna, A2, with its appendage Ap, above which is seen the filiform first
antenna; D.O, dorsal organ; E1, median eye.
Of the cephalic appendages, the first antennae are generally small, and
are never biramous; in Branchipus and its allies they are simple unjointed
rods, in some species of Artemia they are three-jointed, in Apus they are
feebly divided into two joints, while in Estheria they are many-jointed. The
second antennae are the principal organs of locomotion in the Limnadiidae,
where they are large and biramous; in all other Phyllopoda they are
uniramous in the female, being either unjointed triangular plates as in
Chirocephalus (Fig. 2), or minute vestigial filaments as in Apus, in which
genus Zaddach, Huxley, and Claus have all failed to find any trace of a
second antenna in some females. In the male Branchipodidae the second
antennae are modified to form claspers, by which the female is seized, the
various degrees of complication which these claspers exhibit affording
convenient generic characters. In Branchinecta each second antenna is a
thick, three-jointed rod, the last joint forming a claw, while the second joint
is serrate on its inner margin; in Branchipus the base is much thickened, and
bears on its inner side a large filament (perhaps represented by the proximal
tubercle of Branchinecta and Artemia), which looks like an extra antenna.
second antenna, A2, with its appendage Ap, above which is seen the filiform first
antenna; D.O, dorsal organ; E1, median eye.
Of the cephalic appendages, the first antennae are generally small, and
are never biramous; in Branchipus and its allies they are simple unjointed
rods, in some species of Artemia they are three-jointed, in Apus they are
feebly divided into two joints, while in Estheria they are many-jointed. The
second antennae are the principal organs of locomotion in the Limnadiidae,
where they are large and biramous; in all other Phyllopoda they are
uniramous in the female, being either unjointed triangular plates as in
Chirocephalus (Fig. 2), or minute vestigial filaments as in Apus, in which
genus Zaddach, Huxley, and Claus have all failed to find any trace of a
second antenna in some females. In the male Branchipodidae the second
antennae are modified to form claspers, by which the female is seized, the
various degrees of complication which these claspers exhibit affording
convenient generic characters. In Branchinecta each second antenna is a
thick, three-jointed rod, the last joint forming a claw, while the second joint
is serrate on its inner margin; in Branchipus the base is much thickened, and
bears on its inner side a large filament (perhaps represented by the proximal
tubercle of Branchinecta and Artemia), which looks like an extra antenna.
Page 47
In Streptocephalus the terminal joint
of the antenna is bifid, and there is a
basal filament like that of
Branchipus; in Chirocephalus
diaphanus (Figs. 5, 6) the main
branch of the antenna consists of two
large joints, the terminal joint being a
strong claw with a serrated process at
its base, while the proximal joint
bears two appendages on its inner
side; one of these is a small,
subconical tubercle, the second is
more complicated, consisting of a
main stem and five outgrowths. The
main stem is many-jointed and
flexible, its basal joint being longer
than the others, and bearing on its
outer side a large, triangular,
membranous appendage, and four
soft cylindrical appendages, the main Fig. 6.—Chirocephalus diaphanus. Second
stem and its appendages being beset antenna of male, uncoiled.
with curious tubercles, ending in
short spines, whose structure is not understood. Except during the act of
copulation this remarkable apparatus is coiled on the inner side of the
antennary claw, the jointed stem being so coiled that it is often compared to
the coiled proboscis of a butterfly, and the triangular membrane folded like
a fan beside it, so that much of the organ is concealed, and the general
appearance of the head is that shown in Fig. 5. During copulation, the
whole structure is widely extended.
The males of Artemia (Fig. 7) have the second antenna two-jointed, the
basal joint bearing an inner tubercle, the terminal joint being flattened and
bluntly pointed, its outer margin provided with a membranous outgrowth. In
A. fertilis the breadth of the second joint varies greatly, the narrower forms
presenting a certain remote resemblance to Branchinecta. In the males of
Polyartemia the second antennae have a remarkable branched form not
easily comparable with that found in other Branchipodidae.
of the antenna is bifid, and there is a
basal filament like that of
Branchipus; in Chirocephalus
diaphanus (Figs. 5, 6) the main
branch of the antenna consists of two
large joints, the terminal joint being a
strong claw with a serrated process at
its base, while the proximal joint
bears two appendages on its inner
side; one of these is a small,
subconical tubercle, the second is
more complicated, consisting of a
main stem and five outgrowths. The
main stem is many-jointed and
flexible, its basal joint being longer
than the others, and bearing on its
outer side a large, triangular,
membranous appendage, and four
soft cylindrical appendages, the main Fig. 6.—Chirocephalus diaphanus. Second
stem and its appendages being beset antenna of male, uncoiled.
with curious tubercles, ending in
short spines, whose structure is not understood. Except during the act of
copulation this remarkable apparatus is coiled on the inner side of the
antennary claw, the jointed stem being so coiled that it is often compared to
the coiled proboscis of a butterfly, and the triangular membrane folded like
a fan beside it, so that much of the organ is concealed, and the general
appearance of the head is that shown in Fig. 5. During copulation, the
whole structure is widely extended.
The males of Artemia (Fig. 7) have the second antenna two-jointed, the
basal joint bearing an inner tubercle, the terminal joint being flattened and
bluntly pointed, its outer margin provided with a membranous outgrowth. In
A. fertilis the breadth of the second joint varies greatly, the narrower forms
presenting a certain remote resemblance to Branchinecta. In the males of
Polyartemia the second antennae have a remarkable branched form not
easily comparable with that found in other Branchipodidae.
Page 48
The cephalic jaws are fairly
uniform throughout the order. The
mandibles have an undivided molar
surface, and no palp; the first maxilla
is very generally a triangular plate,
with a setose biting edge; mandibles
and maxillae are covered by the
labrum. The second maxilla generally
lies outside the chamber formed by
Fig. 7.—Artemia fertilis. Front view of the head the labrum, and is a simple oval
of a male, showing the large second antennae, plate, with or without a special
A.2; A.1, first antennae. process for the duct of the kidney.
The thoracic limbs, in front of the
genital segments, are not as a rule differentiated into anterior maxillipedes
and posterior locomotive appendages, as in higher forms; we have seen,
however, that all these limbs take part in the prehension of food, and except
in the Limnadiidae they all assist in locomotion. One of the middle thoracic
legs of Artemia (Fig. 8, A) has a flattened stem, with seven processes on its
inner, and two on its outer margin. The gnathobase (gn) is large, and fringed
with long plumose setae, each of which is jointed; this is followed by four
smaller “endites” (or processes on the median side), and then by two larger
ones, the terminal endite (the sixth, excluding the gnathobase) being very
mobile and attached to the main stem by a definite joint. On the outer side
are two processes; a proximal “bract,” a flat plate with crenate edges, partly
divided by a constriction into two, and a distal process, cylindrical and
vascular, called by Sars and others the “epipodite.” In other Branchipodidae
we have essentially the same condition, except that the fifth endite often
becomes much larger than in Artemia, throwing the terminal endite well
over to the outer edge of the limb; such a shift as this, continued farther,
might well lead to the condition found in the Limnadiidae, or Apodidae,
where the lobe which seems to represent the terminal endite of Artemia is
entirely on the outer border of the limb, forming what most writers have
called the exopodite (Lankester’s “flabellum”).[18] In the two last-named
families the basal exite or bract of the Branchipodidae does not appear to be
represented.
uniform throughout the order. The
mandibles have an undivided molar
surface, and no palp; the first maxilla
is very generally a triangular plate,
with a setose biting edge; mandibles
and maxillae are covered by the
labrum. The second maxilla generally
lies outside the chamber formed by
Fig. 7.—Artemia fertilis. Front view of the head the labrum, and is a simple oval
of a male, showing the large second antennae, plate, with or without a special
A.2; A.1, first antennae. process for the duct of the kidney.
The thoracic limbs, in front of the
genital segments, are not as a rule differentiated into anterior maxillipedes
and posterior locomotive appendages, as in higher forms; we have seen,
however, that all these limbs take part in the prehension of food, and except
in the Limnadiidae they all assist in locomotion. One of the middle thoracic
legs of Artemia (Fig. 8, A) has a flattened stem, with seven processes on its
inner, and two on its outer margin. The gnathobase (gn) is large, and fringed
with long plumose setae, each of which is jointed; this is followed by four
smaller “endites” (or processes on the median side), and then by two larger
ones, the terminal endite (the sixth, excluding the gnathobase) being very
mobile and attached to the main stem by a definite joint. On the outer side
are two processes; a proximal “bract,” a flat plate with crenate edges, partly
divided by a constriction into two, and a distal process, cylindrical and
vascular, called by Sars and others the “epipodite.” In other Branchipodidae
we have essentially the same condition, except that the fifth endite often
becomes much larger than in Artemia, throwing the terminal endite well
over to the outer edge of the limb; such a shift as this, continued farther,
might well lead to the condition found in the Limnadiidae, or Apodidae,
where the lobe which seems to represent the terminal endite of Artemia is
entirely on the outer border of the limb, forming what most writers have
called the exopodite (Lankester’s “flabellum”).[18] In the two last-named
families the basal exite or bract of the Branchipodidae does not appear to be
represented.
Page 49
Fig. 8.—A, Thoracic limb of Chirocephalus diaphanus; B, prehensile thoracic
limb of male Estheria. gn, Gnathobase; 1–6, the more distal endites.
The limbs of the Apodidae are remarkable in two ways; those in front of
the genital opening (very constantly ten pairs) are not so nearly alike as in
most genera of the sub-order, the first two pairs especially having the axis
definitely jointed, while the endites are elongated and antenniform; further,
while the first eleven segments bear each a single pair of limbs, as is usual
among Crustacea, many of the post-genital segments bear several pairs;
thus in Apus cancriformis there are thirty-two post-cephalic segments in
front of the telson, the first eleven having each one pair of limbs, while the
next seventeen have fifty-two pairs between them, the last four segments
having none.
In all the Phyllopoda some of the post-cephalic limbs are modified for
reproductive purposes; in the Branchipodidae the last two pairs (the 12th
and 13th generally, the 20th and 21st in Polyartemia) are so modified in
both sexes. In the female these appendages fuse at an early period of larval
life, and surround the median opening of the generative duct (Fig. 2); in the
male the two pairs also fuse, but traces of the limbs are left as eversible
processes round the paired openings of the vasa deferentia.
limb of male Estheria. gn, Gnathobase; 1–6, the more distal endites.
The limbs of the Apodidae are remarkable in two ways; those in front of
the genital opening (very constantly ten pairs) are not so nearly alike as in
most genera of the sub-order, the first two pairs especially having the axis
definitely jointed, while the endites are elongated and antenniform; further,
while the first eleven segments bear each a single pair of limbs, as is usual
among Crustacea, many of the post-genital segments bear several pairs;
thus in Apus cancriformis there are thirty-two post-cephalic segments in
front of the telson, the first eleven having each one pair of limbs, while the
next seventeen have fifty-two pairs between them, the last four segments
having none.
In all the Phyllopoda some of the post-cephalic limbs are modified for
reproductive purposes; in the Branchipodidae the last two pairs (the 12th
and 13th generally, the 20th and 21st in Polyartemia) are so modified in
both sexes. In the female these appendages fuse at an early period of larval
life, and surround the median opening of the generative duct (Fig. 2); in the
male the two pairs also fuse, but traces of the limbs are left as eversible
processes round the paired openings of the vasa deferentia.
Page 50
In the other families, one or more limbs of the female are adapted for
carrying or supporting the eggs. In the Apodidae the appendages of the
eleventh segment have the exopodite in the form of a rounded, watchglass-
shaped plate, fitting over a similarly shaped process of the axis of the limb,
so that a lens-shaped box is formed, into which the eggs pass from the
oviduct. In Limnadiidae the eggs are carried in masses between the body
and the carapace, and are kept in position by special elongations of the
exopodites of two or three legs, either those near the middle of the thorax
(Estheria, Limnadia), or at its posterior end (Limnetis). In female Limnetis
the last thoracic segments bear two remarkable lateral plates, which
apparently also help to support the eggs. In the male Limnadiidae, the first
(Limnetis) or the first two thoracic feet (Limnadia, Estheria) are prehensile
(Fig. 8, B).
Alimentary Canal.—The mouth of the Phyllopoda is overhung by the
large labrum, so that a kind of atrium is formed, outside the mouth itself, in
which mastication is performed; numerous unicellular glands, opening on
the oral face of the labrum, pour their secretion into the atrial chamber, and
may be called salivary, though the nature of their secretion is not known.
The mouth has commonly two swollen and setose lips, running
longitudinally forwards from the bases of the first maxillae, and often
wrapping round the blades of the mandibles. It leads into a vertical
oesophagus, which opens into a small globular stomach, lying entirely
within the head; the terminal part of the oesophagus is slightly invaginated
into the stomach, so that a valvular ring is formed at the junction of the two.
The stomach opens widely behind into a straight intestine, which runs
backwards to about the level of the telson, where it joins a short rectum,
leading to the terminal or ventral anus. The stomach and intestine are lined
by a columnar epithelium, and covered by a thin network of circularly
arranged muscle-fibres; the rectum has a flatter epithelium, and radial
muscles pass from it to the body-wall, so that it can be dilated. The only
special digestive glands are two branched glandular tubes, situated entirely
within the head, which open into the stomach by large ducts, one on each
side. In Chirocephalus the gastric glands are fairly small and simple; in the
Apodidae their branches are more complex and form a considerable mass,
filling all that portion of the head which is not occupied by the nervous
system and the muscles. Backwardly directed gastric glands, like those of
the higher Crustacea, are not found in Branchiopods; both forms occur
carrying or supporting the eggs. In the Apodidae the appendages of the
eleventh segment have the exopodite in the form of a rounded, watchglass-
shaped plate, fitting over a similarly shaped process of the axis of the limb,
so that a lens-shaped box is formed, into which the eggs pass from the
oviduct. In Limnadiidae the eggs are carried in masses between the body
and the carapace, and are kept in position by special elongations of the
exopodites of two or three legs, either those near the middle of the thorax
(Estheria, Limnadia), or at its posterior end (Limnetis). In female Limnetis
the last thoracic segments bear two remarkable lateral plates, which
apparently also help to support the eggs. In the male Limnadiidae, the first
(Limnetis) or the first two thoracic feet (Limnadia, Estheria) are prehensile
(Fig. 8, B).
Alimentary Canal.—The mouth of the Phyllopoda is overhung by the
large labrum, so that a kind of atrium is formed, outside the mouth itself, in
which mastication is performed; numerous unicellular glands, opening on
the oral face of the labrum, pour their secretion into the atrial chamber, and
may be called salivary, though the nature of their secretion is not known.
The mouth has commonly two swollen and setose lips, running
longitudinally forwards from the bases of the first maxillae, and often
wrapping round the blades of the mandibles. It leads into a vertical
oesophagus, which opens into a small globular stomach, lying entirely
within the head; the terminal part of the oesophagus is slightly invaginated
into the stomach, so that a valvular ring is formed at the junction of the two.
The stomach opens widely behind into a straight intestine, which runs
backwards to about the level of the telson, where it joins a short rectum,
leading to the terminal or ventral anus. The stomach and intestine are lined
by a columnar epithelium, and covered by a thin network of circularly
arranged muscle-fibres; the rectum has a flatter epithelium, and radial
muscles pass from it to the body-wall, so that it can be dilated. The only
special digestive glands are two branched glandular tubes, situated entirely
within the head, which open into the stomach by large ducts, one on each
side. In Chirocephalus the gastric glands are fairly small and simple; in the
Apodidae their branches are more complex and form a considerable mass,
filling all that portion of the head which is not occupied by the nervous
system and the muscles. Backwardly directed gastric glands, like those of
the higher Crustacea, are not found in Branchiopods; both forms occur
Page 51
together in the genus Nebalia, but with this exception the forwardly-
directed glands are peculiar to Branchiopods.
Heart.—In Branchipus and its allies, and in Artemia, the heart extends
from the first thoracic segment to the penultimate segment of the body, and
is provided with eighteen pairs of lateral openings, one pair in every
segment through which it passes except the last; it is widely open at its
hinder end, and is prolonged in front for a short distance as a cephalic aorta,
the rest of the blood-spaces being lacunar.
In most, at least, of the other Branchiopods, the heart is closed behind
and is shortened; in Apus and Lepidurus it only extends through the first
eleven post-cephalic segments, while in the Limnadiidae it is shorter still,
the heart of Limnetis passing through four segments only. In all cases there
is a pair of lateral openings in every segment traversed by the heart.
The blood of the Branchipodidae and Apodidae contains dissolved
haemoglobin, the quantity present being so small as to give but a faint
colour to the blood in Branchipus, while Artemia has rather more, and the
blood of Apus is very red. The only other Crustacea in which the blood
contains haemoglobin are the Copepods of the genus Lernanthropus,[19] so
that the appearance of this substance is as irregular and inexplicable in
Crustacea as in Chaetopods and Molluscs.
The nervous system of Branchipus may be described as an illustration of
the condition prevailing in the group. The brain consists of two closely
united ganglia, in each of which three main regions may be distinguished; a
ventral anterior lobe, a dorsal anterior lobe, and a posterior lobe. The
ventral anterior lobes give off nerves to the median eye, to the dorsal organ,
and to a pair of curious sense-organs, comparable with the larval sense-
knobs of many higher forms, situated one on each side of the median eye; in
late larvae Claus describes the terminal apparatus of each frontal sense-
organ as a single large hypodermic cell; W. K. Spencer[20] has lately
described several terminal cells, containing peculiar chitinous bodies, in the
adult. The homologous sense-organs of Limnetis are apparently olfactory.
The dorsal anterior lobes give off the large nerves to the lateral eyes, while
the posterior lobes supply the first antennae. The oesophageal connectives
have a coating of ganglion-cells, and some of these form the ganglion of the
second antenna, the nerve to this appendage leaving the connective just
behind the brain. The post-oral nerve-cords are widely separate, each of
directed glands are peculiar to Branchiopods.
Heart.—In Branchipus and its allies, and in Artemia, the heart extends
from the first thoracic segment to the penultimate segment of the body, and
is provided with eighteen pairs of lateral openings, one pair in every
segment through which it passes except the last; it is widely open at its
hinder end, and is prolonged in front for a short distance as a cephalic aorta,
the rest of the blood-spaces being lacunar.
In most, at least, of the other Branchiopods, the heart is closed behind
and is shortened; in Apus and Lepidurus it only extends through the first
eleven post-cephalic segments, while in the Limnadiidae it is shorter still,
the heart of Limnetis passing through four segments only. In all cases there
is a pair of lateral openings in every segment traversed by the heart.
The blood of the Branchipodidae and Apodidae contains dissolved
haemoglobin, the quantity present being so small as to give but a faint
colour to the blood in Branchipus, while Artemia has rather more, and the
blood of Apus is very red. The only other Crustacea in which the blood
contains haemoglobin are the Copepods of the genus Lernanthropus,[19] so
that the appearance of this substance is as irregular and inexplicable in
Crustacea as in Chaetopods and Molluscs.
The nervous system of Branchipus may be described as an illustration of
the condition prevailing in the group. The brain consists of two closely
united ganglia, in each of which three main regions may be distinguished; a
ventral anterior lobe, a dorsal anterior lobe, and a posterior lobe. The
ventral anterior lobes give off nerves to the median eye, to the dorsal organ,
and to a pair of curious sense-organs, comparable with the larval sense-
knobs of many higher forms, situated one on each side of the median eye; in
late larvae Claus describes the terminal apparatus of each frontal sense-
organ as a single large hypodermic cell; W. K. Spencer[20] has lately
described several terminal cells, containing peculiar chitinous bodies, in the
adult. The homologous sense-organs of Limnetis are apparently olfactory.
The dorsal anterior lobes give off the large nerves to the lateral eyes, while
the posterior lobes supply the first antennae. The oesophageal connectives
have a coating of ganglion-cells, and some of these form the ganglion of the
second antenna, the nerve to this appendage leaving the connective just
behind the brain. The post-oral nerve-cords are widely separate, each of
Page 52
them dilating into a ganglion opposite every appendage, the two ganglia
being connected by two transverse commissures. The ganglia of the three
cephalic jaws, so often fused in the higher Crustacea, are here perfectly
distinct. Closely connected with each thoracic ganglion is a remarkable
unicellular gland, opening to the exterior near the middle ventral line; it is
conceivable that these cells may be properly compared with the larval
nephridia of a Chaetopod,[21] but no evidence in support of such a
comparison has yet been adduced.
Behind the genital segments, where there are no limbs, the nerve-cords
run backwards without dilating into segmental ganglia, except in the
anterior two abdominal segments where small ganglionic enlargements
occur. In Apodidae, on the other hand, those segments which carry more
than one pair of appendages have as many pairs of ganglia, united by
transverse commissures, as they have limbs.
A stomatogastric nervous system exists in Apus, where a nerve arises on
each side from the first post-oral commissure, and runs forward to join its
fellow of the opposite side on the anterior wall of the oesophagus. From the
loop so formed a larger median and a series of smaller lateral nerves pass to
the wall of the alimentary canal. A second nerve to the oesophagus is given
off from the mandibular ganglion of each side.
Reproductive Organs.—In Chirocephalus the ovaries (Fig. 2, Ov) are
hollow epithelial tubes, lying one on each side of the alimentary canal, and
extending from the sixth abdominal segment forwards to the level of the
genital opening; at this point the two ovaries are continuous with ducts,
which bend sharply downwards and open into the single uterus contained
within the projecting egg-pouch and opening to the exterior at the apex of
that organ. Short diverticula of the walls of the uterus receive the ducts of
groups of unicellular glands, the bodies of which contain a peculiar opaque
secretion, said to form the eggshells. In Apodidae the ovaries are similar in
structure, but they are much larger and branch in a complex manner, while
each ovary opens to the exterior independently of the other in the eleventh
post-cephalic segment; nothing like the median uterus of the
Branchipodidae being formed. The epithelium of the ovarian tubes
proliferates, and groups of cells are formed; one becoming an ovum, the
others being nutrient cells like those which will be more fully described in
the Cladocera.
being connected by two transverse commissures. The ganglia of the three
cephalic jaws, so often fused in the higher Crustacea, are here perfectly
distinct. Closely connected with each thoracic ganglion is a remarkable
unicellular gland, opening to the exterior near the middle ventral line; it is
conceivable that these cells may be properly compared with the larval
nephridia of a Chaetopod,[21] but no evidence in support of such a
comparison has yet been adduced.
Behind the genital segments, where there are no limbs, the nerve-cords
run backwards without dilating into segmental ganglia, except in the
anterior two abdominal segments where small ganglionic enlargements
occur. In Apodidae, on the other hand, those segments which carry more
than one pair of appendages have as many pairs of ganglia, united by
transverse commissures, as they have limbs.
A stomatogastric nervous system exists in Apus, where a nerve arises on
each side from the first post-oral commissure, and runs forward to join its
fellow of the opposite side on the anterior wall of the oesophagus. From the
loop so formed a larger median and a series of smaller lateral nerves pass to
the wall of the alimentary canal. A second nerve to the oesophagus is given
off from the mandibular ganglion of each side.
Reproductive Organs.—In Chirocephalus the ovaries (Fig. 2, Ov) are
hollow epithelial tubes, lying one on each side of the alimentary canal, and
extending from the sixth abdominal segment forwards to the level of the
genital opening; at this point the two ovaries are continuous with ducts,
which bend sharply downwards and open into the single uterus contained
within the projecting egg-pouch and opening to the exterior at the apex of
that organ. Short diverticula of the walls of the uterus receive the ducts of
groups of unicellular glands, the bodies of which contain a peculiar opaque
secretion, said to form the eggshells. In Apodidae the ovaries are similar in
structure, but they are much larger and branch in a complex manner, while
each ovary opens to the exterior independently of the other in the eleventh
post-cephalic segment; nothing like the median uterus of the
Branchipodidae being formed. The epithelium of the ovarian tubes
proliferates, and groups of cells are formed; one becoming an ovum, the
others being nutrient cells like those which will be more fully described in
the Cladocera.
Page 53
In Chirocephalus the testes are tubes similar in shape and position to the
ovaries, each communicating in front with a short vas deferens, which
dilates into a vesicula seminalis on its way to the eversible penis; an
essentially similar arrangement is found in all Branchipodidae, but in
Apodidae and Limnadiidae there is no penis.
All the Branchiopoda are dioecious,[22] and many are parthenogenetic.
Among Branchipodidae Artemia is the only genus known to be
parthenogenetic, but parthenogenesis is common in all Apodidae, while the
males of several species of Limnadia are still unknown, although the
females are sometimes exceedingly common. In Artemia, generations in
which the males are about as numerous as the females seem to alternate
fairly quickly with others which contain only parthenogenetic females; in
Apus males are rarely abundant, and often absent for long periods; during
five consecutive years von Siebold failed to discover a male in a locality in
Bavaria, though he examined many thousands of individuals; near Breslau
he found on one occasion about 11 per cent of males (114 in 1026), but in a
subsequent year he found less than 1 per cent; the greatest recorded
percentage of males is that observed by Lubbock in 1863, when he found
33 males among 72 individuals taken near Rouen.
The eggs of most genera can resist prolonged periods of desiccation, and
indeed it seems necessary for the development of many species that the
eggs should be first dried and afterwards placed in water. Many eggs (e.g.
of Chirocephalus diaphanus and Branchipus stagnalis) float when placed in
water after desiccation, the development taking place at the surface of the
water.
Habitat.—All the Phyllopoda, except Artemia, are confined to stagnant
shallow waters, especially to such ponds as are formed during spring rains,
and dry up during the summer. In waters of this kind the species of
Branchipus, Apus, etc., develop rapidly, and produce great numbers of eggs,
which are left in the dried mud at the bottom after evaporation of the water,
where they remain quiescent until a fresh rainy season. The mud from the
beds of such temporary pools often contains large numbers of eggs, which
may be carried by wind, on the legs of birds, and by other means, to
considerable distances. Many exotic species have been made known to
European naturalists by their power of hatching out when mud brought
home by travellers is placed in water. The water of stagnant pools quickly
ovaries, each communicating in front with a short vas deferens, which
dilates into a vesicula seminalis on its way to the eversible penis; an
essentially similar arrangement is found in all Branchipodidae, but in
Apodidae and Limnadiidae there is no penis.
All the Branchiopoda are dioecious,[22] and many are parthenogenetic.
Among Branchipodidae Artemia is the only genus known to be
parthenogenetic, but parthenogenesis is common in all Apodidae, while the
males of several species of Limnadia are still unknown, although the
females are sometimes exceedingly common. In Artemia, generations in
which the males are about as numerous as the females seem to alternate
fairly quickly with others which contain only parthenogenetic females; in
Apus males are rarely abundant, and often absent for long periods; during
five consecutive years von Siebold failed to discover a male in a locality in
Bavaria, though he examined many thousands of individuals; near Breslau
he found on one occasion about 11 per cent of males (114 in 1026), but in a
subsequent year he found less than 1 per cent; the greatest recorded
percentage of males is that observed by Lubbock in 1863, when he found
33 males among 72 individuals taken near Rouen.
The eggs of most genera can resist prolonged periods of desiccation, and
indeed it seems necessary for the development of many species that the
eggs should be first dried and afterwards placed in water. Many eggs (e.g.
of Chirocephalus diaphanus and Branchipus stagnalis) float when placed in
water after desiccation, the development taking place at the surface of the
water.
Habitat.—All the Phyllopoda, except Artemia, are confined to stagnant
shallow waters, especially to such ponds as are formed during spring rains,
and dry up during the summer. In waters of this kind the species of
Branchipus, Apus, etc., develop rapidly, and produce great numbers of eggs,
which are left in the dried mud at the bottom after evaporation of the water,
where they remain quiescent until a fresh rainy season. The mud from the
beds of such temporary pools often contains large numbers of eggs, which
may be carried by wind, on the legs of birds, and by other means, to
considerable distances. Many exotic species have been made known to
European naturalists by their power of hatching out when mud brought
home by travellers is placed in water. The water of stagnant pools quickly
Page 54
dissolves a certain quantity of solid matter from the soil, and often receives
dissolved solids through surface drainage from the neighbouring land; such
salts may remain as the water evaporates, so that the water which remains
after evaporation has proceeded for some time may be very sensibly denser
than that in which the Branchiopods were hatched; these creatures must
therefore be able to endure a considerable increase in the salinity of the
surrounding waters during the course of their lives. My friend Mr. W. W.
Fisher points out that the plants present in such a pond would often
precipitate the carbonate of lime, so that this might be removed as
evaporation went on, but that chlorides would probably remain in solution;
from analyses which Mr. Fisher has been kind enough to make for me, it is
seen that this happened in a small aquarium in my laboratory, in which
Chirocephalus diaphanus lived for four months. In April, mud from the dry
bed of a pond, known to contain eggs of Chirocephalus, was placed in this
aquarium in Oxford, and water was added from the tap. Oxford tap-water
contains about 0·3 grm. salts per litre, the chlorine being equivalent to
0·023 grm. NaCl. Water was added from time to time during May and June,
but in July evaporation was allowed to proceed unchecked. At the end of
July there was about half the original volume of water, the Chirocephalus
being still active; the residue contained 0·96 grm. dissolved solids per litre,
with chlorine equal to 0·19 grm. NaCl, so that the percentage of chlorides
was about eight times the initial percentage, but there were only three and a
fifth times the original amount of total solid matter in solution, the
carbonate of lime having precipitated as a visible film.
Some species of Branchipus (e.g. B. spinosus, M. Edw.) and of Estheria
(E. macgillivrayi, Baird, E. gubernator, Klutzinger) occur in salt pools, but
Artemia flourishes in waters beside whose salinity that endured by any
other Branchiopod is insignificant. In the South of Europe, Artemia salina
may be found in swarms, as it used to be found in Dorsetshire, in the
shallow brine-pans from which salt is commercially prepared; Rathke
quotes an analysis showing that a pool in the Crimea contained living
Artemia when the salts in solution were 271 grms. per litre, and the water
was said to have the colour and consistency of beer.
The behaviour of the animals in the water differs a little; in normal
feeding all the species swim with the back downwards, as has already been
said; the Branchipodidae rarely settle on the ground, or on foreign objects,
dissolved solids through surface drainage from the neighbouring land; such
salts may remain as the water evaporates, so that the water which remains
after evaporation has proceeded for some time may be very sensibly denser
than that in which the Branchiopods were hatched; these creatures must
therefore be able to endure a considerable increase in the salinity of the
surrounding waters during the course of their lives. My friend Mr. W. W.
Fisher points out that the plants present in such a pond would often
precipitate the carbonate of lime, so that this might be removed as
evaporation went on, but that chlorides would probably remain in solution;
from analyses which Mr. Fisher has been kind enough to make for me, it is
seen that this happened in a small aquarium in my laboratory, in which
Chirocephalus diaphanus lived for four months. In April, mud from the dry
bed of a pond, known to contain eggs of Chirocephalus, was placed in this
aquarium in Oxford, and water was added from the tap. Oxford tap-water
contains about 0·3 grm. salts per litre, the chlorine being equivalent to
0·023 grm. NaCl. Water was added from time to time during May and June,
but in July evaporation was allowed to proceed unchecked. At the end of
July there was about half the original volume of water, the Chirocephalus
being still active; the residue contained 0·96 grm. dissolved solids per litre,
with chlorine equal to 0·19 grm. NaCl, so that the percentage of chlorides
was about eight times the initial percentage, but there were only three and a
fifth times the original amount of total solid matter in solution, the
carbonate of lime having precipitated as a visible film.
Some species of Branchipus (e.g. B. spinosus, M. Edw.) and of Estheria
(E. macgillivrayi, Baird, E. gubernator, Klutzinger) occur in salt pools, but
Artemia flourishes in waters beside whose salinity that endured by any
other Branchiopod is insignificant. In the South of Europe, Artemia salina
may be found in swarms, as it used to be found in Dorsetshire, in the
shallow brine-pans from which salt is commercially prepared; Rathke
quotes an analysis showing that a pool in the Crimea contained living
Artemia when the salts in solution were 271 grms. per litre, and the water
was said to have the colour and consistency of beer.
The behaviour of the animals in the water differs a little; in normal
feeding all the species swim with the back downwards, as has already been
said; the Branchipodidae rarely settle on the ground, or on foreign objects,
Page 55
but the Apodidae occasionally wriggle along the bottom on their ventral
surface, and Estheria burrows in mud.
The greater number of species are found in pools in flat, low-lying
regions, and many appear to be especially abundant near the sea; Apus
cancriformis has, however, been found in Armenia at 10,000 feet above sea
level.
Wells and underground waters do not generally contain Phyllopods; but a
species of Branchipus and one of Limnetis, both blind, have been described
from the caves of Carniola.
One of the many puzzles presented by these creatures is the erratic way
in which they are scattered through the regions they inhabit; a single small
pond, a few yards or less in diameter, may be the only place within many
miles in which a given species can be found; in this pond it may, however,
appear regularly season after season for some time, and then suddenly
vanish.
Geographically, the Phyllopoda are cosmopolitan, representatives of
every family and of some genera (e.g. Streptocephalus, Lepidurus,
Estheria) being found in every one of the great zoological regions, though a
few aberrant genera are of limited range, thus Polyartemia is known only
from the northern Palaearctic and Nearctic regions, Thamnocephalus only
from the Central United States. The genus Artemia is not at present known
in Australia.[23] The only recorded British species are Chirocephalus
diaphanus, Artemia salina, and Apus cancriformis,[24] but other continental
islands, for example the West Indian group, are better supplied. The
distribution of the species is very imperfectly known, but on the whole
every main zoological region seems to have its own peculiar species, which
do not pass beyond its boundaries. Branchinecta paludosa and Lepidurus
glacialis are circumpolar, both occurring in Norway, in Lapland, in
Greenland, and in Arctic North America; but with these exceptions the
Palaearctic and Nearctic species seem to be distinct. The European species
Apus cancriformis occurs in Algiers, but the relations between the species
of Northern Africa as a whole and those of Southern Europe on the one
hand, or of Central and Southern Africa on the other, have yet to be worked
out.
The soft-bodied Branchipodidae are not known in the fossil condition;[25]
an Apus, closely related to the modern A. cancriformis, has been found in
surface, and Estheria burrows in mud.
The greater number of species are found in pools in flat, low-lying
regions, and many appear to be especially abundant near the sea; Apus
cancriformis has, however, been found in Armenia at 10,000 feet above sea
level.
Wells and underground waters do not generally contain Phyllopods; but a
species of Branchipus and one of Limnetis, both blind, have been described
from the caves of Carniola.
One of the many puzzles presented by these creatures is the erratic way
in which they are scattered through the regions they inhabit; a single small
pond, a few yards or less in diameter, may be the only place within many
miles in which a given species can be found; in this pond it may, however,
appear regularly season after season for some time, and then suddenly
vanish.
Geographically, the Phyllopoda are cosmopolitan, representatives of
every family and of some genera (e.g. Streptocephalus, Lepidurus,
Estheria) being found in every one of the great zoological regions, though a
few aberrant genera are of limited range, thus Polyartemia is known only
from the northern Palaearctic and Nearctic regions, Thamnocephalus only
from the Central United States. The genus Artemia is not at present known
in Australia.[23] The only recorded British species are Chirocephalus
diaphanus, Artemia salina, and Apus cancriformis,[24] but other continental
islands, for example the West Indian group, are better supplied. The
distribution of the species is very imperfectly known, but on the whole
every main zoological region seems to have its own peculiar species, which
do not pass beyond its boundaries. Branchinecta paludosa and Lepidurus
glacialis are circumpolar, both occurring in Norway, in Lapland, in
Greenland, and in Arctic North America; but with these exceptions the
Palaearctic and Nearctic species seem to be distinct. The European species
Apus cancriformis occurs in Algiers, but the relations between the species
of Northern Africa as a whole and those of Southern Europe on the one
hand, or of Central and Southern Africa on the other, have yet to be worked
out.
The soft-bodied Branchipodidae are not known in the fossil condition;[25]
an Apus, closely related to the modern A. cancriformis, has been found in
Page 56
the Trias, but the most numerous remains have been left, as might be
expected, by the hard-shelled Limnadiidae; carapaces, closely resembling
those of the modern Estheria, are known in beds of all ages from the
Devonian period to recent times; these carapaces are in several cases
associated with fossils of an apparently marine type. None of the fossil
species differ in any important characters from those now living, so that the
Phyllopoda have existed in practically their present form for an enormously
long period; this fact, and the evidence that species of existing genera were
at one time marine, explain the wide distribution of animals at present
restricted to a remarkably limited range of environmental conditions.
Summary of the Characters of the Genera.
Sub-Order Phyllopoda.—Branchiopoda with an elongated body,
provided with at least ten pairs of post-cephalic limbs, the heart
extending through four or more thoracic segments, and having at least
four pairs of ostia.
Fam. 1. Branchipodidae.[26]—Carapace rudimentary, eyes stalked; the
second antennae flat and unjointed in the female, jointed and prehensile
in the male; female generative opening single; telson not laterally
compressed, bearing two flattened lobes, or none. The heart extending
through the thorax and the greater part of the abdomen.
A. Eleven pairs of praegenital ambulatory limbs.
a. Abdomen of six well-formed segments and a telson; anal lobes
well formed, their margins setose.
Branchinecta, Verrill—Second antennae of ♂ without lateral
appendages; ovisac of ♀ elongated. B. paludosa, O. F.
Müll.—Circumpolar.
Branchiopodopsis, G. O. Sars[27]—Second antennae of ♂ as
in Branchinecta; ovisac of ♀ short. B. hodgsoni, G. O.
Sars—Cape of Good Hope.
Branchipus, Schaeffer—Second antennae of ♂ with simple
internal filamentous appendage. B. stagnalis, Linn.—
Central Europe.
expected, by the hard-shelled Limnadiidae; carapaces, closely resembling
those of the modern Estheria, are known in beds of all ages from the
Devonian period to recent times; these carapaces are in several cases
associated with fossils of an apparently marine type. None of the fossil
species differ in any important characters from those now living, so that the
Phyllopoda have existed in practically their present form for an enormously
long period; this fact, and the evidence that species of existing genera were
at one time marine, explain the wide distribution of animals at present
restricted to a remarkably limited range of environmental conditions.
Summary of the Characters of the Genera.
Sub-Order Phyllopoda.—Branchiopoda with an elongated body,
provided with at least ten pairs of post-cephalic limbs, the heart
extending through four or more thoracic segments, and having at least
four pairs of ostia.
Fam. 1. Branchipodidae.[26]—Carapace rudimentary, eyes stalked; the
second antennae flat and unjointed in the female, jointed and prehensile
in the male; female generative opening single; telson not laterally
compressed, bearing two flattened lobes, or none. The heart extending
through the thorax and the greater part of the abdomen.
A. Eleven pairs of praegenital ambulatory limbs.
a. Abdomen of six well-formed segments and a telson; anal lobes
well formed, their margins setose.
Branchinecta, Verrill—Second antennae of ♂ without lateral
appendages; ovisac of ♀ elongated. B. paludosa, O. F.
Müll.—Circumpolar.
Branchiopodopsis, G. O. Sars[27]—Second antennae of ♂ as
in Branchinecta; ovisac of ♀ short. B. hodgsoni, G. O.
Sars—Cape of Good Hope.
Branchipus, Schaeffer—Second antennae of ♂ with simple
internal filamentous appendage. B. stagnalis, Linn.—
Central Europe.
Page 57
Streptocephalus, Baird—Second antennae of ♂ 3–jointed,
the last joint bifid; an external filamentous appendage. S.
torvicornis, Wagn., Poland.
Chirocephalus, Prévost—Second antennae of ♂ 3–jointed,
with a jointed internal appendage, which bears secondary
processes, four cylindrical and one lamellar. C. diaphanus,
Prévost (Fig. 2, p. 20).—Britain, Central Europe.
b. Abdominal segments five or fewer, and a telson. Anal lobes
small or 0, sparsely or not at all setose.
Artemia, Leach—Second antennae of ♂ without filamentous
appendage, 2–jointed, the second joint lamellar. A. salina,
Linn.—Brine pools of the Palaearctic region.
c. Hinder abdominal segments united with telson to form a fin;
anal lobes absent.
Thamnocephalus, Packard—Head with a branched median
process of unknown nature. Only species T. platyurus,
Packard—Kansas, U.S.A.
B. Nineteen pairs of praegenital ambulatory limbs.
Polyartemia, Fischer—Second antennae of ♂ forcipate;
ovisac of ♀ very short. Only species P. forcipata, Fisch.
Fam. 2. Apodidae.[28]—Carapace well developed as a depressed
shield, covering at least half the body. Eyes sessile, covered; no male
clasping organs; anal lobes long, jointed cirri.
Apus, Scopoli—Telson not produced backwards over the
anus; endites of first thoracic limb very long. A.
cancriformis, Schaeffer—Britain, Europe, Algiers, Tunis.
A. australiensis, Central Australia.
Lepidurus, Leach—Telson produced backwards to form a
plate above the anus; endites of first thoracic limb short. L.
productus, Bosc.—Central Europe. L. viridis, Southern
Australia, New Zealand, L. patagonicus, Bergh,
Argentines.
the last joint bifid; an external filamentous appendage. S.
torvicornis, Wagn., Poland.
Chirocephalus, Prévost—Second antennae of ♂ 3–jointed,
with a jointed internal appendage, which bears secondary
processes, four cylindrical and one lamellar. C. diaphanus,
Prévost (Fig. 2, p. 20).—Britain, Central Europe.
b. Abdominal segments five or fewer, and a telson. Anal lobes
small or 0, sparsely or not at all setose.
Artemia, Leach—Second antennae of ♂ without filamentous
appendage, 2–jointed, the second joint lamellar. A. salina,
Linn.—Brine pools of the Palaearctic region.
c. Hinder abdominal segments united with telson to form a fin;
anal lobes absent.
Thamnocephalus, Packard—Head with a branched median
process of unknown nature. Only species T. platyurus,
Packard—Kansas, U.S.A.
B. Nineteen pairs of praegenital ambulatory limbs.
Polyartemia, Fischer—Second antennae of ♂ forcipate;
ovisac of ♀ very short. Only species P. forcipata, Fisch.
Fam. 2. Apodidae.[28]—Carapace well developed as a depressed
shield, covering at least half the body. Eyes sessile, covered; no male
clasping organs; anal lobes long, jointed cirri.
Apus, Scopoli—Telson not produced backwards over the
anus; endites of first thoracic limb very long. A.
cancriformis, Schaeffer—Britain, Europe, Algiers, Tunis.
A. australiensis, Central Australia.
Lepidurus, Leach—Telson produced backwards to form a
plate above the anus; endites of first thoracic limb short. L.
productus, Bosc.—Central Europe. L. viridis, Southern
Australia, New Zealand, L. patagonicus, Bergh,
Argentines.
Page 58
Fam. 3. Limnadiidae.—Body compressed; carapace in the form of a
bivalve shell, the two halves capable of adduction by means of a strong
transverse muscle; second antennae biramous, alike in both sexes; in
the male, the first or the first and second thoracic limbs prehensile;
telson laterally compressed.
A. Only the first thoracic limbs prehensile in the male; the carapace
spheroidal, without lines of growth; head not included within the
carapace-chamber.
Limnetis, Lovén—Compound eyes fused; anal spines
absent; ambulatory limbs 10–12. L. brachyura, O. F. Müll
(Fig. 3, p. 21).—Norway, Central Europe.
B. The first and second thoracic limbs prehensile in the male;
carapace distinctly bivalve, enclosing the head, with concentric
lines of growth round a more or less prominent umbo.
Eulimnadia, Packard—Carapace narrowly ovate, with few
(4–5) lines of growth. E. mauritani, Guérin—Mauritius. E.
texana, Packard—Texas, Kansas.
Limnadia, Brongniart—Carapace broadly ovate, with
numerous lines of growth, without distinct umbones; L.
lenticularis, Linn.—Northern and Central Europe.
Estheria, Rüppell—Carapace with well-marked umbones
and numerous lines of growth, oval; E. tetraceros, Kryneki
—Central Europe.
Leptestheria,[29] G. O. Sars—Carapace compressed, oblong.
Rostrum with a movable spine; thoracic limbs with
accessory lappet on the exopodite. L. siliqua, G. O. Sars—
Cape Town.
Cyclestheria,[30] G. O. Sars. C. hislopi, Baird—Queensland,
India, East Africa, Brazil.
Sub-Order 2. Cladocera.
bivalve shell, the two halves capable of adduction by means of a strong
transverse muscle; second antennae biramous, alike in both sexes; in
the male, the first or the first and second thoracic limbs prehensile;
telson laterally compressed.
A. Only the first thoracic limbs prehensile in the male; the carapace
spheroidal, without lines of growth; head not included within the
carapace-chamber.
Limnetis, Lovén—Compound eyes fused; anal spines
absent; ambulatory limbs 10–12. L. brachyura, O. F. Müll
(Fig. 3, p. 21).—Norway, Central Europe.
B. The first and second thoracic limbs prehensile in the male;
carapace distinctly bivalve, enclosing the head, with concentric
lines of growth round a more or less prominent umbo.
Eulimnadia, Packard—Carapace narrowly ovate, with few
(4–5) lines of growth. E. mauritani, Guérin—Mauritius. E.
texana, Packard—Texas, Kansas.
Limnadia, Brongniart—Carapace broadly ovate, with
numerous lines of growth, without distinct umbones; L.
lenticularis, Linn.—Northern and Central Europe.
Estheria, Rüppell—Carapace with well-marked umbones
and numerous lines of growth, oval; E. tetraceros, Kryneki
—Central Europe.
Leptestheria,[29] G. O. Sars—Carapace compressed, oblong.
Rostrum with a movable spine; thoracic limbs with
accessory lappet on the exopodite. L. siliqua, G. O. Sars—
Cape Town.
Cyclestheria,[30] G. O. Sars. C. hislopi, Baird—Queensland,
India, East Africa, Brazil.
Sub-Order 2. Cladocera.
Page 59
The Cladocera are short-bodied Branchiopods, with not more than six
pairs of thoracic limbs. The second antennae are important organs of
locomotion, and are nearly always biramous; the first antennae are small, at
least in the female; the second maxillae are absent in the adult. The
carapace may extend backwards so as to enclose the whole post-cephalic
portion of the body, or may be reduced to a small dorsal brood-pouch,
leaving the body uncovered.
The Cladocera or “Water-fleas” are never of great size; Leptodora
hyalina, the largest, is only about 15 mm. long, while many Lynceidae are
not more than 0·1 or 0·2 mm. in length.
The head is bent downwards in all the Cladocera, so that parts which are
morphologically anterior, such as the median eye and the first antennae, lie
ventral to or even behind the compound eyes and the second antennae (cf.
Fig. 10).
The compound lateral eyes fuse at an early period of embryonic life, so
that they form a single median mass in the adult, over which a fold of
ectoderm grows, to make a chamber over the eye, like that found in the
Limnadiidae, except that it is completely closed. The fused eyes are
generally large and conspicuous; in some deep-water forms the retinular
elements of the dorsal portion are larger than those of the ventral (e.g.
Bythotrephes, Fig. 13). In one or two species which live at very great
depths, or in caves, the eyes are altogether absent.
The appendages of the head are fairly uniform, the most variable being
the first antennae. In the females of many genera the first antennae are short
and immovable, consisting of a single joint, with a terminal bunch of
sensory hairs, and often a long lateral hair, as in Simocephalus (Figs. 9, 10),
Daphnia, etc. In the female Moina (Fig. 16) they are movable, as they are in
Ceriodaphnia and some others; in Bosmina (Fig. 22) and many
Lyncodaphniidae they are elongated and imperfectly divided into joints by
rings of spines, while in Macrothrix they are flattened plates. In the males
the first antennae are elongated and mobile (cf. Figs. 11, 19).
The second antennae, the chief organs of locomotion, are biramous in all
genera except Holopedium; the number of joints in each ramus, and the
number of the long plumose hairs with which they are provided, are
remarkably constant in whole series of genera, and are therefore useful for
purposes of classification. The creatures row themselves by quick strokes of
pairs of thoracic limbs. The second antennae are important organs of
locomotion, and are nearly always biramous; the first antennae are small, at
least in the female; the second maxillae are absent in the adult. The
carapace may extend backwards so as to enclose the whole post-cephalic
portion of the body, or may be reduced to a small dorsal brood-pouch,
leaving the body uncovered.
The Cladocera or “Water-fleas” are never of great size; Leptodora
hyalina, the largest, is only about 15 mm. long, while many Lynceidae are
not more than 0·1 or 0·2 mm. in length.
The head is bent downwards in all the Cladocera, so that parts which are
morphologically anterior, such as the median eye and the first antennae, lie
ventral to or even behind the compound eyes and the second antennae (cf.
Fig. 10).
The compound lateral eyes fuse at an early period of embryonic life, so
that they form a single median mass in the adult, over which a fold of
ectoderm grows, to make a chamber over the eye, like that found in the
Limnadiidae, except that it is completely closed. The fused eyes are
generally large and conspicuous; in some deep-water forms the retinular
elements of the dorsal portion are larger than those of the ventral (e.g.
Bythotrephes, Fig. 13). In one or two species which live at very great
depths, or in caves, the eyes are altogether absent.
The appendages of the head are fairly uniform, the most variable being
the first antennae. In the females of many genera the first antennae are short
and immovable, consisting of a single joint, with a terminal bunch of
sensory hairs, and often a long lateral hair, as in Simocephalus (Figs. 9, 10),
Daphnia, etc. In the female Moina (Fig. 16) they are movable, as they are in
Ceriodaphnia and some others; in Bosmina (Fig. 22) and many
Lyncodaphniidae they are elongated and imperfectly divided into joints by
rings of spines, while in Macrothrix they are flattened plates. In the males
the first antennae are elongated and mobile (cf. Figs. 11, 19).
The second antennae, the chief organs of locomotion, are biramous in all
genera except Holopedium; the number of joints in each ramus, and the
number of the long plumose hairs with which they are provided, are
remarkably constant in whole series of genera, and are therefore useful for
purposes of classification. The creatures row themselves by quick strokes of
Page 60
these appendages, the movement
being slow and irregular in the
rounder forms, such as Simocephalus
or Daphnia, rapid and well directed
in such elongated lacustrine forms as
Bythotrephes or Leptodora.
The mandibles have no palp; the
first maxillae are very small, and the
second maxillae are absent (Fig. 9).
The carapace varies very much. In
most genera (the Calyptomera of
Sars) it is a large, backwardly-
Fig. 9.—Simocephalus vetulus, female. Ventral
projecting fold of skin, bent
view, without the carapace; A1, A2, first and downwards at the sides so as to form
second antennae; For, head; Md, mandible; Te, a bivalve shell, enclosing the whole
telson; I-IV, first to fourth thoracic appendages. post-cephalic portion of the body, as
in Simocephalus (Fig. 10). The eggs
are laid into the space between the carapace and the dorsal part of the
thorax, both the carapace and the thorax itself being often modified for their
protection and nutrition. In a few forms, the Gymnomera of Sars, the
carapace serves only as a brood-pouch, which is distended when eggs are
laid, but collapses to an inconspicuous appendage at the back of the head
when it is empty (e.g. Leptodora, Fig. 24, Bythotrephes, Fig. 13). In the
Calyptomera the surface of the carapace is frequently provided with a series
of ridges, which may be parallel, rarely branching, as in Simocephalus; or in
two sets which cross nearly at right angles, as in Daphnia; or so arranged as
to form a hexagonal pattern, as in Ceriodaphnia. In a few forms the whole
surface is irregularly covered with spines or scales. The hinder edge of the
carapace is often produced into a median dorsal spine (Daphnia, Fig. 19), or
more rarely there are two spines, one at each ventro-lateral corner
(Scapholeberis, Fig. 20).
being slow and irregular in the
rounder forms, such as Simocephalus
or Daphnia, rapid and well directed
in such elongated lacustrine forms as
Bythotrephes or Leptodora.
The mandibles have no palp; the
first maxillae are very small, and the
second maxillae are absent (Fig. 9).
The carapace varies very much. In
most genera (the Calyptomera of
Sars) it is a large, backwardly-
Fig. 9.—Simocephalus vetulus, female. Ventral
projecting fold of skin, bent
view, without the carapace; A1, A2, first and downwards at the sides so as to form
second antennae; For, head; Md, mandible; Te, a bivalve shell, enclosing the whole
telson; I-IV, first to fourth thoracic appendages. post-cephalic portion of the body, as
in Simocephalus (Fig. 10). The eggs
are laid into the space between the carapace and the dorsal part of the
thorax, both the carapace and the thorax itself being often modified for their
protection and nutrition. In a few forms, the Gymnomera of Sars, the
carapace serves only as a brood-pouch, which is distended when eggs are
laid, but collapses to an inconspicuous appendage at the back of the head
when it is empty (e.g. Leptodora, Fig. 24, Bythotrephes, Fig. 13). In the
Calyptomera the surface of the carapace is frequently provided with a series
of ridges, which may be parallel, rarely branching, as in Simocephalus; or in
two sets which cross nearly at right angles, as in Daphnia; or so arranged as
to form a hexagonal pattern, as in Ceriodaphnia. In a few forms the whole
surface is irregularly covered with spines or scales. The hinder edge of the
carapace is often produced into a median dorsal spine (Daphnia, Fig. 19), or
more rarely there are two spines, one at each ventro-lateral corner
(Scapholeberis, Fig. 20).
Page 61
Fig. 10.—Simocephalus vetulus, × 30. Side view of female, showing the
arrangement of the principal organs. A.2, Second antenna; C.S, cervical suture;
E, fused compound eyes; H, heart; L, forwardly-directed gastric caeca; N, dorsal
organ.
The cuticle of the carapace is often separated from that of the head by a
cervical suture, as in Simocephalus (Fig. 10, C.S.) and near the line of
demarcation many forms exhibit patches of glandular ectoderm which seem
to be homologous with the dorsal adhesive organs of the Limnadiidae. The
commonest condition is that of a median dorsal pit (Fig. 10, N.) by means
of which the animal can fix itself to foreign objects. Certain forms may
remain for long periods of time attached by the dorsal organ to plants, or to
the sides of an aquarium, the only movement being a slow vibration of the
feet, by which a current of water, sufficiently rapid for respiratory purposes,
is established round it.[31] In Sida crystallina (Fig. 11) the dorsal organ is
represented by three structures; in front there is a median raised patch (N.m)
of columnar ectoderm, containing concretions like those described in the
Branchipodidae, and behind this is a pair of cup-shaped organs (N.e), with
raised margins.
The fold of skin which forms the carapace contains the coils of the single
pair of kidneys, and it forms an important organ of respiration, partly from
arrangement of the principal organs. A.2, Second antenna; C.S, cervical suture;
E, fused compound eyes; H, heart; L, forwardly-directed gastric caeca; N, dorsal
organ.
The cuticle of the carapace is often separated from that of the head by a
cervical suture, as in Simocephalus (Fig. 10, C.S.) and near the line of
demarcation many forms exhibit patches of glandular ectoderm which seem
to be homologous with the dorsal adhesive organs of the Limnadiidae. The
commonest condition is that of a median dorsal pit (Fig. 10, N.) by means
of which the animal can fix itself to foreign objects. Certain forms may
remain for long periods of time attached by the dorsal organ to plants, or to
the sides of an aquarium, the only movement being a slow vibration of the
feet, by which a current of water, sufficiently rapid for respiratory purposes,
is established round it.[31] In Sida crystallina (Fig. 11) the dorsal organ is
represented by three structures; in front there is a median raised patch (N.m)
of columnar ectoderm, containing concretions like those described in the
Branchipodidae, and behind this is a pair of cup-shaped organs (N.e), with
raised margins.
The fold of skin which forms the carapace contains the coils of the single
pair of kidneys, and it forms an important organ of respiration, partly from
Page 62
the great size of the blood-vessels it
contains, and partly from the
presence of red, blue, or brown
respiratory pigments in the tissue of
the skin itself.
In most Cladocera the cuticle of
the carapace is cast at every ecdysis,
with that of other parts of the body;
but in Iliocryptus and a few others it
remains after each moult, giving the
carapace an appearance of “lines of
growth,” like that seen in many
Limnadiidae.
The segmentation of the body
behind the head is obscure, but we
can generally recognise (1) a thorax,
of as many segments as there are
pairs of limbs; (2) an abdomen of
three segments; and (3) a telson.
The thoracic limbs of the
Calyptomera are flattened, and
resemble those of the Phyllopoda; as
a type we may examine the third
thoracic limb of Simocephalus (Fig.
Fig. 11.—Sida crystallina, male, × 27. Oxford. 12, C), in which the axis bears a large
A.1, Elongated first antenna; N.e, paired element setose gnathobase (Gn) on its inner
of dorsal organ; N.m, median element of dorsal edge, followed by two small endites;
organ; Te, testes; ♂, opening of vas deferens.
the terminal process, or exopodite
(Ex) is a large flattened plate, with
six long plumose hairs on its edge. The outer margin of the axis bears a
bract (Br) and an epipodite.
In Simocephalus, as in the other Daphniidae, there are five pairs of
thoracic limbs, of which the third and fourth are alike; in the female each
limb of the first pair consists of a jointed axis, with strong biting hairs on
the inner border, and a rudimentary epipodite (Fig. 12, A), the second limb
being more like the third, but with a more prominent gnathobase and a
contains, and partly from the
presence of red, blue, or brown
respiratory pigments in the tissue of
the skin itself.
In most Cladocera the cuticle of
the carapace is cast at every ecdysis,
with that of other parts of the body;
but in Iliocryptus and a few others it
remains after each moult, giving the
carapace an appearance of “lines of
growth,” like that seen in many
Limnadiidae.
The segmentation of the body
behind the head is obscure, but we
can generally recognise (1) a thorax,
of as many segments as there are
pairs of limbs; (2) an abdomen of
three segments; and (3) a telson.
The thoracic limbs of the
Calyptomera are flattened, and
resemble those of the Phyllopoda; as
a type we may examine the third
thoracic limb of Simocephalus (Fig.
Fig. 11.—Sida crystallina, male, × 27. Oxford. 12, C), in which the axis bears a large
A.1, Elongated first antenna; N.e, paired element setose gnathobase (Gn) on its inner
of dorsal organ; N.m, median element of dorsal edge, followed by two small endites;
organ; Te, testes; ♂, opening of vas deferens.
the terminal process, or exopodite
(Ex) is a large flattened plate, with
six long plumose hairs on its edge. The outer margin of the axis bears a
bract (Br) and an epipodite.
In Simocephalus, as in the other Daphniidae, there are five pairs of
thoracic limbs, of which the third and fourth are alike; in the female each
limb of the first pair consists of a jointed axis, with strong biting hairs on
the inner border, and a rudimentary epipodite (Fig. 12, A), the second limb
being more like the third, but with a more prominent gnathobase and a
Page 63
narrower exopodite (B), while the limbs of the fifth pair have the
gnathobase and the exopodite filamentous (D).
In the Sididae there are six pairs of thoracic limbs, which are nearly alike
in the female; in the Bosminidae there are six pairs, the first two modified
for prehension, the last much reduced.
Fig. 12.—Thoracic limbs of female Simocephalus vetulus. A, The first; B, the
second; C, the third; D, the fifth. Br, Bract; Ep, epipodite; Ex, exopodite; Gn,
gnathobase.
gnathobase and the exopodite filamentous (D).
In the Sididae there are six pairs of thoracic limbs, which are nearly alike
in the female; in the Bosminidae there are six pairs, the first two modified
for prehension, the last much reduced.
Fig. 12.—Thoracic limbs of female Simocephalus vetulus. A, The first; B, the
second; C, the third; D, the fifth. Br, Bract; Ep, epipodite; Ex, exopodite; Gn,
gnathobase.
Page 64
In the male, the first thoracic limb is usually provided with a long
sensory process and a prehensible hook (Figs. 11, 19).
In the Gymnomera the limbs are cylindrical, jointed rods, with a
gnathobase on the inner side in the Polyphemidae, but not in Leptodora.
The number varies from four to six pairs.
The abdomen bears no appendages. The telson is compressed in the
Calyptomera, and is produced into two flattened plates, one on each side of
the anal opening. The backwardly directed margins of these plates are
commonly serrated, and the lower corner of each is produced into a curved
spine, which carries secondary teeth. The number and arrangement of these
teeth, though often extremely variable in the same species, are used
extensively as specific characters. Above the anus the telson commonly
bears two long plumose hairs, which are directed backwards.
Fig. 13.—Bythotrephes cederströmii, female, × 20, North Wales, from a
specimen found by A. D. Darbishire. Car, carapace.
In the Gymnomera the telson is not bilaterally compressed, and it may be
produced into a long spine, dorsal to the anus (e.g. Bythotrephes, Fig. 13).
The alimentary canal is extremely simple. The labrum is large, and
forms a chamber above the mouth, into which food is driven by the limbs,
as in the Phyllopoda, food being taken while the animal swims or lies on its
back. The oesophagus runs vertically to join a small stomach, which bends
sharply backwards and passes gradually into an intestine. In the last
segment of the abdomen the intestine joins a short, thin-walled rectum,
provided with radial muscles, by means of which it can be dilated. The
dilatation of the rectum leads to an inhalation of water through the anus,
which may possibly serve as a means of respiration. In the Daphniidae and
sensory process and a prehensible hook (Figs. 11, 19).
In the Gymnomera the limbs are cylindrical, jointed rods, with a
gnathobase on the inner side in the Polyphemidae, but not in Leptodora.
The number varies from four to six pairs.
The abdomen bears no appendages. The telson is compressed in the
Calyptomera, and is produced into two flattened plates, one on each side of
the anal opening. The backwardly directed margins of these plates are
commonly serrated, and the lower corner of each is produced into a curved
spine, which carries secondary teeth. The number and arrangement of these
teeth, though often extremely variable in the same species, are used
extensively as specific characters. Above the anus the telson commonly
bears two long plumose hairs, which are directed backwards.
Fig. 13.—Bythotrephes cederströmii, female, × 20, North Wales, from a
specimen found by A. D. Darbishire. Car, carapace.
In the Gymnomera the telson is not bilaterally compressed, and it may be
produced into a long spine, dorsal to the anus (e.g. Bythotrephes, Fig. 13).
The alimentary canal is extremely simple. The labrum is large, and
forms a chamber above the mouth, into which food is driven by the limbs,
as in the Phyllopoda, food being taken while the animal swims or lies on its
back. The oesophagus runs vertically to join a small stomach, which bends
sharply backwards and passes gradually into an intestine. In the last
segment of the abdomen the intestine joins a short, thin-walled rectum,
provided with radial muscles, by means of which it can be dilated. The
dilatation of the rectum leads to an inhalation of water through the anus,
which may possibly serve as a means of respiration. In the Daphniidae and
Page 65
Bosminidae there are two forwardly-directed digestive glands which open
into the stomach, and in Eurycercus there is a large caecum at the junction
of the rectum with the intestine. The intestine is usually straight, but in
Lynceidae and in some Lyncodaphniidae it is coiled (e.g. Peracantha, Fig.
14).
In Leptodora the alimentary canal is altogether remarkable; the
oesophagus is a long and very narrow tube, which runs back through the
whole length of the thorax and joins the mid-gut in the third abdominal
segment. The mid-gut is not differentiated into stomach and intestine; it has
no diverticula of any kind, and runs straight backwards to join the short
rectum a little in front of the anus.
The heart is always short, and
never has more than a single pair of
lateral openings; it is longest in the
Sididae, which show some
approximation to the Phyllopods in
this, as in the slight degree of
difference between their anterior and
posterior thoracic limbs. The
pericardium lies in the one or two
anterior thoracic segments, dorsal to
the gut. From the heart the blood runs
Fig. 14.—Peracantha truncata, female, × 100.
forwards to the dorsal part of the Oxford.
head, and passes backwards by three
main channels, one entering each
side of the carapace, while the third runs down the body, beneath the
alimentary canal to dilate into a large sinus round the rectum. This ventral
blood-channel gives a branch to each limb, which forms a considerable
dilatation in the epipodite, the blood from the limb returning to the
pericardium by a lateral sinus. From the rectum a large sinus runs forwards
to the pericardium along the dorsal wall of the body. The blood which
enters each half of the carapace is collected in a median vessel and returned
through this to the pericardium.
Those spaces between the viscera which are not filled with blood are
occupied by a peculiar connective tissue, consisting of rounded or
into the stomach, and in Eurycercus there is a large caecum at the junction
of the rectum with the intestine. The intestine is usually straight, but in
Lynceidae and in some Lyncodaphniidae it is coiled (e.g. Peracantha, Fig.
14).
In Leptodora the alimentary canal is altogether remarkable; the
oesophagus is a long and very narrow tube, which runs back through the
whole length of the thorax and joins the mid-gut in the third abdominal
segment. The mid-gut is not differentiated into stomach and intestine; it has
no diverticula of any kind, and runs straight backwards to join the short
rectum a little in front of the anus.
The heart is always short, and
never has more than a single pair of
lateral openings; it is longest in the
Sididae, which show some
approximation to the Phyllopods in
this, as in the slight degree of
difference between their anterior and
posterior thoracic limbs. The
pericardium lies in the one or two
anterior thoracic segments, dorsal to
the gut. From the heart the blood runs
Fig. 14.—Peracantha truncata, female, × 100.
forwards to the dorsal part of the Oxford.
head, and passes backwards by three
main channels, one entering each
side of the carapace, while the third runs down the body, beneath the
alimentary canal to dilate into a large sinus round the rectum. This ventral
blood-channel gives a branch to each limb, which forms a considerable
dilatation in the epipodite, the blood from the limb returning to the
pericardium by a lateral sinus. From the rectum a large sinus runs forwards
to the pericardium along the dorsal wall of the body. The blood which
enters each half of the carapace is collected in a median vessel and returned
through this to the pericardium.
Those spaces between the viscera which are not filled with blood are
occupied by a peculiar connective tissue, consisting of rounded or
Page 66
polyhedral cells, charged with drops of a fatty material which is often
brightly coloured.
The reproductive organs are interesting because of the peculiar
phenomena connected with the nutrition of the two kinds of eggs. The
ovaries or testes are epithelial sacs, one on each side of the body, each
continuous with a duct which opens to the exterior behind the last thoracic
limb. In the female, the opening is dorsal (Fig. 10), in the male it is ventral
(Fig. 11). The external opening is usually simple; but in the male there is
sometimes a penis-like process, on which the vas deferens opens
(Daphnella).
The eggs are of two kinds, the so-called “summer-eggs,” with relatively
little yolk, which develop rapidly without fertilisation, and the so-called
“winter-eggs,” containing much yolk, which require to be fertilised and then
develop slowly.
At one end of the ovary, generally that nearest to the oviduct, there is a
mass of protoplasm, containing nuclei which actively divide; this is the
germarium (Fig. 15, A, B, C). As a result of proliferation in the germarium,
nucleated masses are thrown off into the cavity of the ovary; each such
mass contains four nuclei, and its protoplasm soon becomes divided into
four portions, one round each nucleus, so that four cells are produced. In the
simpler ovaries, such as that of Leptodora (Fig. 15, A), these sets of four
cells are arranged in a linear series within the tube of ovarian epithelium; in
other cases, as in Daphnia, the arrangement is more irregular. In the normal
development of parthenogenetic eggs, one cell out of each set of four
becomes an ovum, the other three feeding it with yolk and then dying.
Weismann[32] has shown that the ovum is always formed from the third cell
of each set, counting from the germarial end, so that in the ovary of
Leptodora drawn in Fig. 15, A, the ova will be formed from the cells
marked E1, E2, E3. At certain times, one or two sets of germinal cells fail to
produce ova; the epithelial wall of the ovary thickens round these cells, so
that they become incompletely separated from the rest in a so-called
“nutrient chamber” (Fig. 15, B, N.C). Germ-cells enclosed in a nutrient
chamber degenerate and are ultimately devoured by the ovarian epithelium.
The significance of these nutrient chambers is unknown.
brightly coloured.
The reproductive organs are interesting because of the peculiar
phenomena connected with the nutrition of the two kinds of eggs. The
ovaries or testes are epithelial sacs, one on each side of the body, each
continuous with a duct which opens to the exterior behind the last thoracic
limb. In the female, the opening is dorsal (Fig. 10), in the male it is ventral
(Fig. 11). The external opening is usually simple; but in the male there is
sometimes a penis-like process, on which the vas deferens opens
(Daphnella).
The eggs are of two kinds, the so-called “summer-eggs,” with relatively
little yolk, which develop rapidly without fertilisation, and the so-called
“winter-eggs,” containing much yolk, which require to be fertilised and then
develop slowly.
At one end of the ovary, generally that nearest to the oviduct, there is a
mass of protoplasm, containing nuclei which actively divide; this is the
germarium (Fig. 15, A, B, C). As a result of proliferation in the germarium,
nucleated masses are thrown off into the cavity of the ovary; each such
mass contains four nuclei, and its protoplasm soon becomes divided into
four portions, one round each nucleus, so that four cells are produced. In the
simpler ovaries, such as that of Leptodora (Fig. 15, A), these sets of four
cells are arranged in a linear series within the tube of ovarian epithelium; in
other cases, as in Daphnia, the arrangement is more irregular. In the normal
development of parthenogenetic eggs, one cell out of each set of four
becomes an ovum, the other three feeding it with yolk and then dying.
Weismann[32] has shown that the ovum is always formed from the third cell
of each set, counting from the germarial end, so that in the ovary of
Leptodora drawn in Fig. 15, A, the ova will be formed from the cells
marked E1, E2, E3. At certain times, one or two sets of germinal cells fail to
produce ova; the epithelial wall of the ovary thickens round these cells, so
that they become incompletely separated from the rest in a so-called
“nutrient chamber” (Fig. 15, B, N.C). Germ-cells enclosed in a nutrient
chamber degenerate and are ultimately devoured by the ovarian epithelium.
The significance of these nutrient chambers is unknown.
Page 67
Fig. 15.—A, Ovary of a parthenogenetic Leptodora hyalina; B, base of another
ovary of the same species, showing a so-called “nutrient chamber”; C, ovary of a
female Daphnia, showing the formation of a winter-egg. E, E1–E3,
Parthenogenetic egg; Ep, ovarian epithelium; G, germarium; N.C, nutrient
chamber; O.D, oviduct; W, winter-egg; 1, 2, 4, the other three cells of the same
group; II, III, two other groups of germ-cells.
The production of a winter-egg is a more complicated process. The
epithelium of the ovarian tube swells up, so that the lumen is nearly
obliterated, and several sets of four germ-cells pass from the germarium to
lie among the swollen epithelial cells. All these groups of germ-cells, except
ovary of the same species, showing a so-called “nutrient chamber”; C, ovary of a
female Daphnia, showing the formation of a winter-egg. E, E1–E3,
Parthenogenetic egg; Ep, ovarian epithelium; G, germarium; N.C, nutrient
chamber; O.D, oviduct; W, winter-egg; 1, 2, 4, the other three cells of the same
group; II, III, two other groups of germ-cells.
The production of a winter-egg is a more complicated process. The
epithelium of the ovarian tube swells up, so that the lumen is nearly
obliterated, and several sets of four germ-cells pass from the germarium to
lie among the swollen epithelial cells. All these groups of germ-cells, except
Page 68
one, disintegrate and are devoured by the ovarian epithelium, one cell of the
remaining group enlarging to form a winter-egg, fed during its growth not
only by the three cells of its own set but also by the epithelial cells of the
ovarian tube, which have devoured the germ-cells of other sets. An ovary
never contains more than a single winter-egg at the same time, the number
of germ-cells which are devoured during its formation varying in the
different species; the Daphnia drawn in Fig. 15, C, has produced three
groups of germ-cells, of which two (II, III), will die, while the cell W from
the remaining group will develop into an ovum; in Moina, Weismann finds
that as many as a dozen cell-groups may be thrown into the ovary before
the production of a winter-egg, so that only one out of forty-eight germ-
cells survives as an ovum.
Fig. 16.—Sketch of a parthenogenetic Moina rectirostris, × 45, the brood-pouch
being emptied and the side of the carapace removed, showing the dome of
thickened epithelium on the thorax, by which nutrient material is thrown into the
brood-pouch, and the ridge which fits against the carapace in the natural
condition so as to close the brood-pouch.
The summer-eggs are always carried until they are hatched by the
parthenogenetic female which produces them. The brood-pouch is the space
between the dorsal wall of the thorax and the carapace. This space is always
remaining group enlarging to form a winter-egg, fed during its growth not
only by the three cells of its own set but also by the epithelial cells of the
ovarian tube, which have devoured the germ-cells of other sets. An ovary
never contains more than a single winter-egg at the same time, the number
of germ-cells which are devoured during its formation varying in the
different species; the Daphnia drawn in Fig. 15, C, has produced three
groups of germ-cells, of which two (II, III), will die, while the cell W from
the remaining group will develop into an ovum; in Moina, Weismann finds
that as many as a dozen cell-groups may be thrown into the ovary before
the production of a winter-egg, so that only one out of forty-eight germ-
cells survives as an ovum.
Fig. 16.—Sketch of a parthenogenetic Moina rectirostris, × 45, the brood-pouch
being emptied and the side of the carapace removed, showing the dome of
thickened epithelium on the thorax, by which nutrient material is thrown into the
brood-pouch, and the ridge which fits against the carapace in the natural
condition so as to close the brood-pouch.
The summer-eggs are always carried until they are hatched by the
parthenogenetic female which produces them. The brood-pouch is the space
between the dorsal wall of the thorax and the carapace. This space is always
Page 69
more or less perfectly closed at the
sides by the pressure of the carapace
against the body, and behind by
vascular processes from the
abdominal segments (Figs. 10, 16,
etc.). The presence of a large blood-
sinus beneath the dorsal wall of the
thorax and in the middle line of the
carapace suggests the possibility that
some special nutrient substances may
pass from the body of the parent into Fig. 17.—Moina rectirostris, ♀ , × 40, showing
the brood-chamber, and in some the ephippial thickening of the carapace which
species the thoracic ectoderm is precedes the laying of a winter-egg.
specially modified as a placenta. In
Moina (Fig. 16) the dorsal wall of the thorax is produced into a dome,
covered by a columnar ectoderm, which contains a dilatation of the dorsal
blood-sinus; and in this form it has been shown that the fluid in the brood-
pouch contains dissolved proteids. Associated with the apparatus for
supplying the brood-pouch with nutriment is a special apparatus for closing
it, in the form of a raised ridge, which projects from the back and sides of
the thorax and fits into a groove of the carapace.
A somewhat similar nutrient apparatus exists in the Polyphemidae, where
the edges of the small carapace are fused with the thorax, so that the brood-
pouch is completely closed, and the young can only escape when the parent
casts her cuticle. In some genera of this family (e.g. Evadne) the young
remain in the parental brood-pouch until they are themselves mature, so that
when they are set free they may already bear parthenogenetic embryos in
their own brood-pouches.
The winter-eggs are fertilised in
the same part of the carapace of the
female in which the parthenogenetic
eggs develop, but after fertilisation
they are thrown off from the body of
Fig. 18.—Newly-cast ephippium of Daphnia,
containing two winter-eggs. the mother, either with or without a
protective envelope formed from the
cuticle of the carapace. The eggs of
Sida are surrounded by a thin layer of a sticky substance, and when cast out
sides by the pressure of the carapace
against the body, and behind by
vascular processes from the
abdominal segments (Figs. 10, 16,
etc.). The presence of a large blood-
sinus beneath the dorsal wall of the
thorax and in the middle line of the
carapace suggests the possibility that
some special nutrient substances may
pass from the body of the parent into Fig. 17.—Moina rectirostris, ♀ , × 40, showing
the brood-chamber, and in some the ephippial thickening of the carapace which
species the thoracic ectoderm is precedes the laying of a winter-egg.
specially modified as a placenta. In
Moina (Fig. 16) the dorsal wall of the thorax is produced into a dome,
covered by a columnar ectoderm, which contains a dilatation of the dorsal
blood-sinus; and in this form it has been shown that the fluid in the brood-
pouch contains dissolved proteids. Associated with the apparatus for
supplying the brood-pouch with nutriment is a special apparatus for closing
it, in the form of a raised ridge, which projects from the back and sides of
the thorax and fits into a groove of the carapace.
A somewhat similar nutrient apparatus exists in the Polyphemidae, where
the edges of the small carapace are fused with the thorax, so that the brood-
pouch is completely closed, and the young can only escape when the parent
casts her cuticle. In some genera of this family (e.g. Evadne) the young
remain in the parental brood-pouch until they are themselves mature, so that
when they are set free they may already bear parthenogenetic embryos in
their own brood-pouches.
The winter-eggs are fertilised in
the same part of the carapace of the
female in which the parthenogenetic
eggs develop, but after fertilisation
they are thrown off from the body of
Fig. 18.—Newly-cast ephippium of Daphnia,
containing two winter-eggs. the mother, either with or without a
protective envelope formed from the
cuticle of the carapace. The eggs of
Sida are surrounded by a thin layer of a sticky substance, and when cast out
Page 70
of the maternal carapace they adhere to foreign objects, such as water-
weeds; those of Polyphemus have a thick, gelatinous coat; in Leptodora and
Bythotrephes the egg secretes a two-layered chitinous shell. In these forms
the cuticle of the parent is not used as a protection for the winter-eggs,
although it is generally, if not invariably, thrown off when the eggs are laid.
In the Lynceidae the cuticle is moulted in such a way that the winter-eggs
remain within it, at least for a time; the cuticle is occasionally modified
before it is thrown off; thus in Camptocercus macrurus the cuticle of the
carapace, in the region of the brood-pouch, becomes thickened and darkly
coloured, forming a fairly strong case round the eggs. The modification of
the cuticle round the brood-pouch is much more pronounced in the
Daphniidae, where it leads to the formation of a saddle-shaped cuticular
box, the “ephippium,” in which the winter-eggs are enclosed. The ripening
of a winter-egg in the ovary of a Daphnia is accompanied by a great
thickening of the cuticle of the carapace (cf. Fig. 18), so that a strong case is
formed in the position of the brood-pouch. The winter-eggs are laid
between the two valves of this case, and shortly afterwards the parent
moults. The eggs are retained within the ephippium, from which the rest of
the cuticle breaks away (Fig. 18). After separation, the ephippium, which
contains a single egg (Moina rectirostris) or usually two (Daphnia, etc.),
either sinks to the bottom, as in Moina, or floats.
The winter-eggs usually go through the early stages of segmentation
within a short time after they are laid, but after this a longer or shorter
period of quiescence occurs, during which the eggs may be dried or frozen
without injury. The sides and floor of a dried-up pond are often crowded
with ephippia, containing winter-eggs which develop quickly when
replaced in water; and the resting-stage of winter-eggs produced in aquaria
can often be materially shortened by drying the ephippia which contain
them, though such desiccation does not appear to be necessary for
development. Under normal conditions large numbers of winter-eggs
remain quiescent through the winter and hatch in the following spring.
The individual developed from a sexually fertilised winter-egg is
invariably a parthenogenetic female: the characters of the succeeding
generations differ in different cases.
In a few forms, of which Moina is the best known, the parthenogenetic
female, produced from a winter-egg, may give rise to males, to sexual
weeds; those of Polyphemus have a thick, gelatinous coat; in Leptodora and
Bythotrephes the egg secretes a two-layered chitinous shell. In these forms
the cuticle of the parent is not used as a protection for the winter-eggs,
although it is generally, if not invariably, thrown off when the eggs are laid.
In the Lynceidae the cuticle is moulted in such a way that the winter-eggs
remain within it, at least for a time; the cuticle is occasionally modified
before it is thrown off; thus in Camptocercus macrurus the cuticle of the
carapace, in the region of the brood-pouch, becomes thickened and darkly
coloured, forming a fairly strong case round the eggs. The modification of
the cuticle round the brood-pouch is much more pronounced in the
Daphniidae, where it leads to the formation of a saddle-shaped cuticular
box, the “ephippium,” in which the winter-eggs are enclosed. The ripening
of a winter-egg in the ovary of a Daphnia is accompanied by a great
thickening of the cuticle of the carapace (cf. Fig. 18), so that a strong case is
formed in the position of the brood-pouch. The winter-eggs are laid
between the two valves of this case, and shortly afterwards the parent
moults. The eggs are retained within the ephippium, from which the rest of
the cuticle breaks away (Fig. 18). After separation, the ephippium, which
contains a single egg (Moina rectirostris) or usually two (Daphnia, etc.),
either sinks to the bottom, as in Moina, or floats.
The winter-eggs usually go through the early stages of segmentation
within a short time after they are laid, but after this a longer or shorter
period of quiescence occurs, during which the eggs may be dried or frozen
without injury. The sides and floor of a dried-up pond are often crowded
with ephippia, containing winter-eggs which develop quickly when
replaced in water; and the resting-stage of winter-eggs produced in aquaria
can often be materially shortened by drying the ephippia which contain
them, though such desiccation does not appear to be necessary for
development. Under normal conditions large numbers of winter-eggs
remain quiescent through the winter and hatch in the following spring.
The individual developed from a sexually fertilised winter-egg is
invariably a parthenogenetic female: the characters of the succeeding
generations differ in different cases.
In a few forms, of which Moina is the best known, the parthenogenetic
female, produced from a winter-egg, may give rise to males, to sexual
Page 71
females, and to parthenogenetic females, so that the cycle of forms which
intervene between one winter-egg and the next is short. A sexual female
produces one or two winter-eggs, and if these are fertilised they are
enclosed in an ephippium and cast off; if, however, the eggs when ripe are
not fertilised, they atrophy, and the female produces parthenogenetic eggs,
being thenceforward incapable of forming sexual “winter” eggs. An
accidental absence of males may thus lead to the occurrence of
parthenogenesis in the whole of the second generation. The regular
production of sexual individuals in the second generation from the winter-
egg appears to depend on a variety of circumstances not yet understood. Mr.
G. H. Grosvenor tells me that Moina from the neighbourhood of Oxford
may give rise to several successive generations of parthenogenetic
individuals, when grown in small aquaria.
In the greater number of Daphniidae, the parthenogenetic female,
produced from a winter-egg, gives rise only to parthenogenetic forms, and it
is not until after half a dozen parthenogenetic generations have been
produced that a few sexual forms appear, mixed with the others. Such
sexual forms are fairly common in April or May in this country; they
produce “winter” eggs and then die, the generations which succeed them
through the summer being entirely parthenogenetic. In late autumn sexual
individuals are again produced, giving rise to a plentiful crop of winter-
eggs, but many parthenogenetic females are still found, and some of these
appear to live and to reproduce through the winter.
In Sida, in the Polyphemidae and Leptodoridae, and in most of the
Lynceidae, sexual individuals are produced only once in every year, while
in a few forms which inhabit great lakes the sexual condition occurs so
rarely that it is still unknown.
Weismann[33] has pointed out that the sexual forms, with their property of
producing eggs which can endure desiccation, recur most frequently in
species such as Moina, which inhabit small pools liable to be dried up at
frequent intervals, while the species which produce sexual forms only once
a year are all inhabitants either of great lakes which are never dry, or of the
sea. Many suggestions have been made as to the environmental stimulus
which induces the production of sexual individuals, but nothing is definitely
known upon the subject.
intervene between one winter-egg and the next is short. A sexual female
produces one or two winter-eggs, and if these are fertilised they are
enclosed in an ephippium and cast off; if, however, the eggs when ripe are
not fertilised, they atrophy, and the female produces parthenogenetic eggs,
being thenceforward incapable of forming sexual “winter” eggs. An
accidental absence of males may thus lead to the occurrence of
parthenogenesis in the whole of the second generation. The regular
production of sexual individuals in the second generation from the winter-
egg appears to depend on a variety of circumstances not yet understood. Mr.
G. H. Grosvenor tells me that Moina from the neighbourhood of Oxford
may give rise to several successive generations of parthenogenetic
individuals, when grown in small aquaria.
In the greater number of Daphniidae, the parthenogenetic female,
produced from a winter-egg, gives rise only to parthenogenetic forms, and it
is not until after half a dozen parthenogenetic generations have been
produced that a few sexual forms appear, mixed with the others. Such
sexual forms are fairly common in April or May in this country; they
produce “winter” eggs and then die, the generations which succeed them
through the summer being entirely parthenogenetic. In late autumn sexual
individuals are again produced, giving rise to a plentiful crop of winter-
eggs, but many parthenogenetic females are still found, and some of these
appear to live and to reproduce through the winter.
In Sida, in the Polyphemidae and Leptodoridae, and in most of the
Lynceidae, sexual individuals are produced only once in every year, while
in a few forms which inhabit great lakes the sexual condition occurs so
rarely that it is still unknown.
Weismann[33] has pointed out that the sexual forms, with their property of
producing eggs which can endure desiccation, recur most frequently in
species such as Moina, which inhabit small pools liable to be dried up at
frequent intervals, while the species which produce sexual forms only once
a year are all inhabitants either of great lakes which are never dry, or of the
sea. Many suggestions have been made as to the environmental stimulus
which induces the production of sexual individuals, but nothing is definitely
known upon the subject.
Page 72
We have said that even in those generations which contain sexual males
and females there are always some parthenogenetic individuals; there is
therefore nothing in the behaviour of Daphniidae, either under natural
conditions or when observed in aquaria, to suggest that there is any natural
or necessary limit to the number of generations which may be
parthenogenetically produced.
The parthenogenetic Daphniidae are extremely sensitive to changes in
their surroundings; small variations in the character and amount of
substances dissolved in the water are often followed by changes in the
length of the posterior spine, in the shape and size of crests on the head, and
in other characters affecting the appearance of the creatures, so that the
determination of species is often a matter of great difficulty. It is remarkable
that the green light which has passed through the leaves of water-plants
appears to have a prejudicial effect upon some species. Warren has shown
that Daphnia magna reproduces more slowly when exposed to green light,
and that individuals grown in this way are more readily susceptible to injury
from the presence of small quantities of salt (sodium chloride) in the water
than individuals which have been exposed to white light.
The majority of the Cladocera belong to the floating fauna of the fresh
waters and seas; a few are littoral in their habits, clinging to water-weeds
near the shore, a very few live near the bottom at considerable depths, but
the majority belong to that floating fauna to which Haeckel gave the name
of “plankton.” The Crustacea are an important element in the plankton,
whether in fresh waters or in the sea, the two great groups which contribute
most largely to it being the Cladocera and the Copepoda. For this reason it
will be more convenient to discuss the habits and distribution of individual
Cladocera and Copepoda together in a chapter specially devoted to the
characters of pelagic faunas (cf. Chap. VII.). We will only add to the present
chapter a table of the families with a diagnosis of the British genera.
Summary of Characters of the British Genera.[34]
Tribe I. Calyptomera, Sars.—The post-cephalic portion of the body
enveloped in a free fold or carapace.
A. Six pairs of thoracic feet, the first pair not prehensile (Ctenopoda).
and females there are always some parthenogenetic individuals; there is
therefore nothing in the behaviour of Daphniidae, either under natural
conditions or when observed in aquaria, to suggest that there is any natural
or necessary limit to the number of generations which may be
parthenogenetically produced.
The parthenogenetic Daphniidae are extremely sensitive to changes in
their surroundings; small variations in the character and amount of
substances dissolved in the water are often followed by changes in the
length of the posterior spine, in the shape and size of crests on the head, and
in other characters affecting the appearance of the creatures, so that the
determination of species is often a matter of great difficulty. It is remarkable
that the green light which has passed through the leaves of water-plants
appears to have a prejudicial effect upon some species. Warren has shown
that Daphnia magna reproduces more slowly when exposed to green light,
and that individuals grown in this way are more readily susceptible to injury
from the presence of small quantities of salt (sodium chloride) in the water
than individuals which have been exposed to white light.
The majority of the Cladocera belong to the floating fauna of the fresh
waters and seas; a few are littoral in their habits, clinging to water-weeds
near the shore, a very few live near the bottom at considerable depths, but
the majority belong to that floating fauna to which Haeckel gave the name
of “plankton.” The Crustacea are an important element in the plankton,
whether in fresh waters or in the sea, the two great groups which contribute
most largely to it being the Cladocera and the Copepoda. For this reason it
will be more convenient to discuss the habits and distribution of individual
Cladocera and Copepoda together in a chapter specially devoted to the
characters of pelagic faunas (cf. Chap. VII.). We will only add to the present
chapter a table of the families with a diagnosis of the British genera.
Summary of Characters of the British Genera.[34]
Tribe I. Calyptomera, Sars.—The post-cephalic portion of the body
enveloped in a free fold or carapace.
A. Six pairs of thoracic feet, the first pair not prehensile (Ctenopoda).
Page 73
Fam. 1. Sididae: second antennae biramous in both sexes. Sida, Straus
(Fig. 11): second antenna with three joints in the dorsal ramus, two in
the ventral; the rostrum large, the teeth on the telson many. Latona,
Straus: second antenna with two joints in the dorsal ramus, three in the
ventral, the proximal joint of the dorsal ramus provided with a setose
appendage. Daphnella, Baird: second antenna with the joints as in
Latona, but with no setose appendage.
Fam. 2. Holopediidae: second antennae not biramous in the female; a
rudimentary second ramus in the male. Holopedium, Zaddach.
B. Four to five or six pairs of thoracic feet, the anterior pair prehensile
(Anomopoda).
A. Ventral ramus of second antenna with three joints, the dorsal ramus
with four.
Fam. 3. Daphniidae: five pairs of thoracic feet, with a gap between the
fourth and fifth pairs. The stomach with two forwardly-directed
diverticula.
(Fig. 11): second antenna with three joints in the dorsal ramus, two in
the ventral; the rostrum large, the teeth on the telson many. Latona,
Straus: second antenna with two joints in the dorsal ramus, three in the
ventral, the proximal joint of the dorsal ramus provided with a setose
appendage. Daphnella, Baird: second antenna with the joints as in
Latona, but with no setose appendage.
Fam. 2. Holopediidae: second antennae not biramous in the female; a
rudimentary second ramus in the male. Holopedium, Zaddach.
B. Four to five or six pairs of thoracic feet, the anterior pair prehensile
(Anomopoda).
A. Ventral ramus of second antenna with three joints, the dorsal ramus
with four.
Fam. 3. Daphniidae: five pairs of thoracic feet, with a gap between the
fourth and fifth pairs. The stomach with two forwardly-directed
diverticula.
Page 74
Fig. 19.—Daphnia obtusa, male, × about 50. Oxford. A.1, First antenna; Th.1,
first thoracic appendage.
i. First antennae of female short.
α A median dorsal spine on posterior margin of carapace. Daphnia,
O. F. Müller (Fig. 19): first antennae of female not mobile. The
head separated from the thorax only by a slight constriction or not
first thoracic appendage.
i. First antennae of female short.
α A median dorsal spine on posterior margin of carapace. Daphnia,
O. F. Müller (Fig. 19): first antennae of female not mobile. The
head separated from the thorax only by a slight constriction or not
Page 75
at all. Cuticle with a quadrate rhomboid pattern. Ceriodaphnia,
Dana: first antennae of female mobile. The head separated by a
deep depression from the thorax. Cuticle with a polygonal pattern.
β A pair of ventral spines on posterior margin of carapace.
Scapholeberis, Schoedler (Fig. 20).
Fig. 20.—Scapholeberis mucronata, female, × 25.
Oxford.
γ No spine on posterior margin of carapace. Simocephalus, Schoedler
(Fig. 10, p. 39): the cuticle with a pattern of parallel branching
ridges.
Fig. 21.—Moina rectirostris, female, × 24. Oxford.
ii. First antennae of female long, mobile. Moina, Baird (Figs. 16, 17,
21): median eye absent. Posterior margin of carapace without a spine.
Dana: first antennae of female mobile. The head separated by a
deep depression from the thorax. Cuticle with a polygonal pattern.
β A pair of ventral spines on posterior margin of carapace.
Scapholeberis, Schoedler (Fig. 20).
Fig. 20.—Scapholeberis mucronata, female, × 25.
Oxford.
γ No spine on posterior margin of carapace. Simocephalus, Schoedler
(Fig. 10, p. 39): the cuticle with a pattern of parallel branching
ridges.
Fig. 21.—Moina rectirostris, female, × 24. Oxford.
ii. First antennae of female long, mobile. Moina, Baird (Figs. 16, 17,
21): median eye absent. Posterior margin of carapace without a spine.
Page 76
Fam. 4. Bosminidae: feet equidistant,
five or six pairs; the first antennae of
the female immobile, with sense-
hairs arranged in rings, not forming
an apical tuft. The intestine uncoiled;
no caeca. Bosmina, Baird (Fig. 22).
Fam. 5. Lyncodaphniidae: four, five,
or six pairs of equidistant thoracic
limbs; the first two pairs prehensile.
First antennae of female mobile, with
Fig. 22.—Bosmina sp., female, × about 80. Lake apical sense-hairs. Intestine coiled or
Constance. straight.
i. Four pairs of thoracic limbs.
Lathonura, Lilljeborg.
ii. Five pairs of thoracic limbs.
a. The four-jointed ramus of
the second antenna with
four swimming hairs.
Macrothrix, Baird: the first
antennae of the female
flattened, curved. The
intestine simple, straight.
Streblocerus, Sars: first
antennae of the female
very little flattened, curved
backwards and outwards.
The intestine coiled, the
stomach with two
forwardly-directed caeca. Fig. 23.—Acroperus leucocephalus, × about 35.
Oxford.
b. The four-jointed ramus of
the second antenna with only three swimming hairs.
Drepanothrix, Sars.
iii. Six pairs of thoracic limbs; the labrum provided with an
appendage. Acantholeberis, Lilljeborg: appendage of labrum long,
five or six pairs; the first antennae of
the female immobile, with sense-
hairs arranged in rings, not forming
an apical tuft. The intestine uncoiled;
no caeca. Bosmina, Baird (Fig. 22).
Fam. 5. Lyncodaphniidae: four, five,
or six pairs of equidistant thoracic
limbs; the first two pairs prehensile.
First antennae of female mobile, with
Fig. 22.—Bosmina sp., female, × about 80. Lake apical sense-hairs. Intestine coiled or
Constance. straight.
i. Four pairs of thoracic limbs.
Lathonura, Lilljeborg.
ii. Five pairs of thoracic limbs.
a. The four-jointed ramus of
the second antenna with
four swimming hairs.
Macrothrix, Baird: the first
antennae of the female
flattened, curved. The
intestine simple, straight.
Streblocerus, Sars: first
antennae of the female
very little flattened, curved
backwards and outwards.
The intestine coiled, the
stomach with two
forwardly-directed caeca. Fig. 23.—Acroperus leucocephalus, × about 35.
Oxford.
b. The four-jointed ramus of
the second antenna with only three swimming hairs.
Drepanothrix, Sars.
iii. Six pairs of thoracic limbs; the labrum provided with an
appendage. Acantholeberis, Lilljeborg: appendage of labrum long,
Page 77
pointed, and setose. Intestine without caecum. Ilyocryptus, Sars:
appendage of the labrum short, truncated. Intestine with a caecum.
B. Both rami of second antenna three-jointed.
Fam. 6. Lynceidae[35]: five or six equidistant pairs of thoracic
feet. Intestine coiled.
i. Six pairs of thoracic limbs. Head and thorax separated by a
deep depression. Intestine with one caecum, stomach with two.
Female carries many summer-eggs. Eurycercus, Baird.
ii. Five pairs of thoracic limbs. Head and thorax separated by a
slight groove or not at all. Anterior digestive caeca absent.
Female carries only one or two summer-eggs.
A. Body elongate, oval.
a. Head carinate, the eye far from the anterior cephalic
margin. Camptocercus, Baird: body laterally compressed.
Second antennae with seven swimming hairs. Telson more than
half as long as the shell. Acroperus, Baird (Fig. 23): body
compressed. Second antennae with eight swimming hairs, of
which one is very small. Telson less than half as long as the
shell.
b. Head not carinate, the eye near the anterior cephalic
margin. Alonopsis, Sars: terminal claws of telson with three
accessory teeth. Alona, Baird: terminal claws of telson with
one accessory tooth (includes sub-genera Leydigia, Alona,
Harporhynchus, Graptoleberis). Peracantha, Baird (Fig. 14):
terminal claws of telson with two accessory teeth (includes
sub-genera Alonella, Pleuroxus, Peracantha).
B. Body small, spheroidal; the head depressed. Chydorus,
Leach: compound eye present. Monopsilus, Sars: compound
eye absent.
Tribe II. Gymnomera, Sars.—The carapace forms a closed brood-pouch,
which does not cover the body; all the thoracic limbs prehensile.
Fam. 7. Polyphemidae: four pairs of thoracic limbs, provided with a
gnathobase.
appendage of the labrum short, truncated. Intestine with a caecum.
B. Both rami of second antenna three-jointed.
Fam. 6. Lynceidae[35]: five or six equidistant pairs of thoracic
feet. Intestine coiled.
i. Six pairs of thoracic limbs. Head and thorax separated by a
deep depression. Intestine with one caecum, stomach with two.
Female carries many summer-eggs. Eurycercus, Baird.
ii. Five pairs of thoracic limbs. Head and thorax separated by a
slight groove or not at all. Anterior digestive caeca absent.
Female carries only one or two summer-eggs.
A. Body elongate, oval.
a. Head carinate, the eye far from the anterior cephalic
margin. Camptocercus, Baird: body laterally compressed.
Second antennae with seven swimming hairs. Telson more than
half as long as the shell. Acroperus, Baird (Fig. 23): body
compressed. Second antennae with eight swimming hairs, of
which one is very small. Telson less than half as long as the
shell.
b. Head not carinate, the eye near the anterior cephalic
margin. Alonopsis, Sars: terminal claws of telson with three
accessory teeth. Alona, Baird: terminal claws of telson with
one accessory tooth (includes sub-genera Leydigia, Alona,
Harporhynchus, Graptoleberis). Peracantha, Baird (Fig. 14):
terminal claws of telson with two accessory teeth (includes
sub-genera Alonella, Pleuroxus, Peracantha).
B. Body small, spheroidal; the head depressed. Chydorus,
Leach: compound eye present. Monopsilus, Sars: compound
eye absent.
Tribe II. Gymnomera, Sars.—The carapace forms a closed brood-pouch,
which does not cover the body; all the thoracic limbs prehensile.
Fam. 7. Polyphemidae: four pairs of thoracic limbs, provided with a
gnathobase.
Page 78
Fresh-water genera.—Polyphemus, Müller, with no rudimentary exites
on first three thoracic limbs. Bythotrephes, Leydig (Fig. 13), with no
trace of processes on the outer sides of the limbs.
Marine genera.—Evadne, Lovén, the head not separated by a
constriction from the thorax. Podon, Lovén, with deep cervical
constriction.
on first three thoracic limbs. Bythotrephes, Leydig (Fig. 13), with no
trace of processes on the outer sides of the limbs.
Marine genera.—Evadne, Lovén, the head not separated by a
constriction from the thorax. Podon, Lovén, with deep cervical
constriction.
Page 79
Fig. 24.—Leptodora hyalina, × 6. Lake Bassenthwaite. A.1, First antenna; Car,
carapace; I, VI, first and sixth thoracic appendages.
Fam. 8. Leptodoridae: six pairs of thoracic limbs, with no gnathobase.
Only genus, Leptodora, Lilljeborg (Fig. 24), from fresh water.
Note.—For extra-European Cladocera consult Daday, “Microskopische Süsswassertiere aus
Patagonien und Chili,” Termés Füzetek, xxv., 1902, p. 201; for Paraguay, Bibliotheca Zoologica, Heft
44; for Ceylon, Termés Füzetek, xxi., 1898; and for Australia, Sars, Christiania Vidensk. Forhand.
1885, No. 8, and 1888, No. 7; and Arch. f. Math. og Naturvid. xviii., 1896, No. 3, and xix., 1897, No.
1.—G. W. S.
carapace; I, VI, first and sixth thoracic appendages.
Fam. 8. Leptodoridae: six pairs of thoracic limbs, with no gnathobase.
Only genus, Leptodora, Lilljeborg (Fig. 24), from fresh water.
Note.—For extra-European Cladocera consult Daday, “Microskopische Süsswassertiere aus
Patagonien und Chili,” Termés Füzetek, xxv., 1902, p. 201; for Paraguay, Bibliotheca Zoologica, Heft
44; for Ceylon, Termés Füzetek, xxi., 1898; and for Australia, Sars, Christiania Vidensk. Forhand.
1885, No. 8, and 1888, No. 7; and Arch. f. Math. og Naturvid. xviii., 1896, No. 3, and xix., 1897, No.
1.—G. W. S.
Page 80
CHAPTER III
CRUSTACEA (CONTINUED): COPEPODA
Order II. Copepoda.
The Copepods are small Crustacea, composed typically of about sixteen
segments, in which the biramous type of limb predominates. They are
devoid of a carapace. Development proceeds gradually by the addition
posteriorly of segments to a Nauplius larval form. Paired compound eyes
are absent, except in Branchiura, the adult retaining the simple eye of the
Nauplius.
In a typical Copepod, such as Calanus hyperboreus (Fig. 25), we can
distinguish the following segments with their appendages: a cephalothorax,
carrying a pair of uniramous first antennae (1st Ant.); a pair of biramous
second antennae (2nd Ant.); mandibles (Md.) with biting gnathobases and a
palp, and a pair of foliaceous first maxillae (Mx.1). Two pairs of appendages
follow, which were looked upon as the two branches of the second
maxillae, but it is now certain that they represent two pairs of appendages,
which may be called second maxillae (Mx.2) and maxillipedes (Mxp.)
respectively. Behind these are five pairs of biramous swimming feet, the
first pair (Th.1) attached to the cephalothorax, the succeeding four pairs to
four distinct thoracic somites. Behind the thorax is a clearly delimited
abdomen composed of five segments, the first of which (Abd.1) carries the
genital opening, and the last a caudal furca.
The Copepods exhibit a great variety of structure, and their classification
is attended with great difficulties. Claus[36] based his attempt at a natural
classification on the character of the mouth and its appendages, dividing the
free-living and semi-parasitic forms as Gnathostomata from the true
parasites or Siphonostomata. This division, although convenient, breaks
down in many places, and it is clear that the parasitic mode of life has been
CRUSTACEA (CONTINUED): COPEPODA
Order II. Copepoda.
The Copepods are small Crustacea, composed typically of about sixteen
segments, in which the biramous type of limb predominates. They are
devoid of a carapace. Development proceeds gradually by the addition
posteriorly of segments to a Nauplius larval form. Paired compound eyes
are absent, except in Branchiura, the adult retaining the simple eye of the
Nauplius.
In a typical Copepod, such as Calanus hyperboreus (Fig. 25), we can
distinguish the following segments with their appendages: a cephalothorax,
carrying a pair of uniramous first antennae (1st Ant.); a pair of biramous
second antennae (2nd Ant.); mandibles (Md.) with biting gnathobases and a
palp, and a pair of foliaceous first maxillae (Mx.1). Two pairs of appendages
follow, which were looked upon as the two branches of the second
maxillae, but it is now certain that they represent two pairs of appendages,
which may be called second maxillae (Mx.2) and maxillipedes (Mxp.)
respectively. Behind these are five pairs of biramous swimming feet, the
first pair (Th.1) attached to the cephalothorax, the succeeding four pairs to
four distinct thoracic somites. Behind the thorax is a clearly delimited
abdomen composed of five segments, the first of which (Abd.1) carries the
genital opening, and the last a caudal furca.
The Copepods exhibit a great variety of structure, and their classification
is attended with great difficulties. Claus[36] based his attempt at a natural
classification on the character of the mouth and its appendages, dividing the
free-living and semi-parasitic forms as Gnathostomata from the true
parasites or Siphonostomata. This division, although convenient, breaks
down in many places, and it is clear that the parasitic mode of life has been
Page 81
acquired more than once in the history of Copepod evolution, while the
free-living groups do not constitute a natural assemblage.
free-living groups do not constitute a natural assemblage.
Page 82
Page 83
Fig. 25.—Calanus hyperboreus, × 30. Abd1, First abdominal segment; 1st Ant,
2nd Ant, 1st and 2nd antennae; Md, mandible; Mx1, Mx2, 1st and 2nd maxillae;
Mxp, maxillipede; Th1, 1st thoracic appendage. (After Giesbrecht.)
Giesbrecht has more recently[37] founded a classification of the free-living
pelagic Copepods upon the segmentation of the body and certain secondary
sexual characters, and he has hinted[38] that this scheme of classification
applies to the semi-parasitic and parasitic forms. Although much detail
remains to be worked out and the position of some families is doubtful,
Giesbrecht’s scheme is the most satisfactory that has hitherto been
suggested, and will be adopted in this chapter.
The peculiarity in structure of the Argulidae, a small group of
ectoparasites on fresh water fish, necessitates their separation from the rest
of the Copepods (Eucopepoda) as a separate Branch, Branchiura.
BRANCH I. EUCOPEPODA.
Sub-Order 1. Gymnoplea.
The division between the front and hind part of the body falls
immediately in front of the genital openings and behind the fifth thoracic
feet. The latter in the male are modified into an asymmetrical copulatory
organ.
TRIBE I. AMPHASCANDRIA.
The first antennae of the male are symmetrical, with highly-developed
sensory hairs.
Fam. Calanidae.—The Calanidae are exclusively marine Crustacea, and
form a common feature of the pelagic plankton in all parts of the world.
Some species of the genus Calanus often occur in vast shoals, making the
sea appear blood-red, and they furnish a most important article of fish food.
These swarms appear to consist chiefly of females, the males being taken
rarely, and only at certain seasons of the year. Some of the Calanidae are
animals of delicate and curious form, owing to the development of plumed
iridescent hairs from various parts of their body, which may often exhibit a
2nd Ant, 1st and 2nd antennae; Md, mandible; Mx1, Mx2, 1st and 2nd maxillae;
Mxp, maxillipede; Th1, 1st thoracic appendage. (After Giesbrecht.)
Giesbrecht has more recently[37] founded a classification of the free-living
pelagic Copepods upon the segmentation of the body and certain secondary
sexual characters, and he has hinted[38] that this scheme of classification
applies to the semi-parasitic and parasitic forms. Although much detail
remains to be worked out and the position of some families is doubtful,
Giesbrecht’s scheme is the most satisfactory that has hitherto been
suggested, and will be adopted in this chapter.
The peculiarity in structure of the Argulidae, a small group of
ectoparasites on fresh water fish, necessitates their separation from the rest
of the Copepods (Eucopepoda) as a separate Branch, Branchiura.
BRANCH I. EUCOPEPODA.
Sub-Order 1. Gymnoplea.
The division between the front and hind part of the body falls
immediately in front of the genital openings and behind the fifth thoracic
feet. The latter in the male are modified into an asymmetrical copulatory
organ.
TRIBE I. AMPHASCANDRIA.
The first antennae of the male are symmetrical, with highly-developed
sensory hairs.
Fam. Calanidae.—The Calanidae are exclusively marine Crustacea, and
form a common feature of the pelagic plankton in all parts of the world.
Some species of the genus Calanus often occur in vast shoals, making the
sea appear blood-red, and they furnish a most important article of fish food.
These swarms appear to consist chiefly of females, the males being taken
rarely, and only at certain seasons of the year. Some of the Calanidae are
animals of delicate and curious form, owing to the development of plumed
iridescent hairs from various parts of their body, which may often exhibit a
Page 84
marked asymmetry, as in the species figured, Calocalanus plumulosus (Fig.
26), from the Mediterranean.
Sars makes a curious
[39]
observation with regard to the
distribution of certain Calanidae. He
reports that along the whole route of
the “Fram,” species such as Calanus
hyperboreus and Euchaeta
norwegica were taken at the surface,
which, in the Norwegian fjords, only
occur at depths of over 100 fathoms.
He suggests that the Norwegian
individuals, instead of migrating
northwards as the warmer climate
supervened, have sought boreal
conditions of temperature by sinking
into the deeper waters.
Fig. 26.—Calocalanus plumulosus, × 15. (After
Giesbrecht.)
TRIBE II.
HETERARTHRANDRIA.
The first antennae of the male are asymmetrical, one, usually the right,
being used as a clasping organ.
The males of the Centropagidae, Candacidae and Pontellidae, besides
possessing the asymmetrically modified thoracic limbs of the fifth pair also
exhibit a modification of one of the first antennae, which is generally
thickened in the middle, and has a peculiar joint in it, or geniculation, which
enables it to be flexed and so used as a clasping organ for holding the
female.
Fam. 1.—Centropagidae.—These Copepods are very common in the
pelagic plankton, and some of the species vie with the Calanidae in plumed
26), from the Mediterranean.
Sars makes a curious
[39]
observation with regard to the
distribution of certain Calanidae. He
reports that along the whole route of
the “Fram,” species such as Calanus
hyperboreus and Euchaeta
norwegica were taken at the surface,
which, in the Norwegian fjords, only
occur at depths of over 100 fathoms.
He suggests that the Norwegian
individuals, instead of migrating
northwards as the warmer climate
supervened, have sought boreal
conditions of temperature by sinking
into the deeper waters.
Fig. 26.—Calocalanus plumulosus, × 15. (After
Giesbrecht.)
TRIBE II.
HETERARTHRANDRIA.
The first antennae of the male are asymmetrical, one, usually the right,
being used as a clasping organ.
The males of the Centropagidae, Candacidae and Pontellidae, besides
possessing the asymmetrically modified thoracic limbs of the fifth pair also
exhibit a modification of one of the first antennae, which is generally
thickened in the middle, and has a peculiar joint in it, or geniculation, which
enables it to be flexed and so used as a clasping organ for holding the
female.
Fam. 1.—Centropagidae.—These Copepods are very common in the
pelagic plankton, and some of the species vie with the Calanidae in plumed
Page 85
ornaments, e.g. Augaptilus filigerus, figured by Giesbrecht in his
monograph. The use of these ornaments, which are possessed by so many
pelagic Copepods, is entirely obscure.[40] Certain of the Centropagidae live
in fresh water. Thus Diaptomus is an exclusively fresh-water genus, and
forms a most important constituent of lake-plankton; various species of
Heterocope occur in the great continental lakes, and certain Eurytemora go
up the estuaries of rivers into brackish water.
An excellent work on the fresh-water Copepods of Germany has been
written by Schmeil,[41] who gives analytical tables for distinguishing various
genera and species. The three fresh-water families are the Centropagidae,
Cyclopidae, and Harpacticidae (see p. 62). The Centropagidae may be
sharply distinguished from the other fresh-water families by the following
characters:—The cephalothorax is distinctly separated from the abdomen;
the first antennae are long and composed of 24–25 segments, in the male
only a single antenna (generally the right) being geniculated and used as a
clasping organ. The fifth pair of limbs are not rudimentary; a heart is
present, and only one egg-sac is found in the female. The second antennae
are distinctly biramous.
Diaptomus.—The furcal processes are short, at most three times as long
as broad; endopodite of the first swimming appendage 2–jointed,
endopodites of succeeding legs 3–jointed.
Heterocope.—The furcal processes are short, at most twice as long as
broad; endopodites of all swimming legs 1–jointed.
Eurytemora.—The furcal processes are long, at least three and a half
times as long as broad; the endopodite of the first pair of legs 1–jointed,
those of the other pairs 2–jointed.
It has been known for a long time that some of the marine Copepods are
phosphorescent, and, indeed, owing to their numbers in the plankton,
contribute very largely to bring about that liquid illumination which will
always excite the admiration of seafarers. In northern seas the chief
phosphorescent Copepods belong to Metridia, a genus of the
Centropagidae; but in the Bay of Naples Giesbrecht[42] states that the
phosphorescent species are the following Centropagids: Pleuromma
abdominale and P. gracile, Leuckartia flavicornis and Heterochaeta
papilligera; Oncaea conifera is also phosphorescent. It is often stated that
monograph. The use of these ornaments, which are possessed by so many
pelagic Copepods, is entirely obscure.[40] Certain of the Centropagidae live
in fresh water. Thus Diaptomus is an exclusively fresh-water genus, and
forms a most important constituent of lake-plankton; various species of
Heterocope occur in the great continental lakes, and certain Eurytemora go
up the estuaries of rivers into brackish water.
An excellent work on the fresh-water Copepods of Germany has been
written by Schmeil,[41] who gives analytical tables for distinguishing various
genera and species. The three fresh-water families are the Centropagidae,
Cyclopidae, and Harpacticidae (see p. 62). The Centropagidae may be
sharply distinguished from the other fresh-water families by the following
characters:—The cephalothorax is distinctly separated from the abdomen;
the first antennae are long and composed of 24–25 segments, in the male
only a single antenna (generally the right) being geniculated and used as a
clasping organ. The fifth pair of limbs are not rudimentary; a heart is
present, and only one egg-sac is found in the female. The second antennae
are distinctly biramous.
Diaptomus.—The furcal processes are short, at most three times as long
as broad; endopodite of the first swimming appendage 2–jointed,
endopodites of succeeding legs 3–jointed.
Heterocope.—The furcal processes are short, at most twice as long as
broad; endopodites of all swimming legs 1–jointed.
Eurytemora.—The furcal processes are long, at least three and a half
times as long as broad; the endopodite of the first pair of legs 1–jointed,
those of the other pairs 2–jointed.
It has been known for a long time that some of the marine Copepods are
phosphorescent, and, indeed, owing to their numbers in the plankton,
contribute very largely to bring about that liquid illumination which will
always excite the admiration of seafarers. In northern seas the chief
phosphorescent Copepods belong to Metridia, a genus of the
Centropagidae; but in the Bay of Naples Giesbrecht[42] states that the
phosphorescent species are the following Centropagids: Pleuromma
abdominale and P. gracile, Leuckartia flavicornis and Heterochaeta
papilligera; Oncaea conifera is also phosphorescent. It is often stated that
Page 86
Sapphirina (p. 69) is phosphorescent,
but its wonderful iridescent blue
colour is purely due to interference
colours, and has nothing to do with
phosphorescence. Giesbrecht has
observed that the phosphorescence is
due to a substance secreted in special
skin-glands, which is jerked into the
water, and on coming into contact
with it emits a phosphorescent glow.
This substance can be dried up
completely in a desiccated specimen
and yet preserve its phosphorescent
properties, the essential condition for
the actual emission of light being
contact with water. Similarly,
specimens preserved in glycerine for
a long period will phosphoresce
when compressed in distilled water.
From this last experiment Giesbrecht
concludes that the phosphorescence
can hardly be due to an oxidation
process, but the nature of the
chemical reaction remains obscure.
Fam. 2. Candacidae.—This
family comprises the single genus
Candace, with numerous species
distributed in the plankton of all seas.
Some species, e.g. C. pectinata,
Brady, have a practically world-wide
distribution, this species being
recorded from the Shetlands and
from the Philippines.
Fam. 3. Pontellidae.—This is a
larger family also comprising widely
distributed species found in the
marine plankton. Anomalocera
but its wonderful iridescent blue
colour is purely due to interference
colours, and has nothing to do with
phosphorescence. Giesbrecht has
observed that the phosphorescence is
due to a substance secreted in special
skin-glands, which is jerked into the
water, and on coming into contact
with it emits a phosphorescent glow.
This substance can be dried up
completely in a desiccated specimen
and yet preserve its phosphorescent
properties, the essential condition for
the actual emission of light being
contact with water. Similarly,
specimens preserved in glycerine for
a long period will phosphoresce
when compressed in distilled water.
From this last experiment Giesbrecht
concludes that the phosphorescence
can hardly be due to an oxidation
process, but the nature of the
chemical reaction remains obscure.
Fam. 2. Candacidae.—This
family comprises the single genus
Candace, with numerous species
distributed in the plankton of all seas.
Some species, e.g. C. pectinata,
Brady, have a practically world-wide
distribution, this species being
recorded from the Shetlands and
from the Philippines.
Fam. 3. Pontellidae.—This is a
larger family also comprising widely
distributed species found in the
marine plankton. Anomalocera
Page 87
Fig. 27.—Dorsal view of Anomalocera pattersoni (Fig. 27) is one of the
pattersoni, ♂, × 20. (After Sars.)
commonest elements in the plankton
of the North Sea.
Sub-Order 2. Podoplea.
The boundary between the fore and hind part of the body falls in front of
the fifth thoracic segment. The appendages of the fifth thoracic pair in the
male are never modified as copulatory organs.
TRIBE I. AMPHARTHRANDRIA.
The first antennae in the male differ greatly from those in the female,
being often geniculated and acting as prehensile organs.
Fams. 1–2. Cyclopidae and Harpacticidae, and other allied families, are
purely free-living forms; they are not usually pelagic in habit, but prefer
creeping among algae in the littoral zone or on the sea-bottom, or especially
in tidal pools. Some genera are, nevertheless, pelagic; e.g. Oithona among
Cyclopidae; Setella, Clytemnestra, and Aegisthus among Harpacticidae.
The sketch (Fig. 28) of Euterpe acutifrons ♀, a species widely distributed
in the Mediterranean and northern seas, exhibits the structure of a typical
Harpacticid, while Fig. 29 shows the form of the first antenna in the male.
Several fresh-water representatives of these free-living families occur.
The genus Cyclops (Cyclopidae) is exclusively fresh-water, while many
Harpacticidae go up into brackish waters: for example on the Norfolk
Broads, Mr. Robert Gurney has taken Tachidius brevicornis, Müller, and T.
littoralis, Poppe; Ophiocamptus brevipes, Sars; Mesochra lilljeborgi,
Boeck; Laophonte littorale, T. and A. Scott; L. mohammed, Blanchard and
Richard; and Dactylopus tisboides, Claus.
Schmeil[43] gives the following scheme for identifying the fresh-water
Cyclopidae and Harpacticidae (see diagnosis of Centropagidae on p. 59):—
Fam. 1. Cyclopidae.—The cephalothorax is clearly separated from the
abdomen. The first antennae of the female when bent back do not stretch
beyond the cephalothorax; in the male both of them are clasping organs.
pattersoni, ♂, × 20. (After Sars.)
commonest elements in the plankton
of the North Sea.
Sub-Order 2. Podoplea.
The boundary between the fore and hind part of the body falls in front of
the fifth thoracic segment. The appendages of the fifth thoracic pair in the
male are never modified as copulatory organs.
TRIBE I. AMPHARTHRANDRIA.
The first antennae in the male differ greatly from those in the female,
being often geniculated and acting as prehensile organs.
Fams. 1–2. Cyclopidae and Harpacticidae, and other allied families, are
purely free-living forms; they are not usually pelagic in habit, but prefer
creeping among algae in the littoral zone or on the sea-bottom, or especially
in tidal pools. Some genera are, nevertheless, pelagic; e.g. Oithona among
Cyclopidae; Setella, Clytemnestra, and Aegisthus among Harpacticidae.
The sketch (Fig. 28) of Euterpe acutifrons ♀, a species widely distributed
in the Mediterranean and northern seas, exhibits the structure of a typical
Harpacticid, while Fig. 29 shows the form of the first antenna in the male.
Several fresh-water representatives of these free-living families occur.
The genus Cyclops (Cyclopidae) is exclusively fresh-water, while many
Harpacticidae go up into brackish waters: for example on the Norfolk
Broads, Mr. Robert Gurney has taken Tachidius brevicornis, Müller, and T.
littoralis, Poppe; Ophiocamptus brevipes, Sars; Mesochra lilljeborgi,
Boeck; Laophonte littorale, T. and A. Scott; L. mohammed, Blanchard and
Richard; and Dactylopus tisboides, Claus.
Schmeil[43] gives the following scheme for identifying the fresh-water
Cyclopidae and Harpacticidae (see diagnosis of Centropagidae on p. 59):—
Fam. 1. Cyclopidae.—The cephalothorax is clearly separated from the
abdomen. The first antennae of the female when bent back do not stretch
beyond the cephalothorax; in the male both of them are clasping organs.
Page 88
The second antennae are without an
exopodite. The fifth pair of limbs are
rudimentary, there is no heart, and
the female carries two egg-sacs.
Cyclops.—Numerous species, split up
according to segmentation of
rudimentary fifth pair of legs,
number of joints in antennae, etc.
Fam. 2. Harpacticidae.—The
cephalothorax is not clearly separated
from the abdomen. The first antennae
are short in both sexes, both being
clasping organs in the male. The
second antennae have a rudimentary
exopodite. The fifth pair of limbs are
rudimentary and plate-shaped; a heart
is absent, and the egg-sacs of the
female may be one or two in number.
1. Ophiocamptus (Moraria).—Body
worm-shaped; first antennae of
female 7–jointed, rostrum forming a
broad plate.
2. Body not worm-shaped; first
antennae of female 8–jointed,
rostrum short and sharp.
Fig. 28.—Euterpe acutifrons, ♀ , × 70. Abd.1,
1st abdominal segment; Th.5, 5th thoracic
segment. (After Giesbrecht.) (a) Endopodites of all thoracic limbs
3–jointed. The first antennae in
female distinctly bent after the second joint. Nitocra.
(b) Endopodite of at least the fourth limb 2–jointed; first antennae in
female not bent. Canthocamptus.
3. Ectinosoma.—Body as in 2, but first antennae are very short, and
the maxillipede does not carry a terminal hooked seta as in 1 and 2.
Fam. 3. Peltiidae.[44]—This is an interesting family, allied to the
Harpacticidae, and includes species with flattened bodies somewhat
exopodite. The fifth pair of limbs are
rudimentary, there is no heart, and
the female carries two egg-sacs.
Cyclops.—Numerous species, split up
according to segmentation of
rudimentary fifth pair of legs,
number of joints in antennae, etc.
Fam. 2. Harpacticidae.—The
cephalothorax is not clearly separated
from the abdomen. The first antennae
are short in both sexes, both being
clasping organs in the male. The
second antennae have a rudimentary
exopodite. The fifth pair of limbs are
rudimentary and plate-shaped; a heart
is absent, and the egg-sacs of the
female may be one or two in number.
1. Ophiocamptus (Moraria).—Body
worm-shaped; first antennae of
female 7–jointed, rostrum forming a
broad plate.
2. Body not worm-shaped; first
antennae of female 8–jointed,
rostrum short and sharp.
Fig. 28.—Euterpe acutifrons, ♀ , × 70. Abd.1,
1st abdominal segment; Th.5, 5th thoracic
segment. (After Giesbrecht.) (a) Endopodites of all thoracic limbs
3–jointed. The first antennae in
female distinctly bent after the second joint. Nitocra.
(b) Endopodite of at least the fourth limb 2–jointed; first antennae in
female not bent. Canthocamptus.
3. Ectinosoma.—Body as in 2, but first antennae are very short, and
the maxillipede does not carry a terminal hooked seta as in 1 and 2.
Fam. 3. Peltiidae.[44]—This is an interesting family, allied to the
Harpacticidae, and includes species with flattened bodies somewhat
Page 89
resembling Isopods, and a similar
habit of rolling themselves up into
balls. No parasitic forms are known,
though Sunaristes paguri on the
French and Scottish coasts is said to
live commensally with hermit-crabs.
We have now enumerated the chief
families of free-living Copepods; the
rest are either true parasites or else
spend a part of their lives as such. A
number of the semi-parasitic and
parasitic Copepods can be placed in
the tribe Ampharthrandria owing to
the characters of their antennae; but it
must be remembered that many
parasitic forms have given up using
the antennae as clasping organs;
however, the sexual differences in the
antennae, and the fact that many of
the species which have lost the
prehensile antennae in the male have Fig. 29.—First antenna of Euterpe acutifrons, ♂.
near relations which preserve it, (After Giesbrecht.)
enable us to proceed with some
certainty. The adoption of this classification necessitates our separating
many families which superficially may seem to resemble one another, e.g.
the semi-parasitic families Lichomolgidae and Ascidicolidae, and the
Dichelestiidae from the other fish-parasites; it also necessitates our treating
the presence of a sucking mouth as of secondary importance. This
characteristic must certainly, however, have been acquired more than once
in the history of the Copepods, for instance in the Asterocheridae and in the
fish-parasites, while it sometimes happens that genera belonging to a
typically Siphonostomatous group possess a gnathostome, or biting mouth,
e.g. Ratania among the Asterocheridae. Again, it is impossible even if we
use the character of the mouth as a criterion to place together all the true
parasites on fishes in one natural group, because the Bomolochidae and
habit of rolling themselves up into
balls. No parasitic forms are known,
though Sunaristes paguri on the
French and Scottish coasts is said to
live commensally with hermit-crabs.
We have now enumerated the chief
families of free-living Copepods; the
rest are either true parasites or else
spend a part of their lives as such. A
number of the semi-parasitic and
parasitic Copepods can be placed in
the tribe Ampharthrandria owing to
the characters of their antennae; but it
must be remembered that many
parasitic forms have given up using
the antennae as clasping organs;
however, the sexual differences in the
antennae, and the fact that many of
the species which have lost the
prehensile antennae in the male have Fig. 29.—First antenna of Euterpe acutifrons, ♂.
near relations which preserve it, (After Giesbrecht.)
enable us to proceed with some
certainty. The adoption of this classification necessitates our separating
many families which superficially may seem to resemble one another, e.g.
the semi-parasitic families Lichomolgidae and Ascidicolidae, and the
Dichelestiidae from the other fish-parasites; it also necessitates our treating
the presence of a sucking mouth as of secondary importance. This
characteristic must certainly, however, have been acquired more than once
in the history of the Copepods, for instance in the Asterocheridae and in the
fish-parasites, while it sometimes happens that genera belonging to a
typically Siphonostomatous group possess a gnathostome, or biting mouth,
e.g. Ratania among the Asterocheridae. Again, it is impossible even if we
use the character of the mouth as a criterion to place together all the true
parasites on fishes in one natural group, because the Bomolochidae and
Page 90
Chondracanthidae, which are otherwise closely similar to the rest of the
fish-parasites, possess no siphon. It seems plain, therefore, that the parasitic
habit has been acquired several times separately by diverging stocks of free-
swimming Copepods, and that it has resulted in the formation of convergent
structures.
Fam. 4. Monstrillidae.[45]—These
are closely related to the
Harpacticidae. The members of this
curious family are parasitic during
larval life and actively free-
swimming when adult. There are
three genera, Monstrilla, Haemocera,
and Thaumaleus. The best known
type is Haemocera danae (often
described as Monstrilla danae). In
the adult state (Fig. 30) there are no
mouth-parts; the mouth is
exceedingly small and leads into a
very small stomach, which ends
blindly, while the whole body
contains reserve food-material in the
form of brown oil-drops. The sole
appendages on the head are the first
antennae; but on the thorax biramous
Fig. 30.—Haemocera danae, × 40. A, Side view feet are present by means of which
♀; B, ventral view ♂. Ant.1, 1st antenna; e, eye;
ov, ovary; ovd, oviduct; St, stomach; Th.1, 1st
the animal can swim with great
thoracic appendage; Th.5, 5th thoracic segment; rapidity. This anomalous organisation
vd, vas deferens. (After Malaquin.) receives an explanation from the
remarkable development through
which the larva passes. The larva is liberated from the parent as a Nauplius
with the structure shown in Fig. 31; it does not possess an alimentary canal.
It makes its way to a specimen of the Serpulid worm, Salmacina dysteri,
into the epidermis of which it penetrates by movements of the antennae,
hanging on all the time by means of the hooks on the mandibles. From the
epidermis it passes through the muscles into the coelom of the worm, and
thence into the blood-vessels, usually coming to rest in the ventral blood-
vessel. As the Nauplius migrates, apparently by amoeboid movements of
fish-parasites, possess no siphon. It seems plain, therefore, that the parasitic
habit has been acquired several times separately by diverging stocks of free-
swimming Copepods, and that it has resulted in the formation of convergent
structures.
Fam. 4. Monstrillidae.[45]—These
are closely related to the
Harpacticidae. The members of this
curious family are parasitic during
larval life and actively free-
swimming when adult. There are
three genera, Monstrilla, Haemocera,
and Thaumaleus. The best known
type is Haemocera danae (often
described as Monstrilla danae). In
the adult state (Fig. 30) there are no
mouth-parts; the mouth is
exceedingly small and leads into a
very small stomach, which ends
blindly, while the whole body
contains reserve food-material in the
form of brown oil-drops. The sole
appendages on the head are the first
antennae; but on the thorax biramous
Fig. 30.—Haemocera danae, × 40. A, Side view feet are present by means of which
♀; B, ventral view ♂. Ant.1, 1st antenna; e, eye;
ov, ovary; ovd, oviduct; St, stomach; Th.1, 1st
the animal can swim with great
thoracic appendage; Th.5, 5th thoracic segment; rapidity. This anomalous organisation
vd, vas deferens. (After Malaquin.) receives an explanation from the
remarkable development through
which the larva passes. The larva is liberated from the parent as a Nauplius
with the structure shown in Fig. 31; it does not possess an alimentary canal.
It makes its way to a specimen of the Serpulid worm, Salmacina dysteri,
into the epidermis of which it penetrates by movements of the antennae,
hanging on all the time by means of the hooks on the mandibles. From the
epidermis it passes through the muscles into the coelom of the worm, and
thence into the blood-vessels, usually coming to rest in the ventral blood-
vessel. As the Nauplius migrates, apparently by amoeboid movements of
Page 91
the whole body, it loses all its
appendages, the eye degenerates, and
the body is reduced to a minute ovoid
mass of cells, representing ectoderm
and endo-mesoderm, surrounded by a
chitinous membrane (Fig. 32, A).
Arrived in the ventral blood-vessel it
begins to grow, and the first organ
formed is a pair of fleshy outgrowths
representing the second antennae
(Fig. 32, B), which act as a nutrient
organ intermediary between host and
parasite. The adult organs now begin Fig. 31.—Free-swimming Nauplius larva of
to be differentiated, as shown in Fig. Haemocera danae; Ant.1, Ant.2, 1st and 2nd
antennae; e, remains of eye; Md, mandible.
32, C, from the undifferentiated (After Malaquin.)
cellular elements of the Nauplius, the
future adult organism being enclosed
in a spiny coat from which it escapes. At this stage it occupies a large part
of its host’s body, lying in the distended ventral blood-vessel, and it escapes
to the outside world by rupturing the body-wall of the worm, leaving behind
it the second antennae, which have performed their function as a kind of
placenta. Malaquin, to whom we owe this account, makes the remarkable
statement that if two or three Monstrillid Nauplii develop together in the
same host they are always males, if only one it may be either male or
female. The only parallel to this extraordinary life-history is found in the
Rhizocephala (see pp. 96–99).
appendages, the eye degenerates, and
the body is reduced to a minute ovoid
mass of cells, representing ectoderm
and endo-mesoderm, surrounded by a
chitinous membrane (Fig. 32, A).
Arrived in the ventral blood-vessel it
begins to grow, and the first organ
formed is a pair of fleshy outgrowths
representing the second antennae
(Fig. 32, B), which act as a nutrient
organ intermediary between host and
parasite. The adult organs now begin Fig. 31.—Free-swimming Nauplius larva of
to be differentiated, as shown in Fig. Haemocera danae; Ant.1, Ant.2, 1st and 2nd
antennae; e, remains of eye; Md, mandible.
32, C, from the undifferentiated (After Malaquin.)
cellular elements of the Nauplius, the
future adult organism being enclosed
in a spiny coat from which it escapes. At this stage it occupies a large part
of its host’s body, lying in the distended ventral blood-vessel, and it escapes
to the outside world by rupturing the body-wall of the worm, leaving behind
it the second antennae, which have performed their function as a kind of
placenta. Malaquin, to whom we owe this account, makes the remarkable
statement that if two or three Monstrillid Nauplii develop together in the
same host they are always males, if only one it may be either male or
female. The only parallel to this extraordinary life-history is found in the
Rhizocephala (see pp. 96–99).
Page 92
Fig. 32.—Later stages in the development of Haemocera danae. Abd, Abdomen;
Ant.1, Ant.2, 1st and 2nd antennae; ch, chitinous investment; e, eye; Ect,
ectoderm; En, endoderm; Mes, mesoderm; Mes & en, mesoderm and endoderm;
R, rostrum; St, mouth and stomach; Th, thoracic appendages. (After Malaquin.)
Fam. 5. Ascidicolidae.[46]—Although the members of this family, which
live semiparasitically in the branchial sac or the gut of Ascidians, betray
Ant.1, Ant.2, 1st and 2nd antennae; ch, chitinous investment; e, eye; Ect,
ectoderm; En, endoderm; Mes, mesoderm; Mes & en, mesoderm and endoderm;
R, rostrum; St, mouth and stomach; Th, thoracic appendages. (After Malaquin.)
Fam. 5. Ascidicolidae.[46]—Although the members of this family, which
live semiparasitically in the branchial sac or the gut of Ascidians, betray
Page 93
their Ampharthrandrian nature by the
sexual differences of their first
antennae, only two genera,
Notodelphys and Agnathaner,
possess true prehensile antennae.
According as the parasitism is more
or less complete, the buccal
appendages either retain their
masticatory structure or else become
reduced to mere organs of fixation. In
Fig. 33.—Side view of Doropygus pulex, ♀ , × Notodelphys both sexes can swim
106. Abd.1, 1st abdominal segment; Ant.1, 1st
antenna; b.p, brood-pouch; Th.1, 1st thoracic
actively and retain normal mouth-
appendage; Th.4, 4th thoracic segment. (After parts; they live parasitically, or
Canu.) perhaps commensally, in the
branchial cavities of Simple or
Compound Ascidians, feeding on the particles swept into the respiratory
chamber of the host. They leave their host at will in search of a new home,
and are frequently taken in the plankton.
Doropygus (Fig. 33), a genus widely distributed in the North Sea and
Mediterranean, also inhabiting the branchial sac of Ascidians, is more
completely parasitic, and the female cannot swim actively. Forms still more
degraded by a parasitic habit are Ascidicola rosea (especially abundant in
the stomach of Ascidiella scabra at Concarneau), in which the female has
lost its segmentation, the mouth-parts and thoracic legs being purely
prehensile, and various species of Enterocola, parasitic in the stomach of
Compound Ascidians, in which the female is a mere sac incapable of free
motion, while the male preserves its swimming powers and a general
Cyclops-form (Fig. 34). We have here the first instance of the remarkable
parallelism between the degree of parasitism and the degree of sexual
dimorphism, a parallelism which holds with great regularity among the
Copepoda, and can be also extended to other classes of parasitic animals.
Fam. 6. Asterocheridae.[47]—These forms retain the power of swimming
actively, and are very little modified in outward appearance by their
parasitic mode of life (Fig. 35), though they possess a true siphon in which
the styliform mandibles work. The siphon is formed by the upper and lower
lips, which are produced into a tube with three longitudinal ridges; in the
outer grooves are the mandibles, while the inner groove forms the sucking
sexual differences of their first
antennae, only two genera,
Notodelphys and Agnathaner,
possess true prehensile antennae.
According as the parasitism is more
or less complete, the buccal
appendages either retain their
masticatory structure or else become
reduced to mere organs of fixation. In
Fig. 33.—Side view of Doropygus pulex, ♀ , × Notodelphys both sexes can swim
106. Abd.1, 1st abdominal segment; Ant.1, 1st
antenna; b.p, brood-pouch; Th.1, 1st thoracic
actively and retain normal mouth-
appendage; Th.4, 4th thoracic segment. (After parts; they live parasitically, or
Canu.) perhaps commensally, in the
branchial cavities of Simple or
Compound Ascidians, feeding on the particles swept into the respiratory
chamber of the host. They leave their host at will in search of a new home,
and are frequently taken in the plankton.
Doropygus (Fig. 33), a genus widely distributed in the North Sea and
Mediterranean, also inhabiting the branchial sac of Ascidians, is more
completely parasitic, and the female cannot swim actively. Forms still more
degraded by a parasitic habit are Ascidicola rosea (especially abundant in
the stomach of Ascidiella scabra at Concarneau), in which the female has
lost its segmentation, the mouth-parts and thoracic legs being purely
prehensile, and various species of Enterocola, parasitic in the stomach of
Compound Ascidians, in which the female is a mere sac incapable of free
motion, while the male preserves its swimming powers and a general
Cyclops-form (Fig. 34). We have here the first instance of the remarkable
parallelism between the degree of parasitism and the degree of sexual
dimorphism, a parallelism which holds with great regularity among the
Copepoda, and can be also extended to other classes of parasitic animals.
Fam. 6. Asterocheridae.[47]—These forms retain the power of swimming
actively, and are very little modified in outward appearance by their
parasitic mode of life (Fig. 35), though they possess a true siphon in which
the styliform mandibles work. The siphon is formed by the upper and lower
lips, which are produced into a tube with three longitudinal ridges; in the
outer grooves are the mandibles, while the inner groove forms the sucking
Page 94
siphon (see transverse section, Fig.
36). In Ratania, however, there is no
siphon. The first antennae possess a
great number of joints, and may be
geniculated in the male (Cancerilla).
The members of this family live as
ectoparasites on various species of
Echinoderms, Sponges, and
Ascidians, but they frequently
change their hosts, and it appears that
one and the same species may
indifferently suck the juices of very
various animals, and even of Algae.
Cancerilla tubulata, however,
appears to live only on the Brittle
Starfish, Amphiura squamata.
Fig. 34.—Enterocola fulgens. A, Ventral view of Fam. 7. Dichelestiidae.—The
♀ , × 35; B, side view of ♂ , × 106. Abd.1, 1st males and females are similarly
abdominal segment; Ant.1, Ant.2, 1st and 2nd parasitic, and the body in both is
antennae; c.m, gland-cells; n, ventral nerve-
cord; og, oviducal gland; ov, ovary; po, vagina; highly deformed, the segmentation
Th.1, 1st thoracic appendage; Th.4, Th.5, 4th being suppressed and the thoracic
and 5th thoracic segments. (After Canu.)
limbs being produced into formless
fleshy lobes; they are placed among
the Ampharthrandria owing to sexual differences in the form of the first
antennae. There is a well-developed siphon in which the mandibular stylets
work, except in Lamproglena, parasitic on the gills of Cyprinoid fishes; the
succeeding mouth-parts are prehensile.
The majority of the species are parasitic on the gills of various fish
(Dichelestium on the Sturgeon, Lernanthropus[48] on Labrax lupus, Serranus
scriba, etc.), but Steuer[49] has recently described a Dichelestiid (Mytilicola)
from the gut of Mytilus galloprovincialis off Trieste. This animal and
Lernanthropus are unique among Crustacea through the possession of a
completely closed blood-vascular system which contains a red fluid; the
older observers believed this fluid to contain haemoglobin, but Steuer, as
the result of careful analysis, denies this. The parasite on the gills of the
Lobster, Nicothoe astaci, possibly belongs here.
36). In Ratania, however, there is no
siphon. The first antennae possess a
great number of joints, and may be
geniculated in the male (Cancerilla).
The members of this family live as
ectoparasites on various species of
Echinoderms, Sponges, and
Ascidians, but they frequently
change their hosts, and it appears that
one and the same species may
indifferently suck the juices of very
various animals, and even of Algae.
Cancerilla tubulata, however,
appears to live only on the Brittle
Starfish, Amphiura squamata.
Fig. 34.—Enterocola fulgens. A, Ventral view of Fam. 7. Dichelestiidae.—The
♀ , × 35; B, side view of ♂ , × 106. Abd.1, 1st males and females are similarly
abdominal segment; Ant.1, Ant.2, 1st and 2nd parasitic, and the body in both is
antennae; c.m, gland-cells; n, ventral nerve-
cord; og, oviducal gland; ov, ovary; po, vagina; highly deformed, the segmentation
Th.1, 1st thoracic appendage; Th.4, Th.5, 4th being suppressed and the thoracic
and 5th thoracic segments. (After Canu.)
limbs being produced into formless
fleshy lobes; they are placed among
the Ampharthrandria owing to sexual differences in the form of the first
antennae. There is a well-developed siphon in which the mandibular stylets
work, except in Lamproglena, parasitic on the gills of Cyprinoid fishes; the
succeeding mouth-parts are prehensile.
The majority of the species are parasitic on the gills of various fish
(Dichelestium on the Sturgeon, Lernanthropus[48] on Labrax lupus, Serranus
scriba, etc.), but Steuer[49] has recently described a Dichelestiid (Mytilicola)
from the gut of Mytilus galloprovincialis off Trieste. This animal and
Lernanthropus are unique among Crustacea through the possession of a
completely closed blood-vascular system which contains a red fluid; the
older observers believed this fluid to contain haemoglobin, but Steuer, as
the result of careful analysis, denies this. The parasite on the gills of the
Lobster, Nicothoe astaci, possibly belongs here.
Page 95
The inclusion of Nicothoe and the
Dichelestiidae among the
Ampharthrandria rests on a
somewhat slender basis; this basis is
afforded by the fact that none of the
parasitic Isokerandria have more than
seven joints in the first antennae,
whereas Nicothoe and some of the
Dichelestiidae[50] have more
numerous joints. In most of the
Dichelestiidae, however, the number
of joints is less than seven and
practically equal in the two sexes.
Fig. 35.—Asterocheres violaceus, ♀ , with egg-
sacs, × 57. (After Giesbrecht.)
Fig. 36.—Diagrammatic transverse section
through the distal part of the siphon of
Rhynchomyzon purpurocinctum
(Asterocheridae). Md, mandible. (After
Giesbrecht.)
Dichelestiidae among the
Ampharthrandria rests on a
somewhat slender basis; this basis is
afforded by the fact that none of the
parasitic Isokerandria have more than
seven joints in the first antennae,
whereas Nicothoe and some of the
Dichelestiidae[50] have more
numerous joints. In most of the
Dichelestiidae, however, the number
of joints is less than seven and
practically equal in the two sexes.
Fig. 35.—Asterocheres violaceus, ♀ , with egg-
sacs, × 57. (After Giesbrecht.)
Fig. 36.—Diagrammatic transverse section
through the distal part of the siphon of
Rhynchomyzon purpurocinctum
(Asterocheridae). Md, mandible. (After
Giesbrecht.)
Page 96
TRIBE II. ISOKERANDRIA.
The first antennae are short, similar in the two sexes, and are never used
by the male as clasping organs. This function may be subserved by the
second maxillae.
Fams. Oncaeidae, Corycaeidae, Lichomolgidae, Ergasilidae,
Bomolochidae, Chondracanthidae, Philichthyidae, Nereicolidae,
Hersiliidae, Caligidae, Lernaeidae, Lernaeopodidae, Choniostomatidae.
The families Oncaeidae and Corycaeidae contain pelagic forms of
flattened shape and great swimming powers, but the structure of the mouth-
parts in the Corycaeidae points to a semi-parasitic habit.
Fam. 1. Oncaeidae.—This family, including the genera Oncaea,
Pachysoma, etc., does not possess the elaborate eyes of the next family, nor
is the sexual dimorphism so marked.
Fam. 2. Corycaeidae.—These are distinguished from the Oncaeidae, not
only by their greater beauty, but also by the possession of very elaborate
eyes, which are furnished with two lenses, one at each end of a fairly long
tube. The females of Sapphirina are occasionally found in the branchial
cavity of Salps, and their alimentary canal never contains solid particles, but
is filled with a fluid substance perhaps derived by suction from their prey. S.
opalina may occur in large shoals, when the wonderful iridescent blue
colour of the males makes the water sparkle as it were with a sort of diurnal
phosphorescence. The animal, however, despite the opinion of the older
observers, is not truly phosphorescent. It may be that the ornamental nature
of some of the males is correlated with the presence of the curious visual
organs, which are on the whole better developed in the females than in the
males. As in so many pelagic Copepods, the body and limbs may bear
plumed setae of great elaboration and beautiful colour, e.g. Copilia vitrea
(Fig. 37).
We now pass on to the rest of the parasitic Copepods,[51] which probably
belong to the tribe Isokerandria, and we meet with the same variety of
degrees of parasitism as in the Ampharthrandria, often leading to very
similar results.
The first antennae are short, similar in the two sexes, and are never used
by the male as clasping organs. This function may be subserved by the
second maxillae.
Fams. Oncaeidae, Corycaeidae, Lichomolgidae, Ergasilidae,
Bomolochidae, Chondracanthidae, Philichthyidae, Nereicolidae,
Hersiliidae, Caligidae, Lernaeidae, Lernaeopodidae, Choniostomatidae.
The families Oncaeidae and Corycaeidae contain pelagic forms of
flattened shape and great swimming powers, but the structure of the mouth-
parts in the Corycaeidae points to a semi-parasitic habit.
Fam. 1. Oncaeidae.—This family, including the genera Oncaea,
Pachysoma, etc., does not possess the elaborate eyes of the next family, nor
is the sexual dimorphism so marked.
Fam. 2. Corycaeidae.—These are distinguished from the Oncaeidae, not
only by their greater beauty, but also by the possession of very elaborate
eyes, which are furnished with two lenses, one at each end of a fairly long
tube. The females of Sapphirina are occasionally found in the branchial
cavity of Salps, and their alimentary canal never contains solid particles, but
is filled with a fluid substance perhaps derived by suction from their prey. S.
opalina may occur in large shoals, when the wonderful iridescent blue
colour of the males makes the water sparkle as it were with a sort of diurnal
phosphorescence. The animal, however, despite the opinion of the older
observers, is not truly phosphorescent. It may be that the ornamental nature
of some of the males is correlated with the presence of the curious visual
organs, which are on the whole better developed in the females than in the
males. As in so many pelagic Copepods, the body and limbs may bear
plumed setae of great elaboration and beautiful colour, e.g. Copilia vitrea
(Fig. 37).
We now pass on to the rest of the parasitic Copepods,[51] which probably
belong to the tribe Isokerandria, and we meet with the same variety of
degrees of parasitism as in the Ampharthrandria, often leading to very
similar results.
Page 97
Fig. 37.—Copilia vitrea (Corycaeidae), ♀, × 20. (After Giesbrecht.)
In the first seven families mentioned below there is no siphon. The
Lichomolgidae and Ergasilidae have not much departed from the free-living
In the first seven families mentioned below there is no siphon. The
Lichomolgidae and Ergasilidae have not much departed from the free-living
Page 98
forms just considered, retaining their segmentation, though in the
Ergasilidae the body may be somewhat distorted (Fig. 39). In both families
the thoracic swimming feet are of normal constitution.
Fam. 3. Lichomolgidae.[52]—
These are semi-parasitic in a number
of animals living on the sea-bottom,
such as Actinians, Echinoderms,
Annelids, Molluscs, and Tunicates.
Lichomolgus agilis (Fig. 38) occurs
in the North Sea, Atlantic, and
Mediterranean, on the gills of large
species of the Nudibranch, Doris,
while L. albeus is found in the
peribranchial cavity and cloaca of
various Ascidians. Sabelliphilus may
infect the gills of Annelids such as
Sabella, and is common at Liverpool.
Fam. 4. Ergasilidae.—Thersites
(Fig. 39) is parasitic on the gills of
various fishes, e.g. T. gasterostei,
which is common on Gasterosteus
aculeatus on the French and North
Sea coasts, and may even be found
on specimens of the fish that have
run up the River Forth into fresh
water. The animal possesses claw-
like second antennae by which it
clings to its host.
Fig. 38.—Lichomolgus agilis, × 10. Abd. 1, 1st
abdominal segment; cpth, cephalothorax; Th.1,
1st thoracic segment; Th.5, 5th thoracic
appendage. (After Canu.)
Ergasilidae the body may be somewhat distorted (Fig. 39). In both families
the thoracic swimming feet are of normal constitution.
Fam. 3. Lichomolgidae.[52]—
These are semi-parasitic in a number
of animals living on the sea-bottom,
such as Actinians, Echinoderms,
Annelids, Molluscs, and Tunicates.
Lichomolgus agilis (Fig. 38) occurs
in the North Sea, Atlantic, and
Mediterranean, on the gills of large
species of the Nudibranch, Doris,
while L. albeus is found in the
peribranchial cavity and cloaca of
various Ascidians. Sabelliphilus may
infect the gills of Annelids such as
Sabella, and is common at Liverpool.
Fam. 4. Ergasilidae.—Thersites
(Fig. 39) is parasitic on the gills of
various fishes, e.g. T. gasterostei,
which is common on Gasterosteus
aculeatus on the French and North
Sea coasts, and may even be found
on specimens of the fish that have
run up the River Forth into fresh
water. The animal possesses claw-
like second antennae by which it
clings to its host.
Fig. 38.—Lichomolgus agilis, × 10. Abd. 1, 1st
abdominal segment; cpth, cephalothorax; Th.1,
1st thoracic segment; Th.5, 5th thoracic
appendage. (After Canu.)
Page 99
Fig. 39.—Thersites gasterostei. A, ♀, × 10; B, ♂,
× 20. Abd. 1 & 2, Fused 1st and 2nd abdominal
segments; Ant.1, Ant.2, 1st and 2nd antennae; e.s,
egg-sac; Th, thoracic appendages. (After
Gerstaecker.)
Similarly characterised by the absence of a siphon are three other
families of fish-parasites, the Bomolochidae, Chondracanthidae, and
Philichthyidae.
Fam. 5. Bomolochidae.—Bomolochus (Fig. 40), parasitic on the skin of
the Sole (Solea) and in the nostrils of Cod (Gadus), is held to be related to
the Ergasilidae. The first thoracic limb is remarkably modified. Were it not
for the absence of a siphon, it would be hard to separate this family from
the Caligidae.
× 20. Abd. 1 & 2, Fused 1st and 2nd abdominal
segments; Ant.1, Ant.2, 1st and 2nd antennae; e.s,
egg-sac; Th, thoracic appendages. (After
Gerstaecker.)
Similarly characterised by the absence of a siphon are three other
families of fish-parasites, the Bomolochidae, Chondracanthidae, and
Philichthyidae.
Fam. 5. Bomolochidae.—Bomolochus (Fig. 40), parasitic on the skin of
the Sole (Solea) and in the nostrils of Cod (Gadus), is held to be related to
the Ergasilidae. The first thoracic limb is remarkably modified. Were it not
for the absence of a siphon, it would be hard to separate this family from
the Caligidae.
Page 100
Fig. 40.—Bomolochus, sp. (Bomolochidae), × 8.
Abd. 1, 1st abdominal segment; Ant.1, Ant.2, 1st
and 2nd antennae; Mx.1, Mx.2, 1st and 2nd
maxillae; Mxp, maxillipede; Th.1, 1st thoracic
appendage. (After Gerstaecker.)
Fam. 6. Chondracanthidae.—These Copepods infest the gills and even
the mouth of various marine fish, such as the Gurnard, Plaice, Skate, Sole,
and many others. The sexual dimorphism is very marked, the female being
large, indistinctly segmented, and with irregular paired processes protruding
from the sides of the body, giving the animal a monstrous form (Fig. 41);
while the male (Fig. 42) is very small, has a completely segmented thorax,
and lives clinging on to the female by its prehensile second antennae—
Chondracanthus, Lernentoma.
Fam. 7. Philichthyidae.—These parasites, which are hardly known to
occur in British waters,[53] are mucus-feeders and infest the skin of Teleosts,
e.g. the Sole; often taking up a position in the lateral line or in a slime canal.
They show a similar sexual dimorphism to the foregoing family, the adult
female being extraordinarily drawn out into finger-like processes (e.g.
Philichthys)[54] or else long, slender, and Nematode-like, with much reduced
Abd. 1, 1st abdominal segment; Ant.1, Ant.2, 1st
and 2nd antennae; Mx.1, Mx.2, 1st and 2nd
maxillae; Mxp, maxillipede; Th.1, 1st thoracic
appendage. (After Gerstaecker.)
Fam. 6. Chondracanthidae.—These Copepods infest the gills and even
the mouth of various marine fish, such as the Gurnard, Plaice, Skate, Sole,
and many others. The sexual dimorphism is very marked, the female being
large, indistinctly segmented, and with irregular paired processes protruding
from the sides of the body, giving the animal a monstrous form (Fig. 41);
while the male (Fig. 42) is very small, has a completely segmented thorax,
and lives clinging on to the female by its prehensile second antennae—
Chondracanthus, Lernentoma.
Fam. 7. Philichthyidae.—These parasites, which are hardly known to
occur in British waters,[53] are mucus-feeders and infest the skin of Teleosts,
e.g. the Sole; often taking up a position in the lateral line or in a slime canal.
They show a similar sexual dimorphism to the foregoing family, the adult
female being extraordinarily drawn out into finger-like processes (e.g.
Philichthys)[54] or else long, slender, and Nematode-like, with much reduced
Page 101
appendages (Lernaeascus), while the
male retains a more normal structure.
As in all the foregoing forms there is
no siphon.
We now return to two semi-
parasitic families, Fam. 8,
Nereicolidae, and Fam. 9,
Hersiliidae, in which there is
certainly no well-developed siphon,
but the upper and under lips protrude,
forming a hollow between them in
which the mouth-parts work. Both
families are ectoparasites which
frequently leave their hosts, and they
retain their segmentation and powers
of swimming. Perhaps the best-
known form is the Hersiliid,
Giardella callianassae, which lives
in the adult state in the galleries
excavated in the sand by Callianassa
subterranea, gaining its nourishment
as an ectoparasite on the Decapod.
The larvae are pelagic, and are said
Fig. 41.—Chondracanthus zei, ♀, × 4. by Thomson[55] to occur in Liverpool
Bay.
List[56] describes Gastrodelphys, a parasite of doubtful position, from the
gills of tubicolous worms, such as Myxicola and Sabella, which possesses a
perfectly siphonostomatous mouth.
The remaining families to be dealt with are those containing all the fish-
parasites which possess a true siphonostome, as well as the
siphonostomatous family Choniostomatidae, which is parasitic on other
Crustacea. In all these forms the mouth is prolonged into a tube in which
the styliform mandibles work.
Fam. 10. Caligidae.—Ectoparasites on fish, lodging most frequently in
the gill-chamber. In most of the genera the segmentation and power of
swimming are retained in both sexes, the sexual dimorphism not being very
male retains a more normal structure.
As in all the foregoing forms there is
no siphon.
We now return to two semi-
parasitic families, Fam. 8,
Nereicolidae, and Fam. 9,
Hersiliidae, in which there is
certainly no well-developed siphon,
but the upper and under lips protrude,
forming a hollow between them in
which the mouth-parts work. Both
families are ectoparasites which
frequently leave their hosts, and they
retain their segmentation and powers
of swimming. Perhaps the best-
known form is the Hersiliid,
Giardella callianassae, which lives
in the adult state in the galleries
excavated in the sand by Callianassa
subterranea, gaining its nourishment
as an ectoparasite on the Decapod.
The larvae are pelagic, and are said
Fig. 41.—Chondracanthus zei, ♀, × 4. by Thomson[55] to occur in Liverpool
Bay.
List[56] describes Gastrodelphys, a parasite of doubtful position, from the
gills of tubicolous worms, such as Myxicola and Sabella, which possesses a
perfectly siphonostomatous mouth.
The remaining families to be dealt with are those containing all the fish-
parasites which possess a true siphonostome, as well as the
siphonostomatous family Choniostomatidae, which is parasitic on other
Crustacea. In all these forms the mouth is prolonged into a tube in which
the styliform mandibles work.
Fam. 10. Caligidae.—Ectoparasites on fish, lodging most frequently in
the gill-chamber. In most of the genera the segmentation and power of
swimming are retained in both sexes, the sexual dimorphism not being very
Page 102
well marked, though the males are
smaller than the females, and were in
some cases originally described as
belonging to a special genus
Nogagus. The females carry two long
egg-sacs; the general structure may
be made out from the ventral view of
Caligus nanus (Fig. 43).
Some of the Caligidae are
distinguished by the terga of the
thoracic segments being expanded to
form large chitinous elytra, e.g.
Cecrops, found parasitic on the gills
of the Tunny and on the Sun-fish
(Orthagoriscus mola). Caligus rapax
is parasitic on the skin and in the gills
of Sea-Trout, Pollan, etc.; and C.
lacustris is common in fresh-water
lakes and streams on Pike and Carp.
Fam. 11. Lernaeidae.—These Fig. 42.—Dwarf male of Lernentoma cornuta
(Chondracanthidae), × 10. Ant.1, Ant.2, 1st and
parasites burrow with their heads 2nd antennae; Th.1, 1st thoracic segment. (After
deep into the skin, or even into the Gerstaecker.)
blood-vessels or body-cavity, of
various marine fish. The body of the adult female Lernaea is extraordinarily
deformed, consisting of a mere shapeless sac with irregular branched
processes on the head, and two egg-sacs attached behind (Fig. 44). Pennella
sagitta[57] bores so deeply into the flesh of its host, Chironectes marmoratus,
that only the egg-sacs and some remarkable branchial processes attached to
its abdomen protrude outside the host to the exterior. Peroderma
cylindricum bores similarly into the flesh of the Sardine, and where it is
common, inflicts considerable damage. The males of these curious animals
are of more normal structure (Fig. 45). Claus[58] states that fertilisation takes
place when both sexes are free-swimming, and of a more or less similar
structure, and that subsequently the female becomes fixed to her host and
degenerates into the shapeless mass shown in Fig. 44.
smaller than the females, and were in
some cases originally described as
belonging to a special genus
Nogagus. The females carry two long
egg-sacs; the general structure may
be made out from the ventral view of
Caligus nanus (Fig. 43).
Some of the Caligidae are
distinguished by the terga of the
thoracic segments being expanded to
form large chitinous elytra, e.g.
Cecrops, found parasitic on the gills
of the Tunny and on the Sun-fish
(Orthagoriscus mola). Caligus rapax
is parasitic on the skin and in the gills
of Sea-Trout, Pollan, etc.; and C.
lacustris is common in fresh-water
lakes and streams on Pike and Carp.
Fam. 11. Lernaeidae.—These Fig. 42.—Dwarf male of Lernentoma cornuta
(Chondracanthidae), × 10. Ant.1, Ant.2, 1st and
parasites burrow with their heads 2nd antennae; Th.1, 1st thoracic segment. (After
deep into the skin, or even into the Gerstaecker.)
blood-vessels or body-cavity, of
various marine fish. The body of the adult female Lernaea is extraordinarily
deformed, consisting of a mere shapeless sac with irregular branched
processes on the head, and two egg-sacs attached behind (Fig. 44). Pennella
sagitta[57] bores so deeply into the flesh of its host, Chironectes marmoratus,
that only the egg-sacs and some remarkable branchial processes attached to
its abdomen protrude outside the host to the exterior. Peroderma
cylindricum bores similarly into the flesh of the Sardine, and where it is
common, inflicts considerable damage. The males of these curious animals
are of more normal structure (Fig. 45). Claus[58] states that fertilisation takes
place when both sexes are free-swimming, and of a more or less similar
structure, and that subsequently the female becomes fixed to her host and
degenerates into the shapeless mass shown in Fig. 44.
Page 103
Fam. 12. Lernaeopodidae.—This
family may be illustrated by the
common gill-parasite of Perch and
Trout, known as Achtheres percarum.
The female (Fig. 46), which is much
larger than the male, and is not
clearly segmented, is attached to the
host by means of the maxillipedes,
which are fused distally into a pad
armed with chitinous hooks. In the
male the maxillipedes are prehensile,
but are not so fused. Besides
Achtheres there are other fresh-water
forms, e.g. Lernaeopoda salmonea
on Salmon, and a number of marine
genera. It appears that the larvae fix
themselves to their hosts by means of
Fig. 43.—Caligus nanus, × 10. Abd.1, 1st
abdominal segment; Ant.1, Ant.2, 1st and 2nd a long glandular thread, which
antennae; Mx.1, Mx.2, 1st and 2nd maxillae; proceeds from the middle of the
Mxp, maxillipede; s, siphon; Th.1, Th.5 1st and forehead.[59]
5th thoracic appendages. (After Gerstaecker.)
Fam. 13. Choniostomatidae.[60]—
The members of this family are all
parasitic on other Crustacea. The majority live parasitically in the marsupial
pouches of female Amphipods, Isopods, Mysidae, and Cumacea, e.g.
Sphaeronella and Stenochotheres in the marsupia of Gammarids; but
Choniostoma occurs in the branchial cavity of Hippolyte, Homoeoscelis is
common in the branchial cavity of Diastylis and Iphinoe, and Aspidoecia on
the outside of the body of the Mysid Erythrops. The males and females live
together in the same marsupium, but the adult males retain the power of
roving about, and do not feed so much as the females, though their mouth-
parts are similarly constructed (Fig. 47). Representatives occur all over the
world, but the majority of species known at present are from the North Sea,
the most abundant being Stenochotheres egregius, parasitic on the
Gammarid Metopa bruzelii, Goës.
The male bears a median glandular thread on the forehead by which it
attaches itself to the females or to the host. Hansen considers that the family
is most closely allied to the Lernaeopodidae.
family may be illustrated by the
common gill-parasite of Perch and
Trout, known as Achtheres percarum.
The female (Fig. 46), which is much
larger than the male, and is not
clearly segmented, is attached to the
host by means of the maxillipedes,
which are fused distally into a pad
armed with chitinous hooks. In the
male the maxillipedes are prehensile,
but are not so fused. Besides
Achtheres there are other fresh-water
forms, e.g. Lernaeopoda salmonea
on Salmon, and a number of marine
genera. It appears that the larvae fix
themselves to their hosts by means of
Fig. 43.—Caligus nanus, × 10. Abd.1, 1st
abdominal segment; Ant.1, Ant.2, 1st and 2nd a long glandular thread, which
antennae; Mx.1, Mx.2, 1st and 2nd maxillae; proceeds from the middle of the
Mxp, maxillipede; s, siphon; Th.1, Th.5 1st and forehead.[59]
5th thoracic appendages. (After Gerstaecker.)
Fam. 13. Choniostomatidae.[60]—
The members of this family are all
parasitic on other Crustacea. The majority live parasitically in the marsupial
pouches of female Amphipods, Isopods, Mysidae, and Cumacea, e.g.
Sphaeronella and Stenochotheres in the marsupia of Gammarids; but
Choniostoma occurs in the branchial cavity of Hippolyte, Homoeoscelis is
common in the branchial cavity of Diastylis and Iphinoe, and Aspidoecia on
the outside of the body of the Mysid Erythrops. The males and females live
together in the same marsupium, but the adult males retain the power of
roving about, and do not feed so much as the females, though their mouth-
parts are similarly constructed (Fig. 47). Representatives occur all over the
world, but the majority of species known at present are from the North Sea,
the most abundant being Stenochotheres egregius, parasitic on the
Gammarid Metopa bruzelii, Goës.
The male bears a median glandular thread on the forehead by which it
attaches itself to the females or to the host. Hansen considers that the family
is most closely allied to the Lernaeopodidae.
Page 104
Fig. 44.—Lernaea branchialis from the
Haddock, ♀, × 1. Ceph, cephalothorax; e.s, egg-
sacs. (After Scott.)
Haddock, ♀, × 1. Ceph, cephalothorax; e.s, egg-
sacs. (After Scott.)
Page 105
Fig. 45.—Lernaea branchialis, ♂ , × 10. Ant.1,
Ant.2, 1st and 2nd antennae; Br, brain; e, eye; g,
stomach; t, testis; vd, vas deferens; ves. sem,
vesicula seminalis. (After Claus.)
Ant.2, 1st and 2nd antennae; Br, brain; e, eye; g,
stomach; t, testis; vd, vas deferens; ves. sem,
vesicula seminalis. (After Claus.)
Page 106
Fig. 46.—Achtheres percarum. A, ♀, × 4; B, ♂,
× 4. Ant.2, 2nd antenna; g, stomach; Mx.2, 2nd
maxilla; Mxp, maxillipede; ov, ovary; ovd,
oviduct. (After Gerstaecker.)
× 4. Ant.2, 2nd antenna; g, stomach; Mx.2, 2nd
maxilla; Mxp, maxillipede; ov, ovary; ovd,
oviduct. (After Gerstaecker.)
Page 107
Fig. 47.—Ventral view of Stenochotheres
egregius (Choniostomatidae), ♂ . A, A′, 1st and
2nd antennae; M, mouth; Mx, 2nd maxilla; T, 1st
thoracic leg. (After Hansen.)
egregius (Choniostomatidae), ♂ . A, A′, 1st and
2nd antennae; M, mouth; Mx, 2nd maxilla; T, 1st
thoracic leg. (After Hansen.)
Page 108
Fig. 48.—Argulus foliaceus, young ♂, × 15. a1, a2, First and second antennae;
ab, abdomen; E, compound eye; l, liver; m, mandibles and first maxillae; mx,
second maxilla (the median eye is seen between the two second maxillae); mxp,
maxillipede; s.g, shell-gland; sp, spine; t, testis; 1, 4, first and fourth swimming
appendages. (After Claus.)
BRANCH II. BRANCHIURA.
ab, abdomen; E, compound eye; l, liver; m, mandibles and first maxillae; mx,
second maxilla (the median eye is seen between the two second maxillae); mxp,
maxillipede; s.g, shell-gland; sp, spine; t, testis; 1, 4, first and fourth swimming
appendages. (After Claus.)
BRANCH II. BRANCHIURA.
Page 109
Fam. Argulidae.[61]—We have yet to mention this group of fish-
parasites, related to the Copepoda, but occupying an isolated position. They
are ectoparasites upon various species of fish, Argulus foliaceus being
common in the fresh waters of Europe, infesting the branchial chamber or
the skin of fresh-water fish, but being frequently taken swimming freely in
the water. Both males and females can swim with great agility, and they
leave their hosts regularly at the breeding season in spring and autumn;
fertilisation is internal, and the female deposits the eggs on stones and other
objects. After leaving its host, an Argulus, if it cannot find a fish of the same
species, can live on almost any other species, and may even attack Frog
tadpoles; while the kinds that infest migratory fish can change with their
hosts from salt to fresh water, or the reverse. America appears to be the
home of the Argulidae.[62]
The structure of an Argulid is exhibited in Fig. 48. In front of the siphon,
within which the styliform mandibles and first maxillae work, there is a
poison-spine (sp); the appendages which correspond to the second maxillae
(mx) are modified into sucking discs, but in the genus Dolops they
terminate in normal claws. The next pair of appendages, usually spoken of
as maxillipedes (mxp), are clasping organs, and behind follow four pairs of
thoracic swimming feet (1–4). The body is foliaceous, and they always
apply themselves to their hosts with the long axis pointing forwards and
parallel to that of the host, while on various parts of the under surface of the
body are spines pointing backward which prevent the parasite being
brushed off by the passage of the host through the water. These animals,
alone among the Copepoda, possess compound eyes.
A short sketch has now been given of the variations in Copepod
organisation, but we cannot leave the subject without pointing out the rich
field which still remains for the morphologist, especially in determining the
true relationships of the parasitic families.
parasites, related to the Copepoda, but occupying an isolated position. They
are ectoparasites upon various species of fish, Argulus foliaceus being
common in the fresh waters of Europe, infesting the branchial chamber or
the skin of fresh-water fish, but being frequently taken swimming freely in
the water. Both males and females can swim with great agility, and they
leave their hosts regularly at the breeding season in spring and autumn;
fertilisation is internal, and the female deposits the eggs on stones and other
objects. After leaving its host, an Argulus, if it cannot find a fish of the same
species, can live on almost any other species, and may even attack Frog
tadpoles; while the kinds that infest migratory fish can change with their
hosts from salt to fresh water, or the reverse. America appears to be the
home of the Argulidae.[62]
The structure of an Argulid is exhibited in Fig. 48. In front of the siphon,
within which the styliform mandibles and first maxillae work, there is a
poison-spine (sp); the appendages which correspond to the second maxillae
(mx) are modified into sucking discs, but in the genus Dolops they
terminate in normal claws. The next pair of appendages, usually spoken of
as maxillipedes (mxp), are clasping organs, and behind follow four pairs of
thoracic swimming feet (1–4). The body is foliaceous, and they always
apply themselves to their hosts with the long axis pointing forwards and
parallel to that of the host, while on various parts of the under surface of the
body are spines pointing backward which prevent the parasite being
brushed off by the passage of the host through the water. These animals,
alone among the Copepoda, possess compound eyes.
A short sketch has now been given of the variations in Copepod
organisation, but we cannot leave the subject without pointing out the rich
field which still remains for the morphologist, especially in determining the
true relationships of the parasitic families.
Page 110
CHAPTER IV
CRUSTACEA (CONTINUED): CIRRIPEDIA—
PHENOMENA OF GROWTH AND SEX—OSTRACODA
Order III. Cirripedia.
The Cirripedes are medium-sized Crustacea, with the body consisting of
few segments, and enveloped in a mantle formed as a fold of the external
integument, which may be strongly protected by calcified plates. The
abdomen is greatly reduced. The larva, after hatching out as a Nauplius, and
passing through a Cypris stage, when it resembles an Ostracod, fixes itself
to a foreign object by means of the first antennae, and becomes a pupa,
which after profound changes gives rise to the adult.
All the Cirripedes, when adult, live either a fixed or parasitic existence,
and as so frequently happens with animals of this kind, they have departed
widely from the ordinary structure of the class to which they belong. Their
anomalous appearance and the mystery surrounding their propagation gave
rise, probably, to the old legend that the Barnacles (Lepadidae), which live
attached to pieces of floating timber, hatched out into Barnacle geese[63]; and
even so late as 1678, in the Royal Society’s Transactions, Sir Robert Moray
describes what he takes to be little birds enclosed in Barnacle shells,
washed ashore on the coast of Scotland: “The little Bill like that of a Goose,
the Eyes marked, the Head, Neck, Breast, Wings, Tail, and Feet formed, the
Feathers everywhere perfectly shaped and blackish coloured, and the Feet
like those of other Water-fowl, to my best remembrance.” Cuvier in his
classification of the animal kingdom included them in the Mollusca; and it
was not until 1830 that J. V. Thompson described their larval stages, and
showed conclusively that they belonged to the Crustacea. Since the work of
this naturalist a number of observers have securely founded our knowledge
of the group, but we may especially mention the epoch-making works of
Darwin,[64] Hoek,[65] and latterly of Gruvel.[66]
CRUSTACEA (CONTINUED): CIRRIPEDIA—
PHENOMENA OF GROWTH AND SEX—OSTRACODA
Order III. Cirripedia.
The Cirripedes are medium-sized Crustacea, with the body consisting of
few segments, and enveloped in a mantle formed as a fold of the external
integument, which may be strongly protected by calcified plates. The
abdomen is greatly reduced. The larva, after hatching out as a Nauplius, and
passing through a Cypris stage, when it resembles an Ostracod, fixes itself
to a foreign object by means of the first antennae, and becomes a pupa,
which after profound changes gives rise to the adult.
All the Cirripedes, when adult, live either a fixed or parasitic existence,
and as so frequently happens with animals of this kind, they have departed
widely from the ordinary structure of the class to which they belong. Their
anomalous appearance and the mystery surrounding their propagation gave
rise, probably, to the old legend that the Barnacles (Lepadidae), which live
attached to pieces of floating timber, hatched out into Barnacle geese[63]; and
even so late as 1678, in the Royal Society’s Transactions, Sir Robert Moray
describes what he takes to be little birds enclosed in Barnacle shells,
washed ashore on the coast of Scotland: “The little Bill like that of a Goose,
the Eyes marked, the Head, Neck, Breast, Wings, Tail, and Feet formed, the
Feathers everywhere perfectly shaped and blackish coloured, and the Feet
like those of other Water-fowl, to my best remembrance.” Cuvier in his
classification of the animal kingdom included them in the Mollusca; and it
was not until 1830 that J. V. Thompson described their larval stages, and
showed conclusively that they belonged to the Crustacea. Since the work of
this naturalist a number of observers have securely founded our knowledge
of the group, but we may especially mention the epoch-making works of
Darwin,[64] Hoek,[65] and latterly of Gruvel.[66]
Page 111
The young Cirripede is hatched out from the maternal mantle-cavity as a
free-swimming Nauplius, a larval form common to most of the
Entomostraca and to some Malacostraca; the Cirripede Nauplius (Fig. 49) is
characterised by the presence of well-developed frontal horns, and usually
by the long spiny processes which spring from various parts of the body. As
an introduction to the study of the group, it will be well to follow the
transformations of this larva in Lepas up to the period when it begins its
sessile existence. The liberated Nauplii swim freely near the surface of the
sea, and remaining in this condition for several days are dispersed widely
from their birthplace; they are then transformed by the process of moulting
into the second larval stage, known as the Cypris (Fig. 50), from its
resemblance to a bivalve Ostracod. The Cypris larva continues to swim
about by means of the six pairs of biramous thoracic legs until it finds a
suitable place on which to fix; in the case of Lepas fixation usually takes
place on loose floating logs; the Cypris fixes itself by means of the first
antennae, at the bases of which a large cement-gland secretes an adhesive
substance. The biramous swimming legs are cast off, and six pairs of
biramous cirri characteristic of the adult take their place; at this stage the
body has the appearance shown in Fig. 51. The region of the head at the
base of the antennae now becomes greatly swollen and elongated to form
the peduncle or stalk of the adult; the larval bivalve carapace is cast off and
on the external surface of the mantle the calcifications begin which will
give rise to the exoskeletal plates of the adult. This region is known as the
“capitulum” of the adult, as opposed to the “peduncle.” The young
Cirripede is now known as a pupa, and from this stage the adult form is
reached by a gradual transition.
free-swimming Nauplius, a larval form common to most of the
Entomostraca and to some Malacostraca; the Cirripede Nauplius (Fig. 49) is
characterised by the presence of well-developed frontal horns, and usually
by the long spiny processes which spring from various parts of the body. As
an introduction to the study of the group, it will be well to follow the
transformations of this larva in Lepas up to the period when it begins its
sessile existence. The liberated Nauplii swim freely near the surface of the
sea, and remaining in this condition for several days are dispersed widely
from their birthplace; they are then transformed by the process of moulting
into the second larval stage, known as the Cypris (Fig. 50), from its
resemblance to a bivalve Ostracod. The Cypris larva continues to swim
about by means of the six pairs of biramous thoracic legs until it finds a
suitable place on which to fix; in the case of Lepas fixation usually takes
place on loose floating logs; the Cypris fixes itself by means of the first
antennae, at the bases of which a large cement-gland secretes an adhesive
substance. The biramous swimming legs are cast off, and six pairs of
biramous cirri characteristic of the adult take their place; at this stage the
body has the appearance shown in Fig. 51. The region of the head at the
base of the antennae now becomes greatly swollen and elongated to form
the peduncle or stalk of the adult; the larval bivalve carapace is cast off and
on the external surface of the mantle the calcifications begin which will
give rise to the exoskeletal plates of the adult. This region is known as the
“capitulum” of the adult, as opposed to the “peduncle.” The young
Cirripede is now known as a pupa, and from this stage the adult form is
reached by a gradual transition.
Page 112
Fig. 49.—Nauplius larva of Lepas fascicularis, × 12. A1, A2, 1st and 2nd
antennae; B, brain; E, eye; H, fronto-lateral horn; M, mandible; S, stomach.
(After Groom.)
antennae; B, brain; E, eye; H, fronto-lateral horn; M, mandible; S, stomach.
(After Groom.)
Page 113
Fig. 50.—Cypris stage in the development of Lepas australis, × 15. A, Peduncle;
A.M, adductor muscle; C, caecum of oesophagus; C.g, cement-glands; Cr, cirri
(thoracic appendages); E, compound eye; E1, simple eye; G, ventral ganglia; I,
intestine; M, mouth; M.C, mantle-cavity; O, ovary; S, stomach. (After Hoek.)
The body of the adult Lepas is retracted into the mantle, and lies free in
the mantle-cavity, but is continuous anteriorly with the tissues of the
peduncle, into which the mantle does not extend. The thorax, with its six
pairs of legs, can be protruded from the mantle-cavity through the slit-like
opening which separates the two valves of the mantle along the ventral
middle line; and when the animal is feeding, the thoracic legs are so
protruded, and by their concerted waving action they drive the food-
particles in the water along the channel between them, until the particles
reach the oral cone, where they are masticated by the mandibles and two
pairs of maxillae, and so passed into the alimentary canal. When the animal
is disturbed it rapidly retracts its limbs, the valves of the mantle are closed
by means of a strong adductor muscle in the head, and the animal is
protected from all external influences. In the acorn-barnacles (Operculata),
which live in great numbers attached to rocks and other objects between
tide-marks, the body is constructed on a similar plan, save that there is no
stalk, and the body is completely enclosed in a hard calcareous box formed
from the mantle, which, when the valves are closed, as they always are
A.M, adductor muscle; C, caecum of oesophagus; C.g, cement-glands; Cr, cirri
(thoracic appendages); E, compound eye; E1, simple eye; G, ventral ganglia; I,
intestine; M, mouth; M.C, mantle-cavity; O, ovary; S, stomach. (After Hoek.)
The body of the adult Lepas is retracted into the mantle, and lies free in
the mantle-cavity, but is continuous anteriorly with the tissues of the
peduncle, into which the mantle does not extend. The thorax, with its six
pairs of legs, can be protruded from the mantle-cavity through the slit-like
opening which separates the two valves of the mantle along the ventral
middle line; and when the animal is feeding, the thoracic legs are so
protruded, and by their concerted waving action they drive the food-
particles in the water along the channel between them, until the particles
reach the oral cone, where they are masticated by the mandibles and two
pairs of maxillae, and so passed into the alimentary canal. When the animal
is disturbed it rapidly retracts its limbs, the valves of the mantle are closed
by means of a strong adductor muscle in the head, and the animal is
protected from all external influences. In the acorn-barnacles (Operculata),
which live in great numbers attached to rocks and other objects between
tide-marks, the body is constructed on a similar plan, save that there is no
stalk, and the body is completely enclosed in a hard calcareous box formed
from the mantle, which, when the valves are closed, as they always are
Page 114
during low tide, completely protect
the animal inside from desiccation or
danger of any kind. Besides the
cement-glands situated in the
peduncle, we can distinguish the
generative organs, consisting of a
pair of ovaries and testes, the
majority of Cirripedes being
hermaphrodite. The testes open at the
end of an elongated median penis
behind the thoracic limbs, while the
ovaries, situated in the peduncle,
have paired openings into the mantle-
cavity on either side of the head. A
pair of maxillary glands or kidneys
are present, and the alimentary canal
is provided with various digestive
glands. Special branchial organs are
not present in the Pedunculate
Cirripedes, but in the Operculate
genera two branchiae are formed
from the plications of the internal
Fig. 51.—Pupa of Lepas pectinata, × 8. A, surface of the mantle. There is no
Antenna; C, carina; M, adductor muscle; S,
scutum; T, tergum. (After Gruvel.) contractile heart, and the circulatory
system is poorly developed. The
Cirripedes are badly furnished with
sensory organs; the remains of a simple Nauplius eye may persist, situated
on the upper part of the stomach, but the chief sense-organs are the sensory
hairs upon the limbs.
the animal inside from desiccation or
danger of any kind. Besides the
cement-glands situated in the
peduncle, we can distinguish the
generative organs, consisting of a
pair of ovaries and testes, the
majority of Cirripedes being
hermaphrodite. The testes open at the
end of an elongated median penis
behind the thoracic limbs, while the
ovaries, situated in the peduncle,
have paired openings into the mantle-
cavity on either side of the head. A
pair of maxillary glands or kidneys
are present, and the alimentary canal
is provided with various digestive
glands. Special branchial organs are
not present in the Pedunculate
Cirripedes, but in the Operculate
genera two branchiae are formed
from the plications of the internal
Fig. 51.—Pupa of Lepas pectinata, × 8. A, surface of the mantle. There is no
Antenna; C, carina; M, adductor muscle; S,
scutum; T, tergum. (After Gruvel.) contractile heart, and the circulatory
system is poorly developed. The
Cirripedes are badly furnished with
sensory organs; the remains of a simple Nauplius eye may persist, situated
on the upper part of the stomach, but the chief sense-organs are the sensory
hairs upon the limbs.
Page 115
Fig. 52.—A, Dwarf male of Scalpellum vulgare, × 27; B, diagram of Stalked
Barnacle. a, Peduncle; al, alimentary canal; b, brain; c, carina; e, remains of
Nauplius eye; gl, cement-gland; m, mantle-cavity; o, its opening; ov, ovary; p,
penis; s, scutum; t, testis; tm, tergum, seen in A as the shaded body above the
reference-line of e and to the right of the carina, on the left of the figure.
The recent Cirripedes fall into six clearly defined Sub-orders.
Sub-Order 1. Pedunculata.
In this division, sometimes combined with the Operculata as Thoracica,
owing to the extremely reduced state of the abdomen, the body is borne on
a distinct stalk, and the bivalve arrangement of the mantle is clearly
retained. The mantle is protected externally by a number of calcareous
plates, the arrangement of which is typical of the various genera. It appears
that in the most primitive and geologically oldest Cirripedes, the probable
ancestors of the Pedunculate and Operculate sub-orders, the arrangement of
the plates was somewhat irregular, and they were far more numerous than in
the modern forms, so that passing from these older types to modern times
we witness a reduction in the number and a greater precision in the
arrangement of the skeletal parts.
Barnacle. a, Peduncle; al, alimentary canal; b, brain; c, carina; e, remains of
Nauplius eye; gl, cement-gland; m, mantle-cavity; o, its opening; ov, ovary; p,
penis; s, scutum; t, testis; tm, tergum, seen in A as the shaded body above the
reference-line of e and to the right of the carina, on the left of the figure.
The recent Cirripedes fall into six clearly defined Sub-orders.
Sub-Order 1. Pedunculata.
In this division, sometimes combined with the Operculata as Thoracica,
owing to the extremely reduced state of the abdomen, the body is borne on
a distinct stalk, and the bivalve arrangement of the mantle is clearly
retained. The mantle is protected externally by a number of calcareous
plates, the arrangement of which is typical of the various genera. It appears
that in the most primitive and geologically oldest Cirripedes, the probable
ancestors of the Pedunculate and Operculate sub-orders, the arrangement of
the plates was somewhat irregular, and they were far more numerous than in
the modern forms, so that passing from these older types to modern times
we witness a reduction in the number and a greater precision in the
arrangement of the skeletal parts.
Page 116
One of the most ancient Cirripedes
known is Turrilepas, which occurs in
the Silurian deposits of England, but
it is also known from earlier deposits,
while undoubted Cirripedes have
been found in the Cambrian of North
America. The body of Turrilepas is
enclosed in imbricating plates, as
shown in Fig. 53, A.
In Archaeolepas of the Upper
Jurassic (Lithographic slates of
Bavaria) the arrangement of scutes
typical of the Lepadidae is
Fig. 53.—A, Turrilepas wrightianus (Silurian), foreshadowed, but the whole of the
× 1; B, Archaeolepas redtenbacheri (Jurassic), ×
1. C, carina; R, rostrum; S, scutum; T, tergum.
peduncle is protected by rows of
(After Zittel.) plates (Fig. 53, B), as in Turrilepas.
The above-mentioned genera did
not survive into the Cretaceous period, their places being taken by the
genera Pollicipes and Scalpellum, which first appeared in the Silurian and
persist to the present time, the older and more primitive Pollicipes being
represented by about half a dozen living species, while the species of
Scalpellum are exceedingly numerous.
Fam. 1. Polyaspidae.—This family includes the three genera, Pollicipes,
Scalpellum, and Lithotrya.
Pollicipes is not only very ancient geologically (being found from the
Ordovician upward), but it preserves the primitive characteristic of
numerous skeletal plates, the peduncle being frequently covered with small
calcareous pieces, which graduate into the larger more regularly placed
scutes on the capitulum (Fig. 54). The species of this genus, many of which
are among the largest Cirripedes, are widely distributed in the temperate
and tropical seas, living for the most part attached to rocks and often in
deep water. P. cornucopia occurs off the English and Scottish coasts.
The members of the genus Scalpellum, which is represented by
exceedingly numerous species in the Cretaceous period, also possess a large
number of plates on the capitulum, and often on the peduncle as well, but
never so many as in Pollicipes. Although the arrangement of the plates
known is Turrilepas, which occurs in
the Silurian deposits of England, but
it is also known from earlier deposits,
while undoubted Cirripedes have
been found in the Cambrian of North
America. The body of Turrilepas is
enclosed in imbricating plates, as
shown in Fig. 53, A.
In Archaeolepas of the Upper
Jurassic (Lithographic slates of
Bavaria) the arrangement of scutes
typical of the Lepadidae is
Fig. 53.—A, Turrilepas wrightianus (Silurian), foreshadowed, but the whole of the
× 1; B, Archaeolepas redtenbacheri (Jurassic), ×
1. C, carina; R, rostrum; S, scutum; T, tergum.
peduncle is protected by rows of
(After Zittel.) plates (Fig. 53, B), as in Turrilepas.
The above-mentioned genera did
not survive into the Cretaceous period, their places being taken by the
genera Pollicipes and Scalpellum, which first appeared in the Silurian and
persist to the present time, the older and more primitive Pollicipes being
represented by about half a dozen living species, while the species of
Scalpellum are exceedingly numerous.
Fam. 1. Polyaspidae.—This family includes the three genera, Pollicipes,
Scalpellum, and Lithotrya.
Pollicipes is not only very ancient geologically (being found from the
Ordovician upward), but it preserves the primitive characteristic of
numerous skeletal plates, the peduncle being frequently covered with small
calcareous pieces, which graduate into the larger more regularly placed
scutes on the capitulum (Fig. 54). The species of this genus, many of which
are among the largest Cirripedes, are widely distributed in the temperate
and tropical seas, living for the most part attached to rocks and often in
deep water. P. cornucopia occurs off the English and Scottish coasts.
The members of the genus Scalpellum, which is represented by
exceedingly numerous species in the Cretaceous period, also possess a large
number of plates on the capitulum, and often on the peduncle as well, but
never so many as in Pollicipes. Although the arrangement of the plates
Page 117
varies much in the different species,
we may describe a fairly typical case,
that of the common Scalpellum
vulgare (Fig. 55, B).
The valves of the capitulum are
held together by the median dorsal
piece called the “carina”; the other
unpaired skeletal piece is the
“rostrum,” in front, just below the
place where the valves gape to allow
the protrusion of the limbs. The
paired pieces receive the names
“scutum,” “tergum,” and “laterals,”
and the peduncle is covered with
rows of small plates.
The genus Scalpellum is a very
large one, and is widely distributed,
though at the time at which Darwin
wrote only six species were known.
The reason for this is to be found in
the fact that the great majority of the
species live at great depths, so that
they remained unknown until the Fig. 54.—Pollicipes mitella, × 1. (After
expeditions of the Challenger and Darwin.)
other deep-sea expeditions brought
them to light. They may affix themselves, generally in considerable
numbers together, on branching organisms, such as Corals, Polyzoa, and
Hydroids, but often also on empty shells, rocks, and other foreign bodies.
The body is colourless or of a pale flesh colour, but a colony of these
animals, expanded and drooping in various attitudes from a piece of coral,
gives the appearance of some graceful exotic flower.
we may describe a fairly typical case,
that of the common Scalpellum
vulgare (Fig. 55, B).
The valves of the capitulum are
held together by the median dorsal
piece called the “carina”; the other
unpaired skeletal piece is the
“rostrum,” in front, just below the
place where the valves gape to allow
the protrusion of the limbs. The
paired pieces receive the names
“scutum,” “tergum,” and “laterals,”
and the peduncle is covered with
rows of small plates.
The genus Scalpellum is a very
large one, and is widely distributed,
though at the time at which Darwin
wrote only six species were known.
The reason for this is to be found in
the fact that the great majority of the
species live at great depths, so that
they remained unknown until the Fig. 54.—Pollicipes mitella, × 1. (After
expeditions of the Challenger and Darwin.)
other deep-sea expeditions brought
them to light. They may affix themselves, generally in considerable
numbers together, on branching organisms, such as Corals, Polyzoa, and
Hydroids, but often also on empty shells, rocks, and other foreign bodies.
The body is colourless or of a pale flesh colour, but a colony of these
animals, expanded and drooping in various attitudes from a piece of coral,
gives the appearance of some graceful exotic flower.
Page 118
Fig. 55.—A, Complemental male of Scalpellum peronii, × 20; B, hermaphrodite
individual of S. vulgare, × 2. a, Complemental males, in situ; b, rostrum. (A,
after Gruvel; B, after Darwin.)
Perhaps the most interesting feature of the genus is the remarkable
variation in the sexual constitution of some of the species. The great
majority of the Pedunculata and all the Operculata are hermaphrodites,
which habitually cross-fertilise one another, and this they are well fitted to
do, since they all live gregariously and are provided with a long exsertile
penis for transferring the spermatozoa from one to the other. In Pollicipes,
however, the individuals of which often live solitarily, it appears that self-
fertilisation may occur. In Scalpellum three different kinds of sexual
constitution may occur: (1) According to Hoek in S. balanoides, taken by
the Challenger, the individuals are ordinary cross-fertilising
individual of S. vulgare, × 2. a, Complemental males, in situ; b, rostrum. (A,
after Gruvel; B, after Darwin.)
Perhaps the most interesting feature of the genus is the remarkable
variation in the sexual constitution of some of the species. The great
majority of the Pedunculata and all the Operculata are hermaphrodites,
which habitually cross-fertilise one another, and this they are well fitted to
do, since they all live gregariously and are provided with a long exsertile
penis for transferring the spermatozoa from one to the other. In Pollicipes,
however, the individuals of which often live solitarily, it appears that self-
fertilisation may occur. In Scalpellum three different kinds of sexual
constitution may occur: (1) According to Hoek in S. balanoides, taken by
the Challenger, the individuals are ordinary cross-fertilising
Page 119
hermaphrodites. (2) In the great majority of species, including the common
S. vulgare, as originally described by Darwin, and since confirmed by Hoek
and Gruvel,[67] the individuals are hermaphrodite, but there are present
affixed to the adult hermaphrodites, just inside the opening of the valves in
a pocket of the mantle, a varying number of exceedingly minute males,
called by Darwin “complemental males.” These tiny organisms are really
little more than bags of spermatozoa, but they possess to varying degrees
the ordinary organs of the adult in a reduced condition. The male of S.
peronii (Fig. 55, A) retains the shape and skeletal plates of the ordinary
form, and differs chiefly in its reduced size; but the more common
condition is exhibited by the male of S. vulgare (Fig. 52, A), where the
scutes are reduced to vestiges round the mantle-opening, and almost the
whole of the body is occupied by the greatly developed generative organs.
(3) In a few species, e.g. S. velutinum and S. ornatum, the individuals are
purely dioecious, being either females of the ordinary structure resembling
the hermaphrodites of the other Lepadidae, or dwarfed males resembling
closely the complemental males described above for S. vulgare.
The nature and derivation of these various conditions will be discussed
when the parallel cases found in Ibla and among the Rhizocephala have
been described.
The remaining genus of the Polyaspidae, also characterised by the
presence of numerous skeletal plates on the capitulum, is Lithotrya (Fig.
56), which bores into rocks and shells, and is an inhabitant of the warm and
tropical seas.
The peduncle of the full-grown animal is completely imbedded in the
rock or shell to which it is attached, and at the basal end of the peduncle is
situated a cup composed of large irregular calcified pieces. This cup is,
however, not formed until the animal has ceased to burrow. The excavation
of the substratum is effected by means of a number of small rasping plates
which cover the peduncle, the whole being set in motion by the peduncular
muscles.
Fam. 2. Pentaspidae.—In this family are placed a number of genera, and
among them the common Lepas, the species of which possess typically five
skeletal plates, viz., a carina and a pair of scuta and of terga, the peduncle
being naked. These forms are a later development of Cirripede evolution,
and did not come into existence till Tertiary times. Some of them, e.g.
S. vulgare, as originally described by Darwin, and since confirmed by Hoek
and Gruvel,[67] the individuals are hermaphrodite, but there are present
affixed to the adult hermaphrodites, just inside the opening of the valves in
a pocket of the mantle, a varying number of exceedingly minute males,
called by Darwin “complemental males.” These tiny organisms are really
little more than bags of spermatozoa, but they possess to varying degrees
the ordinary organs of the adult in a reduced condition. The male of S.
peronii (Fig. 55, A) retains the shape and skeletal plates of the ordinary
form, and differs chiefly in its reduced size; but the more common
condition is exhibited by the male of S. vulgare (Fig. 52, A), where the
scutes are reduced to vestiges round the mantle-opening, and almost the
whole of the body is occupied by the greatly developed generative organs.
(3) In a few species, e.g. S. velutinum and S. ornatum, the individuals are
purely dioecious, being either females of the ordinary structure resembling
the hermaphrodites of the other Lepadidae, or dwarfed males resembling
closely the complemental males described above for S. vulgare.
The nature and derivation of these various conditions will be discussed
when the parallel cases found in Ibla and among the Rhizocephala have
been described.
The remaining genus of the Polyaspidae, also characterised by the
presence of numerous skeletal plates on the capitulum, is Lithotrya (Fig.
56), which bores into rocks and shells, and is an inhabitant of the warm and
tropical seas.
The peduncle of the full-grown animal is completely imbedded in the
rock or shell to which it is attached, and at the basal end of the peduncle is
situated a cup composed of large irregular calcified pieces. This cup is,
however, not formed until the animal has ceased to burrow. The excavation
of the substratum is effected by means of a number of small rasping plates
which cover the peduncle, the whole being set in motion by the peduncular
muscles.
Fam. 2. Pentaspidae.—In this family are placed a number of genera, and
among them the common Lepas, the species of which possess typically five
skeletal plates, viz., a carina and a pair of scuta and of terga, the peduncle
being naked. These forms are a later development of Cirripede evolution,
and did not come into existence till Tertiary times. Some of them, e.g.
Page 120
Oxynaspis, live at considerable
depths attached to corals, etc., but
large numbers float on the surface of
the sea, fixed often on logs and
wreckage of various kinds.
Dichelaspis is found attached to the
shells of large Crustacea.
Conchoderma is an interesting
genus, the species of which live
affixed to various floating objects,
the keels of ships, etc.; the mantle is
often brilliantly coloured, as in C.
virgata, and the skeletal plates are
reduced to the merest vestiges,
leaving the greater part of the body
fleshy.
Fam. 3. Tetraspidae.—This
family includes the single genus Ibla
(Fig. 58), which possesses only four
skeletal plates, a pair of terga and of
scuta, coloured blue, while the
peduncle is covered with brown
spines. There are only two very
similar species known, I. cumingii,
which is found attached to the
Fig. 56.—Lithotrya dorsalis, x 1. B, Basal peduncle of Pollicipes mitella, and I.
calcareous cup; C, carina; R, rostrum; S, scutum; quadrivalvis, living on masses of the
T, tergum. (After Darwin.)
Siphonophore Galeolaria
decumbens. These two species are
quite different in the partition of the sexes. In I. cumingii the large
individuals of normal structure are females, inside the mantle-cavities of
which are attached dwarf males of the form shown in Fig. 59.
These organisms have the peduncle buried completely in the substance of
the female’s mantle, inside which they live; they exhibit a degenerate
structure, but still retain two pairs of cirri. The large individuals of I.
quadrivalvis, on the other hand, are hermaphrodites, but they harbour
depths attached to corals, etc., but
large numbers float on the surface of
the sea, fixed often on logs and
wreckage of various kinds.
Dichelaspis is found attached to the
shells of large Crustacea.
Conchoderma is an interesting
genus, the species of which live
affixed to various floating objects,
the keels of ships, etc.; the mantle is
often brilliantly coloured, as in C.
virgata, and the skeletal plates are
reduced to the merest vestiges,
leaving the greater part of the body
fleshy.
Fam. 3. Tetraspidae.—This
family includes the single genus Ibla
(Fig. 58), which possesses only four
skeletal plates, a pair of terga and of
scuta, coloured blue, while the
peduncle is covered with brown
spines. There are only two very
similar species known, I. cumingii,
which is found attached to the
Fig. 56.—Lithotrya dorsalis, x 1. B, Basal peduncle of Pollicipes mitella, and I.
calcareous cup; C, carina; R, rostrum; S, scutum; quadrivalvis, living on masses of the
T, tergum. (After Darwin.)
Siphonophore Galeolaria
decumbens. These two species are
quite different in the partition of the sexes. In I. cumingii the large
individuals of normal structure are females, inside the mantle-cavities of
which are attached dwarf males of the form shown in Fig. 59.
These organisms have the peduncle buried completely in the substance of
the female’s mantle, inside which they live; they exhibit a degenerate
structure, but still retain two pairs of cirri. The large individuals of I.
quadrivalvis, on the other hand, are hermaphrodites, but they harbour
Page 121
within their mantles minute
complemental males similar to those
of I. cumingii, though they are rather
larger.
Fam. 4. Anaspidae.—This
includes the remaining pedunculate
genera, characterised by the fleshy
nature of the mantle and peduncle,
which are both entirely devoid of
calcifications. The species of Alepas
live upon Echinoderms and various
other animals; Chaetolepas upon
Sertularia, and Gymnolepas upon
Medusae. Anelasma squalicola is an
interesting form, living parasitically
upon the Elasmobranch fishes,
Selache maxima and Spinax niger in
the North Sea. The peduncle is
deeply buried in the flesh of the host,
so that only a portion of the dark blue
capitulum protrudes to the surface.
From the whole surface of the
peduncle a system of branching Fig. 57.—Conchoderma virgata, × 1. C, Carina;
S, scutum; T, tergum. (After Darwin.)
processes is given off, which ramify
far into the tissues of the fish, and
communicate inside the peduncle with the lacunar tissue, which is packed
round all the organs of the Cirripede. There can be small doubt that the
Anelasma derives its nutriment parasitically through this root-system, since
the cirri are mere fleshy lobes unadapted to securing food, and the
alimentary canal is always empty. This animal has a suggestive bearing on
the Rhizocephala, which, as will be shown, derive their nutriment from a
system of roots penetrating the host and growing out from what corresponds
morphologically to the peduncle.
complemental males similar to those
of I. cumingii, though they are rather
larger.
Fam. 4. Anaspidae.—This
includes the remaining pedunculate
genera, characterised by the fleshy
nature of the mantle and peduncle,
which are both entirely devoid of
calcifications. The species of Alepas
live upon Echinoderms and various
other animals; Chaetolepas upon
Sertularia, and Gymnolepas upon
Medusae. Anelasma squalicola is an
interesting form, living parasitically
upon the Elasmobranch fishes,
Selache maxima and Spinax niger in
the North Sea. The peduncle is
deeply buried in the flesh of the host,
so that only a portion of the dark blue
capitulum protrudes to the surface.
From the whole surface of the
peduncle a system of branching Fig. 57.—Conchoderma virgata, × 1. C, Carina;
S, scutum; T, tergum. (After Darwin.)
processes is given off, which ramify
far into the tissues of the fish, and
communicate inside the peduncle with the lacunar tissue, which is packed
round all the organs of the Cirripede. There can be small doubt that the
Anelasma derives its nutriment parasitically through this root-system, since
the cirri are mere fleshy lobes unadapted to securing food, and the
alimentary canal is always empty. This animal has a suggestive bearing on
the Rhizocephala, which, as will be shown, derive their nutriment from a
system of roots penetrating the host and growing out from what corresponds
morphologically to the peduncle.
Page 122
Fig. 58.—Ibla cumingii, ♀ , × 1. S, Scutum; T,
tergum. (After Darwin.)
tergum. (After Darwin.)
Page 123
Fig. 59.—Ibla cumingii, dwarf male, × 32. A,
Antennae; B, part of male imbedded in the
female, to which the torn membrane M belongs;
E, eye; Th, thoracic appendages or cirri. (After
Darwin.)
Antennae; B, part of male imbedded in the
female, to which the torn membrane M belongs;
E, eye; Th, thoracic appendages or cirri. (After
Darwin.)
Page 124
Fig. 60.—Diagram of the shell of an Operculate
Cirripede. a “Ala,” or overlapped portion of a
“compartment”; B, basis; C, carina; C.L, carino-
lateral; L, lateral; R, rostrum; r, “radius,” or
overlapping portion of a compartment; R.L,
rostro-lateral. (After Darwin.)
Sub-Order 2. Operculata.
The “acorn-barnacles” appear later in geological time than the earlier
stalked forms. Verruca and Chthamalus are found in the Chalk, and survive
down to the present day, but Balanus does not occur until middle Tertiary
times. Representatives of the last-named genus are familiar to every one, as
the hard sharp objects which cover rocks and piles near high-water mark on
every sea-coast. If we examine the hard skeleton of one of these animals,
we find that, unlike the Pedunculata, they possess no stalk, the capitulum
being fused on to the surface of attachment by a broad basal disc. Typically,
there may be considered to be eight skeletal pieces forming the outer ring
which invests the soft parts of the animal, an unpaired rostrum and carina,
and laterally a pair of rostro-lateral, lateral, and carino-lateral
“compartments,” as shown in Figs. 60, 63.
The skeletal ring is roofed over by a pair of terga at the carinal end and a
pair of scuta at the rostral end; these four plates make up the operculum by
which the animal can shut itself completely up in its shell, or between the
valves of which it can protrude its limbs for obtaining food.
Cirripede. a “Ala,” or overlapped portion of a
“compartment”; B, basis; C, carina; C.L, carino-
lateral; L, lateral; R, rostrum; r, “radius,” or
overlapping portion of a compartment; R.L,
rostro-lateral. (After Darwin.)
Sub-Order 2. Operculata.
The “acorn-barnacles” appear later in geological time than the earlier
stalked forms. Verruca and Chthamalus are found in the Chalk, and survive
down to the present day, but Balanus does not occur until middle Tertiary
times. Representatives of the last-named genus are familiar to every one, as
the hard sharp objects which cover rocks and piles near high-water mark on
every sea-coast. If we examine the hard skeleton of one of these animals,
we find that, unlike the Pedunculata, they possess no stalk, the capitulum
being fused on to the surface of attachment by a broad basal disc. Typically,
there may be considered to be eight skeletal pieces forming the outer ring
which invests the soft parts of the animal, an unpaired rostrum and carina,
and laterally a pair of rostro-lateral, lateral, and carino-lateral
“compartments,” as shown in Figs. 60, 63.
The skeletal ring is roofed over by a pair of terga at the carinal end and a
pair of scuta at the rostral end; these four plates make up the operculum by
which the animal can shut itself completely up in its shell, or between the
valves of which it can protrude its limbs for obtaining food.
Page 125
Fig. 61.—Balanus tintinnabulum, with the right
half of the shell and of the operculum removed,
seen from the right side. A, Antennae, the size of
which is exaggerated; A.M, adductor muscle; B,
basis; C, carina; Cr, cirri or thoracic
appendages; D, oviduct; G, ovary; L, lateral
compartment; Lb, labrum or upper lip; M, M,
depressor muscles of scutum and tergum; M.C,
mantle-cavity; O, orifice of excretory organ;
O.M, opercular membrane; R, rostrum; S,
scutum; St, region of stomach; T, tergum. (After
Darwin.)
Fig. 62.—Diagrammatic section of the growing
shell of Balanus porcatus. C, Canals; Ct, cuticle;
H, hypodermis (= epidermis); H′, part of shell
secreted by the hypodermis; Hl, hypodermal
lamina; M, part of shell secreted by the mantle.
(After Gruvel.)
The relation of the animal to its shell is shown in Fig. 61. The shell in the
Operculata is not merely secreted as a dead structure on the external surface
half of the shell and of the operculum removed,
seen from the right side. A, Antennae, the size of
which is exaggerated; A.M, adductor muscle; B,
basis; C, carina; Cr, cirri or thoracic
appendages; D, oviduct; G, ovary; L, lateral
compartment; Lb, labrum or upper lip; M, M,
depressor muscles of scutum and tergum; M.C,
mantle-cavity; O, orifice of excretory organ;
O.M, opercular membrane; R, rostrum; S,
scutum; St, region of stomach; T, tergum. (After
Darwin.)
Fig. 62.—Diagrammatic section of the growing
shell of Balanus porcatus. C, Canals; Ct, cuticle;
H, hypodermis (= epidermis); H′, part of shell
secreted by the hypodermis; Hl, hypodermal
lamina; M, part of shell secreted by the mantle.
(After Gruvel.)
The relation of the animal to its shell is shown in Fig. 61. The shell in the
Operculata is not merely secreted as a dead structure on the external surface
Page 126
of the epidermis, but represents a living calciferous tissue interpenetrated by
living laminae (Fig. 62, Hl) derived partly from the external hypodermis
and partly from the lining of the mantle. The hard parts of the shell usually
also contain spaces and canals (C).
The various forms of Acorn-
barnacle may be classified according
to the number of pieces that go to
make up the skeleton; thus starting
with the typical number eight (Fig.
63, A), we find that in various
degrees a fusion between
neighbouring pieces has taken place FCatophragmus
ig. 63.—Diagrams of shells of Operculata. A,
(Octomeridae); B, Balanus,
in the different families. Coronula, etc. (Hexameridae); C, Tetraclita
Fam. 1. Verrucidae.—The ancient (Tetrameridae). C, carina; C.L, carino-lateral; L,
lateral; R, rostrum; R.L, rostro-lateral.
genus Verruca, which is still widely
distributed in all seas, and is found
fixed upon foreign objects on the sea-bottom at various depths, is
interesting on account of the asymmetry of its shell, which bears a different
aspect according to which side one regards it from. This asymmetry is
brought about by the skeletal pieces (carina, rostrum, and paired terga and
scuta) shifting their positions after fixation has taken place.
Fam. 2. Octomeridae.—In this family the eight plates composing the
shell are separate and unfused (Fig. 63, A). The majority of the species
come from the Southern hemisphere, e.g. the members of the genera
Catophragmus and Octomeris, but Pachylasma giganteum occurs in deep
water in the Mediterranean, where it has been found fixed upon Millepore
corals.
Fam. 3. Hexameridae.—This family includes by far the greater number
of the Acorn-barnacles, in which only six plates are present, the laterals
having fused with the carino-laterals (Fig. 63, B). The very large genus
Balanus belongs here, the common B. tintinnabulum of our coasts being
found all over the world, and occurring under a number of inconstant
varietal forms. Especial interest attaches to certain other genera, from their
habit of living parasitically on soft-bodied animals, whose flesh they
penetrate.
living laminae (Fig. 62, Hl) derived partly from the external hypodermis
and partly from the lining of the mantle. The hard parts of the shell usually
also contain spaces and canals (C).
The various forms of Acorn-
barnacle may be classified according
to the number of pieces that go to
make up the skeleton; thus starting
with the typical number eight (Fig.
63, A), we find that in various
degrees a fusion between
neighbouring pieces has taken place FCatophragmus
ig. 63.—Diagrams of shells of Operculata. A,
(Octomeridae); B, Balanus,
in the different families. Coronula, etc. (Hexameridae); C, Tetraclita
Fam. 1. Verrucidae.—The ancient (Tetrameridae). C, carina; C.L, carino-lateral; L,
lateral; R, rostrum; R.L, rostro-lateral.
genus Verruca, which is still widely
distributed in all seas, and is found
fixed upon foreign objects on the sea-bottom at various depths, is
interesting on account of the asymmetry of its shell, which bears a different
aspect according to which side one regards it from. This asymmetry is
brought about by the skeletal pieces (carina, rostrum, and paired terga and
scuta) shifting their positions after fixation has taken place.
Fam. 2. Octomeridae.—In this family the eight plates composing the
shell are separate and unfused (Fig. 63, A). The majority of the species
come from the Southern hemisphere, e.g. the members of the genera
Catophragmus and Octomeris, but Pachylasma giganteum occurs in deep
water in the Mediterranean, where it has been found fixed upon Millepore
corals.
Fam. 3. Hexameridae.—This family includes by far the greater number
of the Acorn-barnacles, in which only six plates are present, the laterals
having fused with the carino-laterals (Fig. 63, B). The very large genus
Balanus belongs here, the common B. tintinnabulum of our coasts being
found all over the world, and occurring under a number of inconstant
varietal forms. Especial interest attaches to certain other genera, from their
habit of living parasitically on soft-bodied animals, whose flesh they
penetrate.
Page 127
Coronula diadema and Tubicinella trachealis live embedded in the skin
of whales, the shell of the first-named being of a highly complicated
structure with hollow triangular compartments into which the mantle is
drawn out.
Xenobalanus globicipitis lives attached to various Cetacea, and is
remarkable for the rudimentary condition of its skeleton, the six plates of
which form a mere disc of attachment from which the greatly elongated
naked body rises, resembling one of the naked Stalked Barnacles.
Fam. 4 Tetrameridae.—In this family only four skeletal plates are
present (Fig. 63, C). This family is chiefly confined to tropical seas or those
of the Southern hemisphere. The chief genera are Tetraclita and Pyrgoma,
found in British seas.
Sub-Order 3. Acrothoracica.
Gruvel includes in this sub-order four genera (Alcippe, Cryptophialus,
Kochlorine, and Lithoglyptes) the species of which live in cavities
excavated in the shells of molluscs or in the hard parts of corals.
of whales, the shell of the first-named being of a highly complicated
structure with hollow triangular compartments into which the mantle is
drawn out.
Xenobalanus globicipitis lives attached to various Cetacea, and is
remarkable for the rudimentary condition of its skeleton, the six plates of
which form a mere disc of attachment from which the greatly elongated
naked body rises, resembling one of the naked Stalked Barnacles.
Fam. 4 Tetrameridae.—In this family only four skeletal plates are
present (Fig. 63, C). This family is chiefly confined to tropical seas or those
of the Southern hemisphere. The chief genera are Tetraclita and Pyrgoma,
found in British seas.
Sub-Order 3. Acrothoracica.
Gruvel includes in this sub-order four genera (Alcippe, Cryptophialus,
Kochlorine, and Lithoglyptes) the species of which live in cavities
excavated in the shells of molluscs or in the hard parts of corals.
Page 128
Fig. 64.—Alcippe lampas. A, ♀, × about 10, seen from the right side, with part
of the right half of the animal removed; B, dwarf male, × about 30. A.M,
adductor muscle; An, antenna; C, 1st pair of cirri; Cr, posterior thoracic
appendages; E, eye; G, testis; M.C, mantle-cavity; O, ovary; P, penis; T,
penultimate thoracic segment; V. vesicula seminalis. (After Darwin.)
Darwin discovered and described Cryptophialus minutus, and placed it in
a sub-order Abdominalia, believing that it was distinguished from all the
foregoing Cirripedes by the presence of a well-developed abdomen. Since
the discovery of other allied genera, it has been decided that the abdomen is
equally reduced in these forms, and that the terminal appendages do not
belong to this region, but to the thorax.
The sexes are separate. The body of the female (Fig. 64, A) is enclosed in
a chitinous mantle, armed with teeth by which the excavation is effected,
and is attached to the cavity in the host by means of a horny disc. Upon this
disc the dwarf males (B) are found.
Alcippe lampas inhabits holes on the inner surface of dead Fusus and
Buccinum shells; Cryptophialus minutus the shells of Concholepas
peruviana; C. striatus [68] the plates of Chiton; Kochlorine hamata the shells
of Haliotis; and Lithoglyptes varians shells and corals from the Indian
Ocean.
of the right half of the animal removed; B, dwarf male, × about 30. A.M,
adductor muscle; An, antenna; C, 1st pair of cirri; Cr, posterior thoracic
appendages; E, eye; G, testis; M.C, mantle-cavity; O, ovary; P, penis; T,
penultimate thoracic segment; V. vesicula seminalis. (After Darwin.)
Darwin discovered and described Cryptophialus minutus, and placed it in
a sub-order Abdominalia, believing that it was distinguished from all the
foregoing Cirripedes by the presence of a well-developed abdomen. Since
the discovery of other allied genera, it has been decided that the abdomen is
equally reduced in these forms, and that the terminal appendages do not
belong to this region, but to the thorax.
The sexes are separate. The body of the female (Fig. 64, A) is enclosed in
a chitinous mantle, armed with teeth by which the excavation is effected,
and is attached to the cavity in the host by means of a horny disc. Upon this
disc the dwarf males (B) are found.
Alcippe lampas inhabits holes on the inner surface of dead Fusus and
Buccinum shells; Cryptophialus minutus the shells of Concholepas
peruviana; C. striatus [68] the plates of Chiton; Kochlorine hamata the shells
of Haliotis; and Lithoglyptes varians shells and corals from the Indian
Ocean.
Page 129
Sub-Order 4. Ascothoracica.
These are small hermaphrodite animals completely enveloped in a soft
mantle, which live attached to and partly buried in various organisms, such
as the branching Black Corals (Gerardia). They retain the thoracic
appendages in a modified state, and the body is segmented into a number of
somites, the last of which probably represents an abdomen.
Laura gerardiae, described by Lacaze Duthiers,[69] is parasitic on the
stem of the “Black Coral,” Gerardia (vol. i. p. 406); it has the shape of a
broad bean, the body being entirely enclosed in a soft mantle, with the
orifice in the position corresponding to the hilum of a bean. The body lying
in the mantle is composed of eleven segments, and is curved into an S-
shape. Its internal anatomy is entirely on the plan of an ordinary Cirripede.
Petrarca bathyactidis, G. H. Fowler,[70] was found in the mesenteric
chambers of the coral Bathyactis, dredged by the Challenger from 4000
metres. The body is nearly spherical, and the mantle-opening forms a long
slit on the ventral surface. The mantle is soft, but is furnished on the ventral
surface with short spines.
The antennae, which form the organs of fixation, remain very much in
the state characteristic of the Cypris larvae of other Cirripedes, being
furnished with two terminal hooks by which attachment is effected. The
thoracic appendages, of which there are the normal number six, are reduced
flabellate structures, and the abdomen forms an indefinitely segmented lobe
of considerable size.
The animal appears to be in an arrested state of development, and so
retains some of the characteristics of the Cypris larvae, but it is very
doubtful how far these characters can be considered primitive.
Other forms are Dendrogaster astericola on Echinoderms, and Synagoga
mira on the “Black Coral,” Parantipathes larix, at Naples.
Sub-Order 5. Apoda.
Darwin described a small hermaphrodite parasite in the mantle chamber
of Alepas cornuta from Saint Vincent, West Indies, which he named
Proteolepas bivincta.
These are small hermaphrodite animals completely enveloped in a soft
mantle, which live attached to and partly buried in various organisms, such
as the branching Black Corals (Gerardia). They retain the thoracic
appendages in a modified state, and the body is segmented into a number of
somites, the last of which probably represents an abdomen.
Laura gerardiae, described by Lacaze Duthiers,[69] is parasitic on the
stem of the “Black Coral,” Gerardia (vol. i. p. 406); it has the shape of a
broad bean, the body being entirely enclosed in a soft mantle, with the
orifice in the position corresponding to the hilum of a bean. The body lying
in the mantle is composed of eleven segments, and is curved into an S-
shape. Its internal anatomy is entirely on the plan of an ordinary Cirripede.
Petrarca bathyactidis, G. H. Fowler,[70] was found in the mesenteric
chambers of the coral Bathyactis, dredged by the Challenger from 4000
metres. The body is nearly spherical, and the mantle-opening forms a long
slit on the ventral surface. The mantle is soft, but is furnished on the ventral
surface with short spines.
The antennae, which form the organs of fixation, remain very much in
the state characteristic of the Cypris larvae of other Cirripedes, being
furnished with two terminal hooks by which attachment is effected. The
thoracic appendages, of which there are the normal number six, are reduced
flabellate structures, and the abdomen forms an indefinitely segmented lobe
of considerable size.
The animal appears to be in an arrested state of development, and so
retains some of the characteristics of the Cypris larvae, but it is very
doubtful how far these characters can be considered primitive.
Other forms are Dendrogaster astericola on Echinoderms, and Synagoga
mira on the “Black Coral,” Parantipathes larix, at Naples.
Sub-Order 5. Apoda.
Darwin described a small hermaphrodite parasite in the mantle chamber
of Alepas cornuta from Saint Vincent, West Indies, which he named
Proteolepas bivincta.
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The body (Fig. 65) is distinctly
segmented into eleven somites, the
last three of which are supposed to
belong to the abdomen; there are no
appendages except the antennae by
which fixation is effected. The
mouth-parts are of normal
constitution.
This animal has not been found
again since Darwin’s discovery, but
Hansen[71] describes a number of
Fig. 65.—Proteolepas bivincta, × 26. A,
Antennae; a, b, 1st and 2nd abdominal
peculiar Nauplius larvae taken in the
segments; O, ovary; P, penis; T, telson; 1–8, plankton of various regions, which he
thoracic segments. (After Darwin.) argues probably belong to members
of this group. A wide field of work is
offered in attempting to find the adults into which various larvae grow.
Sub-Order 6. Rhizocephala.[72]
These remarkable animals are Cirripedes which have taken to living
parasitically on various kinds of Crustacea; the majority infest species of
Decapoda, e.g. Peltogaster on Hermit-Crabs, Sacculina on a number of
Brachyura, Sylon on Shrimps, Lernaeodiscus on Galathea; but one genus,
Duplorbis, has been found in the marsupium of the Isopod Calathura
brachiata from Greenland. Most of the species are solitary, but a few, e.g.
Peltogaster sulcatus, are social. In the adult state the body consists of two
portions: a soft bag-like structure, external to the host, carrying the
reproductive, nervous, and muscular organs, and attached to some part of
the host’s abdomen by means of a chitinous ring; and a system of branching
roots inside the host’s body, which spring from the ring of attachment and
supply the external body with nourishment.
The structure of the external bag-like portion is very simple, and varies
only in details, chiefly of symmetry, in the different genera. In Peltogaster,
which preserves the simplest symmetrical arrangement of the organs, a
diagrammatic section through the long axis of the body (Fig. 66) shows that
it consists of a muscular mantle (m) surrounding a visceral mass, and
segmented into eleven somites, the
last three of which are supposed to
belong to the abdomen; there are no
appendages except the antennae by
which fixation is effected. The
mouth-parts are of normal
constitution.
This animal has not been found
again since Darwin’s discovery, but
Hansen[71] describes a number of
Fig. 65.—Proteolepas bivincta, × 26. A,
Antennae; a, b, 1st and 2nd abdominal
peculiar Nauplius larvae taken in the
segments; O, ovary; P, penis; T, telson; 1–8, plankton of various regions, which he
thoracic segments. (After Darwin.) argues probably belong to members
of this group. A wide field of work is
offered in attempting to find the adults into which various larvae grow.
Sub-Order 6. Rhizocephala.[72]
These remarkable animals are Cirripedes which have taken to living
parasitically on various kinds of Crustacea; the majority infest species of
Decapoda, e.g. Peltogaster on Hermit-Crabs, Sacculina on a number of
Brachyura, Sylon on Shrimps, Lernaeodiscus on Galathea; but one genus,
Duplorbis, has been found in the marsupium of the Isopod Calathura
brachiata from Greenland. Most of the species are solitary, but a few, e.g.
Peltogaster sulcatus, are social. In the adult state the body consists of two
portions: a soft bag-like structure, external to the host, carrying the
reproductive, nervous, and muscular organs, and attached to some part of
the host’s abdomen by means of a chitinous ring; and a system of branching
roots inside the host’s body, which spring from the ring of attachment and
supply the external body with nourishment.
The structure of the external bag-like portion is very simple, and varies
only in details, chiefly of symmetry, in the different genera. In Peltogaster,
which preserves the simplest symmetrical arrangement of the organs, a
diagrammatic section through the long axis of the body (Fig. 66) shows that
it consists of a muscular mantle (m) surrounding a visceral mass, and
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enclosing a mantle-cavity (mc) or
brood-pouch, which stretches
everywhere between mantle and
visceral mass, except along the
surface by which the parasite is
attached to its host, where a
mesentery (mes) is formed. The ring
of attachment is situated in the
middle of this mesentery; the mantle-
cavity, which is completely lined
Fig. 66.—Nearly median longitudinal section
(diagrammatic) of Peltogaster. gn, Brain; m, externally and internally with chitin,
mantle; mc, mantle-cavity; mes, mesentery; op, opens anteriorly by means of a
mantle-opening; ov, ovary; ovd, oviduct; ring, circular aperture (op) guarded by a
ring of attachment; t, testis; vd, vas deferens.
sphincter muscle. The visceral mass
is composed chiefly of the two
ovaries (ov), which open on either
side of the mesentery by means of a
pair of oviducts (ovd); the paired
testes (t) are small tubes lying
posteriorly in the mesentery, and the
nervous ganglion (gn) lies in the
mesentery between oviducts and
mantle-opening. A comparison with
Fig. 67.—Diagrammatic median longitudinal
the condition of a normal Cirripede section through a normal Cirripede, gn, Brain;
(Fig. 67) shows us that the op, mantle-opening; ovd, oviduct; vd, vas
mesenterial surface of the parasite by deferens.
which it is fixed corresponds to the
dorsal surface of an ordinary Pedunculate Cirripede, and that the ring of
attachment corresponds with the stalk or peduncle of a Lepas. The root-
system passes out through the ring of attachment into the body of the host,
and ramifies round the organs of the crab; the roots are covered externally
with a thin chitinous investment, and consist of an epithelium and an
internal mass of branching cells continuous with the lacunar tissue in the
visceral mass.
brood-pouch, which stretches
everywhere between mantle and
visceral mass, except along the
surface by which the parasite is
attached to its host, where a
mesentery (mes) is formed. The ring
of attachment is situated in the
middle of this mesentery; the mantle-
cavity, which is completely lined
Fig. 66.—Nearly median longitudinal section
(diagrammatic) of Peltogaster. gn, Brain; m, externally and internally with chitin,
mantle; mc, mantle-cavity; mes, mesentery; op, opens anteriorly by means of a
mantle-opening; ov, ovary; ovd, oviduct; ring, circular aperture (op) guarded by a
ring of attachment; t, testis; vd, vas deferens.
sphincter muscle. The visceral mass
is composed chiefly of the two
ovaries (ov), which open on either
side of the mesentery by means of a
pair of oviducts (ovd); the paired
testes (t) are small tubes lying
posteriorly in the mesentery, and the
nervous ganglion (gn) lies in the
mesentery between oviducts and
mantle-opening. A comparison with
Fig. 67.—Diagrammatic median longitudinal
the condition of a normal Cirripede section through a normal Cirripede, gn, Brain;
(Fig. 67) shows us that the op, mantle-opening; ovd, oviduct; vd, vas
mesenterial surface of the parasite by deferens.
which it is fixed corresponds to the
dorsal surface of an ordinary Pedunculate Cirripede, and that the ring of
attachment corresponds with the stalk or peduncle of a Lepas. The root-
system passes out through the ring of attachment into the body of the host,
and ramifies round the organs of the crab; the roots are covered externally
with a thin chitinous investment, and consist of an epithelium and an
internal mass of branching cells continuous with the lacunar tissue in the
visceral mass.
Page 132
Fig. 68.—Development of Sacculina neglecta. A, Nauplius stage, × about 70; B,
Cypris stage, × about 70. A1, A2, 1st and 2nd antennae of Nauplius; Ab,
abdomen; Ant, antenna of Cypris; E, undifferentiated cells; F, frontal horn; G,
glands of Cypris; H, tendon of Cypris; M, mandible; T, tentacles.
The developmental history of the Rhizocephala is one of the most
remarkable that embryology has hitherto revealed. It has been most
accurately followed in the case of Sacculina. The young are hatched out in
great numbers from the maternal mantle-cavity as small Nauplii (Fig. 68, A)
of a typical Cirripede nature, but without any alimentary canal. They swim
near the surface of the sea, and become transformed into Cypris larvae of a
typical character (Fig. 68, B). The Cypris larva, after a certain period of free
existence, seeks out a crab and fixes itself by means of the hooks on its
antennae to a hair on any part of the crab’s body. Various races of Sacculina
are known which infest about fifty different species of crabs in various seas;
the best known are S. carcini parasitic on Carcinus maenas at Plymouth and
Roscoff, and S. neglecta on Inachus mauritanicus at Naples. The antenna,
by which the Cypris is fixed, penetrates the base of the hair; the appendages
are thrown away, and a small mass of undifferentiated cells is passed down
Cypris stage, × about 70. A1, A2, 1st and 2nd antennae of Nauplius; Ab,
abdomen; Ant, antenna of Cypris; E, undifferentiated cells; F, frontal horn; G,
glands of Cypris; H, tendon of Cypris; M, mandible; T, tentacles.
The developmental history of the Rhizocephala is one of the most
remarkable that embryology has hitherto revealed. It has been most
accurately followed in the case of Sacculina. The young are hatched out in
great numbers from the maternal mantle-cavity as small Nauplii (Fig. 68, A)
of a typical Cirripede nature, but without any alimentary canal. They swim
near the surface of the sea, and become transformed into Cypris larvae of a
typical character (Fig. 68, B). The Cypris larva, after a certain period of free
existence, seeks out a crab and fixes itself by means of the hooks on its
antennae to a hair on any part of the crab’s body. Various races of Sacculina
are known which infest about fifty different species of crabs in various seas;
the best known are S. carcini parasitic on Carcinus maenas at Plymouth and
Roscoff, and S. neglecta on Inachus mauritanicus at Naples. The antenna,
by which the Cypris is fixed, penetrates the base of the hair; the appendages
are thrown away, and a small mass of undifferentiated cells is passed down
Page 133
the antenna into the body-cavity of the crab. Arrived in the body-cavity it
appears that this small mass of cells is carried about in the blood-stream
until it reaches the spaces round the intestine in the thorax. Here it becomes
applied to the intestine, usually at its upper part, immediately beneath the
stomach of the crab (Fig. 69), and from this point it proceeds to throw out
roots in all directions, and as it grows to extend its main bulk, called the
central tumour (c.t), towards the lower part of the intestine. As the posterior
border of the central tumour grows down towards the hind-gut, the future
organs of the adult Sacculina become differentiated in its substance; the
mantle-cavity being excavated and surrounding the rudiment of the visceral
mass, while as the central tumour grows downwards it leaves behind it an
ever extending system of roots. When the central tumour in process of
differentiation has reached the unpaired diverticulum of the crab’s intestine,
at the junction between thorax and abdomen, all the adult organs are laid
down in miniature, and the whole structure is surrounded by an additional
sac formed by invagination known as the perivisceral space (Fig. 70). The
young “Sacculina interna” remains in this position for some time, and being
applied to the ventral abdominal tissues of the crab just at the point where
thorax and abdomen join, or a little below it, it causes the crab’s epithelium
to degenerate, so that when the crab moults, a little hole is left in this region
of the same size as the body of the Sacculina, owing to the failure of the
epithelium to form chitin here; and thus the little parasite is pushed through
this hole and comes to the exterior as the adolescent “Sacculina externa.”
From this point onwards the crab, being inhibited in its growth through the
action of the parasite, never moults again; so that the Sacculina occupies a
safe position protruding from the crab’s abdomen, which laps over it and
protects it. The remarkable features of this development are, firstly, the
difficulty of understanding how the developing embryo is directed in its
complicated wanderings so as always to reach the same spot where it is
destined to come to the exterior; and, secondly, the loss after the Cypris
stage of all the organs and the resumption of an embryonic undifferentiated
state from which the adult is newly evolved. A certain parallel to this
history is found in that of the Monstrillidae, described on pp. 64–66.
The Rhizocephala are hermaphrodite with the possible exception of
Sylon, which appears to be female and perhaps parthenogenetic, no male
having been seen; but unlike most other hermaphrodite Cirripedes, they
reproduce by a continual round of self-fertilisation. This is the more
appears that this small mass of cells is carried about in the blood-stream
until it reaches the spaces round the intestine in the thorax. Here it becomes
applied to the intestine, usually at its upper part, immediately beneath the
stomach of the crab (Fig. 69), and from this point it proceeds to throw out
roots in all directions, and as it grows to extend its main bulk, called the
central tumour (c.t), towards the lower part of the intestine. As the posterior
border of the central tumour grows down towards the hind-gut, the future
organs of the adult Sacculina become differentiated in its substance; the
mantle-cavity being excavated and surrounding the rudiment of the visceral
mass, while as the central tumour grows downwards it leaves behind it an
ever extending system of roots. When the central tumour in process of
differentiation has reached the unpaired diverticulum of the crab’s intestine,
at the junction between thorax and abdomen, all the adult organs are laid
down in miniature, and the whole structure is surrounded by an additional
sac formed by invagination known as the perivisceral space (Fig. 70). The
young “Sacculina interna” remains in this position for some time, and being
applied to the ventral abdominal tissues of the crab just at the point where
thorax and abdomen join, or a little below it, it causes the crab’s epithelium
to degenerate, so that when the crab moults, a little hole is left in this region
of the same size as the body of the Sacculina, owing to the failure of the
epithelium to form chitin here; and thus the little parasite is pushed through
this hole and comes to the exterior as the adolescent “Sacculina externa.”
From this point onwards the crab, being inhibited in its growth through the
action of the parasite, never moults again; so that the Sacculina occupies a
safe position protruding from the crab’s abdomen, which laps over it and
protects it. The remarkable features of this development are, firstly, the
difficulty of understanding how the developing embryo is directed in its
complicated wanderings so as always to reach the same spot where it is
destined to come to the exterior; and, secondly, the loss after the Cypris
stage of all the organs and the resumption of an embryonic undifferentiated
state from which the adult is newly evolved. A certain parallel to this
history is found in that of the Monstrillidae, described on pp. 64–66.
The Rhizocephala are hermaphrodite with the possible exception of
Sylon, which appears to be female and perhaps parthenogenetic, no male
having been seen; but unlike most other hermaphrodite Cirripedes, they
reproduce by a continual round of self-fertilisation. This is the more
Page 134
remarkable in that the vestiges of
what appears to be a male sex are
still found in Sacculina and
Peltogaster; certain of the Cypris
larvae in these genera, instead of
fixing on and inoculating other crabs,
become attached round the mantle-
openings of young parasites of the
same species as themselves, which
have recently attained to the exterior
of their hosts (Fig. 71). These larvae,
which remind us of the
complemental males in Scalpellum,
etc., never produce spermatozoa, but
rapidly degenerate where they are
fixed, and appear never to play any
rôle in the reproduction of their
species. The nature of this
remarkable phenomenon, together
Fig. 69.—The mid-gut of Inachus mauritanicus with the sexual condition of the
with a young Sacculina overlying it, × 2. c.t, Cirripedes in general, will be
“Central tumour” of the parasite; d.i, d.s,
inferior and superior diverticula of alimentary discussed in the next section.
canal of host; n, “nucleus,” or body-rudiment of Much remains to be elucidated in
Sacculina; r, its roots; x, definitive position of
the parasite. the life-histories of these curious
animals, and it seems probable that
intermediate stages may exist,
showing us how the extreme discontinuity of development has been
reached. Suggestive in this respect is the newly discovered parasite of the
Isopod, Calathura, which the author has named Duplorbis calathurae.[73]
This animal does not appear to possess a root-system, but is attached to its
host by a tube which passes right through the mesentery and opens into the
mantle-cavity of the parasite. It may be suggested that this tube corresponds
to the stalk of the normal Cirripede, but its exact mode of formation would
certainly throw much light on the question of Rhizocephalan development.
what appears to be a male sex are
still found in Sacculina and
Peltogaster; certain of the Cypris
larvae in these genera, instead of
fixing on and inoculating other crabs,
become attached round the mantle-
openings of young parasites of the
same species as themselves, which
have recently attained to the exterior
of their hosts (Fig. 71). These larvae,
which remind us of the
complemental males in Scalpellum,
etc., never produce spermatozoa, but
rapidly degenerate where they are
fixed, and appear never to play any
rôle in the reproduction of their
species. The nature of this
remarkable phenomenon, together
Fig. 69.—The mid-gut of Inachus mauritanicus with the sexual condition of the
with a young Sacculina overlying it, × 2. c.t, Cirripedes in general, will be
“Central tumour” of the parasite; d.i, d.s,
inferior and superior diverticula of alimentary discussed in the next section.
canal of host; n, “nucleus,” or body-rudiment of Much remains to be elucidated in
Sacculina; r, its roots; x, definitive position of
the parasite. the life-histories of these curious
animals, and it seems probable that
intermediate stages may exist,
showing us how the extreme discontinuity of development has been
reached. Suggestive in this respect is the newly discovered parasite of the
Isopod, Calathura, which the author has named Duplorbis calathurae.[73]
This animal does not appear to possess a root-system, but is attached to its
host by a tube which passes right through the mesentery and opens into the
mantle-cavity of the parasite. It may be suggested that this tube corresponds
to the stalk of the normal Cirripede, but its exact mode of formation would
certainly throw much light on the question of Rhizocephalan development.
Page 135
Fig. 70.—Later stage in the development of the
“Sacculina interna,” × 2. b, Body of Sacculina;
c.t, “central tumour”; d.i, d.s, inferior and
superior diverticula of alimentary canal of host;
o, opening of perivisceral cavity of Sacculina; r,
its roots.
“Sacculina interna,” × 2. b, Body of Sacculina;
c.t, “central tumour”; d.i, d.s, inferior and
superior diverticula of alimentary canal of host;
o, opening of perivisceral cavity of Sacculina; r,
its roots.
Page 136
Fig. 71.—Fourteen Cypris larvae fixed round
the mantle-opening (o) of a young Sacculina
externa, × 20.
Phenomena of Growth and Sex in the Crustacea.
In the foregoing account of the Cirripedia we have met with certain
peculiar sexual relations in which closely allied species exhibit marked
differences in regard to the distribution of the qualities of sex among their
individuals; we have seen that the majority of species are hermaphrodite,
unlike most Crustacea which, with the other exception of the parasitic
Isopoda, are normally dioecious; and that in some species complemental
males exist side by side with the hermaphrodites, while, in yet others, the
individuals are either females or dwarf males.
Before examining the causes of these conditions, it will be opportune to
consider a number of facts which throw light on the question of sex and
hermaphroditism in general. We may then return to the discussion of the
hermaphroditism found in particular in the Cirripedia and Isopoda.
Parasitic Castration.—Giard[74] was the first to observe that a number of
parasites exert a remarkable influence on the sexual characters of their host,
such that the generative glands become reduced, or may completely
degenerate, while the secondary sexual characters become materially
the mantle-opening (o) of a young Sacculina
externa, × 20.
Phenomena of Growth and Sex in the Crustacea.
In the foregoing account of the Cirripedia we have met with certain
peculiar sexual relations in which closely allied species exhibit marked
differences in regard to the distribution of the qualities of sex among their
individuals; we have seen that the majority of species are hermaphrodite,
unlike most Crustacea which, with the other exception of the parasitic
Isopoda, are normally dioecious; and that in some species complemental
males exist side by side with the hermaphrodites, while, in yet others, the
individuals are either females or dwarf males.
Before examining the causes of these conditions, it will be opportune to
consider a number of facts which throw light on the question of sex and
hermaphroditism in general. We may then return to the discussion of the
hermaphroditism found in particular in the Cirripedia and Isopoda.
Parasitic Castration.—Giard[74] was the first to observe that a number of
parasites exert a remarkable influence on the sexual characters of their host,
such that the generative glands become reduced, or may completely
degenerate, while the secondary sexual characters become materially
Page 137
altered. This was proved to occur in the most widely different hosts,
affected by the most widely different parasites (e.g. Crustacea, Insecta,
Worms). Moreover, it was apparent that the affection does not consist in the
parasite merely destroying the generative organs, with which it often does
not come into contact, but rather in the general disturbance of the
metabolism set up by its presence.
The most completely studied cases of parasitic castration are those of the
Rhizocephalous Sacculina neglecta, parasitic on the spider-crab, Inachus
mauritanicus,[75] and of Peltogaster curvatus on the Hermit-crab,
Eupagurus excavatus, var. meticulosa.[76] The ordinary males of I.
mauritanicus have the appearance shown in Fig. 72, A. The abdomen is
small and bears a pair of copulatory styles, while the chelipedes are long
and swollen. In the female (B) the abdomen is much larger and trough-
shaped, and carries four pairs of ovigerous appendages; the chelae are small
and narrow.
affected by the most widely different parasites (e.g. Crustacea, Insecta,
Worms). Moreover, it was apparent that the affection does not consist in the
parasite merely destroying the generative organs, with which it often does
not come into contact, but rather in the general disturbance of the
metabolism set up by its presence.
The most completely studied cases of parasitic castration are those of the
Rhizocephalous Sacculina neglecta, parasitic on the spider-crab, Inachus
mauritanicus,[75] and of Peltogaster curvatus on the Hermit-crab,
Eupagurus excavatus, var. meticulosa.[76] The ordinary males of I.
mauritanicus have the appearance shown in Fig. 72, A. The abdomen is
small and bears a pair of copulatory styles, while the chelipedes are long
and swollen. In the female (B) the abdomen is much larger and trough-
shaped, and carries four pairs of ovigerous appendages; the chelae are small
and narrow.
Page 138
Fig. 72.—Illustrating the effect of parasitic Sacculina neglecta on Inachus
mauritanicus, nat. size. A, Normal male; Inachus; B, normal female; C, male
infested by Sacculina (final stage); D, abdomen of infested female; E, infested
male in an early stage of its modification.
Now it is found that in about 70 per cent of males infected with
Sacculina the body takes on to varying degrees the female characters, the
abdomen becoming broad as in the female, with a tendency to develop the
ovigerous appendages, while the chelae become reduced (Fig. 72, C). This
assumption of the female characteristics by the male under the influence of
the parasite may be so perfect that the abdomen and chelae become
typically female in dimensions, while the abdomen develops not only the
copulatory styles typical of the male, but also the four pairs of ovigerous
appendages typical of the female. The parasitised females, on the other
hand, though they may show a degenerate condition of the ovigerous
appendages (Fig. 72, D), never develop a single positively male
mauritanicus, nat. size. A, Normal male; Inachus; B, normal female; C, male
infested by Sacculina (final stage); D, abdomen of infested female; E, infested
male in an early stage of its modification.
Now it is found that in about 70 per cent of males infected with
Sacculina the body takes on to varying degrees the female characters, the
abdomen becoming broad as in the female, with a tendency to develop the
ovigerous appendages, while the chelae become reduced (Fig. 72, C). This
assumption of the female characteristics by the male under the influence of
the parasite may be so perfect that the abdomen and chelae become
typically female in dimensions, while the abdomen develops not only the
copulatory styles typical of the male, but also the four pairs of ovigerous
appendages typical of the female. The parasitised females, on the other
hand, though they may show a degenerate condition of the ovigerous
appendages (Fig. 72, D), never develop a single positively male
Page 139
characteristic. On dissecting crabs of these various categories it is found
that the generative organs are in varying conditions of degeneration and
disintegration.
The most remarkable fact in this history is the subsequent behaviour of
males which have assumed perfect female external characters, if the
Sacculina drops off and the crabs recover from the disease. It is found that
under these circumstances these males may regenerate from the remains of
their gonads a perfect hermaphrodite gland, capable of producing mature
ova and spermatozoa. The females appear quite incapable, on the other
hand, of producing the male primary elements of sex on recovery, any more
than they can produce the secondary. Exactly analogous facts have been
observed in the case of the hermit-crabs parasitised by Peltogaster, but here
the affected males produce small ova in their testes before the parasite is got
rid of. Here, too, the females seem incapable of assuming male characters
under the influence of the parasite.
To summarise shortly the conclusions to be deduced from these facts—
certain animals react to the presence of parasites by altering their sexual
condition. This alteration consists in the female sex in an arrest of
reproductive activity, in the male sex in the arrest of reproductive activity
coupled with the assumption of all the external characters proper to the
female. But in these males it is not merely the external characters that have
been altered; their capacity for subsequently developing hermaphrodite
glands shows that their whole organisation has been converted towards the
female state. That this alteration consists in a reorganisation of the
metabolic activities of the body is clearly suggested, and in the succeeding
paragraph we furnish some further evidence in support of this view.
that the generative organs are in varying conditions of degeneration and
disintegration.
The most remarkable fact in this history is the subsequent behaviour of
males which have assumed perfect female external characters, if the
Sacculina drops off and the crabs recover from the disease. It is found that
under these circumstances these males may regenerate from the remains of
their gonads a perfect hermaphrodite gland, capable of producing mature
ova and spermatozoa. The females appear quite incapable, on the other
hand, of producing the male primary elements of sex on recovery, any more
than they can produce the secondary. Exactly analogous facts have been
observed in the case of the hermit-crabs parasitised by Peltogaster, but here
the affected males produce small ova in their testes before the parasite is got
rid of. Here, too, the females seem incapable of assuming male characters
under the influence of the parasite.
To summarise shortly the conclusions to be deduced from these facts—
certain animals react to the presence of parasites by altering their sexual
condition. This alteration consists in the female sex in an arrest of
reproductive activity, in the male sex in the arrest of reproductive activity
coupled with the assumption of all the external characters proper to the
female. But in these males it is not merely the external characters that have
been altered; their capacity for subsequently developing hermaphrodite
glands shows that their whole organisation has been converted towards the
female state. That this alteration consists in a reorganisation of the
metabolic activities of the body is clearly suggested, and in the succeeding
paragraph we furnish some further evidence in support of this view.
Page 140
Fig. 73.—Inachus mauritanicus, × 1. A, Low male; B, middle male; C, high
male; the great chela of the right side is the only appendage represented.
Partial and Temporary Hermaphroditism. High and Low Dimorphism.
The reproductive phases of animals are frequently rhythmic, periods of
growth alternating with periods of reproduction. This is well exemplified in
the case of the ordinary males of Inachus mauritanicus, of some other
Oxyrhynchous crabs, and of the Crayfish Cambarus.[77] During the breeding
season the males of I. mauritanicus fall into three chief categories: Small
males with swollen chelae (Fig. 73, A), middle-sized males with flattened
chelae (B), and large males with enormously swollen chelae (C). On
dissecting specimens of the first and third categories it is found that the
testes occupy a large part of the thoracic cavity and are full of spermatozoa,
while in the middle-sized males with female-like chelae the testes appear
shrivelled and contain few spermatozoa. These non-breeding crabs are, in
fact, undergoing a period of active growth and sexual suppression before
attaining the final state of development exhibited by the large breeding
males. This phenomenon is obviously parallel to the “high and low
dimorphism”[78] so common in Lamellicorn beetles, where the males of
many species are divided into two chief categories, viz. “low males” of
male; the great chela of the right side is the only appendage represented.
Partial and Temporary Hermaphroditism. High and Low Dimorphism.
The reproductive phases of animals are frequently rhythmic, periods of
growth alternating with periods of reproduction. This is well exemplified in
the case of the ordinary males of Inachus mauritanicus, of some other
Oxyrhynchous crabs, and of the Crayfish Cambarus.[77] During the breeding
season the males of I. mauritanicus fall into three chief categories: Small
males with swollen chelae (Fig. 73, A), middle-sized males with flattened
chelae (B), and large males with enormously swollen chelae (C). On
dissecting specimens of the first and third categories it is found that the
testes occupy a large part of the thoracic cavity and are full of spermatozoa,
while in the middle-sized males with female-like chelae the testes appear
shrivelled and contain few spermatozoa. These non-breeding crabs are, in
fact, undergoing a period of active growth and sexual suppression before
attaining the final state of development exhibited by the large breeding
males. This phenomenon is obviously parallel to the “high and low
dimorphism”[78] so common in Lamellicorn beetles, where the males of
many species are divided into two chief categories, viz. “low males” of
Page 141
small size in which the secondary sexual characters are poorly developed,
and “high males” of large size in which these characters are proportionately
much more highly developed than in the low males. The only difference
between the two cases is that whereas in the beetles growth ceases on the
attainment of maturity in the low degree, in the Crustacea the low male
passes through a period of growth and sexual suppression to reach the high
degree of development.
The condition of the middle-sized males may be looked upon as one of
partial hermaphroditism, indications of the female state being found in the
flattened chelae and in the reduced state of the testes. This interpretation is
greatly strengthened by the state of affairs observed in the life-history of the
male Sand-hoppers, Amphipods of the genus Orchestia.[79] In the young
males of several species of this genus, at the time of year when they are not
actively breeding, small ova are developed in the upper part of the testes of
more than half of the male individuals, these ova being broken down and
reabsorbed as the breeding season reaches its height. Nor is this
phenomenon confined to this genus; in the males of a number of widely
different Crustacea these small ova are found in the testes at certain periods
of the life-history (e.g. Astacus[80]), when the animal is not breeding.
The foregoing facts indicate unmistakably that the males of a number of
Crustacea under certain metabolic conditions, i.e. when a stage of active
growth as opposed to a stage of reproductive activity is initiated, alter their
sexual constitution in such a way that the latent female characteristics are
developed, and the organism appears as a partial hermaphrodite. In the
preceding paragraph we saw that the males of a number of animals,
especially Crustacea, react to the metabolic disturbance set up by the
presence of a parasite in exactly the same way, i.e. by developing into
partial or total hermaphrodites. From these two converging bodies of facts
we may conclude, firstly, that sex and metabolism are two closely
connected phenomena; and, secondly, that the male sex is especially liable
to assume hermaphrodite characters whenever its metabolic requirements
are conservative, assimilatory, or in a preponderating degree anabolic, as
when a phase of active growth is initiated, or the drain on the system, due to
the presence of a parasite, is to be made good.
Normal Hermaphroditism in Cirripedia and Isopoda Epicarida.
and “high males” of large size in which these characters are proportionately
much more highly developed than in the low males. The only difference
between the two cases is that whereas in the beetles growth ceases on the
attainment of maturity in the low degree, in the Crustacea the low male
passes through a period of growth and sexual suppression to reach the high
degree of development.
The condition of the middle-sized males may be looked upon as one of
partial hermaphroditism, indications of the female state being found in the
flattened chelae and in the reduced state of the testes. This interpretation is
greatly strengthened by the state of affairs observed in the life-history of the
male Sand-hoppers, Amphipods of the genus Orchestia.[79] In the young
males of several species of this genus, at the time of year when they are not
actively breeding, small ova are developed in the upper part of the testes of
more than half of the male individuals, these ova being broken down and
reabsorbed as the breeding season reaches its height. Nor is this
phenomenon confined to this genus; in the males of a number of widely
different Crustacea these small ova are found in the testes at certain periods
of the life-history (e.g. Astacus[80]), when the animal is not breeding.
The foregoing facts indicate unmistakably that the males of a number of
Crustacea under certain metabolic conditions, i.e. when a stage of active
growth as opposed to a stage of reproductive activity is initiated, alter their
sexual constitution in such a way that the latent female characteristics are
developed, and the organism appears as a partial hermaphrodite. In the
preceding paragraph we saw that the males of a number of animals,
especially Crustacea, react to the metabolic disturbance set up by the
presence of a parasite in exactly the same way, i.e. by developing into
partial or total hermaphrodites. From these two converging bodies of facts
we may conclude, firstly, that sex and metabolism are two closely
connected phenomena; and, secondly, that the male sex is especially liable
to assume hermaphrodite characters whenever its metabolic requirements
are conservative, assimilatory, or in a preponderating degree anabolic, as
when a phase of active growth is initiated, or the drain on the system, due to
the presence of a parasite, is to be made good.
Normal Hermaphroditism in Cirripedia and Isopoda Epicarida.
Page 142
The above-mentioned groups contain the only normally hermaphrodite
Crustacea, and since they are in most respects highly specialised, we may
be certain that they have been secondarily derived from dioecious ancestors.
They both lead a sessile or parasitic life, and it is noteworthy that this habit
is often associated with hermaphroditism, e.g. in Tunicates. A sessile or
parasitic mode of life is one in which the metabolic functions are vegetative
and assimilatory rather than actively kinetic or metabolic. It is in this state
that we have seen the males of a number of Crustacea taking on a
temporary or partial hermaphroditism. We may, therefore, inquire, whether
in these cases of normal hermaphroditism there is any evidence to show that
here too the hermaphroditism has been acquired by the male sex as a
response to the change in the metabolic conditions. In the parasitic Isopoda
Epicarida (see pp. 129–136) the hermaphroditism is of a very simple kind;
all the individuals are at first males, whose function it is to fix on and
fertilise the adult parasites. These subsequently develop into females which
are in their turn cross-fertilised by the young larvae derived from a previous
generation. All the individuals being alike, it seems probable that they have
been derived from one sex, and the general nature of hermaphroditism
deduced above may lead us to suppose that that sex was originally male, the
female having been suppressed. In certain Cirripedia, e.g. most species of
Scalpellum, there exist, besides the hermaphrodite individuals,
complemental males, so that here a superficial conclusion might be drawn
that the hermaphrodites represent the female sex. But if we can suggest that
the complemental males are in reality similar in derivation to the
hermaphrodite individuals, we shall be in a position to claim that the
hermaphrodite Cirripedes are similar to the Isopoda Epicarida, and have
probably also been derived from the male sex. There is decided evidence
pointing to this conclusion. In the first place, the complemental males of at
least one species of Scalpellum, S. peronii, do show an incipient
hermaphroditism[81] in the presence of small ova in their generative glands,
which, however, never come to maturity.
The condition of the degenerate males in the Rhizocephala may also be
interpreted in the same manner. These never pass beyond the Cypris stage
of development, in which they resemble in detail the Cypris larvae of the
ordinary hermaphrodite individuals, and they are quite useless in the
propagation of their species.
Crustacea, and since they are in most respects highly specialised, we may
be certain that they have been secondarily derived from dioecious ancestors.
They both lead a sessile or parasitic life, and it is noteworthy that this habit
is often associated with hermaphroditism, e.g. in Tunicates. A sessile or
parasitic mode of life is one in which the metabolic functions are vegetative
and assimilatory rather than actively kinetic or metabolic. It is in this state
that we have seen the males of a number of Crustacea taking on a
temporary or partial hermaphroditism. We may, therefore, inquire, whether
in these cases of normal hermaphroditism there is any evidence to show that
here too the hermaphroditism has been acquired by the male sex as a
response to the change in the metabolic conditions. In the parasitic Isopoda
Epicarida (see pp. 129–136) the hermaphroditism is of a very simple kind;
all the individuals are at first males, whose function it is to fix on and
fertilise the adult parasites. These subsequently develop into females which
are in their turn cross-fertilised by the young larvae derived from a previous
generation. All the individuals being alike, it seems probable that they have
been derived from one sex, and the general nature of hermaphroditism
deduced above may lead us to suppose that that sex was originally male, the
female having been suppressed. In certain Cirripedia, e.g. most species of
Scalpellum, there exist, besides the hermaphrodite individuals,
complemental males, so that here a superficial conclusion might be drawn
that the hermaphrodites represent the female sex. But if we can suggest that
the complemental males are in reality similar in derivation to the
hermaphrodite individuals, we shall be in a position to claim that the
hermaphrodite Cirripedes are similar to the Isopoda Epicarida, and have
probably also been derived from the male sex. There is decided evidence
pointing to this conclusion. In the first place, the complemental males of at
least one species of Scalpellum, S. peronii, do show an incipient
hermaphroditism[81] in the presence of small ova in their generative glands,
which, however, never come to maturity.
The condition of the degenerate males in the Rhizocephala may also be
interpreted in the same manner. These never pass beyond the Cypris stage
of development, in which they resemble in detail the Cypris larvae of the
ordinary hermaphrodite individuals, and they are quite useless in the
propagation of their species.
Page 143
It is more reasonable to suppose that these Cypris larvae, which fix on
the mantle-openings of adult parasites, are in reality identical with the
ordinary Cypris which infest crabs and develop into the hermaphrodites,
than that they represent a whole male sex doomed beforehand to
uselessness and degeneration. If we suppose that the Cirripedes have passed
through a state of protandric hermaphroditism similar to that of the Isopoda
Epicarida, it is plain that all the larvae must have originally possessed the
instinct of first fixing on the adult parasites, and we may suppose that this
instinct has been retained in the Rhizocephala, but is now only actually
fulfilled by a certain proportion of the larvae, which, under existing
circumstances, are useless and fail to develop further; while the rest of the
larvae, not finding an adult parasite to fix upon, go straight on to infect their
hosts and develop into the adult hermaphrodites.
The same explanation would apply to the complemental males in
Scalpellum, etc., these individuals being also potential hermaphrodites,
which are arrested in development, though not so completely as in the
Rhizocephala, owing to the position they have taken up.
This theory throws light on another dark feature of Cirripede life-history,
namely, the gregarious instinct. The associations of Cirripedes are not
formed by a number of Cypris larvae fixing together on the same spot, but
rather by the Cypris larvae seeking out adolescent individuals of their own
species and fixing on or near them. Now, if we suppose that the Cirripedes
have passed through a condition of protandric hermaphroditism similar to
that of the Isopoda Epicarida, it is clear that a slight modification of the
sexual instinct of the larvae would lead to the gregarious habit, while its
retention in some individuals in its original form accounts for their finding
their way to the mantles of adult individuals and developing into the so-
called complemental males.
Certain Cirripedes, viz. certain species of Scalpellum and Ibla and all the
Acrothoracica, are dioecious. It is impossible to decide at present whether
these species retain the primitive dioecious condition of the ancestral
Cirripedes, or whether they too have been derived from an hermaphrodite
state, but in the present state of knowledge they hardly affect the validity of
the theory that has been proposed to account for the nature of the
complemental males and the hermaphrodite individuals.
the mantle-openings of adult parasites, are in reality identical with the
ordinary Cypris which infest crabs and develop into the hermaphrodites,
than that they represent a whole male sex doomed beforehand to
uselessness and degeneration. If we suppose that the Cirripedes have passed
through a state of protandric hermaphroditism similar to that of the Isopoda
Epicarida, it is plain that all the larvae must have originally possessed the
instinct of first fixing on the adult parasites, and we may suppose that this
instinct has been retained in the Rhizocephala, but is now only actually
fulfilled by a certain proportion of the larvae, which, under existing
circumstances, are useless and fail to develop further; while the rest of the
larvae, not finding an adult parasite to fix upon, go straight on to infect their
hosts and develop into the adult hermaphrodites.
The same explanation would apply to the complemental males in
Scalpellum, etc., these individuals being also potential hermaphrodites,
which are arrested in development, though not so completely as in the
Rhizocephala, owing to the position they have taken up.
This theory throws light on another dark feature of Cirripede life-history,
namely, the gregarious instinct. The associations of Cirripedes are not
formed by a number of Cypris larvae fixing together on the same spot, but
rather by the Cypris larvae seeking out adolescent individuals of their own
species and fixing on or near them. Now, if we suppose that the Cirripedes
have passed through a condition of protandric hermaphroditism similar to
that of the Isopoda Epicarida, it is clear that a slight modification of the
sexual instinct of the larvae would lead to the gregarious habit, while its
retention in some individuals in its original form accounts for their finding
their way to the mantles of adult individuals and developing into the so-
called complemental males.
Certain Cirripedes, viz. certain species of Scalpellum and Ibla and all the
Acrothoracica, are dioecious. It is impossible to decide at present whether
these species retain the primitive dioecious condition of the ancestral
Cirripedes, or whether they too have been derived from an hermaphrodite
state, but in the present state of knowledge they hardly affect the validity of
the theory that has been proposed to account for the nature of the
complemental males and the hermaphrodite individuals.
Page 144
Order IV. Ostracoda.
The Ostracoda are small Crustacea, the body consisting of very few—
about eight—segments, and being completely enclosed in a carapace, which
has the form of a bivalve shell. Development is direct, without a Nauplius
stage.
The Ostracoda[82] are marine and fresh-water animals that can be divided
into several families, differing slightly in habits and in structures correlated
with those habits.
The Cypridae and Cytheridae
include all the fresh-water and a vast
majority of marine genera, adapted
for a sluggish life among water-
plants, though some can swim with
considerable activity. The common
Cypris and Candona of our ponds
and streams are familiar instances.
The movements of these animals are Fig. 74.—Candona reptans. A, Natural size; B,
effected by means of the two pairs of X 15. a, 1st antennae; b, 2nd antennae; c,
uniramous pediform antennae which walking legs. (After Baird.)
move together and in a vertical
straight line. In the Cypridae (Fig. 74) there are, besides the mandibles, two
pairs of maxillae, a pair of walking legs, and, lastly, a pair of appendages,
which are doubled up into the carapace, and are used for cleaning purposes.
In the marine Cytheridae there is only one maxilla, the last three
appendages being pediform and used in walking. The telson in the
Cytheridae is rudimentary, but is well developed in the Cypridae. The heart
is altogether absent.
In many of the fresh-water forms, e.g. common species of Candona and
Cypris, males are never found, and parthenogenetic reproduction by the
females appears to proceed uninterruptedly. Weismann[83] kept females of
Cypris reptans breeding parthenogenetically for eight years. He also
remarks on the fact that these, and indeed all parthenogenetic female
Ostracoda, retain the receptaculum seminis, used normally for storing the
spermatozoa derived from the male, unimpaired.
The Ostracoda are small Crustacea, the body consisting of very few—
about eight—segments, and being completely enclosed in a carapace, which
has the form of a bivalve shell. Development is direct, without a Nauplius
stage.
The Ostracoda[82] are marine and fresh-water animals that can be divided
into several families, differing slightly in habits and in structures correlated
with those habits.
The Cypridae and Cytheridae
include all the fresh-water and a vast
majority of marine genera, adapted
for a sluggish life among water-
plants, though some can swim with
considerable activity. The common
Cypris and Candona of our ponds
and streams are familiar instances.
The movements of these animals are Fig. 74.—Candona reptans. A, Natural size; B,
effected by means of the two pairs of X 15. a, 1st antennae; b, 2nd antennae; c,
uniramous pediform antennae which walking legs. (After Baird.)
move together and in a vertical
straight line. In the Cypridae (Fig. 74) there are, besides the mandibles, two
pairs of maxillae, a pair of walking legs, and, lastly, a pair of appendages,
which are doubled up into the carapace, and are used for cleaning purposes.
In the marine Cytheridae there is only one maxilla, the last three
appendages being pediform and used in walking. The telson in the
Cytheridae is rudimentary, but is well developed in the Cypridae. The heart
is altogether absent.
In many of the fresh-water forms, e.g. common species of Candona and
Cypris, males are never found, and parthenogenetic reproduction by the
females appears to proceed uninterruptedly. Weismann[83] kept females of
Cypris reptans breeding parthenogenetically for eight years. He also
remarks on the fact that these, and indeed all parthenogenetic female
Ostracoda, retain the receptaculum seminis, used normally for storing the
spermatozoa derived from the male, unimpaired.
Page 145
Some of the Cytheridae occur in deep water. Thus Cythere dictyon was
frequently taken by the Challenger in depths of over 1000 fathoms, but the
majority prefer shallow water.
Fig. 75.—Asterope oblonga, ♀, removed from its carapace, × 25. A, Alimentary
canal; A1, A2, 1st and 2nd antennae; E, eye; G, gills; G.O, generative opening;
H, heart; M, mandible; T, 6th appendage; T′, last appendage (cleaning foot).
(After Claus.)
The Halocypridae and Cypridinidae comprise marine genera of a
pelagic habit. The first antennae are chiefly sensory, but the second
antennae are biramous, and they do not merely move up and down, as in the
preceding families, but sideways like oars, the valves of the shells being
excavated to admit of free movements. There are two pairs of maxillae; the
succeeding limbs differ in the two families. In the Cypridinidae, e.g.
Asterope (Fig. 75), the first leg (T) is lamelliform and is used as an
accessory maxilla, while the second leg (T’) is turned upwards into the shell
as a cleaning organ. In the Halocypridae the first leg is pediform, and
differs in the two sexes, while the second leg is rudimentary and points
backwards. In Asterope peculiar branchial organs (G) are present on the
frequently taken by the Challenger in depths of over 1000 fathoms, but the
majority prefer shallow water.
Fig. 75.—Asterope oblonga, ♀, removed from its carapace, × 25. A, Alimentary
canal; A1, A2, 1st and 2nd antennae; E, eye; G, gills; G.O, generative opening;
H, heart; M, mandible; T, 6th appendage; T′, last appendage (cleaning foot).
(After Claus.)
The Halocypridae and Cypridinidae comprise marine genera of a
pelagic habit. The first antennae are chiefly sensory, but the second
antennae are biramous, and they do not merely move up and down, as in the
preceding families, but sideways like oars, the valves of the shells being
excavated to admit of free movements. There are two pairs of maxillae; the
succeeding limbs differ in the two families. In the Cypridinidae, e.g.
Asterope (Fig. 75), the first leg (T) is lamelliform and is used as an
accessory maxilla, while the second leg (T’) is turned upwards into the shell
as a cleaning organ. In the Halocypridae the first leg is pediform, and
differs in the two sexes, while the second leg is rudimentary and points
backwards. In Asterope peculiar branchial organs (G) are present on the
Page 146
back. Both families possess a heart; the Halocypridae are blind, while the
Cypridinidae possess eyes.
The Polycopidae and Cytherellidae are curious marine families of a
pelagic habit, with biramous second antennae well adapted for swimming,
and very broad. The first maxilla in the Polycopidae is also employed in
swimming, while the second is modified into a branchial organ; the
maxillae of the Cytherellidae are more normal in structure, but both carry
branchial lamellae. The posterior limbs are altogether absent in
Polycopidae, and in the Cytherellidae are only represented by the
copulatory organs of the male.
Cypridinidae possess eyes.
The Polycopidae and Cytherellidae are curious marine families of a
pelagic habit, with biramous second antennae well adapted for swimming,
and very broad. The first maxilla in the Polycopidae is also employed in
swimming, while the second is modified into a branchial organ; the
maxillae of the Cytherellidae are more normal in structure, but both carry
branchial lamellae. The posterior limbs are altogether absent in
Polycopidae, and in the Cytherellidae are only represented by the
copulatory organs of the male.
Page 147
Page 148
CHAPTER V
CRUSTACEA (CONTINUED): MALACOSTRACA:
LEPTOSTRACA—PHYLLOCARIDA:
EUMALACOSTRACA: SYNCARIDA—ANASPIDACEA:
PERACARIDA—MYSIDACEA—CUMACEA—ISOPODA—
AMPHIPODA: HOPLOCARIDA—STOMATOPODA
SUB-CLASS II.—MALACOSTRACA.
The Malacostraca are generally large Crustacea, and they are
characterised by the presence of a definite and constant number of segments
composing the body. In addition to the paired eyes we can distinguish two
pairs of antennae, a mandibular segment, and two maxillary segments
composing the head region proper; there then follow eight thoracic
segments, the limbs belonging to the anterior thoracic segments being often
turned forwards towards the mouth, and modified in structure to act as
maxillipedes, while at any rate the last four are used in locomotion and are
termed “pereiopods.”[84] The abdomen is composed of six segments, which
typically carry as many pairs of biramous “pleopods,” and the body
terminates in a telson. Not counting the paired eyes or the telson, there are
present nineteen segments. The excretory organs in the adult open at the
bases of the second antennae, and are known as “green glands,” but in the
larva maxillary glands may be present homologous to those which persist in
the adult Entomostraca. This is the typical arrangement, but sometimes the
maxillary glands persist in adult Malacostraca, e.g. Nebalia, Anaspides, and
some Isopods.
The hepato-pancreatic diverticula are directed posteriorly, and not
anteriorly as in most Entomostraca, and the stomach is often furnished with
chitinous teeth and ridges forming an elaborate gastric mill, especially in
the larger Decapods.
CRUSTACEA (CONTINUED): MALACOSTRACA:
LEPTOSTRACA—PHYLLOCARIDA:
EUMALACOSTRACA: SYNCARIDA—ANASPIDACEA:
PERACARIDA—MYSIDACEA—CUMACEA—ISOPODA—
AMPHIPODA: HOPLOCARIDA—STOMATOPODA
SUB-CLASS II.—MALACOSTRACA.
The Malacostraca are generally large Crustacea, and they are
characterised by the presence of a definite and constant number of segments
composing the body. In addition to the paired eyes we can distinguish two
pairs of antennae, a mandibular segment, and two maxillary segments
composing the head region proper; there then follow eight thoracic
segments, the limbs belonging to the anterior thoracic segments being often
turned forwards towards the mouth, and modified in structure to act as
maxillipedes, while at any rate the last four are used in locomotion and are
termed “pereiopods.”[84] The abdomen is composed of six segments, which
typically carry as many pairs of biramous “pleopods,” and the body
terminates in a telson. Not counting the paired eyes or the telson, there are
present nineteen segments. The excretory organs in the adult open at the
bases of the second antennae, and are known as “green glands,” but in the
larva maxillary glands may be present homologous to those which persist in
the adult Entomostraca. This is the typical arrangement, but sometimes the
maxillary glands persist in adult Malacostraca, e.g. Nebalia, Anaspides, and
some Isopods.
The hepato-pancreatic diverticula are directed posteriorly, and not
anteriorly as in most Entomostraca, and the stomach is often furnished with
chitinous teeth and ridges forming an elaborate gastric mill, especially in
the larger Decapods.
Page 149
SERIES 1. LEPTOSTRACA.
Division. Phyllocarida.
The small shrimp-like Crustacean
Nebalia, which is found burrowing in
the superficial layers of sand in the
littoral and sometimes the deeper
regions of most seas, has been
regarded, ever since its anatomy was
made out by Claus,[85] as a connecting
link between Entomostraca and
Malacostraca, and has been placed in
a separate group Leptostraca.
The segmentation of the body is
Malacostracan, save that two extra
segments are present in the abdomen,
and the paired compound eyes are
borne upon stalks. The eight thoracic
limbs are all very similar; they are
built on the typical biramous plan,
and each carries a bract; they have
been compared, owing to their
flattened, expanded shape, to the
foliaceous limbs of the Phyllopods.
The abdominal appendages are also
biramous. The heart is greatly
elongated, stretching through thorax
and abdomen; there are present both
the antennary excretory glands Fig. 76.—Nebalia geoffroyi, ♀ , × 20. A.1, A.2,
characteristic of adult Malacostraca 1st and 2nd antennae; Ab.1, Ab.6, 1st and 6th
and the maxillary glands abdominal appendages; A.G. antennary gland;
C, half of caudal fork; E, eye; G, ventral
characteristic of adult Entomostraca, ganglionic chain; H, heart; I, intestine; L, upper
and both the posterior and anterior liver-diverticulum; M, adductor muscle of
livers characteristic of the two Orders halves of carapace; MX, palp of 1st maxilla; O,
ovary; R, rostrum. (After Claus.)
respectively are present. This
combination of characters justifies
Division. Phyllocarida.
The small shrimp-like Crustacean
Nebalia, which is found burrowing in
the superficial layers of sand in the
littoral and sometimes the deeper
regions of most seas, has been
regarded, ever since its anatomy was
made out by Claus,[85] as a connecting
link between Entomostraca and
Malacostraca, and has been placed in
a separate group Leptostraca.
The segmentation of the body is
Malacostracan, save that two extra
segments are present in the abdomen,
and the paired compound eyes are
borne upon stalks. The eight thoracic
limbs are all very similar; they are
built on the typical biramous plan,
and each carries a bract; they have
been compared, owing to their
flattened, expanded shape, to the
foliaceous limbs of the Phyllopods.
The abdominal appendages are also
biramous. The heart is greatly
elongated, stretching through thorax
and abdomen; there are present both
the antennary excretory glands Fig. 76.—Nebalia geoffroyi, ♀ , × 20. A.1, A.2,
characteristic of adult Malacostraca 1st and 2nd antennae; Ab.1, Ab.6, 1st and 6th
and the maxillary glands abdominal appendages; A.G. antennary gland;
C, half of caudal fork; E, eye; G, ventral
characteristic of adult Entomostraca, ganglionic chain; H, heart; I, intestine; L, upper
and both the posterior and anterior liver-diverticulum; M, adductor muscle of
livers characteristic of the two Orders halves of carapace; MX, palp of 1st maxilla; O,
ovary; R, rostrum. (After Claus.)
respectively are present. This
combination of characters justifies
Page 150
the belief that Nebalia represents a primitive form, standing to some extent
in an intermediate position between Entomostraca and Malacostraca, but it
may be doubted if the special relationship to the Phyllopoda, claimed on the
strength of the foliaceous appearance of the thoracic limbs, can be
legitimately pressed.
Nebalia shows the clearest signs of relationship to the other primitive
Malacostraca, and especially to the Mysidae, which it resembles not only in
general form and in the essentially biramous character of its appendages,
but also in many embryological points and in the similarity in development
of the brood-pouch.[86]
A large number of very ancient palaeozoic fossils are known which are
placed provisionally with Nebalia in the Division Phyllocarida, and some of
these are no doubt closely related to the existing isolated genus.
Hymenocaris from the Cambrian.
SERIES 2. EUMALACOSTRACA.
Before entering on a description of the members of this Series it is
necessary to introduce and justify a new scheme of classification which has
been proposed by Dr. W. T. Calman. This scheme necessitates the
abandonment of the old Order Schizopoda, and also ignores the distinction
which used to be considered fundamental between the sessile-eyed
Crustacea (Edriophthalmata) and the stalk-eyed forms (Podophthalmata).
The old group of Schizopoda, to which Nebalia and the isolated form
Anaspides, to be considered later, are undoubtedly related, represent very
clearly the stem-forms from which the various branches of the
Malacostracan stock diverge. No doubt they are themselves specialised in
many directions, since they are a dominant group in present day seas, but
their organisation is fundamentally of a primitive type. We see this
especially in the comparative absence of fusion or reduction of the
segments of the body externally and of the nervous system internally, and in
the simple undifferentiated character of the trunk-limbs, all of which
conform to the primitive biramous type. The most anterior thoracic limbs of
the Schizopods are of particular interest. In the higher Malacostraca three of
these limbs are usually turned forwards towards the mouth to act as
maxillipedes, and the most anterior of all, the first maxillipede, is apt,
in an intermediate position between Entomostraca and Malacostraca, but it
may be doubted if the special relationship to the Phyllopoda, claimed on the
strength of the foliaceous appearance of the thoracic limbs, can be
legitimately pressed.
Nebalia shows the clearest signs of relationship to the other primitive
Malacostraca, and especially to the Mysidae, which it resembles not only in
general form and in the essentially biramous character of its appendages,
but also in many embryological points and in the similarity in development
of the brood-pouch.[86]
A large number of very ancient palaeozoic fossils are known which are
placed provisionally with Nebalia in the Division Phyllocarida, and some of
these are no doubt closely related to the existing isolated genus.
Hymenocaris from the Cambrian.
SERIES 2. EUMALACOSTRACA.
Before entering on a description of the members of this Series it is
necessary to introduce and justify a new scheme of classification which has
been proposed by Dr. W. T. Calman. This scheme necessitates the
abandonment of the old Order Schizopoda, and also ignores the distinction
which used to be considered fundamental between the sessile-eyed
Crustacea (Edriophthalmata) and the stalk-eyed forms (Podophthalmata).
The old group of Schizopoda, to which Nebalia and the isolated form
Anaspides, to be considered later, are undoubtedly related, represent very
clearly the stem-forms from which the various branches of the
Malacostracan stock diverge. No doubt they are themselves specialised in
many directions, since they are a dominant group in present day seas, but
their organisation is fundamentally of a primitive type. We see this
especially in the comparative absence of fusion or reduction of the
segments of the body externally and of the nervous system internally, and in
the simple undifferentiated character of the trunk-limbs, all of which
conform to the primitive biramous type. The most anterior thoracic limbs of
the Schizopods are of particular interest. In the higher Malacostraca three of
these limbs are usually turned forwards towards the mouth to act as
maxillipedes, and the most anterior of all, the first maxillipede, is apt,
Page 151
especially in the Decapoda, to take on a flattened foliaceous form owing to
the expansion of the basal segments to act as gnathobases (see Fig. 1, A, p.
10). Now this appendage in the Schizopods preserves its typical biramous
character, and resembles the succeeding thoracic limbs, but in many of the
species the basal joints show a tendency to be produced into biting blades
(Fig. 1, E, p. 10), thus indicating the first step in the evolution of the
foliaceous first maxillipede of the Decapoda. The primitive character of the
Schizopods is also indicated by the fact that most of the Decapoda with
uniramous limbs on the five hinder thoracic segments pass through what is
known as the “Mysis stage” in development, when these limbs are
biramous, the exopodites being subsequently lost in most cases.
The “Schizopoda” include a very large number of pelagic Crustacea of
moderate size, which superficially appear to resemble one another very
closely. The slender, elongated body, the presence of biramous limbs on all
the thoracic and abdominal segments, and the possession of a single row of
gills at the bases of the thoracic limbs, are, generally speaking, typical of
the families Mysidae, Lophogastridae, Eucopiidae, and Euphausiidae,
which go to make up the old Order Schizopoda.
It has, however, been pointed out first by Boas,[87] and subsequently by
Hansen and Calman,[88] that the Euphausiidae are in many respects distinct
from the other three families, and agree with the Decapoda, while the
Eucopiidae, Lophogastridae, and Mysidae agree with the Cumacea,
Isopoda, and Amphipoda.
It has, therefore, been suggested by these authors that the classification of
the Malacostraca should be revised, and Calman (loc. cit.) has brought
forward the following scheme:—
The division Peracarida, including the Eucopiidae, Lophogastridae, and
Mysidae (= Mysidacea), the Cumacea, Isopoda, and Amphipoda, is
characterised by the fact that when a carapace is present it leaves at least
four of the thoracic segments free and uncoalesced: by the presence of a
brood-pouch formed from the oostegites on the thoracic limbs of the
female: by the elongated heart: by the few and simple hepatic caeca: by the
filiform spermatozoa: and by the direct method of development without a
complicated larval metamorphosis. The biting face of the mandible has a
movable joint, the “lacinia mobilis.”[89]
the expansion of the basal segments to act as gnathobases (see Fig. 1, A, p.
10). Now this appendage in the Schizopods preserves its typical biramous
character, and resembles the succeeding thoracic limbs, but in many of the
species the basal joints show a tendency to be produced into biting blades
(Fig. 1, E, p. 10), thus indicating the first step in the evolution of the
foliaceous first maxillipede of the Decapoda. The primitive character of the
Schizopods is also indicated by the fact that most of the Decapoda with
uniramous limbs on the five hinder thoracic segments pass through what is
known as the “Mysis stage” in development, when these limbs are
biramous, the exopodites being subsequently lost in most cases.
The “Schizopoda” include a very large number of pelagic Crustacea of
moderate size, which superficially appear to resemble one another very
closely. The slender, elongated body, the presence of biramous limbs on all
the thoracic and abdominal segments, and the possession of a single row of
gills at the bases of the thoracic limbs, are, generally speaking, typical of
the families Mysidae, Lophogastridae, Eucopiidae, and Euphausiidae,
which go to make up the old Order Schizopoda.
It has, however, been pointed out first by Boas,[87] and subsequently by
Hansen and Calman,[88] that the Euphausiidae are in many respects distinct
from the other three families, and agree with the Decapoda, while the
Eucopiidae, Lophogastridae, and Mysidae agree with the Cumacea,
Isopoda, and Amphipoda.
It has, therefore, been suggested by these authors that the classification of
the Malacostraca should be revised, and Calman (loc. cit.) has brought
forward the following scheme:—
The division Peracarida, including the Eucopiidae, Lophogastridae, and
Mysidae (= Mysidacea), the Cumacea, Isopoda, and Amphipoda, is
characterised by the fact that when a carapace is present it leaves at least
four of the thoracic segments free and uncoalesced: by the presence of a
brood-pouch formed from the oostegites on the thoracic limbs of the
female: by the elongated heart: by the few and simple hepatic caeca: by the
filiform spermatozoa: and by the direct method of development without a
complicated larval metamorphosis. The biting face of the mandible has a
movable joint, the “lacinia mobilis.”[89]
Page 152
The division Eucarida, on the other hand, including the Euphausiidae
and the Decapoda, shows the converse of these characters. The carapace
coalesces with all the thoracic segments, there is never a brood-pouch
formed from oostegites, the hepatic caeca are much ramified, the heart is
short, the spermatozoa are spherical with radiating pseudopodia, the
development is indirect with a complicated metamorphosis, and the
mandible is without a lacinia mobilis.
Corresponding divisions are made by Calman to receive the other
Malacostraca, namely, the Phyllocarida for Nebalia, the Syncarida for
Anaspides, and the Hoplocarida for the Stomatopoda or Squillidae.
The important array of characters which separates the Euphausiidae from
the other Schizopods and unites them with the Decapoda can no longer be
neglected, and the consideration of Anaspides and its allies will further
emphasise the extreme difficulty of retaining the Schizopoda as a natural
group. In the sequel Calman’s proposed scheme will be adopted.
DIVISION 1. SYNCARIDA.
There is no carapace, and all the eight thoracic segments may be free and
distinct. Eyes may be pedunculate or sessile. The mandible is without a
lacinia mobilis. There is no brood-pouch, the eggs being deposited and
hidden after fertilisation. The spermatozoa are filiform, the hepatic caeca
very numerous, and the heart tubular and elongated, with ostia only in one
place in the anterior thoracic region. The auditory organ is at the base of the
first antennae.
Order. Anaspidacea.
Fam. 1. Anaspididae.—The mountain-shrimp of Tasmania, Anaspides
tasmaniae, was first described by Thomson[90] in 1893 from specimens
taken in a little pool near the summit of Mount Wellington; it was
redescribed by Calman,[91] who drew attention to its remarkable
resemblance to certain Carboniferous fossils of Europe and N. America
(Gampsonyx, Palaeocaris, etc.).
and the Decapoda, shows the converse of these characters. The carapace
coalesces with all the thoracic segments, there is never a brood-pouch
formed from oostegites, the hepatic caeca are much ramified, the heart is
short, the spermatozoa are spherical with radiating pseudopodia, the
development is indirect with a complicated metamorphosis, and the
mandible is without a lacinia mobilis.
Corresponding divisions are made by Calman to receive the other
Malacostraca, namely, the Phyllocarida for Nebalia, the Syncarida for
Anaspides, and the Hoplocarida for the Stomatopoda or Squillidae.
The important array of characters which separates the Euphausiidae from
the other Schizopods and unites them with the Decapoda can no longer be
neglected, and the consideration of Anaspides and its allies will further
emphasise the extreme difficulty of retaining the Schizopoda as a natural
group. In the sequel Calman’s proposed scheme will be adopted.
DIVISION 1. SYNCARIDA.
There is no carapace, and all the eight thoracic segments may be free and
distinct. Eyes may be pedunculate or sessile. The mandible is without a
lacinia mobilis. There is no brood-pouch, the eggs being deposited and
hidden after fertilisation. The spermatozoa are filiform, the hepatic caeca
very numerous, and the heart tubular and elongated, with ostia only in one
place in the anterior thoracic region. The auditory organ is at the base of the
first antennae.
Order. Anaspidacea.
Fam. 1. Anaspididae.—The mountain-shrimp of Tasmania, Anaspides
tasmaniae, was first described by Thomson[90] in 1893 from specimens
taken in a little pool near the summit of Mount Wellington; it was
redescribed by Calman,[91] who drew attention to its remarkable
resemblance to certain Carboniferous fossils of Europe and N. America
(Gampsonyx, Palaeocaris, etc.).
Page 153
The creature appears to be confined to the deep pools of the rivers and
tarns on the mountains of the southern and western portions of Tasmania.[92]
The waters in which it occurs are always cold and absolutely clear, and
there is no record of its living at altitudes much below 2000 feet, while it
frequently occurs at 4000 feet. The body may attain upwards of two inches
in length; it is deeply pigmented with black chromatophores, and it is held
perfectly horizontal without any flexure. The animal rarely swims unless
disturbed, usually walking about on stones and water-plants at the bottom of
deep pools. In walking the endopodites of the thoracic limbs are chiefly
instrumental, but they are assisted by the exopodites of the abdominal
limbs.
When frightened the shrimp can dart rapidly forwards or sideways by the
strokes of its powerful tail-fan, but it never jumps backwards as do the other
Malacostraca. It appears to browse upon the algal slime covering the rocks
and on the submerged liver-worts and mosses, but it does not refuse animal
food, even feeding on the dead bodies of members of its own species. The
thoracic limbs, which are all biramous except the last pair, carry a double
series of remarkable plate-like gills on their coxopodites. The slender and
setose exopodites of the thoracic limbs are respiratory in function, being
kept in continual motion even when the animal is at rest, and serving to
keep up a current of fresh water round the gills.
Anaspides shows a remarkable combination of structural characters,
some of which are peculiar, while others are possessed in common with the
Peracarida or Eucarida. The chief peculiar characters are the entire absence
of a carapace, and the freedom of the eight thoracic segments, with eight
free thoracic ganglia in the nerve-cord; the peculiar double series of plate-
like gills; the structure of the alimentary canal; and the fact that the eggs,
instead of being carried in a brood-pouch, or affixed to the abdominal
limbs, are deposited under stones and among water-plants.[93]
tarns on the mountains of the southern and western portions of Tasmania.[92]
The waters in which it occurs are always cold and absolutely clear, and
there is no record of its living at altitudes much below 2000 feet, while it
frequently occurs at 4000 feet. The body may attain upwards of two inches
in length; it is deeply pigmented with black chromatophores, and it is held
perfectly horizontal without any flexure. The animal rarely swims unless
disturbed, usually walking about on stones and water-plants at the bottom of
deep pools. In walking the endopodites of the thoracic limbs are chiefly
instrumental, but they are assisted by the exopodites of the abdominal
limbs.
When frightened the shrimp can dart rapidly forwards or sideways by the
strokes of its powerful tail-fan, but it never jumps backwards as do the other
Malacostraca. It appears to browse upon the algal slime covering the rocks
and on the submerged liver-worts and mosses, but it does not refuse animal
food, even feeding on the dead bodies of members of its own species. The
thoracic limbs, which are all biramous except the last pair, carry a double
series of remarkable plate-like gills on their coxopodites. The slender and
setose exopodites of the thoracic limbs are respiratory in function, being
kept in continual motion even when the animal is at rest, and serving to
keep up a current of fresh water round the gills.
Anaspides shows a remarkable combination of structural characters,
some of which are peculiar, while others are possessed in common with the
Peracarida or Eucarida. The chief peculiar characters are the entire absence
of a carapace, and the freedom of the eight thoracic segments, with eight
free thoracic ganglia in the nerve-cord; the peculiar double series of plate-
like gills; the structure of the alimentary canal; and the fact that the eggs,
instead of being carried in a brood-pouch, or affixed to the abdominal
limbs, are deposited under stones and among water-plants.[93]
Page 154
Fig. 77.—Anaspides tasmaniae in natural position for walking, × 1. The last two
pereiopods point backwards and are overlapped by the first two pleopods.
The Peracaridan features, uniting it especially with the Mysidacea, are
the structure of the elongated heart, the filiform spermatozoa, and the fact
that no complicated metamorphosis is passed through, the young hatching
out in a condition similar to, though possibly not identical with, the adult
form.
The Eucaridan, especially Decapodan, features are the presence of an
auditory sac on the basal joint of the antennules, and the modification of the
endopodites of the first two abdominal appendages in the male to form a
copulatory organ.
A type of a new genus of this family was found by me in the littoral zone
of the Great Lake of Tasmania at an elevation of 3700 feet, and named
Paranaspides lacustris.
This little shrimp (Fig. 78), which does not appear to grow to more than
an inch in length, is totally different in appearance from Anaspides, being
pale green and transparent, with a very marked dorsal hump as in Mysis, to
which it bears a very striking superficial resemblance. It leads a more active
pereiopods point backwards and are overlapped by the first two pleopods.
The Peracaridan features, uniting it especially with the Mysidacea, are
the structure of the elongated heart, the filiform spermatozoa, and the fact
that no complicated metamorphosis is passed through, the young hatching
out in a condition similar to, though possibly not identical with, the adult
form.
The Eucaridan, especially Decapodan, features are the presence of an
auditory sac on the basal joint of the antennules, and the modification of the
endopodites of the first two abdominal appendages in the male to form a
copulatory organ.
A type of a new genus of this family was found by me in the littoral zone
of the Great Lake of Tasmania at an elevation of 3700 feet, and named
Paranaspides lacustris.
This little shrimp (Fig. 78), which does not appear to grow to more than
an inch in length, is totally different in appearance from Anaspides, being
pale green and transparent, with a very marked dorsal hump as in Mysis, to
which it bears a very striking superficial resemblance. It leads a more active
Page 155
swimming life than Anaspides, and with this habit is correlated the flexure
of the body and the greater size of the tail-fan and the scale of the second
antenna. The mandible is peculiar in being furnished with a four-jointed
biramous palp, while that of Anaspides is three-jointed and uniramous, and
the first thoracic appendage is provided with a setose biting lobe on the
antepenultimate joint, thus more resembling a maxillipede. In other respects
it agrees essentially in structure with Anaspides.
Fig. 78.—Paranaspides lacustris, × 4. a1, a2, First and second antennae; Ab.1,
first abdominal segment; ep, epipodites or gills on the thoracic legs; md,
mandible; Pl.1, first pleopod; T, telson; Th.8, eighth free thoracic segment; U,
uropod, or sixth pleopod.
Fam. 2. Koonungidae.—The sole representative of this family,
Koonunga cursor, has been recently described by Mr. O. A. Sayce,[94] of
Melbourne University, from a small stream some miles to the west of
Melbourne. Although plainly belonging to the Anaspidacea, this interesting
little animal, which only measures a few millimetres in length, and follows
a similar habit to Anaspides, running about with its body unflexed, differs
from all the other members of the Division in possessing sessile instead of
stalked eyes, in the first thoracic segment being fixed to the head, and in a
number of minor anatomical points.
It is impossible at present to assign the Carboniferous forms
(Gampsonyx, Palaeocaris, etc.) to their exact position in the Division, but it
seems that they agreed more closely with Anaspides than with the other two
genera. From the position in which the fossils are preserved, it would
of the body and the greater size of the tail-fan and the scale of the second
antenna. The mandible is peculiar in being furnished with a four-jointed
biramous palp, while that of Anaspides is three-jointed and uniramous, and
the first thoracic appendage is provided with a setose biting lobe on the
antepenultimate joint, thus more resembling a maxillipede. In other respects
it agrees essentially in structure with Anaspides.
Fig. 78.—Paranaspides lacustris, × 4. a1, a2, First and second antennae; Ab.1,
first abdominal segment; ep, epipodites or gills on the thoracic legs; md,
mandible; Pl.1, first pleopod; T, telson; Th.8, eighth free thoracic segment; U,
uropod, or sixth pleopod.
Fam. 2. Koonungidae.—The sole representative of this family,
Koonunga cursor, has been recently described by Mr. O. A. Sayce,[94] of
Melbourne University, from a small stream some miles to the west of
Melbourne. Although plainly belonging to the Anaspidacea, this interesting
little animal, which only measures a few millimetres in length, and follows
a similar habit to Anaspides, running about with its body unflexed, differs
from all the other members of the Division in possessing sessile instead of
stalked eyes, in the first thoracic segment being fixed to the head, and in a
number of minor anatomical points.
It is impossible at present to assign the Carboniferous forms
(Gampsonyx, Palaeocaris, etc.) to their exact position in the Division, but it
seems that they agreed more closely with Anaspides than with the other two
genera. From the position in which the fossils are preserved, it would
Page 156
appear that they followed a similar walking habit to Anaspides, and that the
body was unflexed.
DIVISION 2. PERACARIDA.
The carapace, when present, leaves at least four of the thoracic somites
distinct; the first thoracic segment is always fused with the head. The eyes
are pedunculate or sessile.
The mandible possesses a lacinia mobilis. A brood-pouch is formed in the
female from oostegites attached to the thoracic limbs. The hepatic caeca are
few and simple; the heart is elongated and tubular; the spermatozoa are
filiform, and development takes place without a complicated
metamorphosis.
Order I. Mysidacea.
The Mysidacea, although pelagic, are not very often met with in the true
plankton on the surface; they generally swim some way below the surface,
going down in many cases into the abysses. For this reason they thrive
excellently in aquaria, and the common Mysis vulgaris is often present in
such numbers in the tanks at the Zoological station at Naples as to damage
the other inmates by the mere press of numbers. The Mysidacea, like the
majority of the Peracarida, undergo a direct development, and hatch out
with the structure of the adult fully formed.
Many of the Mysidacea bear auditory sacs upon the sixth pair of
pleopods, a characteristic not found in the Euphausiacea.
Fam. 1. Eucopiidae.—The curious form Eucopia australis (Fig. 79)
described by Sars,[95] may be chosen as an example of the Mysidacea.
The peculiarity of this form consists chiefly in the immense elongation of
the endopodites of the fifth, sixth, and seventh thoracic appendages.
Characteristic of the Mysidacea is the freedom of the hinder thoracic
segments from fusion with the carapace, otherwise this animal is seen
closely to resemble the Euphausia figured (Fig. 102). Eucopia australis,
like so many of the Mysidacea, is a deep-sea animal, being brought up with
body was unflexed.
DIVISION 2. PERACARIDA.
The carapace, when present, leaves at least four of the thoracic somites
distinct; the first thoracic segment is always fused with the head. The eyes
are pedunculate or sessile.
The mandible possesses a lacinia mobilis. A brood-pouch is formed in the
female from oostegites attached to the thoracic limbs. The hepatic caeca are
few and simple; the heart is elongated and tubular; the spermatozoa are
filiform, and development takes place without a complicated
metamorphosis.
Order I. Mysidacea.
The Mysidacea, although pelagic, are not very often met with in the true
plankton on the surface; they generally swim some way below the surface,
going down in many cases into the abysses. For this reason they thrive
excellently in aquaria, and the common Mysis vulgaris is often present in
such numbers in the tanks at the Zoological station at Naples as to damage
the other inmates by the mere press of numbers. The Mysidacea, like the
majority of the Peracarida, undergo a direct development, and hatch out
with the structure of the adult fully formed.
Many of the Mysidacea bear auditory sacs upon the sixth pair of
pleopods, a characteristic not found in the Euphausiacea.
Fam. 1. Eucopiidae.—The curious form Eucopia australis (Fig. 79)
described by Sars,[95] may be chosen as an example of the Mysidacea.
The peculiarity of this form consists chiefly in the immense elongation of
the endopodites of the fifth, sixth, and seventh thoracic appendages.
Characteristic of the Mysidacea is the freedom of the hinder thoracic
segments from fusion with the carapace, otherwise this animal is seen
closely to resemble the Euphausia figured (Fig. 102). Eucopia australis,
like so many of the Mysidacea, is a deep-sea animal, being brought up with
Page 157
the dredge from over 1000 fathoms; it is very widely distributed over the
Atlantic Ocean.
Fig. 79.—Eucopia australis, young female, × 3. A, 1st antenna; Ab.1, 1st
abdominal segment; Ab.6, 6th abdominal appendage; E, eye; T, telson; Th, 5th
thoracic appendage. (After Sars.)
Fam. 2. Lophogastridae.—The members of this family (Lophogaster,
Gnathophausia) agree with the Eucopiidae in the possession of branched
gills on some of the thoracic limbs, in the absence of auditory sacs on the
sixth pair of pleopods, in the presence of normally developed pleopods in
both the male and female, and in the brood-lamellae being developed on all
seven of the thoracic limbs. The endopodites of the posterior thoracic limbs
are, however, of a normal size.
Fam. 3. Mysidae.—These differ from both the foregoing families in the
absence of gills, in the presence of an auditory sac on the sixth pleopods, in
the reduction of the other pleopods in the female, and in the brood-lamellae
being developed only on the more posterior pairs of thoracic limbs. A
number of closely related genera compose this family, of which Mysis,
Boreomysis, and Siriella may be mentioned. Mysis oculata, var. relicta, is a
fresh-water form from the lakes of northern and central Europe.
Atlantic Ocean.
Fig. 79.—Eucopia australis, young female, × 3. A, 1st antenna; Ab.1, 1st
abdominal segment; Ab.6, 6th abdominal appendage; E, eye; T, telson; Th, 5th
thoracic appendage. (After Sars.)
Fam. 2. Lophogastridae.—The members of this family (Lophogaster,
Gnathophausia) agree with the Eucopiidae in the possession of branched
gills on some of the thoracic limbs, in the absence of auditory sacs on the
sixth pair of pleopods, in the presence of normally developed pleopods in
both the male and female, and in the brood-lamellae being developed on all
seven of the thoracic limbs. The endopodites of the posterior thoracic limbs
are, however, of a normal size.
Fam. 3. Mysidae.—These differ from both the foregoing families in the
absence of gills, in the presence of an auditory sac on the sixth pleopods, in
the reduction of the other pleopods in the female, and in the brood-lamellae
being developed only on the more posterior pairs of thoracic limbs. A
number of closely related genera compose this family, of which Mysis,
Boreomysis, and Siriella may be mentioned. Mysis oculata, var. relicta, is a
fresh-water form from the lakes of northern and central Europe.
Page 158
Page 159
Page 160
Fig. 80.—Dorsal view of male Diastylis stygia,
× 12. A, 2nd antenna; Ab.6, 6th abdominal
appendage. (After Sars.)
Order II. Cumacea.[96]
The Cumacea are a group of small marine animals rarely attaining an
inch in length, which agree with the Mysidacea in the characters noted
above as diagnostic of the Division Peracarida; they possess, however, in
addition a number of peculiar properties, and Sars believes them to be of a
primitive nature showing relationship to Nebalia, and possibly to an
ancestral Zoaea-like form. They follow a habit similar to that of the
Mysidacea, being caught either in the surface-plankton or in great depths,
many of the deep-sea forms being blind. They are, however, not true
plankton forms, and they appear to attain a greater development both in
point of variety and size in the seas of the northern hemisphere. The
thoracic limbs may be biramous, but there is a tendency among many of the
genera to lose the exopodites of some of the thoracic legs, an exopodite
never being present on the last few thoracic limbs of the female and on the
last in the male. In the Cumidae the four posterior pairs in both sexes have
no exopodites. The first three thoracic appendages following the maxillae
are distinguished as maxillipedes; they are uniramous, and the first pair
carries an epipodite and a large gill upon the basal joints. Pleopods are only
developed in the male sex.
The flagellum of the second antennae in the male may be enormously
elongated, as in the Atlantic deep-sea species shown in Fig. 80, so as to
exceed in length the rest of the body.
Fam. 1. Cumidae.—No sharp demarcation between thorax and
abdomen. Four posterior pairs of legs in both sexes without exopodites.
Male with five well-developed pleopods in addition to the uropods. Telson
wanting. Cuma, Cyclaspis, etc.
Fam. 2. Lampropidae.—Body-form resembles that of Cumidae. All the
thoracic limbs except the last have exopodites. The male has three pairs of
pleopods. Telson present. Lamprops, Platyaspis, etc.
Fam. 3. Leuconidae.—Body-form similar to above. Male has only two
pairs of pleopods. Mouth-parts peculiar, much less setose than in other
families. Telson absent. Leucon, Eudorella.
× 12. A, 2nd antenna; Ab.6, 6th abdominal
appendage. (After Sars.)
Order II. Cumacea.[96]
The Cumacea are a group of small marine animals rarely attaining an
inch in length, which agree with the Mysidacea in the characters noted
above as diagnostic of the Division Peracarida; they possess, however, in
addition a number of peculiar properties, and Sars believes them to be of a
primitive nature showing relationship to Nebalia, and possibly to an
ancestral Zoaea-like form. They follow a habit similar to that of the
Mysidacea, being caught either in the surface-plankton or in great depths,
many of the deep-sea forms being blind. They are, however, not true
plankton forms, and they appear to attain a greater development both in
point of variety and size in the seas of the northern hemisphere. The
thoracic limbs may be biramous, but there is a tendency among many of the
genera to lose the exopodites of some of the thoracic legs, an exopodite
never being present on the last few thoracic limbs of the female and on the
last in the male. In the Cumidae the four posterior pairs in both sexes have
no exopodites. The first three thoracic appendages following the maxillae
are distinguished as maxillipedes; they are uniramous, and the first pair
carries an epipodite and a large gill upon the basal joints. Pleopods are only
developed in the male sex.
The flagellum of the second antennae in the male may be enormously
elongated, as in the Atlantic deep-sea species shown in Fig. 80, so as to
exceed in length the rest of the body.
Fam. 1. Cumidae.—No sharp demarcation between thorax and
abdomen. Four posterior pairs of legs in both sexes without exopodites.
Male with five well-developed pleopods in addition to the uropods. Telson
wanting. Cuma, Cyclaspis, etc.
Fam. 2. Lampropidae.—Body-form resembles that of Cumidae. All the
thoracic limbs except the last have exopodites. The male has three pairs of
pleopods. Telson present. Lamprops, Platyaspis, etc.
Fam. 3. Leuconidae.—Body-form similar to above. Male has only two
pairs of pleopods. Mouth-parts peculiar, much less setose than in other
families. Telson absent. Leucon, Eudorella.
Page 161
Fam. 4. Diastylidae.—Anterior part of thorax sharply marked off from
posterior part. Male has two pairs of pleopods. Telson present. Diastylis
(Fig. 80). D. goodsiri from the Arctic ocean measures over an inch in
length.
Fam. 5. Pseudocumidae.—Rather similar to Diastylidae, but differ in
reduced size of telson and presence of exopodites on third and fourth
thoracic legs of female. This family is represented by three very similar
marine forms of the genus Pseudocuma; but, as Sars has shown,[97] the
Caspian Sea contains thirteen peculiar species, only one of which can be
referred to the genus Pseudocuma, while the rest may be partitioned among
four genera, Pterocuma, Stenocuma, Caspiocuma, Schizorhynchus.
Order III. Isopoda.
The Isopoda and the Amphipoda are frequently classed together as
Arthrostraca or Edriophthalmata, owing to a number of features which they
share in common, as, for instance, the sessile eyes which distinguish them
from the podophthalmatous Schizopoda and Decapoda, the absence of a
carapace, and the thoracic limbs which are uniramous throughout their
whole existence. For the rest, in the presence of brood-plates and the other
diagnostic characters, they are plainly allied to the other Peracarida, and an
easy transition is effected from the Mysidacea to the Isopoda through the
Chelifera or Anisopoda. Only one thoracic segment is usually fused with
the head, the appendage of this segment being the maxillipede; in the
Chelifera among Isopoda, and the Caprellidae among Amphipoda, two
thoracic segments are fused with the head.
The Isopoda are distinguished from the Amphipoda by the dorso-ventral
flattening of the body, as opposed to the lateral flattening in the Amphipoda,
by the posterior position of the heart, and by the branchial organs being
situated on the abdominal instead of on the thoracic limbs.
The Isopoda, following Sars’[98] classification, fall into six sub-orders—
the Chelifera, Flabellifera, Valvifera, Asellota, Oniscoida, and Epicarida,—
to which must be added the Phreatoicidea.
Sub-Order 1. Chelifera.
posterior part. Male has two pairs of pleopods. Telson present. Diastylis
(Fig. 80). D. goodsiri from the Arctic ocean measures over an inch in
length.
Fam. 5. Pseudocumidae.—Rather similar to Diastylidae, but differ in
reduced size of telson and presence of exopodites on third and fourth
thoracic legs of female. This family is represented by three very similar
marine forms of the genus Pseudocuma; but, as Sars has shown,[97] the
Caspian Sea contains thirteen peculiar species, only one of which can be
referred to the genus Pseudocuma, while the rest may be partitioned among
four genera, Pterocuma, Stenocuma, Caspiocuma, Schizorhynchus.
Order III. Isopoda.
The Isopoda and the Amphipoda are frequently classed together as
Arthrostraca or Edriophthalmata, owing to a number of features which they
share in common, as, for instance, the sessile eyes which distinguish them
from the podophthalmatous Schizopoda and Decapoda, the absence of a
carapace, and the thoracic limbs which are uniramous throughout their
whole existence. For the rest, in the presence of brood-plates and the other
diagnostic characters, they are plainly allied to the other Peracarida, and an
easy transition is effected from the Mysidacea to the Isopoda through the
Chelifera or Anisopoda. Only one thoracic segment is usually fused with
the head, the appendage of this segment being the maxillipede; in the
Chelifera among Isopoda, and the Caprellidae among Amphipoda, two
thoracic segments are fused with the head.
The Isopoda are distinguished from the Amphipoda by the dorso-ventral
flattening of the body, as opposed to the lateral flattening in the Amphipoda,
by the posterior position of the heart, and by the branchial organs being
situated on the abdominal instead of on the thoracic limbs.
The Isopoda, following Sars’[98] classification, fall into six sub-orders—
the Chelifera, Flabellifera, Valvifera, Asellota, Oniscoida, and Epicarida,—
to which must be added the Phreatoicidea.
Sub-Order 1. Chelifera.
Page 162
The Chelifera, including the families (1) Apseudidae and (2) Tanaidae,
are interesting in that they afford a transition between the ordinary Isopods
and the Mysidacea. The important features in which they resemble the
Mysidacea are, first, the fusion of the first two thoracic segments with the
head, with the coincident formation of a kind of carapace in which the
respiratory functions are discharged by a pair of branchial lamellae attached
to the maxillipedes; and, second, the presence of very small exopodites on
the first two thoracic appendages of the Apseudidae.
The second pair of thoracic limbs, i.e. the pair behind the maxillipedes,
are developed both in the Apseudidae and Tanaidae into a pair of powerful
chelae, and these frequently show marked sexual differences, being much
more highly developed in the males than in the females. The biramous and
flattened pleopods are purely natatory in function, and the uropods or
pleopods of the sixth pair are terminal in position and slender.
Both families, of which the Apseudidae contain the larger forms,
sometimes attaining to an inch in length, are littoral in habit, or occur in
sand and ooze at considerable depths, many of the genera being blind.
Many Tanaids (e.g. Leptochelia, Tanais, Heterotanais, etc.) live in the algal
growths of the littoral zone, and being highly heliotropic they are easy to
collect if a basinful of algae is placed in a strong light. The females carry
the eggs about with them in a brood-pouch formed, as is usual in the
Peracarida, by lamellae produced from the bases of the thoracic limbs. The
males on coming to maturity do not appear to grow any more, or to take
food, their mouth-parts frequently degenerating and the alimentary canal
being devoid of food. They are thus in the position of insects which do not
moult after coming to maturity; and, as in Insects, the males are apt to show
a kind of high and low dimorphism—certain of the males being small with
secondary sexual characters little different from those of the females, while
others are large with these characters highly developed. Fritz Müller, in his
Facts for Darwin, observes that in a Brazilian species of Leptochelia,
apparently identical with the European L. dubia, the males occur under two
totally distinct forms—one in which the chelae are greatly developed, and
another in which the chelae resemble those of the female, but the antennae
in this form are provided with far longer and more numerous sensory hairs
than in the first form. Müller suggested that these two varieties were
produced by natural selection, the characters of the one form compensating
for the absence of the characters of the other. A general consideration of the
are interesting in that they afford a transition between the ordinary Isopods
and the Mysidacea. The important features in which they resemble the
Mysidacea are, first, the fusion of the first two thoracic segments with the
head, with the coincident formation of a kind of carapace in which the
respiratory functions are discharged by a pair of branchial lamellae attached
to the maxillipedes; and, second, the presence of very small exopodites on
the first two thoracic appendages of the Apseudidae.
The second pair of thoracic limbs, i.e. the pair behind the maxillipedes,
are developed both in the Apseudidae and Tanaidae into a pair of powerful
chelae, and these frequently show marked sexual differences, being much
more highly developed in the males than in the females. The biramous and
flattened pleopods are purely natatory in function, and the uropods or
pleopods of the sixth pair are terminal in position and slender.
Both families, of which the Apseudidae contain the larger forms,
sometimes attaining to an inch in length, are littoral in habit, or occur in
sand and ooze at considerable depths, many of the genera being blind.
Many Tanaids (e.g. Leptochelia, Tanais, Heterotanais, etc.) live in the algal
growths of the littoral zone, and being highly heliotropic they are easy to
collect if a basinful of algae is placed in a strong light. The females carry
the eggs about with them in a brood-pouch formed, as is usual in the
Peracarida, by lamellae produced from the bases of the thoracic limbs. The
males on coming to maturity do not appear to grow any more, or to take
food, their mouth-parts frequently degenerating and the alimentary canal
being devoid of food. They are thus in the position of insects which do not
moult after coming to maturity; and, as in Insects, the males are apt to show
a kind of high and low dimorphism—certain of the males being small with
secondary sexual characters little different from those of the females, while
others are large with these characters highly developed. Fritz Müller, in his
Facts for Darwin, observes that in a Brazilian species of Leptochelia,
apparently identical with the European L. dubia, the males occur under two
totally distinct forms—one in which the chelae are greatly developed, and
another in which the chelae resemble those of the female, but the antennae
in this form are provided with far longer and more numerous sensory hairs
than in the first form. Müller suggested that these two varieties were
produced by natural selection, the characters of the one form compensating
for the absence of the characters of the other. A general consideration of the
Page 163
sexual dimorphism in the Tanaidae[99]
lends some support to this view, since
the smaller species with feeble chelae
do appear to be compensated by a
greater development of sensory hairs
on the antennae, but the specific
differences are so difficult to
appreciate in the Tanaidae that it is
possible that the two forms of the
male in Müller’s supposed single
species really belonged to two
separate species.
lends some support to this view, since
the smaller species with feeble chelae
do appear to be compensated by a
greater development of sensory hairs
on the antennae, but the specific
differences are so difficult to
appreciate in the Tanaidae that it is
possible that the two forms of the
male in Müller’s supposed single
species really belonged to two
separate species.
Page 164
Page 165
Fig. 81.—Apseudes spinosus, ♂ , × 15. A, 1st
antenna; Ab, 6th abdominal appendage; T, 2nd
thoracic appendage. (After Sars.)
Sub-Order 2. Flabellifera.
The Flabellifera include a number of rather heterogeneous families which
resemble one another, however, in the uropods being lateral and not
terminal, and being expanded together with the telson to form a caudal fan
for swimming. The pleopods are sometimes natatory and sometimes
branchial in function. Some of the families are parasitic or semi-parasitic in
habit.
Fam. 1. Anthuridae.—These are elongated cylindrical creatures found
in mud and among weeds upon the sea-bottom; their mouth-parts are
evidently intended for piercing and sucking, but whether they are parasitic
at certain periods on other animals is not exactly known. Anthura,
Paranthura, Cruregens.
Fam. 2. Gnathiidae.[100]—These forms appear to be related to the
Anthuridae; they are ectoparasitic on various kinds of fish during larval life,
but on assuming the adult state they do not feed any more, subsisting
merely on the nourishment amassed during the larval periods. The larvae
themselves are continually leaving their hosts, and can be taken in great
numbers living freely among weeds on the sea-bottom. The larvae, together
with the adults of Gnathia maxillaris, are extremely abundant among the
roots of the sea-weed Poseidonia cavolinii in the Bay of Naples. The young
larvae hatch out from the body of the female in the state shown in Fig. 82,
A. This minute larva fixes upon a fish, and after a time it is transformed into
the so-called Praniza larva (B), in which the gut is so distended with the
fluid sucked from the host that the segmentation in the hind part of the
thorax is entirely lost. When this larva moults it may, however, reacquire
temporarily its segmentation. After a certain period of this parasitic mode of
life the Praniza finally abandons its host, and becomes transformed into the
adult male or female. This may take place at very different stages in the
growth of the larva, the range of variation in size of the adults being 1–8
mm., and it must be remembered that when once the adult condition is
assumed growth entirely ceases. What it is that determines the stage of
growth in each individual when it shall be transformed into the adult is not
antenna; Ab, 6th abdominal appendage; T, 2nd
thoracic appendage. (After Sars.)
Sub-Order 2. Flabellifera.
The Flabellifera include a number of rather heterogeneous families which
resemble one another, however, in the uropods being lateral and not
terminal, and being expanded together with the telson to form a caudal fan
for swimming. The pleopods are sometimes natatory and sometimes
branchial in function. Some of the families are parasitic or semi-parasitic in
habit.
Fam. 1. Anthuridae.—These are elongated cylindrical creatures found
in mud and among weeds upon the sea-bottom; their mouth-parts are
evidently intended for piercing and sucking, but whether they are parasitic
at certain periods on other animals is not exactly known. Anthura,
Paranthura, Cruregens.
Fam. 2. Gnathiidae.[100]—These forms appear to be related to the
Anthuridae; they are ectoparasitic on various kinds of fish during larval life,
but on assuming the adult state they do not feed any more, subsisting
merely on the nourishment amassed during the larval periods. The larvae
themselves are continually leaving their hosts, and can be taken in great
numbers living freely among weeds on the sea-bottom. The larvae, together
with the adults of Gnathia maxillaris, are extremely abundant among the
roots of the sea-weed Poseidonia cavolinii in the Bay of Naples. The young
larvae hatch out from the body of the female in the state shown in Fig. 82,
A. This minute larva fixes upon a fish, and after a time it is transformed into
the so-called Praniza larva (B), in which the gut is so distended with the
fluid sucked from the host that the segmentation in the hind part of the
thorax is entirely lost. When this larva moults it may, however, reacquire
temporarily its segmentation. After a certain period of this parasitic mode of
life the Praniza finally abandons its host, and becomes transformed into the
adult male or female. This may take place at very different stages in the
growth of the larva, the range of variation in size of the adults being 1–8
mm., and it must be remembered that when once the adult condition is
assumed growth entirely ceases. What it is that determines the stage of
growth in each individual when it shall be transformed into the adult is not
Page 166
known. The males and females differ
from one another so extraordinarily
that it was for long denied that they
were both derived from the Praniza
larvae. This is nevertheless the case.
The change from the Praniza to the
female (Fig. 82, C) is not very great.
The ovary absorbs all the
nourishment in the gut and comes to
occupy the whole of the body, all the
other organs degenerating, including
the alimentary canal and mouth-
parts. Indeed, only the limbs with
their muscles and the nervous system
remain. The change to the male (D)
is more radical. The food is here
stored in the liver, which increases in
the male just as the ovary does in the
female. The segmentation is
reacquired, and the massive square
Fig. 82.—Gnathia maxillaris. A, Segmented head is formed from the hinder part
larva, × 10; B, Praniza larva, × 5; C, gravid
female, × 5; D, male, × 5.
of the head in the Praniza, the
anterior portion with its stylet-like
appendages being thrown away. The
powerful nippers of the male are not formed inside the cases of the old
styliform mandibles, but are independent and possibly not homologous
organs. The meaning of the marked sexual dimorphism and the use of the
males’ nippers are not in the least known, though the animals are easy to
keep under observation. In captivity the males never take the slightest
notice of either larval or adult females.
Fam. 3. Cymothoidae.[101]—This is a group of parasites more completely
parasitic than the foregoing, but their outer organisation does not differ
greatly from an ordinary Isopodan form. A great many very similar species
are known which infest the gill-chambers, mouths, and skin of various
fishes. The chief interest that attaches to them is found in the fact that a
number of them, and perhaps all, are hermaphrodite, each individual acting
as a male when free-swimming and young, and then subsequently settling
from one another so extraordinarily
that it was for long denied that they
were both derived from the Praniza
larvae. This is nevertheless the case.
The change from the Praniza to the
female (Fig. 82, C) is not very great.
The ovary absorbs all the
nourishment in the gut and comes to
occupy the whole of the body, all the
other organs degenerating, including
the alimentary canal and mouth-
parts. Indeed, only the limbs with
their muscles and the nervous system
remain. The change to the male (D)
is more radical. The food is here
stored in the liver, which increases in
the male just as the ovary does in the
female. The segmentation is
reacquired, and the massive square
Fig. 82.—Gnathia maxillaris. A, Segmented head is formed from the hinder part
larva, × 10; B, Praniza larva, × 5; C, gravid
female, × 5; D, male, × 5.
of the head in the Praniza, the
anterior portion with its stylet-like
appendages being thrown away. The
powerful nippers of the male are not formed inside the cases of the old
styliform mandibles, but are independent and possibly not homologous
organs. The meaning of the marked sexual dimorphism and the use of the
males’ nippers are not in the least known, though the animals are easy to
keep under observation. In captivity the males never take the slightest
notice of either larval or adult females.
Fam. 3. Cymothoidae.[101]—This is a group of parasites more completely
parasitic than the foregoing, but their outer organisation does not differ
greatly from an ordinary Isopodan form. A great many very similar species
are known which infest the gill-chambers, mouths, and skin of various
fishes. The chief interest that attaches to them is found in the fact that a
number of them, and perhaps all, are hermaphrodite, each individual acting
as a male when free-swimming and young, and then subsequently settling
Page 167
down and becoming female. This condition is exactly the same as that
occurring universally in the great group of parasitic Isopoda, the Epicarida,
to be considered later. There is no evidence that the Cymothoidae are
phyletically related to the Epicarida, so that the similar sexual organisation
appears to be due to convergence resulting from similar conditions of life.
The general question of hermaphroditism in the Crustacea has been shortly
discussed on pp. 105–106. Cymothoa.
Fam. 4. Cirolanidae.—In this family is placed the largest Isopod known
—the deep-sea Bathynomus giganteus, found in the Gulf of Mexico and the
Indian Ocean, sometimes measuring a foot long by four inches broad. A
common small littoral form is Cirolana.
Fam. 5. Serolidae.[102]—The genus Serolis comprises flattened forms
bearing a curious resemblance to Trilobites, which Milne Edwards
considered more than superficial. The genus is confined to the littoral and
deep waters of the southern hemisphere.
Fam. 6. Sphaeromidae.[103]—These are flattened, broad-bodied forms,
most commonly met with in the Mediterranean and warmer seas. Without
being actually parasitic, they are frequently found as scavengers in decaying
material, and they show some relationship to the parasitic Cymothoidae. In
some of the genera, e.g. Cymodoce, the ovigerous female shows a
degenerate condition of the mouth-parts, while the maxillipedes undergo an
enlargement, and are used for causing a current through the brood-chamber.
Sub-Order 3. Valvifera.
The Valvifera, illustrated by the Idotheidae and Arcturidae, are
characterised by the uropods being turned back and expanded to form
folding doors covering up the delicate pleopods, which are mostly
respiratory in function, though the anterior pairs may serve as swimming
organs. Arcturus is a typically deep sea genus, many species, remarkably
furnished with spiny processes, having been taken by the Challenger in the
southern hemisphere. The Idotheidae are more littoral forms, several
species of Idothea being commonly met with off the British coasts,
occasionally penetrating into brackish or even fresh water.
occurring universally in the great group of parasitic Isopoda, the Epicarida,
to be considered later. There is no evidence that the Cymothoidae are
phyletically related to the Epicarida, so that the similar sexual organisation
appears to be due to convergence resulting from similar conditions of life.
The general question of hermaphroditism in the Crustacea has been shortly
discussed on pp. 105–106. Cymothoa.
Fam. 4. Cirolanidae.—In this family is placed the largest Isopod known
—the deep-sea Bathynomus giganteus, found in the Gulf of Mexico and the
Indian Ocean, sometimes measuring a foot long by four inches broad. A
common small littoral form is Cirolana.
Fam. 5. Serolidae.[102]—The genus Serolis comprises flattened forms
bearing a curious resemblance to Trilobites, which Milne Edwards
considered more than superficial. The genus is confined to the littoral and
deep waters of the southern hemisphere.
Fam. 6. Sphaeromidae.[103]—These are flattened, broad-bodied forms,
most commonly met with in the Mediterranean and warmer seas. Without
being actually parasitic, they are frequently found as scavengers in decaying
material, and they show some relationship to the parasitic Cymothoidae. In
some of the genera, e.g. Cymodoce, the ovigerous female shows a
degenerate condition of the mouth-parts, while the maxillipedes undergo an
enlargement, and are used for causing a current through the brood-chamber.
Sub-Order 3. Valvifera.
The Valvifera, illustrated by the Idotheidae and Arcturidae, are
characterised by the uropods being turned back and expanded to form
folding doors covering up the delicate pleopods, which are mostly
respiratory in function, though the anterior pairs may serve as swimming
organs. Arcturus is a typically deep sea genus, many species, remarkably
furnished with spiny processes, having been taken by the Challenger in the
southern hemisphere. The Idotheidae are more littoral forms, several
species of Idothea being commonly met with off the British coasts,
occasionally penetrating into brackish or even fresh water.
Page 168
Fig. 83.—Munnopsis typica (Munnopsidae), ♂ ,
× 2. A, 2nd antenna; Ab, abdomen; T, 5th
thoracic appendage or 4th leg. (After Sars.)
Sub-Order 4. Asellota.
In this group the abdominal segments are fused dorsally to form a shield-
like caudal region; the pleopods are respiratory in function and reduced in
numbers, the first pair being often expanded and produced backwards to
form an operculum covering the rest. Several of the Asellota are fresh-
water, Asellus aquaticus (Asellidae) being extremely abundant all over
Europe in weed-grown ditches, the mud of slowly-moving streams, and
even on the shores of large lakes. They are mostly sluggish in habit, but the
marine Munnopsidae (Fig. 83, Munnopsis) are expert swimmers, the
swimming organs being fashioned by the expansion and elongation of the
thoracic legs.
Sub-Order 5. Oniscoida.
× 2. A, 2nd antenna; Ab, abdomen; T, 5th
thoracic appendage or 4th leg. (After Sars.)
Sub-Order 4. Asellota.
In this group the abdominal segments are fused dorsally to form a shield-
like caudal region; the pleopods are respiratory in function and reduced in
numbers, the first pair being often expanded and produced backwards to
form an operculum covering the rest. Several of the Asellota are fresh-
water, Asellus aquaticus (Asellidae) being extremely abundant all over
Europe in weed-grown ditches, the mud of slowly-moving streams, and
even on the shores of large lakes. They are mostly sluggish in habit, but the
marine Munnopsidae (Fig. 83, Munnopsis) are expert swimmers, the
swimming organs being fashioned by the expansion and elongation of the
thoracic legs.
Sub-Order 5. Oniscoida.
Page 169
The Oniscoida[104] are terrestrial forms in which the abdomen is fully
segmented, the pleopods are respiratory, their endopodites being delicate
branchiae, while their exopodites are plate-like and form protective
opercula for the gills, and the uropods are biramous and not expanded. The
epimera of the segments are greatly produced. The terrestrial Isopods,
although air-breathers,[105] are dependent on moisture, and are only found in
damp situations. It seems probable that they have been derived from marine
Isopods, since the more generalised of them, e.g., Ligia (Fig. 84), common
on the English coasts, are only found in damp caves and crannies in the
rocks.
Fig. 84.—Ligia oceanica, ventral and dorsal views, × 1. (From original drawings
prepared for Professor Weldon.)
The related Ligidium is found far inland, but always in the
neighbourhood of water. These two genera may be distinguished by the
numerous joints in the flagellum of the second antennae, the flagellum
being in all cases the portion of the antenna succeeding the long fifth joint.
Philoscia muscorum occurs usually near the coast, but it is also found
inland in England under trees in damp moss. This genus and the common
Oniscus, found in woods, are distinguished by the presence of three joints
in the flagellum of the second antenna. Philoscia can be distinguished from
Oniscus by its narrower body and the pretty marbled appearance of its back.
The genus Trichoniscus has four joints in the flagellum; various species are
segmented, the pleopods are respiratory, their endopodites being delicate
branchiae, while their exopodites are plate-like and form protective
opercula for the gills, and the uropods are biramous and not expanded. The
epimera of the segments are greatly produced. The terrestrial Isopods,
although air-breathers,[105] are dependent on moisture, and are only found in
damp situations. It seems probable that they have been derived from marine
Isopods, since the more generalised of them, e.g., Ligia (Fig. 84), common
on the English coasts, are only found in damp caves and crannies in the
rocks.
Fig. 84.—Ligia oceanica, ventral and dorsal views, × 1. (From original drawings
prepared for Professor Weldon.)
The related Ligidium is found far inland, but always in the
neighbourhood of water. These two genera may be distinguished by the
numerous joints in the flagellum of the second antennae, the flagellum
being in all cases the portion of the antenna succeeding the long fifth joint.
Philoscia muscorum occurs usually near the coast, but it is also found
inland in England under trees in damp moss. This genus and the common
Oniscus, found in woods, are distinguished by the presence of three joints
in the flagellum of the second antenna. Philoscia can be distinguished from
Oniscus by its narrower body and the pretty marbled appearance of its back.
The genus Trichoniscus has four joints in the flagellum; various species are
Page 170
found in woods. In Porcellio and Armadillidium there are only two joints in
the flagellum, while Armadillidium, the common garden wood-louse, can
be distinguished from all others by the flattened shape of the uropods, and
the habit of rolling up into a ball like an Armadillo.
There is also a very peculiar species, Platyarthrus hoffmannseggii, which
occurs in England and Northern Europe, and always lives in ants’ nests. It is
supposed that they serve as scavengers for the ants, which tend them
carefully, and evidently treat them as domestic animals of some kind. The
small creature is quite white and blind, and has exceedingly short antennae.
Sub-Order 6. Epicarida.
The Epicarida include an immense number of Isopods, parasitic upon
other Crustacea. In the adult state they become greatly deformed, and offer
very few characters of classificatory value, but they all pass through certain
highly characteristic larval stages which are essentially similar in the
different families. All the species are protandric hermaphrodites, each
individual being male while in a larval state, and then losing its male
organisation and becoming female as the parasitic habit is assumed.
Two series of families are recognised according to the larval stages
passed through, the Cryptoniscina, in which the adult male organisation is
assumed in the Cryptoniscus stage, and the female condition is imposed
directly upon this form, and the Bopyrina, in which the Cryptoniscus
passes into a further larval stage, the Bopyrus, which performs the function
of the male, and upon which the female organisation is imposed as the
parasitic habit is assumed.
The following is a list of the Epicarida with the Crustacea which serve as
their hosts[106]:—
the flagellum, while Armadillidium, the common garden wood-louse, can
be distinguished from all others by the flattened shape of the uropods, and
the habit of rolling up into a ball like an Armadillo.
There is also a very peculiar species, Platyarthrus hoffmannseggii, which
occurs in England and Northern Europe, and always lives in ants’ nests. It is
supposed that they serve as scavengers for the ants, which tend them
carefully, and evidently treat them as domestic animals of some kind. The
small creature is quite white and blind, and has exceedingly short antennae.
Sub-Order 6. Epicarida.
The Epicarida include an immense number of Isopods, parasitic upon
other Crustacea. In the adult state they become greatly deformed, and offer
very few characters of classificatory value, but they all pass through certain
highly characteristic larval stages which are essentially similar in the
different families. All the species are protandric hermaphrodites, each
individual being male while in a larval state, and then losing its male
organisation and becoming female as the parasitic habit is assumed.
Two series of families are recognised according to the larval stages
passed through, the Cryptoniscina, in which the adult male organisation is
assumed in the Cryptoniscus stage, and the female condition is imposed
directly upon this form, and the Bopyrina, in which the Cryptoniscus
passes into a further larval stage, the Bopyrus, which performs the function
of the male, and upon which the female organisation is imposed as the
parasitic habit is assumed.
The following is a list of the Epicarida with the Crustacea which serve as
their hosts[106]:—
Page 171
Microniscidae on Copepoda.
Cryptoniscidae on Ostracoda.
Liriopsidae on Rhizocephala.
Cryptoniscina Hemioniscidae on Cirripedia.
Cabiropsidae on Isopoda.
Podasconidae on Amphipoda.
Asconiscidae on Schizopoda.
Dajidae
Phryxidae
Bopyrina on Decapoda
Bopyridae
Entoniscidae
In all cases the first larval form
which hatches out from the maternal
brood-pouch is called the Epicaridian
larva (Fig. 85).
This little larva has two pairs of
antennae, a pair of curious frontal
processes, and a pair of mandibles.
The other mouth-parts are missing;
there are only six thoracic limbs, but
the full complement of six biramous
pleopods are present, and at the end
of the body there may be a long tube
of unknown function.
Fig. 85.—Epicaridian larva, probably belonging As a type of the Cryptoniscina we
to one of the Cryptoniscina. A, 2nd antenna; Ab, may take the Liriopsidae,[107]
abdominal appendages; T, thoracic appendages. parasitic on the Rhizocephala, which
(From Bonnier, after Hansen.)
are, of course, themselves parasitic
on the Decapoda, the whole
association forming a very remarkable study in Carcinology.
Almost every species of the Rhizocephala is subject to the attacks of
Liriopsids, the latter fixing either on the Rhizocephala themselves, or else
on the Decapod host at a point near the fixation of the Rhizocephalous
parasite. An exceedingly common Liriopsid is Danalia curvata, parasitic on
Sacculina neglecta, which is itself parasitic on the spider-crab, Inachus
mauritanicus, at Naples. The adult Danalia is a mere curved bag full of
eggs or developing embryos, and without any other recognisable organs
Cryptoniscidae on Ostracoda.
Liriopsidae on Rhizocephala.
Cryptoniscina Hemioniscidae on Cirripedia.
Cabiropsidae on Isopoda.
Podasconidae on Amphipoda.
Asconiscidae on Schizopoda.
Dajidae
Phryxidae
Bopyrina on Decapoda
Bopyridae
Entoniscidae
In all cases the first larval form
which hatches out from the maternal
brood-pouch is called the Epicaridian
larva (Fig. 85).
This little larva has two pairs of
antennae, a pair of curious frontal
processes, and a pair of mandibles.
The other mouth-parts are missing;
there are only six thoracic limbs, but
the full complement of six biramous
pleopods are present, and at the end
of the body there may be a long tube
of unknown function.
Fig. 85.—Epicaridian larva, probably belonging As a type of the Cryptoniscina we
to one of the Cryptoniscina. A, 2nd antenna; Ab, may take the Liriopsidae,[107]
abdominal appendages; T, thoracic appendages. parasitic on the Rhizocephala, which
(From Bonnier, after Hansen.)
are, of course, themselves parasitic
on the Decapoda, the whole
association forming a very remarkable study in Carcinology.
Almost every species of the Rhizocephala is subject to the attacks of
Liriopsids, the latter fixing either on the Rhizocephala themselves, or else
on the Decapod host at a point near the fixation of the Rhizocephalous
parasite. An exceedingly common Liriopsid is Danalia curvata, parasitic on
Sacculina neglecta, which is itself parasitic on the spider-crab, Inachus
mauritanicus, at Naples. The adult Danalia is a mere curved bag full of
eggs or developing embryos, and without any other recognisable organs
Page 172
except two pairs of spermathecae upon the ventral surface where the
spermatozoa derived from the larval males are stored.
In Fig. 86 is represented a female
of Inachus mauritanicus which
carried upon it two Sacculinae and a
Danalia curvata, and upon the latter
are seen two minute larval males in
the act of fertilising the adult
Danalia. The eggs develop into the
Epicaridian stage, after which the
larva passes into the Cryptoniscus
stage (Fig. 87). In this larval form the Fig. 86.—Inachus mauritanicus, ♀ , × 1,
segments are clearly delimited; the carrying two Sacculina neglecta (a, b), and a
only mouth-parts present are the Danalia curvata (c), the latter bearing two
dwarf males.
mandibles, but there are seven pairs
of thoracic limbs and the full number
of pleopods. This Cryptoniscus stage is found in all the Epicarida, and only
differs in detail in the various families.
In the Cryptoniscina the Cryptoniscus larva is the male, and at this stage
possesses a pair of large testes in the thorax. The ovaries are also present at
this stage as very small bodies applied to the anterior ends of the testes. The
larval males in this state seek out adult fixed Danaliae and fertilise them;
and, when this is accomplished, they themselves become fixed to the host
and begin to develop into the adult female condition. The limbs are all lost,
and out of the mouth grows a long proboscis (Fig. 88, P), which penetrates
the tissues of the host. The ovaries begin to grow, and a remarkable process
of absorption in the testes takes place. These organs, when fixation occurs,
are never empty of spermatozoa, and are frequently crammed with them.
After fixation some large cells at the interior borders of the testes begin to
feed upon the remains of these organs and to grow enormously in size and
to multiply by amitosis. These phagocytes, as they really are, attain an
enormous size, but they are doomed to degeneration, the chromatin
becoming dispersed through the cytoplasm, and the nuclei dividing first by
amitosis and then breaking up and disappearing. As the parasite grows, the
heart at the posterior end of the body ceases to beat; the ovaries increase
enormously at the expense of the alimentary canal, and on the ventral
surface two pairs of spermathecae are invaginated ready to receive the
spermatozoa derived from the larval males are stored.
In Fig. 86 is represented a female
of Inachus mauritanicus which
carried upon it two Sacculinae and a
Danalia curvata, and upon the latter
are seen two minute larval males in
the act of fertilising the adult
Danalia. The eggs develop into the
Epicaridian stage, after which the
larva passes into the Cryptoniscus
stage (Fig. 87). In this larval form the Fig. 86.—Inachus mauritanicus, ♀ , × 1,
segments are clearly delimited; the carrying two Sacculina neglecta (a, b), and a
only mouth-parts present are the Danalia curvata (c), the latter bearing two
dwarf males.
mandibles, but there are seven pairs
of thoracic limbs and the full number
of pleopods. This Cryptoniscus stage is found in all the Epicarida, and only
differs in detail in the various families.
In the Cryptoniscina the Cryptoniscus larva is the male, and at this stage
possesses a pair of large testes in the thorax. The ovaries are also present at
this stage as very small bodies applied to the anterior ends of the testes. The
larval males in this state seek out adult fixed Danaliae and fertilise them;
and, when this is accomplished, they themselves become fixed to the host
and begin to develop into the adult female condition. The limbs are all lost,
and out of the mouth grows a long proboscis (Fig. 88, P), which penetrates
the tissues of the host. The ovaries begin to grow, and a remarkable process
of absorption in the testes takes place. These organs, when fixation occurs,
are never empty of spermatozoa, and are frequently crammed with them.
After fixation some large cells at the interior borders of the testes begin to
feed upon the remains of these organs and to grow enormously in size and
to multiply by amitosis. These phagocytes, as they really are, attain an
enormous size, but they are doomed to degeneration, the chromatin
becoming dispersed through the cytoplasm, and the nuclei dividing first by
amitosis and then breaking up and disappearing. As the parasite grows, the
heart at the posterior end of the body ceases to beat; the ovaries increase
enormously at the expense of the alimentary canal, and on the ventral
surface two pairs of spermathecae are invaginated ready to receive the
Page 173
spermatozoa of a larval male. In the
adult condition, after fertilisation has
taken place and the ovaries occupy
almost the whole of the body, the
remains of the phagocytic cells can
be seen on the dorsal surface in a
degenerate state. They evidently are
not used as food, and their sole
function is to make away with the
male organisation when it has
become useless.[108]
In the series Bopyrina, after the
free-living Epicaridian and
Cryptoniscus stages, a further larval
state is assumed, called the Bopyrus,
which is the functional male, and,
after performing this function, passes
on to the adult female condition.
The family Bopyridae is parasitic
in the branchial chamber of
Decapoda, especially Macrura and
Anomura. When one of these
Decapods is infested with an adult
Bopyrid the gill-chamber in which it
is situated is greatly swollen, as
Fig. 87.—Ventral view of Cryptoniscus larva of shown in Fig. 90. A very common
Danalia curvata, ♂, × 25.
Bopyrid is Bopyrus fougerouxi,
parasitic in the gill-chambers of
Palaemon serratus. The Bopyrus larva or functional male has the
appearance shown in Fig. 91. It differs from the Cryptoniscus stage in
possessing a rudimentary pair of anterior thoracic limbs and seven pairs
normally developed, while the abdominal limbs are plate-like and branchial
in function. The male can often be found attached to the female beneath the
last pair of incubatory lamellae.
The adult female condition, which is assumed after the Bopyrid stage is
passed through, is illustrated in Fig. 92. The body acquires a remarkable
adult condition, after fertilisation has
taken place and the ovaries occupy
almost the whole of the body, the
remains of the phagocytic cells can
be seen on the dorsal surface in a
degenerate state. They evidently are
not used as food, and their sole
function is to make away with the
male organisation when it has
become useless.[108]
In the series Bopyrina, after the
free-living Epicaridian and
Cryptoniscus stages, a further larval
state is assumed, called the Bopyrus,
which is the functional male, and,
after performing this function, passes
on to the adult female condition.
The family Bopyridae is parasitic
in the branchial chamber of
Decapoda, especially Macrura and
Anomura. When one of these
Decapods is infested with an adult
Bopyrid the gill-chamber in which it
is situated is greatly swollen, as
Fig. 87.—Ventral view of Cryptoniscus larva of shown in Fig. 90. A very common
Danalia curvata, ♂, × 25.
Bopyrid is Bopyrus fougerouxi,
parasitic in the gill-chambers of
Palaemon serratus. The Bopyrus larva or functional male has the
appearance shown in Fig. 91. It differs from the Cryptoniscus stage in
possessing a rudimentary pair of anterior thoracic limbs and seven pairs
normally developed, while the abdominal limbs are plate-like and branchial
in function. The male can often be found attached to the female beneath the
last pair of incubatory lamellae.
The adult female condition, which is assumed after the Bopyrid stage is
passed through, is illustrated in Fig. 92. The body acquires a remarkable
Page 174
asymmetry, due to the unequal
pressure exerted by the walls of the
gill-chamber. The antennae and
mandibles (Fig. 92, B) are entirely
covered up by the largely expanded
maxillipedes; maxillae are, as usual,
entirely absent. Very large lamellae
grow out from the bases of the
thoracic limbs to form a brood-
pouch, and in this manner the adult
condition is attained.
Fig. 88.—Side view of Danalia curvata, × 15,
shortly after fixation and loss of larval The final complication in the life-
appendages. A, Alimentary canal; E, eye; H, histories of these Isopoda is reached
heart; N, phagocytic cells; O, ovary; P,
proboscis. by the family Entoniscidae, which
are parasitic when adult inside the
thoracic cavity of Brachyura and
Paguridae. The cephalothorax of a
Carcinus maenas, which contains an
adult Portunion maenadis (P), is
shown in Fig. 93. The parasite is of a
reddish colour when alive.
Fig. 89.—Optical section (dorsal view) of
Danalia curvata, in the same stage as Fig. 88. A,
Alimentary canal; Ec, ectoderm; H, heart; N,
phagocytic cells; O, ovaries; P, proboscis.
pressure exerted by the walls of the
gill-chamber. The antennae and
mandibles (Fig. 92, B) are entirely
covered up by the largely expanded
maxillipedes; maxillae are, as usual,
entirely absent. Very large lamellae
grow out from the bases of the
thoracic limbs to form a brood-
pouch, and in this manner the adult
condition is attained.
Fig. 88.—Side view of Danalia curvata, × 15,
shortly after fixation and loss of larval The final complication in the life-
appendages. A, Alimentary canal; E, eye; H, histories of these Isopoda is reached
heart; N, phagocytic cells; O, ovary; P,
proboscis. by the family Entoniscidae, which
are parasitic when adult inside the
thoracic cavity of Brachyura and
Paguridae. The cephalothorax of a
Carcinus maenas, which contains an
adult Portunion maenadis (P), is
shown in Fig. 93. The parasite is of a
reddish colour when alive.
Fig. 89.—Optical section (dorsal view) of
Danalia curvata, in the same stage as Fig. 88. A,
Alimentary canal; Ec, ectoderm; H, heart; N,
phagocytic cells; O, ovaries; P, proboscis.
Page 175
Fig. 90.—Galathea intermedia, with a
Pleurocrypta microbranchiata under its left
branchiostegite (B), × 1. (After Sars.)
Pleurocrypta microbranchiata under its left
branchiostegite (B), × 1. (After Sars.)
Page 176
Fig. 91.—Ventral view of male Bopyrus
fougerouxi, × 30. A, 1st and 2nd antennae; T, 8th
(last) thoracic appendage. (After Bonnier.)
fougerouxi, × 30. A, 1st and 2nd antennae; T, 8th
(last) thoracic appendage. (After Bonnier.)
Page 177
Fig. 92.—Bopyrus fougerouxi. A, Ventral view of
female carrying a male (M) between her
abdominal appendages, × 8; B, ventral view of
part of head of female, the maxillipedes and the
left mandible having been removed. A.1, A.2, 1st
and 2nd antennae; M, male; Mn, right mandible;
Mx, left maxillipede; O, oostegite; T, left 4th
thoracic appendage or 3rd leg. (After Bonnier.)
The Entoniscidae pass through a free living Epicaridian and Cryptoniscus
stage, and become adult males in the Bopyrus stage. It is stated, however,
by Giard and Bonnier[109] that these individuals, which actually function as
males, never grow up into adult females, though all the adult females have
passed through a male stage in which the male genital ducts are not formed.
The hermaphroditism, therefore, in these animals at any rate is absolutely
female carrying a male (M) between her
abdominal appendages, × 8; B, ventral view of
part of head of female, the maxillipedes and the
left mandible having been removed. A.1, A.2, 1st
and 2nd antennae; M, male; Mn, right mandible;
Mx, left maxillipede; O, oostegite; T, left 4th
thoracic appendage or 3rd leg. (After Bonnier.)
The Entoniscidae pass through a free living Epicaridian and Cryptoniscus
stage, and become adult males in the Bopyrus stage. It is stated, however,
by Giard and Bonnier[109] that these individuals, which actually function as
males, never grow up into adult females, though all the adult females have
passed through a male stage in which the male genital ducts are not formed.
The hermaphroditism, therefore, in these animals at any rate is absolutely
Page 178
useless from a reproductive point of
view, and this justifies our looking
for some other explanation of it, such
as was suggested on p. 105.
Fig. 93.—Cephalothorax of Carcinus maenas,
seen from the ventral side, containing a parasitic
Portunion maenadis (P), × ½. (After Bonnier.)
Fig. 94.—Portunion maenadis, ♀ :—A, Young, × 10; B, older, × 5; C, adult,
before the eggs are laid, × 3. A, 2nd antenna; Ab, abdomen; B, anterior lobe of
brood-pouch; B′, its lateral lobe; H, head; 1, 2, 1st and 2nd incubatory lamellae
(oostegites). (After Giard and Bonnier.)
The Bopyrus fixes in the gill-chamber of the host and becomes converted
into the adult female by a series of transformations. As these changes take
place it invaginates the wall of the gill-chamber and pushes its way into the
view, and this justifies our looking
for some other explanation of it, such
as was suggested on p. 105.
Fig. 93.—Cephalothorax of Carcinus maenas,
seen from the ventral side, containing a parasitic
Portunion maenadis (P), × ½. (After Bonnier.)
Fig. 94.—Portunion maenadis, ♀ :—A, Young, × 10; B, older, × 5; C, adult,
before the eggs are laid, × 3. A, 2nd antenna; Ab, abdomen; B, anterior lobe of
brood-pouch; B′, its lateral lobe; H, head; 1, 2, 1st and 2nd incubatory lamellae
(oostegites). (After Giard and Bonnier.)
The Bopyrus fixes in the gill-chamber of the host and becomes converted
into the adult female by a series of transformations. As these changes take
place it invaginates the wall of the gill-chamber and pushes its way into the
Page 179
thoracic cavity of the crab, though it lies all the time enveloped in the
invaginated wall of the gill-chamber, and not free in the body-cavity of the
crab. The transformations which it undergoes are shown in Fig. 94. The
body first assumes a grub-like appearance (A), and two pairs of incubatory
lamellae (1, 2) grow out from the first and second thoracic segments. In the
next stage (B) these lamellae assume gigantic proportions, and four pairs of
branchiae grow out from the abdominal segments (Ab). In the final stage
(C) the incubatory lamellae have further increased in size, and constitute the
main bulk of the body; the enormous mass of eggs is passed into the
incubatory pouch, and all that remains of the rest of the body is the small
head (H) and the abdomen (Ab), furnished with its branchiae.
Communication with the external world is kept up through an aperture
which leads from the brood-pouch into the gill-chamber of the host, and
through this aperture the young are hatched out when they are developed
sufficiently.
The presence of these parasites, although they are never in actual contact
with the internal organs of the crab, calls forth the same phenomenon of
parasitic castration as was observed in the Rhizocephala. A remarkable
association is also found to exist between the Entoniscidae and
Rhizocephala, of such a kind that, on the whole, a crab infested with a
Rhizocephalan is more likely to harbour an Entoniscid than one without.
The explanation of this association is probably that a crab with a Sacculina
inside it is prevented from moulting as often as an uninfected crab, and, in
consequence, the larval stages of the Entoniscid in the crab’s gill-chamber
are more safely passed through.
Sub-Order 7. Phreatoicidea.[110]
The members of this sub-order, although agreeing with the Isopoda in the
essentials of their anatomy, resemble the Amphipoda in being rather
laterally compressed, and in having the hand of the first free thoracic limb
enlarged and subchelate. The abdomen is greatly produced laterally by
expansions of the segments. In fact, the shape of the body and of the limbs
is very Amphipodan.—Phreatoicus from New Zealand, Southern Australia,
and Tasmania. Phreatoicopsis,[111] a very large form from Gippsland,
Victoria. Only one family exists, Phreatoicidae.
invaginated wall of the gill-chamber, and not free in the body-cavity of the
crab. The transformations which it undergoes are shown in Fig. 94. The
body first assumes a grub-like appearance (A), and two pairs of incubatory
lamellae (1, 2) grow out from the first and second thoracic segments. In the
next stage (B) these lamellae assume gigantic proportions, and four pairs of
branchiae grow out from the abdominal segments (Ab). In the final stage
(C) the incubatory lamellae have further increased in size, and constitute the
main bulk of the body; the enormous mass of eggs is passed into the
incubatory pouch, and all that remains of the rest of the body is the small
head (H) and the abdomen (Ab), furnished with its branchiae.
Communication with the external world is kept up through an aperture
which leads from the brood-pouch into the gill-chamber of the host, and
through this aperture the young are hatched out when they are developed
sufficiently.
The presence of these parasites, although they are never in actual contact
with the internal organs of the crab, calls forth the same phenomenon of
parasitic castration as was observed in the Rhizocephala. A remarkable
association is also found to exist between the Entoniscidae and
Rhizocephala, of such a kind that, on the whole, a crab infested with a
Rhizocephalan is more likely to harbour an Entoniscid than one without.
The explanation of this association is probably that a crab with a Sacculina
inside it is prevented from moulting as often as an uninfected crab, and, in
consequence, the larval stages of the Entoniscid in the crab’s gill-chamber
are more safely passed through.
Sub-Order 7. Phreatoicidea.[110]
The members of this sub-order, although agreeing with the Isopoda in the
essentials of their anatomy, resemble the Amphipoda in being rather
laterally compressed, and in having the hand of the first free thoracic limb
enlarged and subchelate. The abdomen is greatly produced laterally by
expansions of the segments. In fact, the shape of the body and of the limbs
is very Amphipodan.—Phreatoicus from New Zealand, Southern Australia,
and Tasmania. Phreatoicopsis,[111] a very large form from Gippsland,
Victoria. Only one family exists, Phreatoicidae.
Page 180
Order IV. Amphipoda.
In this order the body is flattened laterally, the heart is anterior in
position, and the branchial organs are attached to the thoracic limbs.
There are three well defined sub-orders, (i.) the Crevettina, including a
vast assemblage of very similar animals, of which the common Gammarus
and Orchestia may serve as examples; (ii.) the Laemodipoda or Caprellids,
and (iii.) the Hyperina.
We cannot do more than touch on the organisation of these sub-orders.
Sub-Order 1. Crevettina.
In this sub-order only one thoracic segment is fused with the head; the
basal joints of the thoracic limbs are expanded to form broad lateral plates,
and the abdomen is well developed, with six pairs of pleopods, the last three
pairs being always turned backwards, and stiffened to act as uropods.
This group has numerous fresh-water representatives, e.g. Gammarus of
several species, the blind well-shrimp Niphargus, and the S. American
Hyalella; but the vast majority of the species are marine, and are found
especially in the littoral zone wherever the rocks are covered with a rich
growth of algae, Polyzoa, etc. The Talitridae or “Sand-hoppers” have
deserted the waters and live entirely in the sand and under rocks on the
shore, and one common European species, Orchestia gammarellus,
penetrates far inland, and may be found in gardens where the soil is moist
many miles from the sea.
The Rev. T. R. R. Stebbing, in his standard work[112] on this group,
recognises forty-one families, and more than 1000 species, so that we can
only mention a few of the families, many of which, indeed, differ from one
another in small characters.
Fam. Lysianassidae.—The first joint of the first antenna is short, with an
accessory flagellum. Mandible with a palp, and with an almost smooth
cutting edge. The third joint of the second gnathopod is elongated. This
family is entirely marine, comprising forty-eight genera, with species
distributed in all seas. One genus, Pseudalibrotus, inhabits the brackish
water of the Caspian Sea. Lysianassa has several common British and
Mediterranean species.
In this order the body is flattened laterally, the heart is anterior in
position, and the branchial organs are attached to the thoracic limbs.
There are three well defined sub-orders, (i.) the Crevettina, including a
vast assemblage of very similar animals, of which the common Gammarus
and Orchestia may serve as examples; (ii.) the Laemodipoda or Caprellids,
and (iii.) the Hyperina.
We cannot do more than touch on the organisation of these sub-orders.
Sub-Order 1. Crevettina.
In this sub-order only one thoracic segment is fused with the head; the
basal joints of the thoracic limbs are expanded to form broad lateral plates,
and the abdomen is well developed, with six pairs of pleopods, the last three
pairs being always turned backwards, and stiffened to act as uropods.
This group has numerous fresh-water representatives, e.g. Gammarus of
several species, the blind well-shrimp Niphargus, and the S. American
Hyalella; but the vast majority of the species are marine, and are found
especially in the littoral zone wherever the rocks are covered with a rich
growth of algae, Polyzoa, etc. The Talitridae or “Sand-hoppers” have
deserted the waters and live entirely in the sand and under rocks on the
shore, and one common European species, Orchestia gammarellus,
penetrates far inland, and may be found in gardens where the soil is moist
many miles from the sea.
The Rev. T. R. R. Stebbing, in his standard work[112] on this group,
recognises forty-one families, and more than 1000 species, so that we can
only mention a few of the families, many of which, indeed, differ from one
another in small characters.
Fam. Lysianassidae.—The first joint of the first antenna is short, with an
accessory flagellum. Mandible with a palp, and with an almost smooth
cutting edge. The third joint of the second gnathopod is elongated. This
family is entirely marine, comprising forty-eight genera, with species
distributed in all seas. One genus, Pseudalibrotus, inhabits the brackish
water of the Caspian Sea. Lysianassa has several common British and
Mediterranean species.
Page 181
Fam. Haustoriidae.—The members of this family are specially adapted
for burrowing, the joints of the hinder thoracic limbs being expanded, and
furnished with spines for digging. Some of the species are common on the
British coasts, e.g. Haustorius arenarius. Pontoporeia has an interesting
distribution, one species, P. femorata, being entirely marine, in the Arctic
and North Atlantic, P. affinis inhabiting the Atlantic, and also fresh-water
lakes in Europe and North America, P. microphthalma being confined to the
Caspian Sea, and P. loyi to Lakes Superior and Michigan.
Fam. Gammaridae.—Includes fifty-two genera. The first antennae are
slender, with the accessory flagellum very variable. The mandibles have a
dentate cutting edge, spine-row, and molar surface, and a three-jointed palp.
The first two thoracic limbs are subchelate. This family includes a few
marine, but mostly brackish and fresh-water species. Crangonyx is entirely
subterranean in habitat, as is Niphargus, N. forelii occurring, however, in
the deep waters of Lake Geneva. Both these genera are blind. Gammarus
has thirty species, G. locusta being the common species on the North
Atlantic coasts, and G. pulex the common fresh-water species of streams
and lakes in Europe. A number of Gammaridae inhabit the Caspian Sea, e.g.
Boeckia, Gmelina, Niphargoides, etc., while the enormous Gammarid fauna
of Lake Baikal, constituting numerous genera, showing a great variety of
structure, some of them being blind, belong to this family, e.g.
Macrohectopus (Constantia), Acanthogammarus, Heterogammarus, etc.
for burrowing, the joints of the hinder thoracic limbs being expanded, and
furnished with spines for digging. Some of the species are common on the
British coasts, e.g. Haustorius arenarius. Pontoporeia has an interesting
distribution, one species, P. femorata, being entirely marine, in the Arctic
and North Atlantic, P. affinis inhabiting the Atlantic, and also fresh-water
lakes in Europe and North America, P. microphthalma being confined to the
Caspian Sea, and P. loyi to Lakes Superior and Michigan.
Fam. Gammaridae.—Includes fifty-two genera. The first antennae are
slender, with the accessory flagellum very variable. The mandibles have a
dentate cutting edge, spine-row, and molar surface, and a three-jointed palp.
The first two thoracic limbs are subchelate. This family includes a few
marine, but mostly brackish and fresh-water species. Crangonyx is entirely
subterranean in habitat, as is Niphargus, N. forelii occurring, however, in
the deep waters of Lake Geneva. Both these genera are blind. Gammarus
has thirty species, G. locusta being the common species on the North
Atlantic coasts, and G. pulex the common fresh-water species of streams
and lakes in Europe. A number of Gammaridae inhabit the Caspian Sea, e.g.
Boeckia, Gmelina, Niphargoides, etc., while the enormous Gammarid fauna
of Lake Baikal, constituting numerous genera, showing a great variety of
structure, some of them being blind, belong to this family, e.g.
Macrohectopus (Constantia), Acanthogammarus, Heterogammarus, etc.
Page 182
Fig. 95.—Gammarus locusta, ♂ (above) and ♀ (below), × 4. Abd.1, First
abdominal segment; T, telson; Th, seventh free thoracic segment (= 8th thoracic
segment); U, third uropod. (After Della Valle.)
Fam. Talitridae.—This family may be distinguished by the absence of a
palp on the mandible, and by one ramus of the uropods being very small or
wanting. The various kinds of “Sand-hoppers” belong here, familiar
creatures on every sandy coast between tide-marks. The genera Talitrus and
Talorchestia always frequent sand, while Orchestia is generally found under
stones and among weed. Some species of Orchestia, e.g. O. gammarellus,
live inland in moist places at some distance from the sea; one species of
Talitrus (T. sylvaticus) occurs at great elevations in forests in Southern
Australia.
Hyale is a coastal genus, and is also found on floating objects in the
Sargasso Sea. Hyalella is confined to Lake Titicaca and the fresh waters of
South America. Chiltonia from S. Australasia.
Fam. Corophiidae.—The members of this family have a rather flattened
body and small abdomen, and the side-plates on the thorax are small. The
uropods are also small and weak. Some species of the genus Corophium are
characteristic of the Caspian Sea.
Sub-Order 2. Laemodipoda.
abdominal segment; T, telson; Th, seventh free thoracic segment (= 8th thoracic
segment); U, third uropod. (After Della Valle.)
Fam. Talitridae.—This family may be distinguished by the absence of a
palp on the mandible, and by one ramus of the uropods being very small or
wanting. The various kinds of “Sand-hoppers” belong here, familiar
creatures on every sandy coast between tide-marks. The genera Talitrus and
Talorchestia always frequent sand, while Orchestia is generally found under
stones and among weed. Some species of Orchestia, e.g. O. gammarellus,
live inland in moist places at some distance from the sea; one species of
Talitrus (T. sylvaticus) occurs at great elevations in forests in Southern
Australia.
Hyale is a coastal genus, and is also found on floating objects in the
Sargasso Sea. Hyalella is confined to Lake Titicaca and the fresh waters of
South America. Chiltonia from S. Australasia.
Fam. Corophiidae.—The members of this family have a rather flattened
body and small abdomen, and the side-plates on the thorax are small. The
uropods are also small and weak. Some species of the genus Corophium are
characteristic of the Caspian Sea.
Sub-Order 2. Laemodipoda.
Page 183
Fig. 96.—Caprella grandimana, × 4. a, Abdomen; g, gills; t, 3rd (first free)
thoracic segment; t′, 8th thoracic segment. (After P. Mayer.)
Fam. 1. Caprellidae[113] are also chiefly littoral forms, swarming among
rocks covered by algae, though they are by no means so easy to detect as
the Gammaridae and Tanaidae which haunt similar situations. In a basinful
of algae or Polyzoa taken from the rocks fringing the Bay of Naples, the
latter are easily collected, the Tanaidae always crawling out of the weeds in
the direction of the light, while the Gammarids dart about in all directions;
but the Caprellidae, with their branching stick-like forms, harmonise so
well with their surroundings that it requires an experienced eye to detect
them. The body is elongated and thin, resembling that of a stick-insect. The
first two thoracic segments are more or less completely fused with the head;
the second and third thoracic limbs end in claws; the two following thoracic
limbs are normal in the genus Proto, rudimentary in Protella, and absent in
the remaining genera, though their gills remain as conspicuous flabellate
structures. The three hind legs are normal, and the abdomen is reduced to a
tiny wart at the hind end of the greatly elongated thorax.
P. Mayer has described cases of external hermaphroditism as being fairly
common in certain species, e.g. Caprella acutifrons, and this is interesting if
we take into consideration the frequent partial hermaphroditism exhibited
by the gonad of Orchestia at certain times of year (see p. 104).
Fam. 2. Cyamidae.—These are closely related to the Caprellidae in the
form of the limbs and the reduced state of the abdomen. Cyamus ceti, which
lives ectoparasitically on the skin of whales, has the body expanded
laterally instead of being elongated, as in the Caprellids.
Sub-Order 3. Hyperina.
thoracic segment; t′, 8th thoracic segment. (After P. Mayer.)
Fam. 1. Caprellidae[113] are also chiefly littoral forms, swarming among
rocks covered by algae, though they are by no means so easy to detect as
the Gammaridae and Tanaidae which haunt similar situations. In a basinful
of algae or Polyzoa taken from the rocks fringing the Bay of Naples, the
latter are easily collected, the Tanaidae always crawling out of the weeds in
the direction of the light, while the Gammarids dart about in all directions;
but the Caprellidae, with their branching stick-like forms, harmonise so
well with their surroundings that it requires an experienced eye to detect
them. The body is elongated and thin, resembling that of a stick-insect. The
first two thoracic segments are more or less completely fused with the head;
the second and third thoracic limbs end in claws; the two following thoracic
limbs are normal in the genus Proto, rudimentary in Protella, and absent in
the remaining genera, though their gills remain as conspicuous flabellate
structures. The three hind legs are normal, and the abdomen is reduced to a
tiny wart at the hind end of the greatly elongated thorax.
P. Mayer has described cases of external hermaphroditism as being fairly
common in certain species, e.g. Caprella acutifrons, and this is interesting if
we take into consideration the frequent partial hermaphroditism exhibited
by the gonad of Orchestia at certain times of year (see p. 104).
Fam. 2. Cyamidae.—These are closely related to the Caprellidae in the
form of the limbs and the reduced state of the abdomen. Cyamus ceti, which
lives ectoparasitically on the skin of whales, has the body expanded
laterally instead of being elongated, as in the Caprellids.
Sub-Order 3. Hyperina.
Page 184
These are an equally distinct and
curious group of Amphipods,
characterised by the large size of the
head and the transparency of the
body. Instead of haunting the littoral
zone they are pelagic in habit, and
many of them live inside transparent
pelagic Molluscs, Tunicates, or
Jellyfish. A well known form is
Phronima sedentaria, which inhabits
Fig. 97.—Phronima sedentaria, ♀ , in a the glassy barrel-like cases of the
Pyrosoma colony, × 1. (After Claus, from Tunicate Pyrosoma in the
Gerstaecker and Ortmann.) Mediterranean. The female is often
taken in the plankton together with
her brood in one of these curious glass houses; the zooids of the Pyrosoma
colony are completely eaten away and the external surface of the case,
instead of being rough with the tentacles of the zooids, is worn to a smooth,
glass-like surface. It has been observed that the female actively navigates
her house upon the surface of the sea; she clings on with her thoracic legs
inside, while the abdomen is pushed out through an opening of the
Pyrosoma case behind, and by its alternate flexion and extension drives the
boat forwards, the water being thus made to enter at the front aperture and
supply the female and her brood with nourishment.
DIVISION 3. HOPLOCARIDA.
The carapace leaves at least four of the thoracic somites distinct. The
eyes are pedunculate. The mandibles are without a lacinia mobilis; there are
no oostegites, the eggs being carried in a chamber formed by the
maxillipedes. The hepatic caeca are much ramified, the heart is greatly
elongated, stretching through thorax and abdomen, with a pair of ostia in
each segment. The spermatozoa are spherical, and there is a complicated
and peculiar metamorphosis.
Order. Stomatopoda.
curious group of Amphipods,
characterised by the large size of the
head and the transparency of the
body. Instead of haunting the littoral
zone they are pelagic in habit, and
many of them live inside transparent
pelagic Molluscs, Tunicates, or
Jellyfish. A well known form is
Phronima sedentaria, which inhabits
Fig. 97.—Phronima sedentaria, ♀ , in a the glassy barrel-like cases of the
Pyrosoma colony, × 1. (After Claus, from Tunicate Pyrosoma in the
Gerstaecker and Ortmann.) Mediterranean. The female is often
taken in the plankton together with
her brood in one of these curious glass houses; the zooids of the Pyrosoma
colony are completely eaten away and the external surface of the case,
instead of being rough with the tentacles of the zooids, is worn to a smooth,
glass-like surface. It has been observed that the female actively navigates
her house upon the surface of the sea; she clings on with her thoracic legs
inside, while the abdomen is pushed out through an opening of the
Pyrosoma case behind, and by its alternate flexion and extension drives the
boat forwards, the water being thus made to enter at the front aperture and
supply the female and her brood with nourishment.
DIVISION 3. HOPLOCARIDA.
The carapace leaves at least four of the thoracic somites distinct. The
eyes are pedunculate. The mandibles are without a lacinia mobilis; there are
no oostegites, the eggs being carried in a chamber formed by the
maxillipedes. The hepatic caeca are much ramified, the heart is greatly
elongated, stretching through thorax and abdomen, with a pair of ostia in
each segment. The spermatozoa are spherical, and there is a complicated
and peculiar metamorphosis.
Order. Stomatopoda.
Page 185
Fig. 98.—Lateral view of Squilla sp., × 1. A.1, A.2, 1st and 2nd antennae; Ab.1,
1st abdominal segment; Ab.6, 6th abdominal appendage; C, cephalothorax,
consisting of the head fused with the first five thoracic segments; E, eye; M, 2nd
maxillipede; T, telson. (After Gerstaecker and Ortmann.)
The Stomatopoda are rather large animals, occasionally reaching a foot in
length, all of which exhibit a very similar structure; Squilla mantis and S.
desmaresti are found on the south coast of England not very frequently; but
they are very common in the Mediterranean, living in holes or in the sand
within the littoral zone of shallow water. They differ from all the other
Malacostraca by a combination of characters, and Calman proposes the
term Hoplocarida for a division equivalent to the Peracarida, Eucarida, etc.
The abdomen is very broad and well developed, ending in a widely
expanded telson. There is a carapace which covers the four anterior thoracic
segments, leaving the four posterior segments free. The portion of the head
carrying the stalked eyes constitutes an apparently separate segment
articulated to the head. The antennae, mandibles, and maxillae are normal;
there then follow five pairs of uniramous thoracic limbs turned forwards as
maxillipedes and ending in claws; the second pair of these is modified into
a huge raptorial arm, exactly resembling that of a Praying Mantis (cf. vol. v.
p. 242), by means of which the Squilla seizes its prey. The last three
thoracic limbs are small and biramous. The pleopods are powerful,
flattened, biramous swimming organs with small hooks or “retinaculae”
upon their endopodites, which link together each member of a pair in the
middle, and with large branching gills upon the exopodites.
The internal anatomy exhibits several primitive features. The nervous
system is not at all concentrated, there being a separate ganglion for each
1st abdominal segment; Ab.6, 6th abdominal appendage; C, cephalothorax,
consisting of the head fused with the first five thoracic segments; E, eye; M, 2nd
maxillipede; T, telson. (After Gerstaecker and Ortmann.)
The Stomatopoda are rather large animals, occasionally reaching a foot in
length, all of which exhibit a very similar structure; Squilla mantis and S.
desmaresti are found on the south coast of England not very frequently; but
they are very common in the Mediterranean, living in holes or in the sand
within the littoral zone of shallow water. They differ from all the other
Malacostraca by a combination of characters, and Calman proposes the
term Hoplocarida for a division equivalent to the Peracarida, Eucarida, etc.
The abdomen is very broad and well developed, ending in a widely
expanded telson. There is a carapace which covers the four anterior thoracic
segments, leaving the four posterior segments free. The portion of the head
carrying the stalked eyes constitutes an apparently separate segment
articulated to the head. The antennae, mandibles, and maxillae are normal;
there then follow five pairs of uniramous thoracic limbs turned forwards as
maxillipedes and ending in claws; the second pair of these is modified into
a huge raptorial arm, exactly resembling that of a Praying Mantis (cf. vol. v.
p. 242), by means of which the Squilla seizes its prey. The last three
thoracic limbs are small and biramous. The pleopods are powerful,
flattened, biramous swimming organs with small hooks or “retinaculae”
upon their endopodites, which link together each member of a pair in the
middle, and with large branching gills upon the exopodites.
The internal anatomy exhibits several primitive features. The nervous
system is not at all concentrated, there being a separate ganglion for each
Page 186
segment; and the heart stretches right through thorax and abdomen, with a
pair of ostia in each segment. There are also ten hepatic diverticula given
off segmentally from the intestine.
The female has the curious habit of carrying the developing eggs in a
chamber improvised by the apposition of the maxillipedes, so that it looks
rather as if she were in the act of devouring her own brood.
The metamorphosis of the larvae, despite the work of Claus[114] and
Brooks,[115] is not very accurately known, especially uncertain being the
identification of the different larvae with their adult forms. The chief
interest consists in the fact that certain of the anterior thoracic limbs
develop in their normal order and degenerate, to be reformed later, just as in
the Phyllosoma larva of the Loricata (see pp. 165, 166).
In one series of larvae, probably not of Squilla itself, but of related
genera, the young hatch out as “Erichthoidina” (Fig. 99), with the thoracic
appendages developed as biramous organs as far as the fifth pair, and with a
single abdominal pair of limbs.
The abdominal series of limbs is
next completed; the second thoracic
limb assumes its adult raptorial
structure, but the succeeding three
limbs become greatly reduced and
may entirely degenerate, leaving the Fig. 99.—Erichthoidina larva of a Stomatopod,
posterior six thoracic segments with five pairs of maxillipedes, and the first pair
without limbs. of abdominal appendages, × 10. (From Balfour,
after Claus.)
Usually the anterior three pairs are
only reduced, and then redevelop
side by side with the small posterior limbs as they appear. This larva is then
termed the “Erichthus” (Fig. 100); but when they completely disappear the
larva is called a “Pseudozoaea,” owing to its resemblance to the Zoaea stage
of the Decapoda, which is also characterised by the suppressed
development of the thoracic segments.
pair of ostia in each segment. There are also ten hepatic diverticula given
off segmentally from the intestine.
The female has the curious habit of carrying the developing eggs in a
chamber improvised by the apposition of the maxillipedes, so that it looks
rather as if she were in the act of devouring her own brood.
The metamorphosis of the larvae, despite the work of Claus[114] and
Brooks,[115] is not very accurately known, especially uncertain being the
identification of the different larvae with their adult forms. The chief
interest consists in the fact that certain of the anterior thoracic limbs
develop in their normal order and degenerate, to be reformed later, just as in
the Phyllosoma larva of the Loricata (see pp. 165, 166).
In one series of larvae, probably not of Squilla itself, but of related
genera, the young hatch out as “Erichthoidina” (Fig. 99), with the thoracic
appendages developed as biramous organs as far as the fifth pair, and with a
single abdominal pair of limbs.
The abdominal series of limbs is
next completed; the second thoracic
limb assumes its adult raptorial
structure, but the succeeding three
limbs become greatly reduced and
may entirely degenerate, leaving the Fig. 99.—Erichthoidina larva of a Stomatopod,
posterior six thoracic segments with five pairs of maxillipedes, and the first pair
without limbs. of abdominal appendages, × 10. (From Balfour,
after Claus.)
Usually the anterior three pairs are
only reduced, and then redevelop
side by side with the small posterior limbs as they appear. This larva is then
termed the “Erichthus” (Fig. 100); but when they completely disappear the
larva is called a “Pseudozoaea,” owing to its resemblance to the Zoaea stage
of the Decapoda, which is also characterised by the suppressed
development of the thoracic segments.
Page 187
Fig. 100.—Older Erichthus larva, with six pairs of abdominal appendages, × 15.
(From Balfour, after Claus.)
The so-called “Alima” larva of Squilla is also a Pseudozoaea, but it is
apparently arrived at directly without the previous formation and
degeneration of the anterior thoracic limbs, the larva hatching out from the
egg in the Pseudozoaeal stage.
Fam. Squillidae.—Of the six known genera none extend into the cold
subarctic seas; the majority are characteristic of the warm or tropical seas
(Gonodactylus), some of the species having very wide ranges, e.g. G.
chiragra, which is completely circumtropical, and appears to have entered
the Mediterranean at some period, though it is very rare there.
(From Balfour, after Claus.)
The so-called “Alima” larva of Squilla is also a Pseudozoaea, but it is
apparently arrived at directly without the previous formation and
degeneration of the anterior thoracic limbs, the larva hatching out from the
egg in the Pseudozoaeal stage.
Fam. Squillidae.—Of the six known genera none extend into the cold
subarctic seas; the majority are characteristic of the warm or tropical seas
(Gonodactylus), some of the species having very wide ranges, e.g. G.
chiragra, which is completely circumtropical, and appears to have entered
the Mediterranean at some period, though it is very rare there.
Page 188
CHAPTER VI
CRUSTACEA (CONTINUED)—EUMALACOSTRACA
(CONTINUED): EUCARIDA—EUPHAUSIACEA—
COMPOUND EYES—DECAPODA
DIVISION 4. EUCARIDA.
The carapace fuses with all the thoracic segments. The eyes are
pedunculate. The mandible is without a lacinia mobilis. There are no
oostegites, the eggs being attached to the endopodites of the pleopods. The
hepatic caeca are much ramified, the heart is abbreviated and saccular, the
spermatozoa are spherical with radiating pseudopodia, and development is
typically attended by a complicated larval metamorphosis.
Order I. Euphausiacea.
The Euphausiidae[116] agree with
the Decapoda in passing through a
complicated larval metamorphosis.
The young hatch out as Nauplii, with
uniramous first antennae and
biramous second antennae and
mandibles. In the next stage, or
Fig. 101.—Calyptopis larva of Euphausia
“Calyptopis” (Fig. 101), which
pellucida, × about 20. A.1, 1st antenna; Ab.6, corresponds exactly to the Zoaea of
6th abdominal segment; E, eye; M, maxillipede. the Decapoda, two pairs of maxillae
(After Sars.)
and a pair of biramous maxillipedes
are added; the hinder thoracic
segments are undifferentiated, but the abdomen is fully segmented, and the
rudiments of the sixth pair of pleopods are already visible.
CRUSTACEA (CONTINUED)—EUMALACOSTRACA
(CONTINUED): EUCARIDA—EUPHAUSIACEA—
COMPOUND EYES—DECAPODA
DIVISION 4. EUCARIDA.
The carapace fuses with all the thoracic segments. The eyes are
pedunculate. The mandible is without a lacinia mobilis. There are no
oostegites, the eggs being attached to the endopodites of the pleopods. The
hepatic caeca are much ramified, the heart is abbreviated and saccular, the
spermatozoa are spherical with radiating pseudopodia, and development is
typically attended by a complicated larval metamorphosis.
Order I. Euphausiacea.
The Euphausiidae[116] agree with
the Decapoda in passing through a
complicated larval metamorphosis.
The young hatch out as Nauplii, with
uniramous first antennae and
biramous second antennae and
mandibles. In the next stage, or
Fig. 101.—Calyptopis larva of Euphausia
“Calyptopis” (Fig. 101), which
pellucida, × about 20. A.1, 1st antenna; Ab.6, corresponds exactly to the Zoaea of
6th abdominal segment; E, eye; M, maxillipede. the Decapoda, two pairs of maxillae
(After Sars.)
and a pair of biramous maxillipedes
are added; the hinder thoracic
segments are undifferentiated, but the abdomen is fully segmented, and the
rudiments of the sixth pair of pleopods are already visible.
Page 189
In the next stage (“Furcilia”) the other abdominal pleopods are added, the
whole series being completed before the thoracic appendages number more
than two or three. This stage corresponds to the Metazoaea of the
Decapoda, and the interference in the orderly differentiation of the
segments with their appendages from before backwards is a phenomenon
which we shall meet again when we treat of Decapod metamorphosis. It is
evidently a secondary modification, furnishing the larva precociously with
its most important swimming organs so as to enable it to lead a pelagic
existence. The frequent violation of the law of metameric segmentation, that
the most anterior segments being the first formed should be the first to be
fully differentiated, leads us to suppose that the larval stages of the Eucarida
at any rate do not represent phylogenetic adult stages through which the
Malacostraca have passed. Nor do they, perhaps, even represent primitive
larval stages, but have been secondarily acquired from an embryonic
condition which used to be passed through within the egg-membranes, as in
Nebalia and the Mysidacea, when the order of differentiation of the
segments was normal. The case is a little different with the Nauplius larva.
This larval form, in an identical condition, is found both in the
Entomostraca as a general rule, and again in certain Malacostraca, viz. the
Euphausiidae and the Peneidea. Whatever its phylogenetic meaning may be,
we may be quite certain that the ancestor of the two great divisions of the
Crustacea had a free-swimming Nauplius larva, and this conclusion is
confirmed by the probable presence of a Nauplius larva in Trilobites.
The Euphausiidae, in contradistinction to the Mysidae, are frequently met
with in the surface-plankton. Euphausia pellucida (Fig. 102) is of universal
distribution, and is frequently taken at the surface as well as at considerable
depths.
Many noteworthy features in Euphausiid organisation are brought out in
Fig. 102. The shrimp-like appearance of the carapace and antennae indicate
the special Decapodan affinities of the family; noteworthy, also, are the
single series of gills and the biramous thoracic and abdominal limbs, similar
to those of the Mysidacea. The Euphausiidae also possess phosphorescent
organs of a highly developed kind, and these are usually situated, as in the
type figured, upon the outer margins of the stalked eyes, on the bases of the
second and seventh thoracic limbs, and on the ventral median line on the
first four abdominal segments. These organs are lantern-like structures
provided with a lens, a reflector, and a light-producing tissue, and they are
whole series being completed before the thoracic appendages number more
than two or three. This stage corresponds to the Metazoaea of the
Decapoda, and the interference in the orderly differentiation of the
segments with their appendages from before backwards is a phenomenon
which we shall meet again when we treat of Decapod metamorphosis. It is
evidently a secondary modification, furnishing the larva precociously with
its most important swimming organs so as to enable it to lead a pelagic
existence. The frequent violation of the law of metameric segmentation, that
the most anterior segments being the first formed should be the first to be
fully differentiated, leads us to suppose that the larval stages of the Eucarida
at any rate do not represent phylogenetic adult stages through which the
Malacostraca have passed. Nor do they, perhaps, even represent primitive
larval stages, but have been secondarily acquired from an embryonic
condition which used to be passed through within the egg-membranes, as in
Nebalia and the Mysidacea, when the order of differentiation of the
segments was normal. The case is a little different with the Nauplius larva.
This larval form, in an identical condition, is found both in the
Entomostraca as a general rule, and again in certain Malacostraca, viz. the
Euphausiidae and the Peneidea. Whatever its phylogenetic meaning may be,
we may be quite certain that the ancestor of the two great divisions of the
Crustacea had a free-swimming Nauplius larva, and this conclusion is
confirmed by the probable presence of a Nauplius larva in Trilobites.
The Euphausiidae, in contradistinction to the Mysidae, are frequently met
with in the surface-plankton. Euphausia pellucida (Fig. 102) is of universal
distribution, and is frequently taken at the surface as well as at considerable
depths.
Many noteworthy features in Euphausiid organisation are brought out in
Fig. 102. The shrimp-like appearance of the carapace and antennae indicate
the special Decapodan affinities of the family; noteworthy, also, are the
single series of gills and the biramous thoracic and abdominal limbs, similar
to those of the Mysidacea. The Euphausiidae also possess phosphorescent
organs of a highly developed kind, and these are usually situated, as in the
type figured, upon the outer margins of the stalked eyes, on the bases of the
second and seventh thoracic limbs, and on the ventral median line on the
first four abdominal segments. These organs are lantern-like structures
provided with a lens, a reflector, and a light-producing tissue, and they are
Page 190
under the control of the nervous system. Their exact use is not known, any
more than is the use of phosphorescence in the majority of organisms which
produce it; but in certain cases it appears that the Euphausiids make use of
their phosphorescent organs as bull’s eye lanterns for illuminating the dark
regions into which they penetrate or in which some of them permanently
dwell. At any rate, associated with the presence of these organs in some
deep-sea Euphausiids are remarkable modifications of the eyes; and we
may perhaps here fittingly introduce a short discussion of these visual
modifications in deep-sea Crustacea, and the conditions which call them
forth.
Fig. 102.—Euphausia pellucida, female, × 5. G, Last gill; L, luminous organ of
first leg; L′, luminous organ of 2nd abdominal segment; T, biramous thoracic
appendages. (After Sars.)
The compound eyes of Crustacea resemble those of Insects in that they
are composed of a very large number of similar elements or “ommatidia,”
more or less isolated from one another by pigment. Each ommatidium
consists typically of a corneal lens (Fig. 103, c), secreted by flat corneagen
cells (c.g) below; beneath the corneal lens is a transparent refractive body
called the “crystalline cone” (cr), which is produced by a number of cells
surrounding it called the “vitrellae” (v). Below the crystalline cone comes
the “rhabdom” (rh), produced and nourished by “retinulacells” (r). The
rhabdom is a transversely striated rod, constituting the true sensory part of
each ommatidium, and is in connexion at its lower end with a nerve-fibre
(n), passing to the optic ganglion. The rhabdoms rest upon a membrane (f)
called the “membrana fenestrata.” Each ommatidium is isolated from its
more than is the use of phosphorescence in the majority of organisms which
produce it; but in certain cases it appears that the Euphausiids make use of
their phosphorescent organs as bull’s eye lanterns for illuminating the dark
regions into which they penetrate or in which some of them permanently
dwell. At any rate, associated with the presence of these organs in some
deep-sea Euphausiids are remarkable modifications of the eyes; and we
may perhaps here fittingly introduce a short discussion of these visual
modifications in deep-sea Crustacea, and the conditions which call them
forth.
Fig. 102.—Euphausia pellucida, female, × 5. G, Last gill; L, luminous organ of
first leg; L′, luminous organ of 2nd abdominal segment; T, biramous thoracic
appendages. (After Sars.)
The compound eyes of Crustacea resemble those of Insects in that they
are composed of a very large number of similar elements or “ommatidia,”
more or less isolated from one another by pigment. Each ommatidium
consists typically of a corneal lens (Fig. 103, c), secreted by flat corneagen
cells (c.g) below; beneath the corneal lens is a transparent refractive body
called the “crystalline cone” (cr), which is produced by a number of cells
surrounding it called the “vitrellae” (v). Below the crystalline cone comes
the “rhabdom” (rh), produced and nourished by “retinulacells” (r). The
rhabdom is a transversely striated rod, constituting the true sensory part of
each ommatidium, and is in connexion at its lower end with a nerve-fibre
(n), passing to the optic ganglion. The rhabdoms rest upon a membrane (f)
called the “membrana fenestrata.” Each ommatidium is isolated from its
Page 191
fellows which surround it by a
complete cylinder of pigment, part of
which is especially crowded round
the crystalline cone, and is known as
“irido-pigment” (ip), while the part
which surrounds the rhabdom is
called “retino-pigment” (rp).
When the pigment is arranged in
this way, as in Fig. A, only those rays
of light which strike an ommatidium
approximately at right angles to the Fig. 103.—A, Sections (diagrammatic) of
corneal surface can be perceived, Crustacean compound eye, A, with pigment in
light-position for mosaic vision; B, with
since only these can reach the top of pigment in dark-position for refractive vision. c,
the rhabdom; the others pass through Corneal lens; c.g, corneagen cells; cr, crystalline
cone; f, basal membrane, or membrana
the crystalline cones obliquely, and fenestrata; ip, irido-pigment; n, nerve; r,
are absorbed by the cylinder of retinula; rh, rhabdom; rp, retino-pigment; v,
pigment surrounding each vitrella.
ommatidium, so that they neither
reach the rhabdom of the ommatidium which they originally entered, nor
can they penetrate to the rhabdom of neighbouring ommatidia. This gives
rise to what is known as “mosaic vision,” that is to say, each ommatidium
only perceives the rays of light which are parallel to its long axis, and in
this way an image is built up of which the various points are perceived side
by side by means of separate eye-elements. The distinctness and efficiency
of this mode of vision depends chiefly upon the number of ommatidia
present, and the completeness with which they are isolated from one
another by the pigment. Now this form of vision, depending as it does upon
the absorption of a great number of the light-rays by pigment, and the
transmission of only a limited number to the sensory surface, is only
possible when there is a strong light, and there is no need for economising
the light-rays. The most important discovery was made by Exner,[117] that
the majority of animals with compound eyes had the power of so arranging
the pigment in their eyes as to enable them to see in two ways. In bright
light the pigment is situated as in Fig. 103, A, so as completely to isolate the
rhabdoms from one another (day-position); but in the dusk the pigment
actively migrates, the irido-pigment passing to the surface (B) near the tops
of the crystalline cones, and the retino-pigment passing interiorly to rest on
complete cylinder of pigment, part of
which is especially crowded round
the crystalline cone, and is known as
“irido-pigment” (ip), while the part
which surrounds the rhabdom is
called “retino-pigment” (rp).
When the pigment is arranged in
this way, as in Fig. A, only those rays
of light which strike an ommatidium
approximately at right angles to the Fig. 103.—A, Sections (diagrammatic) of
corneal surface can be perceived, Crustacean compound eye, A, with pigment in
light-position for mosaic vision; B, with
since only these can reach the top of pigment in dark-position for refractive vision. c,
the rhabdom; the others pass through Corneal lens; c.g, corneagen cells; cr, crystalline
cone; f, basal membrane, or membrana
the crystalline cones obliquely, and fenestrata; ip, irido-pigment; n, nerve; r,
are absorbed by the cylinder of retinula; rh, rhabdom; rp, retino-pigment; v,
pigment surrounding each vitrella.
ommatidium, so that they neither
reach the rhabdom of the ommatidium which they originally entered, nor
can they penetrate to the rhabdom of neighbouring ommatidia. This gives
rise to what is known as “mosaic vision,” that is to say, each ommatidium
only perceives the rays of light which are parallel to its long axis, and in
this way an image is built up of which the various points are perceived side
by side by means of separate eye-elements. The distinctness and efficiency
of this mode of vision depends chiefly upon the number of ommatidia
present, and the completeness with which they are isolated from one
another by the pigment. Now this form of vision, depending as it does upon
the absorption of a great number of the light-rays by pigment, and the
transmission of only a limited number to the sensory surface, is only
possible when there is a strong light, and there is no need for economising
the light-rays. The most important discovery was made by Exner,[117] that
the majority of animals with compound eyes had the power of so arranging
the pigment in their eyes as to enable them to see in two ways. In bright
light the pigment is situated as in Fig. 103, A, so as completely to isolate the
rhabdoms from one another (day-position); but in the dusk the pigment
actively migrates, the irido-pigment passing to the surface (B) near the tops
of the crystalline cones, and the retino-pigment passing interiorly to rest on
Page 192
the membrana fenestrata at the bases of the rhabdoms (night-position).
When this happens the rays of light which strike the ommatidia at all sorts
of angles, instead of being largely absorbed by the pigment, are refracted by
the crystalline cones and distributed over the tops of the rhabdoms, passing
freely from one ommatidium to another. In this way the eye acts on this
occasion, not by mosaic vision, but on the principle of refraction, as in the
Vertebrate eye. Of course the distinctness of vision is lost, but an immense
economy in the use of light-rays is effected, and the creature can perceive
objects and movements dimly in the dusk which by mosaic vision it could
not see at all. The pigment is contained in living cells or chromatophores,
and it is carried about by the active amoeboid movements of these cells
with great rapidity.
Now, besides the active adaptability to different degrees of light brought
about in the individual by these means, we find Crustacea living under
special conditions in which the eyes are permanently modified for seeing in
the dusk, and this naturally occurs in many deep-sea forms.
Doflein[118] has examined the eyes of a great number of deep-sea
Brachyura dredged by the Valdivia Expedition, and as the result of this
investigation he states that the eyes of deep-sea Brachyura are never
composed of so many ommatidia, nor are they so deeply pigmented as those
of littoral or shallow water forms. At the same time an immense range of
variation occurs among deep-sea forms which are apparently subjected to
similar conditions of darkness, a variation stretching from almost normal
eyes to their complete degeneration and the fusion of the eye-stalks with the
carapace; and this variation is very difficult to account for. A very frequent
condition for crabs living at about 100 fathoms, and even more, is for either
the irido-pigment or the retino-pigment to be absent, for the number of
ommatidia to be reduced, and for the corneal lenses to be greatly arched.
There can be little doubt that these crabs use their eyes, not for mosaic
vision, but to obtain the superposition-image characteristic of the Vertebrate
eye. In deeper waters, where no daylight penetrates at all, this type of eye is
also met with, and also further stages in degeneration where all pigment is
absent, and the ommatidia show further signs of reduction and
degeneration, e.g. Cyclodorippe dromioides. In a few forms, e.g.
Cymonomus granulatus among Brachyura, and numerous Macrura, the
ommatidia may entirely disappear, and the eye-stalks may become fused
with the carapace or converted into tactile organs.
When this happens the rays of light which strike the ommatidia at all sorts
of angles, instead of being largely absorbed by the pigment, are refracted by
the crystalline cones and distributed over the tops of the rhabdoms, passing
freely from one ommatidium to another. In this way the eye acts on this
occasion, not by mosaic vision, but on the principle of refraction, as in the
Vertebrate eye. Of course the distinctness of vision is lost, but an immense
economy in the use of light-rays is effected, and the creature can perceive
objects and movements dimly in the dusk which by mosaic vision it could
not see at all. The pigment is contained in living cells or chromatophores,
and it is carried about by the active amoeboid movements of these cells
with great rapidity.
Now, besides the active adaptability to different degrees of light brought
about in the individual by these means, we find Crustacea living under
special conditions in which the eyes are permanently modified for seeing in
the dusk, and this naturally occurs in many deep-sea forms.
Doflein[118] has examined the eyes of a great number of deep-sea
Brachyura dredged by the Valdivia Expedition, and as the result of this
investigation he states that the eyes of deep-sea Brachyura are never
composed of so many ommatidia, nor are they so deeply pigmented as those
of littoral or shallow water forms. At the same time an immense range of
variation occurs among deep-sea forms which are apparently subjected to
similar conditions of darkness, a variation stretching from almost normal
eyes to their complete degeneration and the fusion of the eye-stalks with the
carapace; and this variation is very difficult to account for. A very frequent
condition for crabs living at about 100 fathoms, and even more, is for either
the irido-pigment or the retino-pigment to be absent, for the number of
ommatidia to be reduced, and for the corneal lenses to be greatly arched.
There can be little doubt that these crabs use their eyes, not for mosaic
vision, but to obtain the superposition-image characteristic of the Vertebrate
eye. In deeper waters, where no daylight penetrates at all, this type of eye is
also met with, and also further stages in degeneration where all pigment is
absent, and the ommatidia show further signs of reduction and
degeneration, e.g. Cyclodorippe dromioides. In a few forms, e.g.
Cymonomus granulatus among Brachyura, and numerous Macrura, the
ommatidia may entirely disappear, and the eye-stalks may become fused
with the carapace or converted into tactile organs.
Page 193
Progressive stages in degeneration, correlated with the depth in which the
animals are found, are afforded by closely related species, or even by
individuals of apparently the same species. Thus in the large Serolidae of
Antarctic seas, Serolis schytei occurs in 7–128 metres, and has well-
developed eyes; S. bronleyana, from 730 to 3600 metres, has small and
semi-degenerate eyes; while S. antarctica in 730–2920 metres is completely
blind. Lispognathus thompsoni is a deep-water spider-crab, and the
individuals taken at various depths are said to exhibit progressive stages in
degeneration according to the depth from which they come.
At the same time many anomalies occur which are difficult to explain. In
the middle depths, i.e. at about 100 fathoms, side by side with species
which have semi-degenerate or, at any rate, poorly pigmented eyes, occur
species with intensely pigmented eyes composed of very numerous
ommatidia, e.g. the Galatheid Munidopsis and several shrimps, while in the
true abysses many of the species have quite normal pigmented eyes. This is
especially the case with the deep-sea Pagurids, of which Alcock describes
only one species, Parapylocheles scorpio, as having poorly pigmented eyes.
An attempt to account for this was made by Milne Edwards and Bouvier,[119]
who pointed out that the truly deep-sea forms with well-developed eyes
were always Crustacea of a roving habit, which were perhaps capable of
penetrating into better lit regions, and to whom well-developed eyes might
be useful, while the degenerate forms were sluggish. This explanation
cannot be held to account for the phenomenon, as too many deep-sea forms
with fairly normal eyes are known which are never taken outside deep
waters. Doflein (loc. cit.) points out that in the Brachyura of the deep sea
there is a remarkable correlation between the degree of degeneration of the
eye and the size of the eggs—the large-egged forms having unpigmented
and degenerate eyes, while the species with small eggs have pigmented
eyes. He supposes that the species with large eggs undergo a direct
development without pelagic free-swimming larvae, and that since they
never reach the surface their eyes never meet with the necessary stimulus of
light for the development of pigment; whereas the small-egged species
undergo a pelagic larval existence when this stimulus is present and gives
the necessary initiative for the development of the pigment.
Another factor enters into the question of eye-degeneration in the
Crustacea. The great majority of deep-sea animals, including many deep-
sea Crustacea, are phosphorescent, and it is certain that although daylight
animals are found, are afforded by closely related species, or even by
individuals of apparently the same species. Thus in the large Serolidae of
Antarctic seas, Serolis schytei occurs in 7–128 metres, and has well-
developed eyes; S. bronleyana, from 730 to 3600 metres, has small and
semi-degenerate eyes; while S. antarctica in 730–2920 metres is completely
blind. Lispognathus thompsoni is a deep-water spider-crab, and the
individuals taken at various depths are said to exhibit progressive stages in
degeneration according to the depth from which they come.
At the same time many anomalies occur which are difficult to explain. In
the middle depths, i.e. at about 100 fathoms, side by side with species
which have semi-degenerate or, at any rate, poorly pigmented eyes, occur
species with intensely pigmented eyes composed of very numerous
ommatidia, e.g. the Galatheid Munidopsis and several shrimps, while in the
true abysses many of the species have quite normal pigmented eyes. This is
especially the case with the deep-sea Pagurids, of which Alcock describes
only one species, Parapylocheles scorpio, as having poorly pigmented eyes.
An attempt to account for this was made by Milne Edwards and Bouvier,[119]
who pointed out that the truly deep-sea forms with well-developed eyes
were always Crustacea of a roving habit, which were perhaps capable of
penetrating into better lit regions, and to whom well-developed eyes might
be useful, while the degenerate forms were sluggish. This explanation
cannot be held to account for the phenomenon, as too many deep-sea forms
with fairly normal eyes are known which are never taken outside deep
waters. Doflein (loc. cit.) points out that in the Brachyura of the deep sea
there is a remarkable correlation between the degree of degeneration of the
eye and the size of the eggs—the large-egged forms having unpigmented
and degenerate eyes, while the species with small eggs have pigmented
eyes. He supposes that the species with large eggs undergo a direct
development without pelagic free-swimming larvae, and that since they
never reach the surface their eyes never meet with the necessary stimulus of
light for the development of pigment; whereas the small-egged species
undergo a pelagic larval existence when this stimulus is present and gives
the necessary initiative for the development of the pigment.
Another factor enters into the question of eye-degeneration in the
Crustacea. The great majority of deep-sea animals, including many deep-
sea Crustacea, are phosphorescent, and it is certain that although daylight
Page 194
never penetrates into the abysses of the ocean, yet there is considerable
illumination derived from the phosphorescence of the inhabitants of these
regions.
Alcock[120] points out in this connexion that the Pagurids, which are
conspicuous in the great depths as animals with normally developed eyes,
carry about anemones with them, and these organisms are very frequently
phosphorescent to a high degree. It may well be, therefore, that the Pagurids
are enabled to use their eyes in the normal manner owing to the
phosphorescent light which they carry about with them, and this use of
phosphorescent light may apply to a number of deep-sea Crustacea whose
eyes are not at all or only partially degenerate.
An extremely interesting case of the use of phosphorescent light is given
by Chun.[121] In a number of Euphausiids occurring in deep waters each
compound eye is divided into two parts—a frontal and ventro-lateral—
which differ from one another very greatly in the nature and disposition of
their ommatidia.
In the frontal portion (Fig. 104, A)
the ommatidia are few in number and
long, the corneal lenses are highly
arched, and the pigment is reduced to
a few clumps in the iris. This part of
the eye is evidently adapted for
forming a vague superposition-image
in the dusk. The ventro-lateral part
(B), on the other hand, is composed
of numerous small ommatidia, the
crystalline cones of which can be
completely isolated from one another
by the irido-pigment. Immediately
Fig. 104.—Section of eye of Stylocheiron below this part of the eye is a
mastigophorum. A, Frontal portion; B, ventro- phosphorescent organ (C) provided
lateral portion; C, phosphorescent organ; D, with a lens and tapetum. Chun
entrance of optic nerve; c, corneal lens; cr,
crystalline cone; pg, pigment; ret, retinula; rh, suggests that the ventro-lateral part
rhabdom. (After Chun.) of the eye is used for obtaining a
clear mosaic image of objects
illuminated by the phosphorescent organ, while the frontal part of the eye is
illumination derived from the phosphorescence of the inhabitants of these
regions.
Alcock[120] points out in this connexion that the Pagurids, which are
conspicuous in the great depths as animals with normally developed eyes,
carry about anemones with them, and these organisms are very frequently
phosphorescent to a high degree. It may well be, therefore, that the Pagurids
are enabled to use their eyes in the normal manner owing to the
phosphorescent light which they carry about with them, and this use of
phosphorescent light may apply to a number of deep-sea Crustacea whose
eyes are not at all or only partially degenerate.
An extremely interesting case of the use of phosphorescent light is given
by Chun.[121] In a number of Euphausiids occurring in deep waters each
compound eye is divided into two parts—a frontal and ventro-lateral—
which differ from one another very greatly in the nature and disposition of
their ommatidia.
In the frontal portion (Fig. 104, A)
the ommatidia are few in number and
long, the corneal lenses are highly
arched, and the pigment is reduced to
a few clumps in the iris. This part of
the eye is evidently adapted for
forming a vague superposition-image
in the dusk. The ventro-lateral part
(B), on the other hand, is composed
of numerous small ommatidia, the
crystalline cones of which can be
completely isolated from one another
by the irido-pigment. Immediately
Fig. 104.—Section of eye of Stylocheiron below this part of the eye is a
mastigophorum. A, Frontal portion; B, ventro- phosphorescent organ (C) provided
lateral portion; C, phosphorescent organ; D, with a lens and tapetum. Chun
entrance of optic nerve; c, corneal lens; cr,
crystalline cone; pg, pigment; ret, retinula; rh, suggests that the ventro-lateral part
rhabdom. (After Chun.) of the eye is used for obtaining a
clear mosaic image of objects
illuminated by the phosphorescent organ, while the frontal part of the eye is
Page 195
used for obtaining general visual impressions in dimly lit regions. This
curious differentiation of the eye into two parts apparently only occurs in
predaceous animals, which capture their prey alive upon the bottom, and to
whom a clear vision of moving organisms is a necessity.
Another instance of Crustaceans making use of their own light is given
by Alcock,[122] who found two deep-sea prawns, Heterocarpus alphonsi and
Aristaeus coruscans, at about 500 fathoms in the Indian Ocean. These
animals produce a highly phosphorescent substance which they eject from
the antennary glands, and they possess very large, deeply-pigmented eyes.
The whole subject of the modification of the pigment and structure of
Crustacean eyes is an interesting one, because it presents us with one of
those cases in which the direct response to a stimulus acting within the
lifetime of the individual seems to run parallel to the fixed adaptations of a
whole species, which have become hereditary and apparently independent
of the external stimulus of light or of the absence of light. As far as is
known, however, the direct response of the individual to the absence of
light is limited to the reduction or disappearance of the pigment, and does
not extend to those structural changes in the ommatidia which are
characteristic of so many deep-sea forms.
Order II. Decapoda.[123]
The Decapoda, together with the Euphausiidae, make up the Division
Eucarida, the members of which differ from the Orders hitherto described in
a number of characters, e.g. the presence of a carapace covering the whole
of the thorax, the absence of a brood-pouch formed of oostegites, the
presence of a short heart, of spermatozoa with radiating pseudopodia, and
of a complicated larval metamorphosis, of which the Zoaea stages are most
prominent.
The Decapoda differ from the Euphausiidae chiefly in the anterior three
thoracic limbs being turned forwards towards the mouth to act as
maxillipedes, and in the five succeeding thoracic limbs being nearly always
uniramous and ambulatory or chelate; there are typically present three serial
rows of gills attached to the thoracic segments, an upper series
(“pleurobranchiae”) attached to the body-wall above the articulation of the
limbs, a middle series (“arthrobranchiae”) attached at the articulation of the
curious differentiation of the eye into two parts apparently only occurs in
predaceous animals, which capture their prey alive upon the bottom, and to
whom a clear vision of moving organisms is a necessity.
Another instance of Crustaceans making use of their own light is given
by Alcock,[122] who found two deep-sea prawns, Heterocarpus alphonsi and
Aristaeus coruscans, at about 500 fathoms in the Indian Ocean. These
animals produce a highly phosphorescent substance which they eject from
the antennary glands, and they possess very large, deeply-pigmented eyes.
The whole subject of the modification of the pigment and structure of
Crustacean eyes is an interesting one, because it presents us with one of
those cases in which the direct response to a stimulus acting within the
lifetime of the individual seems to run parallel to the fixed adaptations of a
whole species, which have become hereditary and apparently independent
of the external stimulus of light or of the absence of light. As far as is
known, however, the direct response of the individual to the absence of
light is limited to the reduction or disappearance of the pigment, and does
not extend to those structural changes in the ommatidia which are
characteristic of so many deep-sea forms.
Order II. Decapoda.[123]
The Decapoda, together with the Euphausiidae, make up the Division
Eucarida, the members of which differ from the Orders hitherto described in
a number of characters, e.g. the presence of a carapace covering the whole
of the thorax, the absence of a brood-pouch formed of oostegites, the
presence of a short heart, of spermatozoa with radiating pseudopodia, and
of a complicated larval metamorphosis, of which the Zoaea stages are most
prominent.
The Decapoda differ from the Euphausiidae chiefly in the anterior three
thoracic limbs being turned forwards towards the mouth to act as
maxillipedes, and in the five succeeding thoracic limbs being nearly always
uniramous and ambulatory or chelate; there are typically present three serial
rows of gills attached to the thoracic segments, an upper series
(“pleurobranchiae”) attached to the body-wall above the articulation of the
limbs, a middle series (“arthrobranchiae”) attached at the articulation of the
Page 196
limbs, and a lower series (“podobranchiae”) attached to the basal joints of
the limbs. These gills are enclosed in a special branchial chamber on each
side of the thorax, formed by lateral wings of the carapace known as
“branchiostegites.” The gills of each series are never all present in the same
animal, the anterior and posterior members showing a special tendency to
be reduced and to disappear. In this manner “branchial formulae” can be
constructed for the various kinds of Decapods, which differ from the ideal
formula in a manner distinctive of each kind. The second maxilla is always
provided with an oar-like appendage on its outer margin (exopodite),
known as the “scaphognathite,” which, by its rhythmical movement, keeps
up a constant current of water through the gill-chamber.
A complicated auditory organ is present on the basal joint of the first
antennae; this is a sac communicating with the exterior and lined internally
with sensory hairs. The animal is said to place small pieces of sand, etc., in
its ears to act as otoliths. Anaspides (see p. 116) is the only other Crustacean
which has an auditory organ in this position.
The larval histories of the Decapods[124] are of great interest, and will be
given under the headings of the various groups. The first discoverer of the
metamorphosis of the Decapoda was the Irish naturalist J. V. Thompson,
certainly one of the ablest of British zoologists. In 1828, in his Zoological
Researches, he describes certain Zoaeas of the Brachyura and proves that
these animals are not an adult genus, as supposed, but larval forms. But
Rathke, in 1829, described the direct development of the Crayfish; and
Westwood, after describing the direct development of Gecarcinus, utterly
denied Thompson’s assertions concerning metamorphosis. Thompson
replied in the Royal Society Transactions for 1835, and described the
Megalopa stage of Cancer pagurus. Rathke,[125] although previously an
opponent of Thompson, subsequently made confirmatory observations upon
the larvae of the Anomura; and Spence Bate clinched the matter by
describing Brachyuran metamorphosis with great accuracy in the
Philosophical Transactions for 1859. Since then a mass of work has been
done on the subject, though much detail still remains to be elucidated.
The Decapoda fall into three sub-orders, which graduate into one another
—(i.) the Macrura, including the Lobsters, Crayfishes, Shrimps, and
Prawns; (ii.) the Anomura, including the Hermit-lobsters and Hermit-crabs;
and (iii.) the Brachyura or true Crabs.
the limbs. These gills are enclosed in a special branchial chamber on each
side of the thorax, formed by lateral wings of the carapace known as
“branchiostegites.” The gills of each series are never all present in the same
animal, the anterior and posterior members showing a special tendency to
be reduced and to disappear. In this manner “branchial formulae” can be
constructed for the various kinds of Decapods, which differ from the ideal
formula in a manner distinctive of each kind. The second maxilla is always
provided with an oar-like appendage on its outer margin (exopodite),
known as the “scaphognathite,” which, by its rhythmical movement, keeps
up a constant current of water through the gill-chamber.
A complicated auditory organ is present on the basal joint of the first
antennae; this is a sac communicating with the exterior and lined internally
with sensory hairs. The animal is said to place small pieces of sand, etc., in
its ears to act as otoliths. Anaspides (see p. 116) is the only other Crustacean
which has an auditory organ in this position.
The larval histories of the Decapods[124] are of great interest, and will be
given under the headings of the various groups. The first discoverer of the
metamorphosis of the Decapoda was the Irish naturalist J. V. Thompson,
certainly one of the ablest of British zoologists. In 1828, in his Zoological
Researches, he describes certain Zoaeas of the Brachyura and proves that
these animals are not an adult genus, as supposed, but larval forms. But
Rathke, in 1829, described the direct development of the Crayfish; and
Westwood, after describing the direct development of Gecarcinus, utterly
denied Thompson’s assertions concerning metamorphosis. Thompson
replied in the Royal Society Transactions for 1835, and described the
Megalopa stage of Cancer pagurus. Rathke,[125] although previously an
opponent of Thompson, subsequently made confirmatory observations upon
the larvae of the Anomura; and Spence Bate clinched the matter by
describing Brachyuran metamorphosis with great accuracy in the
Philosophical Transactions for 1859. Since then a mass of work has been
done on the subject, though much detail still remains to be elucidated.
The Decapoda fall into three sub-orders, which graduate into one another
—(i.) the Macrura, including the Lobsters, Crayfishes, Shrimps, and
Prawns; (ii.) the Anomura, including the Hermit-lobsters and Hermit-crabs;
and (iii.) the Brachyura or true Crabs.
Page 197
Sub-Order 1. Macrura.
This sub-order[126] is characterised by the large abdomen, furnished with
five pairs of biramous pleopods, and ending in a powerful tail-fan
composed of the telson and the greatly expanded sixth pair of pleopods, the
whole apparatus being locomotory. The second antennae are furnished with
very large external scales, representing the exopodites of those appendages.
Some of the Shrimps and Prawns closely resemble the “Schizopods,” but
the pereiopods are nearly always uniramous.[127] Several subdivisions of the
Macrura are recognised.
Tribe 1. Nephropsidea.
This tribe includes the Lobsters and Crayfishes, animals well known
from their serviceableness to man. There are three families, which will be
treated separately.
Fam. 1. Nephropsidae. The podobranchs are not united with the
epipodites, and the last thoracic segment is fixed and fused to the carapace.
The chelae are generally asymmetrical. The most important Lobsters are the
European and the American species—Homarus vulgaris (= Astacus
gammarus) and H. americanus respectively; these animals engage a large
number of people in the fisheries. It is estimated that in America about
£150,000 are spent every year on Lobsters.
The genus Nephrops contains the small Norwegian lobster and other
forms.
Herrick[128] gives some interesting particulars with regard to the life-
history of the American species. The largest recorded specimen weighed
about twenty-five pounds, and measured twenty inches from rostrum to tail;
similar European specimens have been recorded, but, on the average, they
are not so large as the American forms.
The Lobster, like all Crustacea, undergoes a series of moults as the result
of increase in size, shedding the whole of the external integument in one
piece. This is accomplished by a split taking place on the dorsal surface at
the junction of thorax and abdomen; through the slit so formed the Lobster
retracts first his thorax with all the limbs, and then his abdomen. When first
This sub-order[126] is characterised by the large abdomen, furnished with
five pairs of biramous pleopods, and ending in a powerful tail-fan
composed of the telson and the greatly expanded sixth pair of pleopods, the
whole apparatus being locomotory. The second antennae are furnished with
very large external scales, representing the exopodites of those appendages.
Some of the Shrimps and Prawns closely resemble the “Schizopods,” but
the pereiopods are nearly always uniramous.[127] Several subdivisions of the
Macrura are recognised.
Tribe 1. Nephropsidea.
This tribe includes the Lobsters and Crayfishes, animals well known
from their serviceableness to man. There are three families, which will be
treated separately.
Fam. 1. Nephropsidae. The podobranchs are not united with the
epipodites, and the last thoracic segment is fixed and fused to the carapace.
The chelae are generally asymmetrical. The most important Lobsters are the
European and the American species—Homarus vulgaris (= Astacus
gammarus) and H. americanus respectively; these animals engage a large
number of people in the fisheries. It is estimated that in America about
£150,000 are spent every year on Lobsters.
The genus Nephrops contains the small Norwegian lobster and other
forms.
Herrick[128] gives some interesting particulars with regard to the life-
history of the American species. The largest recorded specimen weighed
about twenty-five pounds, and measured twenty inches from rostrum to tail;
similar European specimens have been recorded, but, on the average, they
are not so large as the American forms.
The Lobster, like all Crustacea, undergoes a series of moults as the result
of increase in size, shedding the whole of the external integument in one
piece. This is accomplished by a split taking place on the dorsal surface at
the junction of thorax and abdomen; through the slit so formed the Lobster
retracts first his thorax with all the limbs, and then his abdomen. When first
Page 198
issuing from the old shell the animal’s integument is soft and pulpy, but the
increase in size of the body is already manifest; this increase per moult,
which is approximately the same in young and adult animals, varies from
13 to 15 per cent of the animal’s length. According to this computation, a
Lobster 2 inches long has moulted fourteen times, 5 inches twenty times,
and 10 inches twenty-five times, and it may be roughly estimated that a 10–
inch Lobster is four years old. Young Lobsters probably moult twice a year,
and so do adult males, but females only moult once a year soon after the
young are hatched out.
The process of moulting or ecdysis is an exceedingly dangerous one to
the Lobster and to Crustacea in general, and is very frequently fatal. There
is, first of all, the danger of the act not being accomplished skilfully, when
death always ensues. The Lobster remains soft and unprotected for about
six weeks after the ecdysis, and is very apt to fall a prey to the predaceous
fish, such as Sharks, Skates, Cod, etc., which feed upon it. There are,
however, some peculiar adaptations connected with the process which are
of interest. In order to facilitate the ecdysis, areas of absorption are formed
upon the dorsal and ventral surfaces of the carapace, on the narrower parts
of the chelipedes, and at other places; in these areas the calcium carbonate
is absorbed, and the old shell becomes elastic and thin, so as to allow a
more easy escape for the moulting Lobster. It has been noticed that while
this is taking place large concretions of calcium carbonate are formed at the
sides of the stomach, known as “gastroliths,” which perhaps represent the
waste lime that has been abstracted from the areas of absorption. After
moulting the Lobster is in great need of lime for stiffening his shell, and it
has been noticed that on these occasions he is very greedy of this substance,
even devouring his own cast-off skin.
The male Lobster is especially prized on account of his larger chelae, but
in both sexes the chelipedes are differentiated into a smaller cutting pincer
and a larger crushing one. Lobsters may be right or left handed, with the
large crushing claw on the right or left hand, and sometimes specimens
occur with the smaller cutting pincers on both chelipedes, and very rarely,
indeed, with crushing claws on both sides. Crustacea very commonly have
the power of casting off a limb if they are seized by it or if it is injured, and
of regenerating a new one. In the Lobster a so-called breaking joint is
situated on each leg at the suture between the fused second and third
segments; a membrane being pushed inwards from the skin, which not only
increase in size of the body is already manifest; this increase per moult,
which is approximately the same in young and adult animals, varies from
13 to 15 per cent of the animal’s length. According to this computation, a
Lobster 2 inches long has moulted fourteen times, 5 inches twenty times,
and 10 inches twenty-five times, and it may be roughly estimated that a 10–
inch Lobster is four years old. Young Lobsters probably moult twice a year,
and so do adult males, but females only moult once a year soon after the
young are hatched out.
The process of moulting or ecdysis is an exceedingly dangerous one to
the Lobster and to Crustacea in general, and is very frequently fatal. There
is, first of all, the danger of the act not being accomplished skilfully, when
death always ensues. The Lobster remains soft and unprotected for about
six weeks after the ecdysis, and is very apt to fall a prey to the predaceous
fish, such as Sharks, Skates, Cod, etc., which feed upon it. There are,
however, some peculiar adaptations connected with the process which are
of interest. In order to facilitate the ecdysis, areas of absorption are formed
upon the dorsal and ventral surfaces of the carapace, on the narrower parts
of the chelipedes, and at other places; in these areas the calcium carbonate
is absorbed, and the old shell becomes elastic and thin, so as to allow a
more easy escape for the moulting Lobster. It has been noticed that while
this is taking place large concretions of calcium carbonate are formed at the
sides of the stomach, known as “gastroliths,” which perhaps represent the
waste lime that has been abstracted from the areas of absorption. After
moulting the Lobster is in great need of lime for stiffening his shell, and it
has been noticed that on these occasions he is very greedy of this substance,
even devouring his own cast-off skin.
The male Lobster is especially prized on account of his larger chelae, but
in both sexes the chelipedes are differentiated into a smaller cutting pincer
and a larger crushing one. Lobsters may be right or left handed, with the
large crushing claw on the right or left hand, and sometimes specimens
occur with the smaller cutting pincers on both chelipedes, and very rarely,
indeed, with crushing claws on both sides. Crustacea very commonly have
the power of casting off a limb if they are seized by it or if it is injured, and
of regenerating a new one. In the Lobster a so-called breaking joint is
situated on each leg at the suture between the fused second and third
segments; a membrane being pushed inwards from the skin, which not only
Page 199
serves to form a weak joint where rupture may easily take place, but also to
stop excessive bleeding after rupture. In the newly-hatched larvae there is a
normal joint between the second and third segments; and autotomy, or the
voluntary throwing away of a limb, never occurs until the fourth larval
stage, when the breaking joint is formed. Autotomy is a reflex act under the
control of the segmental ganglion; if a Crab or Lobster be anæsthetised, and
then a limb be injured or broken off below the breaking joint, the animal
forgets to throw the injured leg or stump off at the breaking joint, a
proceeding which always occurs under normal conditions. The regeneration
of a limb starts from a papilla which grows out of the breaking joint, and
after a number of moults acquires the specific form of the limb that has
been lost. A number of interesting observations have been made upon the
regeneration of the limbs in Crustacea. It was in the Hermit-crab that
Morgan[129] proved that regeneration and the liability to injury do not always
run parallel, as Weismann held they should, since the rudimentary posterior
thoracic limbs, which are never injured in nature, can regenerate when
artificially removed as easily as any others. Przibram[130] has shown that in
the shrimp Alpheus, whose chelipedes are highly asymmetrical, if the large
one be cut off, the small one immediately begins to grow and to take on the
form of the large one, while the regenerated limb is formed as the small
variety. This remarkable inversion in the symmetry of the animal clearly
ensures that, if the large chela is injured and thrown away, the least amount
of time is wasted in providing the shrimp with a new large claw.
To return to the Lobster; for the majority of the individuals there is a
definite breeding season, viz. July and August, but a certain proportion
breed earlier or later. A female begins to “berry” at about eight inches in
length, and to produce more and more eggs up to about eighteen inches,
when as many as 160,000 eggs are produced at a time; after this there is a
decline in numbers. A female normally breeds only once in two years. Strict
laws are enforced forbidding the sale of Lobsters and Crabs “in berry” in
both England and America. The period of incubation, during which the
developing eggs are attached to the swimmerets of the female, lasts about
ten or eleven months, so that the larvae are hatched out approximately in
the following June. On hatching, the larva, which measures about one-third
of an inch, and is in the Mysis stage (i.e. it possesses all the thoracic limbs
in a biramous condition, but is without the abdominal limbs), swims at first
on the surface. After five or six months of this life, during which the
stop excessive bleeding after rupture. In the newly-hatched larvae there is a
normal joint between the second and third segments; and autotomy, or the
voluntary throwing away of a limb, never occurs until the fourth larval
stage, when the breaking joint is formed. Autotomy is a reflex act under the
control of the segmental ganglion; if a Crab or Lobster be anæsthetised, and
then a limb be injured or broken off below the breaking joint, the animal
forgets to throw the injured leg or stump off at the breaking joint, a
proceeding which always occurs under normal conditions. The regeneration
of a limb starts from a papilla which grows out of the breaking joint, and
after a number of moults acquires the specific form of the limb that has
been lost. A number of interesting observations have been made upon the
regeneration of the limbs in Crustacea. It was in the Hermit-crab that
Morgan[129] proved that regeneration and the liability to injury do not always
run parallel, as Weismann held they should, since the rudimentary posterior
thoracic limbs, which are never injured in nature, can regenerate when
artificially removed as easily as any others. Przibram[130] has shown that in
the shrimp Alpheus, whose chelipedes are highly asymmetrical, if the large
one be cut off, the small one immediately begins to grow and to take on the
form of the large one, while the regenerated limb is formed as the small
variety. This remarkable inversion in the symmetry of the animal clearly
ensures that, if the large chela is injured and thrown away, the least amount
of time is wasted in providing the shrimp with a new large claw.
To return to the Lobster; for the majority of the individuals there is a
definite breeding season, viz. July and August, but a certain proportion
breed earlier or later. A female begins to “berry” at about eight inches in
length, and to produce more and more eggs up to about eighteen inches,
when as many as 160,000 eggs are produced at a time; after this there is a
decline in numbers. A female normally breeds only once in two years. Strict
laws are enforced forbidding the sale of Lobsters and Crabs “in berry” in
both England and America. The period of incubation, during which the
developing eggs are attached to the swimmerets of the female, lasts about
ten or eleven months, so that the larvae are hatched out approximately in
the following June. On hatching, the larva, which measures about one-third
of an inch, and is in the Mysis stage (i.e. it possesses all the thoracic limbs
in a biramous condition, but is without the abdominal limbs), swims at first
on the surface. After five or six months of this life, during which the
Page 200
abdominal pleopods are added from before backwards, it sinks to the
bottom, loses the exopodites of the thoracic limbs, and is converted into the
young Lobster, measuring about half an inch in length. The little Lobster
starts in deepish water, and gradually crawls towards the shore; here it
passes its adolescence, but on coming to maturity it migrates out again into
the deep water.
Fam. 2. Astacidae.—In this family, which includes all the European and
North American Crayfishes, Astacus (Potamobius) and Cambarus, the
podobranchs are united with the epipodites, the last thoracic segment is
free, there is only one pleurobranch or none at all, the gills have a central
lamina, but the filaments are without terminal hooks, and the endopodites of
the first two pairs of abdominal appendages in the male serve as copulatory
organs. For the distribution, etc., of these forms see p. 213.
Fam. 3. Parastacidae.—This family includes the Crayfishes of the
Southern Hemisphere, viz. Parastacus from South America, Astacopsis and
Engaeus from Australia, Paranephrops from New Zealand, and Astacoides
from Madagascar. These genera agree with the Potamobiidae in the union of
the podobranchs with the epipodites, and in the free condition of the last
thoracic segment, but there are generally four pleurobranchs, the gills are
without a lamina, the filaments have terminal hooks, and there are no sexual
appendages in the male. For distribution, etc., see also p. 213.
The larval development in the Crayfishes is still more abbreviated than in
the Lobsters, the Mysis stage being passed through within the egg-
membranes. The young, when they hatch out, are furnished with hooks
upon the chelipedes, by which they anchor themselves to the pleopods of
the mother.
Tribe 2. Eryonidea.
These are remarkably archaic animals of great rarity, though they were
common enough in Triassic seas, and have come down to us as fossils from
those times, being thus among the oldest Decapoda known. They only
survive now as deep sea species, and the genus discovered by the
Challenger,[131] Willemoesia (Fig. 105), confirmed the expectations of the
Challenger naturalists that the abysses of the ocean would contain relics
from older periods which had managed to survive where the competition
bottom, loses the exopodites of the thoracic limbs, and is converted into the
young Lobster, measuring about half an inch in length. The little Lobster
starts in deepish water, and gradually crawls towards the shore; here it
passes its adolescence, but on coming to maturity it migrates out again into
the deep water.
Fam. 2. Astacidae.—In this family, which includes all the European and
North American Crayfishes, Astacus (Potamobius) and Cambarus, the
podobranchs are united with the epipodites, the last thoracic segment is
free, there is only one pleurobranch or none at all, the gills have a central
lamina, but the filaments are without terminal hooks, and the endopodites of
the first two pairs of abdominal appendages in the male serve as copulatory
organs. For the distribution, etc., of these forms see p. 213.
Fam. 3. Parastacidae.—This family includes the Crayfishes of the
Southern Hemisphere, viz. Parastacus from South America, Astacopsis and
Engaeus from Australia, Paranephrops from New Zealand, and Astacoides
from Madagascar. These genera agree with the Potamobiidae in the union of
the podobranchs with the epipodites, and in the free condition of the last
thoracic segment, but there are generally four pleurobranchs, the gills are
without a lamina, the filaments have terminal hooks, and there are no sexual
appendages in the male. For distribution, etc., see also p. 213.
The larval development in the Crayfishes is still more abbreviated than in
the Lobsters, the Mysis stage being passed through within the egg-
membranes. The young, when they hatch out, are furnished with hooks
upon the chelipedes, by which they anchor themselves to the pleopods of
the mother.
Tribe 2. Eryonidea.
These are remarkably archaic animals of great rarity, though they were
common enough in Triassic seas, and have come down to us as fossils from
those times, being thus among the oldest Decapoda known. They only
survive now as deep sea species, and the genus discovered by the
Challenger,[131] Willemoesia (Fig. 105), confirmed the expectations of the
Challenger naturalists that the abysses of the ocean would contain relics
from older periods which had managed to survive where the competition
Page 201
was not so keen. The genus
Willemoesia is very widely
distributed, being dredged up from
below a thousand fathoms in the
Indian Ocean, the Mediterranean,
North and South Atlantic, and the
Pacific oceans. All the walking legs
are chelate, and the animal is quite
blind, as are all the Eryonidea, the
eye-stalks being fused with the
carapace.
Only a single family Eryonidae is
recognised.
Fig. 105.—Willemoesia inornata, × ⅓. (From a
figure prepared for Professor Weldon.)
Tribe 3. Peneidea.—Tribe 4. Caridea.
We will now consider the Shrimps and Prawns, since in them occurs the
most complete metamorphosis found in the Decapoda. The Peneidea are
Willemoesia is very widely
distributed, being dredged up from
below a thousand fathoms in the
Indian Ocean, the Mediterranean,
North and South Atlantic, and the
Pacific oceans. All the walking legs
are chelate, and the animal is quite
blind, as are all the Eryonidea, the
eye-stalks being fused with the
carapace.
Only a single family Eryonidae is
recognised.
Fig. 105.—Willemoesia inornata, × ⅓. (From a
figure prepared for Professor Weldon.)
Tribe 3. Peneidea.—Tribe 4. Caridea.
We will now consider the Shrimps and Prawns, since in them occurs the
most complete metamorphosis found in the Decapoda. The Peneidea are
Page 202
distinguished from the ordinary Prawns and Shrimps (Caridea) by having
the first three instead of the first two pereiopods chelate. The genus Peneus
affords several species which are of commercial value as objects of food;
the edible Prawns of the Mediterranean belong to this genus, while in the
North Sea two of the Caridea, viz. the Shrimp, Crangon vulgaris, and the
Prawn, Palaemon serratus, are the forms very commonly eaten. Both
subdivisions are well represented in the deep sea fauna from all parts of the
world. Glyphocrangon spinulosa (Fig. 110, p. 164) is a deep sea Shrimp
with eyes that have lost their pigment, and with the body covered with
spines, while the last abdominal segment is fused with the telson to form a
sharp bayonet-like process at the hind end of the body. Some of the deep-
sea Prawns of the Indian Ocean are described by Alcock[132] as possessing
peculiar secondary sexual characters. Thus Parapeneus rectacutus ♂ has
one lash of the first pair of antennae peculiarly bent to form a clasping
organ, while Aristaeus crassipes has a hook on the end of the third
maxillipede. In the latter the females have much longer rostra than the
males, and are in general more powerfully built, so that they seem to have
usurped the proper functions of the male, and probably engage in combats
with one another over his person.
As a general rule the Shrimps and
Prawns occur in large shoals in the
shallow waters of the littoral zone,
and they have a remarkable power of
adapting their colours to the
surroundings in which they happen to
be at any particular moment.[133] This
is brought about by the variously
coloured chromatophores, which
contract and expand in obedience to a
stimulus transmitted through the eyes
of the animal. A number of the
Palaemonidae go up rivers into fresh
water, while one family, the Atyidae,
Fig. 106.—Nauplius larva of Peneus, sp. × 25. live in the completely fresh water of
(From Balfour, after F. Müller). rivers and inland lakes. The Peneidea
undergo a very complete
metamorphosis which is primitive in respect to the order of formation of the
the first three instead of the first two pereiopods chelate. The genus Peneus
affords several species which are of commercial value as objects of food;
the edible Prawns of the Mediterranean belong to this genus, while in the
North Sea two of the Caridea, viz. the Shrimp, Crangon vulgaris, and the
Prawn, Palaemon serratus, are the forms very commonly eaten. Both
subdivisions are well represented in the deep sea fauna from all parts of the
world. Glyphocrangon spinulosa (Fig. 110, p. 164) is a deep sea Shrimp
with eyes that have lost their pigment, and with the body covered with
spines, while the last abdominal segment is fused with the telson to form a
sharp bayonet-like process at the hind end of the body. Some of the deep-
sea Prawns of the Indian Ocean are described by Alcock[132] as possessing
peculiar secondary sexual characters. Thus Parapeneus rectacutus ♂ has
one lash of the first pair of antennae peculiarly bent to form a clasping
organ, while Aristaeus crassipes has a hook on the end of the third
maxillipede. In the latter the females have much longer rostra than the
males, and are in general more powerfully built, so that they seem to have
usurped the proper functions of the male, and probably engage in combats
with one another over his person.
As a general rule the Shrimps and
Prawns occur in large shoals in the
shallow waters of the littoral zone,
and they have a remarkable power of
adapting their colours to the
surroundings in which they happen to
be at any particular moment.[133] This
is brought about by the variously
coloured chromatophores, which
contract and expand in obedience to a
stimulus transmitted through the eyes
of the animal. A number of the
Palaemonidae go up rivers into fresh
water, while one family, the Atyidae,
Fig. 106.—Nauplius larva of Peneus, sp. × 25. live in the completely fresh water of
(From Balfour, after F. Müller). rivers and inland lakes. The Peneidea
undergo a very complete
metamorphosis which is primitive in respect to the order of formation of the
Page 203
segments from before backwards. The larva hatches out as a Nauplius (Fig.
106), which by the orderly addition of segments behind is converted into
the Protozoaea (Fig. 107), possessing two pairs of biramous maxillipedes. It
should be noted that the maxillae, which are foliaceous in the adult, are laid
down in this condition in the larva, and this principle holds good throughout
Crustacean metamorphosis, viz. that when a limb is foliaceous in the adult
it is foliaceous in the larva, and when biramous in the adult it is biramous in
the larva. Whilst the rest of the thoracic limbs are still rudimentary, the sixth
pair of pleopods are being precociously developed (Fig. 108), being the
only precociously formed limbs in the Peneidea, though the abdominal
segments are fully marked off before the thoracic segments, and so must be
considered as precocious in development. When the biramous thoracic
limbs are completed the abdominal biramous pleopods are added, beginning
from in front backwards. Thus the Mysis stage (Fig. 109) is reached, which
resembles in all particulars the adult condition of the Schizopoda. The adult
Prawn develops from this stage by the loss of some or all of the exopodites
on the thoracic pereiopods.
Some of the Peneid larvae take on very peculiar forms, e.g. the Zoaeae of
the Sergestidae,[134] which often develop the most wonderful spines all over
the body.
106), which by the orderly addition of segments behind is converted into
the Protozoaea (Fig. 107), possessing two pairs of biramous maxillipedes. It
should be noted that the maxillae, which are foliaceous in the adult, are laid
down in this condition in the larva, and this principle holds good throughout
Crustacean metamorphosis, viz. that when a limb is foliaceous in the adult
it is foliaceous in the larva, and when biramous in the adult it is biramous in
the larva. Whilst the rest of the thoracic limbs are still rudimentary, the sixth
pair of pleopods are being precociously developed (Fig. 108), being the
only precociously formed limbs in the Peneidea, though the abdominal
segments are fully marked off before the thoracic segments, and so must be
considered as precocious in development. When the biramous thoracic
limbs are completed the abdominal biramous pleopods are added, beginning
from in front backwards. Thus the Mysis stage (Fig. 109) is reached, which
resembles in all particulars the adult condition of the Schizopoda. The adult
Prawn develops from this stage by the loss of some or all of the exopodites
on the thoracic pereiopods.
Some of the Peneid larvae take on very peculiar forms, e.g. the Zoaeae of
the Sergestidae,[134] which often develop the most wonderful spines all over
the body.
Page 204
Fig. 107.—Protozoea larva of Peneus, sp. × 25.
(From Balfour, after F. Müller.)
(From Balfour, after F. Müller.)
Page 205
Fig. 108.—Zoaea larva of Peneus, sp. × 25. A,
A′, 1st and 2nd antennae; Ab.6, 6th abdominal
appendage; Mxp, 2nd maxillipede; T, 4th–8th
thoracic appendages (future walking legs).
(After F. Müller.)
A′, 1st and 2nd antennae; Ab.6, 6th abdominal
appendage; Mxp, 2nd maxillipede; T, 4th–8th
thoracic appendages (future walking legs).
(After F. Müller.)
Page 206
Fig. 109.—Mysis stage in the development of Peneus, sp. A.2, 2nd antenna;
Ab.6, 6th abdominal appendage; T, telson; Th, the biramous thoracic appendages.
(After Claus.)
The Caridea have a greatly abbreviated metamorphosis, the larva
hatching out at a late Zoaea stage with all three pairs of maxillipedes fully
formed and with a fully segmented abdomen. The succeeding thoracic
limbs are added in order from before backwards, though the sixth pair of
pleopods appear precociously as in the Peneidea. The other swimmerets do
not begin to develop until the thoracic limbs are complete. Some Caridea
show a yet more abbreviated metamorphosis, e.g. the fresh-water
Palaemonetes varians of S. Europe, which hatches out at the Mysis stage.
We see, therefore, in the metamorphosis of the Macrura several
apparently primitive features. In the first place, a free swimming Nauplius
stage is preserved in certain forms, identical in all respects with the
Nauplius of the Entomostraca. Secondly, the thoracic limbs when they are
first developed are biramous, thus giving rise to the characteristic Mysis
stage which links the Macrura on to the “Schizopoda.” Thirdly, the order of
differentiation of the segments is typically from in front backwards, the
only precociously developed appendage being the sixth abdominal. None of
these characters are reproduced in the higher Decapoda in which there is
never a free-living Nauplius, the first larval stage being the Zoaea; a
Ab.6, 6th abdominal appendage; T, telson; Th, the biramous thoracic appendages.
(After Claus.)
The Caridea have a greatly abbreviated metamorphosis, the larva
hatching out at a late Zoaea stage with all three pairs of maxillipedes fully
formed and with a fully segmented abdomen. The succeeding thoracic
limbs are added in order from before backwards, though the sixth pair of
pleopods appear precociously as in the Peneidea. The other swimmerets do
not begin to develop until the thoracic limbs are complete. Some Caridea
show a yet more abbreviated metamorphosis, e.g. the fresh-water
Palaemonetes varians of S. Europe, which hatches out at the Mysis stage.
We see, therefore, in the metamorphosis of the Macrura several
apparently primitive features. In the first place, a free swimming Nauplius
stage is preserved in certain forms, identical in all respects with the
Nauplius of the Entomostraca. Secondly, the thoracic limbs when they are
first developed are biramous, thus giving rise to the characteristic Mysis
stage which links the Macrura on to the “Schizopoda.” Thirdly, the order of
differentiation of the segments is typically from in front backwards, the
only precociously developed appendage being the sixth abdominal. None of
these characters are reproduced in the higher Decapoda in which there is
never a free-living Nauplius, the first larval stage being the Zoaea; a
Page 207
number of the thoracic pereiopods, and usually all of them, are uniramous
from the start; and the whole of the abdominal segments with their limbs
tend to be precociously developed before the hinder thoracic segments
make a distinct appearance.
Tribe 3. Peneidea.[135]
The third legs are chelate except in genera in which the legs are much
reduced. The third maxillipedes are seven-jointed, the second maxillipedes
have normal end-joints, and the first maxillipedes are without a lobe on the
base of the exopodite. The pleura of the first abdominal segment are not
overlapped by those of the second. The abdomen is without a sharp bend.
The branchiae are usually not phyllobranchs.
Fam 1. Peneidae.—The last two pairs of legs are well developed, and
there is a nearly complete series of gills. Cerataspis,[136] a pelagic form.
Parapeneus, Peneus, Aristaeus, etc.
Fam. 2. Sergestidae.—The last or last two pairs of legs are reduced or
lost. The gill-series is incomplete or wanting. Sergestes possesses gills, and
the front end of the thorax is not greatly elongated. Lucifer has no gills, and
the front of the thorax is greatly elongated, giving a very anomalous
appearance to the animal. All the members of this family are pelagic in
habit.
Fam. 3. Stenopodidae.—One or both legs of the third pair are longer
and much stouter than those of the first two pairs. On a number of small
anatomical points this family, including the littoral genus Stenopus from the
Mediterranean and other warmer seas and Spongicola commensal with
Hexactinellid sponges from Japan, is separated by some authors in a Tribe
by itself.
Tribe 4. Caridea.
The third legs are not chelate. The third maxillipedes are 4–6 jointed, the
end-joint of the second maxillipede nearly always lies as a strip along the
end of the joint before it, and the first maxillipedes have a lobe on the base
of the exopodites. The pleura of the second abdominal segment overlap
from the start; and the whole of the abdominal segments with their limbs
tend to be precociously developed before the hinder thoracic segments
make a distinct appearance.
Tribe 3. Peneidea.[135]
The third legs are chelate except in genera in which the legs are much
reduced. The third maxillipedes are seven-jointed, the second maxillipedes
have normal end-joints, and the first maxillipedes are without a lobe on the
base of the exopodite. The pleura of the first abdominal segment are not
overlapped by those of the second. The abdomen is without a sharp bend.
The branchiae are usually not phyllobranchs.
Fam 1. Peneidae.—The last two pairs of legs are well developed, and
there is a nearly complete series of gills. Cerataspis,[136] a pelagic form.
Parapeneus, Peneus, Aristaeus, etc.
Fam. 2. Sergestidae.—The last or last two pairs of legs are reduced or
lost. The gill-series is incomplete or wanting. Sergestes possesses gills, and
the front end of the thorax is not greatly elongated. Lucifer has no gills, and
the front of the thorax is greatly elongated, giving a very anomalous
appearance to the animal. All the members of this family are pelagic in
habit.
Fam. 3. Stenopodidae.—One or both legs of the third pair are longer
and much stouter than those of the first two pairs. On a number of small
anatomical points this family, including the littoral genus Stenopus from the
Mediterranean and other warmer seas and Spongicola commensal with
Hexactinellid sponges from Japan, is separated by some authors in a Tribe
by itself.
Tribe 4. Caridea.
The third legs are not chelate. The third maxillipedes are 4–6 jointed, the
end-joint of the second maxillipede nearly always lies as a strip along the
end of the joint before it, and the first maxillipedes have a lobe on the base
of the exopodites. The pleura of the second abdominal segment overlap
Page 208
those of the first. The abdomen has a sharp bend; the branchiae are
phyllobranchs.
Fam. 1. Pasiphaeidae.—In this family the end-joint of the second
maxillipedes is normally formed, and exopodites are usually present on all
the thoracic limbs. Rostrum small or wanting. Rather numerous genera are
known, most of which inhabit the deep sea, though a few come into the
littoral zone. Pasiphaea chiefly in the deep sea, Leptochela in the tropical
littoral zone.
Fam. 2. Acanthephyridae.—The end-joint of the second maxillipede is
modified as in other Caridea, and the rostrum is very strong and serrate, but
in the presence of exopodites, and in the form of the mouth-parts, this
family agrees with the preceding. It is also a characteristic deep-sea family.
Acanthephyra, Hymenodora, Nematocarcinus, etc.
Fam. 3. Atyidae.—This is an entirely fresh-water family, especially
characteristic of the rivers and lakes of the tropics, some of the forms being
exceedingly large and taking the place of the Crayfishes in these waters.
Characteristic of this family is the fact that the fingers of the chelae are
spoon-shaped, and carry peculiar tufts of bristles. Exopodites are present on
the thoracic limbs of some of the genera (Troglocaris, Xiphocaris from
Australia and the Malay Islands, Atyephyra from S. and W. Europe), but are
absent in others. Caridina, widely spread and common in Indo-Malay and
Africa; Atya from West Indies, West Africa, and Pacific Islands.
Fam. 4. Alpheidae.[137]—The exopodites are absent, and the rostrum is
absent or very feeble. The chelae are powerful, and usually very
asymmetrically developed. Alpheus has an enormous number of species
which live chiefly in the tropical seas, where they haunt especially the
coral-reefs, making their homes among the coral or in sponges, etc.
Although occurring in the Mediterranean they penetrate very rarely into
colder seas.
Fam. 5 Psalidopodidae.—This family, characterised by the absence of
chelae on the second thoracic limbs, which carry instead a terminal brush of
hairs, and by the rudimentary condition of the eyes, is represented by the
genus Psalidopus from the deep waters of the Indian Ocean.
Fam. 6. Pandalidae.—The first thoracic limb is without chelae, only six-
jointed. The rostrum is large and toothed. The genus Pandalus has
phyllobranchs.
Fam. 1. Pasiphaeidae.—In this family the end-joint of the second
maxillipedes is normally formed, and exopodites are usually present on all
the thoracic limbs. Rostrum small or wanting. Rather numerous genera are
known, most of which inhabit the deep sea, though a few come into the
littoral zone. Pasiphaea chiefly in the deep sea, Leptochela in the tropical
littoral zone.
Fam. 2. Acanthephyridae.—The end-joint of the second maxillipede is
modified as in other Caridea, and the rostrum is very strong and serrate, but
in the presence of exopodites, and in the form of the mouth-parts, this
family agrees with the preceding. It is also a characteristic deep-sea family.
Acanthephyra, Hymenodora, Nematocarcinus, etc.
Fam. 3. Atyidae.—This is an entirely fresh-water family, especially
characteristic of the rivers and lakes of the tropics, some of the forms being
exceedingly large and taking the place of the Crayfishes in these waters.
Characteristic of this family is the fact that the fingers of the chelae are
spoon-shaped, and carry peculiar tufts of bristles. Exopodites are present on
the thoracic limbs of some of the genera (Troglocaris, Xiphocaris from
Australia and the Malay Islands, Atyephyra from S. and W. Europe), but are
absent in others. Caridina, widely spread and common in Indo-Malay and
Africa; Atya from West Indies, West Africa, and Pacific Islands.
Fam. 4. Alpheidae.[137]—The exopodites are absent, and the rostrum is
absent or very feeble. The chelae are powerful, and usually very
asymmetrically developed. Alpheus has an enormous number of species
which live chiefly in the tropical seas, where they haunt especially the
coral-reefs, making their homes among the coral or in sponges, etc.
Although occurring in the Mediterranean they penetrate very rarely into
colder seas.
Fam. 5 Psalidopodidae.—This family, characterised by the absence of
chelae on the second thoracic limbs, which carry instead a terminal brush of
hairs, and by the rudimentary condition of the eyes, is represented by the
genus Psalidopus from the deep waters of the Indian Ocean.
Fam. 6. Pandalidae.—The first thoracic limb is without chelae, only six-
jointed. The rostrum is large and toothed. The genus Pandalus has
Page 209
numerous representatives in the northern littoral, P. annulicornis being one
of the prawns most commonly met with in the fish-markets.
Fam. 7. Hippolytidae.—The first and second thoracic limbs bear chelae,
the carpus of the second being divided into two or more segments. The first
pair of chelae are not distinctly stronger than the second. Virbius has many
species in the littoral zone of all seas, and one species, V. acuminatus, is
pelagic. Hippolyte also has numerous littoral forms distributed all over the
world, but chiefly in the arctic or subarctic seas. H. varians, common on the
English coasts, shows interesting colour-reactions to its surroundings.[138]
of the prawns most commonly met with in the fish-markets.
Fam. 7. Hippolytidae.—The first and second thoracic limbs bear chelae,
the carpus of the second being divided into two or more segments. The first
pair of chelae are not distinctly stronger than the second. Virbius has many
species in the littoral zone of all seas, and one species, V. acuminatus, is
pelagic. Hippolyte also has numerous littoral forms distributed all over the
world, but chiefly in the arctic or subarctic seas. H. varians, common on the
English coasts, shows interesting colour-reactions to its surroundings.[138]
Page 210
Fam. 8. Palaemonidae.—The first
two pairs of legs are chelate, the
carpus of the second not being
subdivided. Palaemon serratus, a
very common prawn in the British
littoral. Palaemonetes in the brackish
and fresh waters of Europe and N.
America.
Fam. 9. Glyphocrangonidae.—
The first pair of legs are subchelate,
the carpus of the second pair is
subdivided, and the rostrum is long.
Glyphocrangon (Fig. 110) with
numerous species entirely confined
to deep water.
Fam. 10. Crangonidae.—The
first pair of legs are subchelate, the
Fig. 110.—Glyphocrangon spinulosa, from the
right side, × 1. (From an original drawing
carpus of the second pair is not
prepared for Professor Weldon.) subdivided, and the rostrum is short.
Crangon vulgaris is the common
Shrimp of the North Sea.
Tribe 5. Loricata.
The Loricata include the Langouste (Palinurus) of the Mediterranean
coasts, which replaces there the Lobster of the North Sea as an article of
food, and the peculiarly shaped Scyllarus arctus (Fig. 111), which is also
prized in the Mediterranean as a delicacy. The bright red “Crayfishes,”
Panulirus and Iasus, of the Australian coasts are also largely used as food.
Besides its peculiarity in shape, S. arctus has remarkable scales on the
second antennae in place of flagella. The larva hatches out as the so-called
Phyllosoma, which must be regarded as a greatly flattened and modified[139]
Mysis stage.
In the embryo of Palinurus just before hatching (Fig. 112) we can
recognise the limbs of the head and thorax normally developed in order.
There are present three thoracic limbs, besides the maxillipedes. When the
two pairs of legs are chelate, the
carpus of the second not being
subdivided. Palaemon serratus, a
very common prawn in the British
littoral. Palaemonetes in the brackish
and fresh waters of Europe and N.
America.
Fam. 9. Glyphocrangonidae.—
The first pair of legs are subchelate,
the carpus of the second pair is
subdivided, and the rostrum is long.
Glyphocrangon (Fig. 110) with
numerous species entirely confined
to deep water.
Fam. 10. Crangonidae.—The
first pair of legs are subchelate, the
Fig. 110.—Glyphocrangon spinulosa, from the
right side, × 1. (From an original drawing
carpus of the second pair is not
prepared for Professor Weldon.) subdivided, and the rostrum is short.
Crangon vulgaris is the common
Shrimp of the North Sea.
Tribe 5. Loricata.
The Loricata include the Langouste (Palinurus) of the Mediterranean
coasts, which replaces there the Lobster of the North Sea as an article of
food, and the peculiarly shaped Scyllarus arctus (Fig. 111), which is also
prized in the Mediterranean as a delicacy. The bright red “Crayfishes,”
Panulirus and Iasus, of the Australian coasts are also largely used as food.
Besides its peculiarity in shape, S. arctus has remarkable scales on the
second antennae in place of flagella. The larva hatches out as the so-called
Phyllosoma, which must be regarded as a greatly flattened and modified[139]
Mysis stage.
In the embryo of Palinurus just before hatching (Fig. 112) we can
recognise the limbs of the head and thorax normally developed in order.
There are present three thoracic limbs, besides the maxillipedes. When the
Page 211
Phyllosoma hatches out the first
maxillipedes have become quite
rudimentary, and the second much
reduced, while the second antennae
and second maxillae are also reduced
in size. The metamorphosis is
completed by the re-development of
the limbs and segments that have
been secondarily suppressed during
larval life, and by the appearance of
the pleopods.
This process is again met with in
the Squillidae (p. 143), but it
resembles the suppression, in so
many Decapodan metamorphoses, of
anterior limbs and the precocious
development of segments and limbs
lying posteriorly. In the ordinary
Decapoda, however, the suppressed
Fig. 111.—Dorsal view of Scyllarus arctus, × ½. limbs are merely not formed till later;
(From an original figure prepared for Professor while in the Loricata the limbs
Weldon.)
develop in the correct order, and
subsequently degenerate. It is natural
to wonder whether the condition of affairs in the Loricata represents the
primitive process, and whether the precocious development of segments in
the other Decapoda owes its origin to these animals having once had the
direct mode of development when the segments were formed in the proper
order, and to their having subsequently acquired the larval stages first of all
by the degeneration, and then by the suppression of certain segments which
were not of use during larval life. The complete metamorphosis, however,
of the Peneidea, in which the segments and limbs appear in the right order,
rather goes to show that this is the primitive mode of development in the
Decapoda, and that the disarrangement in the order of appearance of the
segments, both in the Squillidae and in the Loricata and other Decapods,
has been independently acquired in the two cases to meet the needs of the
larval existence.
maxillipedes have become quite
rudimentary, and the second much
reduced, while the second antennae
and second maxillae are also reduced
in size. The metamorphosis is
completed by the re-development of
the limbs and segments that have
been secondarily suppressed during
larval life, and by the appearance of
the pleopods.
This process is again met with in
the Squillidae (p. 143), but it
resembles the suppression, in so
many Decapodan metamorphoses, of
anterior limbs and the precocious
development of segments and limbs
lying posteriorly. In the ordinary
Decapoda, however, the suppressed
Fig. 111.—Dorsal view of Scyllarus arctus, × ½. limbs are merely not formed till later;
(From an original figure prepared for Professor while in the Loricata the limbs
Weldon.)
develop in the correct order, and
subsequently degenerate. It is natural
to wonder whether the condition of affairs in the Loricata represents the
primitive process, and whether the precocious development of segments in
the other Decapoda owes its origin to these animals having once had the
direct mode of development when the segments were formed in the proper
order, and to their having subsequently acquired the larval stages first of all
by the degeneration, and then by the suppression of certain segments which
were not of use during larval life. The complete metamorphosis, however,
of the Peneidea, in which the segments and limbs appear in the right order,
rather goes to show that this is the primitive mode of development in the
Decapoda, and that the disarrangement in the order of appearance of the
segments, both in the Squillidae and in the Loricata and other Decapods,
has been independently acquired in the two cases to meet the needs of the
larval existence.
Page 212
Fam. 1. Palinuridae.—The
cephalothorax is subcylindrical, the
eyes are not enclosed in separate
orbits formed by the edge of the
carapace, and the second antennae
possess flagella. Palinurus, with P.
elephas, the European Rock Lobster
or Langouste. Iasus with two species
in the Antarctic littoral; Panulirus in
the tropical littoral.
Fam. 2. Scyllaridae.—The
cephalothorax is depressed, the eyes
are enclosed in separate orbits
formed by the edge of the carapace,
and the second antennae have flat
scales in the place of flagella.
Scyllarus (Fig. 111), with the
European S. arctus; Ibacus in rather
deep water with several species, Fig. 112.—Embryonic area of developing
Palinurus quadricornis. Ab.1, 1st abdominal
chiefly found in the southern segment; E, compound eye; E′, median simple
hemisphere. eye; L, upper lip; L′, lower lip; M, mandible;
Mx.1, Mx.2, 1st and 2nd maxillae; Mxp.1, 1st
maxillipede; T, 6th (antepenultimate) thoracic
appendage. (After Claus.)
cephalothorax is subcylindrical, the
eyes are not enclosed in separate
orbits formed by the edge of the
carapace, and the second antennae
possess flagella. Palinurus, with P.
elephas, the European Rock Lobster
or Langouste. Iasus with two species
in the Antarctic littoral; Panulirus in
the tropical littoral.
Fam. 2. Scyllaridae.—The
cephalothorax is depressed, the eyes
are enclosed in separate orbits
formed by the edge of the carapace,
and the second antennae have flat
scales in the place of flagella.
Scyllarus (Fig. 111), with the
European S. arctus; Ibacus in rather
deep water with several species, Fig. 112.—Embryonic area of developing
Palinurus quadricornis. Ab.1, 1st abdominal
chiefly found in the southern segment; E, compound eye; E′, median simple
hemisphere. eye; L, upper lip; L′, lower lip; M, mandible;
Mx.1, Mx.2, 1st and 2nd maxillae; Mxp.1, 1st
maxillipede; T, 6th (antepenultimate) thoracic
appendage. (After Claus.)
Page 213
Fig. 113.—Phyllosoma larva of Palinurus, sp. ×
5. Ab, Abdomen; Mxp, 3rd maxillipede; T,
antepenultimate (6th) thoracic appendage. (After
Claus.)
Tribe 6. Thalassinidea.
This tribe is included by some authors in the Anomura, and held to be
closely related to the Galatheidea, but the unreduced abdomen is carried
straight and unflexed, and gives a very Macrurous appearance to the animal.
The Anomurous characters are the frequent reduction or absence of the
antennal scale, the fact that only the first two pairs of pereiopods are ever
chelate, and the reduced series of gills. The body is symmetrical, but the
first pair of chelae is always highly asymmetrical. The posterior pairs of
pereiopods, although small, are not characteristically reduced as in the
Anomura. The animals belonging to this Tribe attain two or three inches in
length, and generally burrow in sand or mud either in the littoral zone or in
deeper waters; at the same time they can swim with considerable activity by
means of the pleopods.
Fam. Callianassidae.—Callianassa subterranea is common at Naples,
Gebia littoralis in the North Sea.
Sub-Order 2. Anomura
In this division are included the so-called Hermit-lobsters and Hermit-
crabs, in which the condition of the abdomen is roughly intermediate
5. Ab, Abdomen; Mxp, 3rd maxillipede; T,
antepenultimate (6th) thoracic appendage. (After
Claus.)
Tribe 6. Thalassinidea.
This tribe is included by some authors in the Anomura, and held to be
closely related to the Galatheidea, but the unreduced abdomen is carried
straight and unflexed, and gives a very Macrurous appearance to the animal.
The Anomurous characters are the frequent reduction or absence of the
antennal scale, the fact that only the first two pairs of pereiopods are ever
chelate, and the reduced series of gills. The body is symmetrical, but the
first pair of chelae is always highly asymmetrical. The posterior pairs of
pereiopods, although small, are not characteristically reduced as in the
Anomura. The animals belonging to this Tribe attain two or three inches in
length, and generally burrow in sand or mud either in the littoral zone or in
deeper waters; at the same time they can swim with considerable activity by
means of the pleopods.
Fam. Callianassidae.—Callianassa subterranea is common at Naples,
Gebia littoralis in the North Sea.
Sub-Order 2. Anomura
In this division are included the so-called Hermit-lobsters and Hermit-
crabs, in which the condition of the abdomen is roughly intermediate
Page 214
between that of the Macrura and that of the Brachyura. It is not much
reduced in size, and the pleopods of the sixth pair are fairly well developed,
but it is usually carried flexed towards the thorax, and is never a powerful
locomotory organ as in the Macrura. The antennal scale, if present at all, is
a mere spine, not the large leaf-like structure of the Macrura; and there is
never a partition between the two first antennae as in the Brachyura.
The last or last two pairs of pereiopods are reduced, and are turned on to
the dorsal surface or carried inside the branchial chamber; but this curious
character is met with again in certain Brachyura (Dromiacea and
Oxystomata).
Tribe 1. Galatheidea.[140]
These are symmetrical crabs with a long carapace; the abdomen, which is
as broad as the carapace, is always carried flexed under the thorax, and the
sixth pair of pleopods are expanded to form with the telson a fan-like tail.
The most anterior pereiopods are always much elongated and chelate; while
the last pair are much reduced, and either turned up on to the dorsal surface,
or else carried in the branchial chamber. The exact meaning of this last
characteristic in these forms is doubtful; some of the species are said to
carry shells temporarily upon their backs, a proceeding probably assisted by
the last pair of thoracic limbs, while in others their limbs may be used for
cleaning out the branchial chamber. Most of the Galatheidea, for instance,
the common Porcellana and Galathea, are littoral animals, and may be
found hiding under stones and in crevices on the shore; but a number occur
in deep water, e.g. Munida and Munidopsis.
The shallow-water species have ordinarily developed eyes; the various
species of Munida, which occur in fairly deep but by no means abyssal
regions, have usually very large and highly pigmented eyes; while in
Munidopsis, which is characteristic of very deep water, the eyes are
degenerate and colourless, as shown in Fig. 114.
The Zoaeae, or young larval stages of the Galatheidea, are characterised
by the immense length of the spines upon the carapace (Fig. 115). The
young Zoaea which hatches out from the egg resembles in other respects
that of the Brachyura. The Metazoaea, however, differs from that of the
Brachyura in the fact that the third maxillipede is first present as a biramous
reduced in size, and the pleopods of the sixth pair are fairly well developed,
but it is usually carried flexed towards the thorax, and is never a powerful
locomotory organ as in the Macrura. The antennal scale, if present at all, is
a mere spine, not the large leaf-like structure of the Macrura; and there is
never a partition between the two first antennae as in the Brachyura.
The last or last two pairs of pereiopods are reduced, and are turned on to
the dorsal surface or carried inside the branchial chamber; but this curious
character is met with again in certain Brachyura (Dromiacea and
Oxystomata).
Tribe 1. Galatheidea.[140]
These are symmetrical crabs with a long carapace; the abdomen, which is
as broad as the carapace, is always carried flexed under the thorax, and the
sixth pair of pleopods are expanded to form with the telson a fan-like tail.
The most anterior pereiopods are always much elongated and chelate; while
the last pair are much reduced, and either turned up on to the dorsal surface,
or else carried in the branchial chamber. The exact meaning of this last
characteristic in these forms is doubtful; some of the species are said to
carry shells temporarily upon their backs, a proceeding probably assisted by
the last pair of thoracic limbs, while in others their limbs may be used for
cleaning out the branchial chamber. Most of the Galatheidea, for instance,
the common Porcellana and Galathea, are littoral animals, and may be
found hiding under stones and in crevices on the shore; but a number occur
in deep water, e.g. Munida and Munidopsis.
The shallow-water species have ordinarily developed eyes; the various
species of Munida, which occur in fairly deep but by no means abyssal
regions, have usually very large and highly pigmented eyes; while in
Munidopsis, which is characteristic of very deep water, the eyes are
degenerate and colourless, as shown in Fig. 114.
The Zoaeae, or young larval stages of the Galatheidea, are characterised
by the immense length of the spines upon the carapace (Fig. 115). The
young Zoaea which hatches out from the egg resembles in other respects
that of the Brachyura. The Metazoaea, however, differs from that of the
Brachyura in the fact that the third maxillipede is first present as a biramous
Page 215
swimming
organ, and at its
first appearance
is not developed
in its definitive
form. The other
thoracic limbs
are not
schizopodous
when they
appear, and
indeed in nearly
all respects the
development
proceeds as in
the Brachyura.
Fam. 1.
Aegleidae.—
The gills are
trichobranchiae,
and there are
eight Fig. 114.—Dorsal view of Munidopsis hamata,
× ½. (From an original figure prepared for
arthrobranchs. Professor Weldon.)
There are no
limbs on the
second abdominal segment of the male. The abdomen
is not carried folded on to the thorax. The first two
characteristics separate this family from all the other
Galatheidea. Aeglea laevis, a fresh-water species from
the rivers of temperate S. America, is the sole
representative.
Fam. 2. Galatheidae.—The abdomen is not folded
against the thorax. The members of this family are
often littoral in habit (Galathea, Fig. 116), but often go
down into great depths (Munidopsis, Fig. 114).
organ, and at its
first appearance
is not developed
in its definitive
form. The other
thoracic limbs
are not
schizopodous
when they
appear, and
indeed in nearly
all respects the
development
proceeds as in
the Brachyura.
Fam. 1.
Aegleidae.—
The gills are
trichobranchiae,
and there are
eight Fig. 114.—Dorsal view of Munidopsis hamata,
× ½. (From an original figure prepared for
arthrobranchs. Professor Weldon.)
There are no
limbs on the
second abdominal segment of the male. The abdomen
is not carried folded on to the thorax. The first two
characteristics separate this family from all the other
Galatheidea. Aeglea laevis, a fresh-water species from
the rivers of temperate S. America, is the sole
representative.
Fam. 2. Galatheidae.—The abdomen is not folded
against the thorax. The members of this family are
often littoral in habit (Galathea, Fig. 116), but often go
down into great depths (Munidopsis, Fig. 114).
Page 216
Fam. 3.
Porcellanidae.
—The abdomen
is folded against
the thorax, and
the body has a
crab-like form.
These are
always littoral in
habit, never
descending into
the depths.
Pachycheles in
the tropics,
Porcellana with
numerous
species in all
seas, P. Fig. 116.—Dorsal view of Galathea strigosa, ×
½. (From an original figure prepared for
platycheles Professor Weldon.)
being a common
British species.
Porcellanidae.
—The abdomen
is folded against
the thorax, and
the body has a
crab-like form.
These are
always littoral in
habit, never
descending into
the depths.
Pachycheles in
the tropics,
Porcellana with
numerous
species in all
seas, P. Fig. 116.—Dorsal view of Galathea strigosa, ×
½. (From an original figure prepared for
platycheles Professor Weldon.)
being a common
British species.
Page 217
Fig. 115.—Zoaea of
Porcellana, × 20. T,
Telson. (After Claus.)
Tribe 2. Hippidea.
The Mole-crabs have the habit of burrowing in sand, and their limbs are
peculiarly modified into digging organs for this purpose (see Fig. 117). In
other respects they are seen to be closely related to the Galatheidea by the
form of the carapace, the condition of the abdomen, and the reduced last
thoracic limbs.
In Albunea, which is found in the Mediterranean, the first antennae[141]
are greatly lengthened and apposed to one another, and by means of a
system of interlocking hairs they form a tube down which the water is
sucked for respiration. The object of this arrangement is to ensure a supply
of clear water, filtered from particles of sand, when the crab is buried
beneath the surface, on these occasions the tip of the antennal tube being
protruded above the surface of the sand. An exactly similar tube is used by
the true Crab Corystes cassivelaunus, which has similar burrowing habits,
but here the tube is formed from the second antennae and not from the first,
so that the tubes in the two cases afford beautiful instances of analogous or
homoplastic structures between which there is no homology (see p. 189).
Fam. 1. Albuneidae.—The first legs are subchelate; the carapace is
flattened, without expansions covering the legs. Albunea with several
species in the Mediterranean, West Indies, and Indo-Pacific.
Porcellana, × 20. T,
Telson. (After Claus.)
Tribe 2. Hippidea.
The Mole-crabs have the habit of burrowing in sand, and their limbs are
peculiarly modified into digging organs for this purpose (see Fig. 117). In
other respects they are seen to be closely related to the Galatheidea by the
form of the carapace, the condition of the abdomen, and the reduced last
thoracic limbs.
In Albunea, which is found in the Mediterranean, the first antennae[141]
are greatly lengthened and apposed to one another, and by means of a
system of interlocking hairs they form a tube down which the water is
sucked for respiration. The object of this arrangement is to ensure a supply
of clear water, filtered from particles of sand, when the crab is buried
beneath the surface, on these occasions the tip of the antennal tube being
protruded above the surface of the sand. An exactly similar tube is used by
the true Crab Corystes cassivelaunus, which has similar burrowing habits,
but here the tube is formed from the second antennae and not from the first,
so that the tubes in the two cases afford beautiful instances of analogous or
homoplastic structures between which there is no homology (see p. 189).
Fam. 1. Albuneidae.—The first legs are subchelate; the carapace is
flattened, without expansions covering the legs. Albunea with several
species in the Mediterranean, West Indies, and Indo-Pacific.
Page 218
Fig. 117.—Remipes scutellatus, dorsal and ventral views, × 1. (From original
drawings prepared for Professor Weldon.)
Fam. 2. Hippidae.—The first legs are simple, the carapace is
subcylindrical with expansions covering the legs. Remipes (Fig. 117) and
Hippa in tropical or sub-tropical seas.
Tribe 3. Paguridea.[142]
The ordinary Hermit-crabs, common on the English as on every coast,
are characterised by the fleshy asymmetrical abdomen from which all the
hard matter has disappeared, and which is carried tucked away in an empty
Gasteropod shell. The abdomen is spirally wound in accordance with the
shape of the shell, and a firm attachment is effected by means of the sixth
pair of pleopods, especially that of the left side, which is fashioned into the
form of a hook and is curled round the columella of the shell; this
attachment is so secure that in trying to pull a Hermit-crab out of its shell
the body is torn apart before the hold gives way. The other pleopods are in a
much reduced condition, being generally altogether absent from the right
side of the abdomen, and often greatly reduced on the left side, especially in
the male, though in the female they are still used for the attachment of the
eggs.
drawings prepared for Professor Weldon.)
Fam. 2. Hippidae.—The first legs are simple, the carapace is
subcylindrical with expansions covering the legs. Remipes (Fig. 117) and
Hippa in tropical or sub-tropical seas.
Tribe 3. Paguridea.[142]
The ordinary Hermit-crabs, common on the English as on every coast,
are characterised by the fleshy asymmetrical abdomen from which all the
hard matter has disappeared, and which is carried tucked away in an empty
Gasteropod shell. The abdomen is spirally wound in accordance with the
shape of the shell, and a firm attachment is effected by means of the sixth
pair of pleopods, especially that of the left side, which is fashioned into the
form of a hook and is curled round the columella of the shell; this
attachment is so secure that in trying to pull a Hermit-crab out of its shell
the body is torn apart before the hold gives way. The other pleopods are in a
much reduced condition, being generally altogether absent from the right
side of the abdomen, and often greatly reduced on the left side, especially in
the male, though in the female they are still used for the attachment of the
eggs.
Page 219
The last two pereiopods are much reduced and are concealed inside the
shell, which they help to carry. The great chelae are usually asymmetrically
developed, that on the right side being much larger than that on the left, and
often serving the purpose of shutting the entrance to the shell when the crab
is withdrawn inside.
The constant association of a large group of animals like the Hermit-
crabs with the appropriated empty houses of another group is sufficiently
curious, but it does not stop there. In almost every case there are present
one or more Sea-anemones growing on the outside of the shell, and each
kind of Hermit-crab generally carries a special kind of Anemone. Thus at
Plymouth, Eupagurus bernhardus is generally symbiotic with Sagartia
parasitica, or else with a colony of Hydractinia echinata, while E.
prideauxii is usually associated with Adamsia palliata. In the latter case the
shell is frequently absorbed, so that the Anemone comes to envelop the crab
like a blanket. Instead of Anemones carried turret-like and imposing aloft,
or enveloping the inmate of the shell like a blanket, some of the Hermits
have Sponges, an unexpected association; and it is a common sight at
Naples to find the little red round Sponge, Suberites, running around
animated by its Hermit within. It is held that Anemone and crab mutually
assist one another, that the Anemone stings the crab’s enemies, and that the
Hermit-crab carries the Anemone to new feeding-grounds. It is also said
that when a crab grows too big for its shell, and is forced to seek another, it
persuades the Anemone to loosen its attachment to the deserted shell and to
be transplanted to the new one, and that there is something mesmeric in its
power, because nobody else can pull an Anemone off a shell without either
cutting it off at the base or tearing it to pieces. Other animals as well
sometimes enter into this partnership. At Plymouth a Polychaet worm,
Nereis fucata, frequently inhabits the Whelk’s shell, together with
Eupagurus bernhardus, and puts out its head for a share of each meal; and
at Naples the Amphipod Lysianax punctatus is almost always present in the
shells of Eupagurus prideauxii.
Besides the ordinary twisted Pagurids which inhabit Gasteropod shells,
there are a few which preserve the symmetry of the body. The interesting
Pylocheles miersii[143] (Fig. 118), taken by the Investigator in the Andaman
Sea at 185 fathoms, inhabits pieces of bamboo; it is perfectly symmetrical,
with well-developed pleopods and symmetrical chelae, which, when the
shell, which they help to carry. The great chelae are usually asymmetrically
developed, that on the right side being much larger than that on the left, and
often serving the purpose of shutting the entrance to the shell when the crab
is withdrawn inside.
The constant association of a large group of animals like the Hermit-
crabs with the appropriated empty houses of another group is sufficiently
curious, but it does not stop there. In almost every case there are present
one or more Sea-anemones growing on the outside of the shell, and each
kind of Hermit-crab generally carries a special kind of Anemone. Thus at
Plymouth, Eupagurus bernhardus is generally symbiotic with Sagartia
parasitica, or else with a colony of Hydractinia echinata, while E.
prideauxii is usually associated with Adamsia palliata. In the latter case the
shell is frequently absorbed, so that the Anemone comes to envelop the crab
like a blanket. Instead of Anemones carried turret-like and imposing aloft,
or enveloping the inmate of the shell like a blanket, some of the Hermits
have Sponges, an unexpected association; and it is a common sight at
Naples to find the little red round Sponge, Suberites, running around
animated by its Hermit within. It is held that Anemone and crab mutually
assist one another, that the Anemone stings the crab’s enemies, and that the
Hermit-crab carries the Anemone to new feeding-grounds. It is also said
that when a crab grows too big for its shell, and is forced to seek another, it
persuades the Anemone to loosen its attachment to the deserted shell and to
be transplanted to the new one, and that there is something mesmeric in its
power, because nobody else can pull an Anemone off a shell without either
cutting it off at the base or tearing it to pieces. Other animals as well
sometimes enter into this partnership. At Plymouth a Polychaet worm,
Nereis fucata, frequently inhabits the Whelk’s shell, together with
Eupagurus bernhardus, and puts out its head for a share of each meal; and
at Naples the Amphipod Lysianax punctatus is almost always present in the
shells of Eupagurus prideauxii.
Besides the ordinary twisted Pagurids which inhabit Gasteropod shells,
there are a few which preserve the symmetry of the body. The interesting
Pylocheles miersii[143] (Fig. 118), taken by the Investigator in the Andaman
Sea at 185 fathoms, inhabits pieces of bamboo; it is perfectly symmetrical,
with well-developed pleopods and symmetrical chelae, which, when the
Page 220
animal is withdrawn, completely shut
up the entrance to its house (Fig. 118,
A).
It is doubtful whether this animal
ever inhabited a spiral shell or not in
its past history; but there is no doubt
that a number of peculiar crabs,
which caused the older systematists
much trouble, are Pagurids, derived
from asymmetrical shell-haunting
ancestors that have secondarily taken
to a different mode of life, and lost,
or partially lost those characteristics
of ordinary Hermit-crabs which are
associated with life in a spiral shell.
These are the Lithodidae and the
“Robber-crab,” Birgus latro, of
tropical coral islands.
Although the Robber-crab and the
Lithodidae bear a certain superficial
resemblance to one another in that
they lead a free existence, and have
reacquired to a great extent their Fig. 118.—Pylocheles miersii, × 1. A, End view
symmetry, yet it is clear that they of a piece of mangrove or bamboo, the opening
have been independently derived of which is closed by the great chelae (c) of the
Pagurid; B, the animal removed from its house.
from different groups of (After Alcock.)
asymmetrical Hermit-crabs, and that
their resemblance to one another is
due to convergence.
Birgus latro (Fig. 119), a gigantic crab, frequently over a foot in length,
lives on land, and inhabits the coasts of coral islands in the Indian and
Pacific Oceans where cocoa-nut trees grow. It feeds on the pulp of the
cocoa-nut, which it extracts by hammering with its heavy chela on the “eye-
hole” until room is made for the small chela to enter and extract the pulp.
There is not the slightest doubt that the animal often ascends the cocoa-nut
trees for the purpose of picking the nuts, a fact illustrated by a fine
up the entrance to its house (Fig. 118,
A).
It is doubtful whether this animal
ever inhabited a spiral shell or not in
its past history; but there is no doubt
that a number of peculiar crabs,
which caused the older systematists
much trouble, are Pagurids, derived
from asymmetrical shell-haunting
ancestors that have secondarily taken
to a different mode of life, and lost,
or partially lost those characteristics
of ordinary Hermit-crabs which are
associated with life in a spiral shell.
These are the Lithodidae and the
“Robber-crab,” Birgus latro, of
tropical coral islands.
Although the Robber-crab and the
Lithodidae bear a certain superficial
resemblance to one another in that
they lead a free existence, and have
reacquired to a great extent their Fig. 118.—Pylocheles miersii, × 1. A, End view
symmetry, yet it is clear that they of a piece of mangrove or bamboo, the opening
have been independently derived of which is closed by the great chelae (c) of the
Pagurid; B, the animal removed from its house.
from different groups of (After Alcock.)
asymmetrical Hermit-crabs, and that
their resemblance to one another is
due to convergence.
Birgus latro (Fig. 119), a gigantic crab, frequently over a foot in length,
lives on land, and inhabits the coasts of coral islands in the Indian and
Pacific Oceans where cocoa-nut trees grow. It feeds on the pulp of the
cocoa-nut, which it extracts by hammering with its heavy chela on the “eye-
hole” until room is made for the small chela to enter and extract the pulp.
There is not the slightest doubt that the animal often ascends the cocoa-nut
trees for the purpose of picking the nuts, a fact illustrated by a fine
Page 221
photograph by Dr. Andrews, exhibited in the Crustacean Gallery in the
Natural History Departments of the British Museum. It uses the husk of the
nut to line its burrow, and it is said to have the habit of putting its abdomen
into the nut-shell for protection and carrying it about with it. Owing to its
terrestrial mode of life, the branchial chamber is highly modified, being
divided into two portions—a dorsal space, the lining of which is thrown
into vascular ridges and folds for aerial respiration, and a lower portion
where the rudimentary branchiae are situated. Although the Robber-crab
lives ordinarily on land, it must be supposed that these branchiae are of
some service; the young are hatched out as ordinary Zoaeas in the sea, and
go through a pelagic existence before seeking the land. At the present time
the Robber-crab is confined to the Pacific and the islands of the Indian
Ocean, wherever the cocoa-nut grows. It seems, however, that its
association with the cocoa-nut is a comparatively modern one. Mr. C.
Hedley, of Sydney, who has had great experience of the Pacific Islands,
informs me that the cocoa-nut is not, as is usually supposed, a native of
these coral islands, but has been introduced, probably from Mexico, by the
Polynesian mariners before the discovery of America by Columbus. Before
the introduction of the cocoa-nut the Robber-crab must have fed on some
other tree, possibly the Screw Pine, Pandanus.
The abdomen is full of oil, and is much prized as a delicacy by the
natives, who tell many strange legends about the creature, but the
philosopher may well find its structure more strange than fiction, and the
consideration of its morphology an intellectual feast.
The appearance of the thorax and of the thoracic limbs is thoroughly
Pagurid; the structure of the abdomen is highly peculiar.
From the ventral surface (Fig. 119) we can see at the tip of the tail three
small calcified plates, which represent the fifth and sixth terga and the
telson. Attached to the sixth segment are the much reduced and rudimentary
pleopods of that segment, and on the left hand side of the body in the
female are three well-developed pleopods of the first, second, and third
segments, which are used for carrying the eggs. The extraordinary
asymmetry of these limbs compared with the complete symmetry of the
abdomen itself is only explicable on the hypothesis that these animals are
descended from Hermit-crabs which had lost the pleopods on the right side.
Natural History Departments of the British Museum. It uses the husk of the
nut to line its burrow, and it is said to have the habit of putting its abdomen
into the nut-shell for protection and carrying it about with it. Owing to its
terrestrial mode of life, the branchial chamber is highly modified, being
divided into two portions—a dorsal space, the lining of which is thrown
into vascular ridges and folds for aerial respiration, and a lower portion
where the rudimentary branchiae are situated. Although the Robber-crab
lives ordinarily on land, it must be supposed that these branchiae are of
some service; the young are hatched out as ordinary Zoaeas in the sea, and
go through a pelagic existence before seeking the land. At the present time
the Robber-crab is confined to the Pacific and the islands of the Indian
Ocean, wherever the cocoa-nut grows. It seems, however, that its
association with the cocoa-nut is a comparatively modern one. Mr. C.
Hedley, of Sydney, who has had great experience of the Pacific Islands,
informs me that the cocoa-nut is not, as is usually supposed, a native of
these coral islands, but has been introduced, probably from Mexico, by the
Polynesian mariners before the discovery of America by Columbus. Before
the introduction of the cocoa-nut the Robber-crab must have fed on some
other tree, possibly the Screw Pine, Pandanus.
The abdomen is full of oil, and is much prized as a delicacy by the
natives, who tell many strange legends about the creature, but the
philosopher may well find its structure more strange than fiction, and the
consideration of its morphology an intellectual feast.
The appearance of the thorax and of the thoracic limbs is thoroughly
Pagurid; the structure of the abdomen is highly peculiar.
From the ventral surface (Fig. 119) we can see at the tip of the tail three
small calcified plates, which represent the fifth and sixth terga and the
telson. Attached to the sixth segment are the much reduced and rudimentary
pleopods of that segment, and on the left hand side of the body in the
female are three well-developed pleopods of the first, second, and third
segments, which are used for carrying the eggs. The extraordinary
asymmetry of these limbs compared with the complete symmetry of the
abdomen itself is only explicable on the hypothesis that these animals are
descended from Hermit-crabs which had lost the pleopods on the right side.
Page 222
Fig. 119.—Birgus latro, ♀ , × ⅙ , ventral view. Ab, First pleopod; T, last
pereiopod.
These appendages are entirely absent in the male. The ventral surface of
the abdomen is curiously warty and rugose, and is very soft and pulpy
owing to the immense store of oil which it contains.
If we look at the dorsal surface of the abdomen we find that, unlike that
of the Hermit-crabs, it is completely protected by a number of hard plates
(Fig. 120, B). Beneath the carapace can be seen a number of small plates
belonging to the last thoracic segment; following these there are four large
plates (1–4) representing the terga of the first four abdominal segments; the
fifth, sixth, and the telson are, as has been stated, carried on the under side
of the abdomen, but they are represented diagrammatically (5, 6, T) in the
dorsal view. Besides the large terga, there are a number of small plates
laterally, usually two to each segment, but they show a tendency to
subdivide and increase in the largest specimens. This condition of affairs is
pereiopod.
These appendages are entirely absent in the male. The ventral surface of
the abdomen is curiously warty and rugose, and is very soft and pulpy
owing to the immense store of oil which it contains.
If we look at the dorsal surface of the abdomen we find that, unlike that
of the Hermit-crabs, it is completely protected by a number of hard plates
(Fig. 120, B). Beneath the carapace can be seen a number of small plates
belonging to the last thoracic segment; following these there are four large
plates (1–4) representing the terga of the first four abdominal segments; the
fifth, sixth, and the telson are, as has been stated, carried on the under side
of the abdomen, but they are represented diagrammatically (5, 6, T) in the
dorsal view. Besides the large terga, there are a number of small plates
laterally, usually two to each segment, but they show a tendency to
subdivide and increase in the largest specimens. This condition of affairs is
Page 223
very different to that in the naked
fleshy abdomen of an ordinary
Pagurid, but it can easily be deduced
from that of the genus Cenobita,
ordinary Hermit-crabs found in the
Indo-Pacific Oceans, from which the
Robber-crab has evidently
descended. In Cenobita (Fig. 120, A)
we see the same system of plates
upon the dorsal surface of the
abdomen, but they are much smaller,
Fig. 120.—Dorsal view of abdomen, A, of and the lateral plates are not so
Cenobita, sp.; B, of Birgus latro. T, Telson; 1–6, numerous; indeed, the greater part of
1st–6th abdominal segments. the abdomen remains fleshy and
uncalcified. The under surface of the
abdomen shows the same rugosity as is found in Birgus, and from a number
of other anatomical characters it is evident that the Robber-crab is a highly
modified Cenobita that has deserted its shell and developed a symmetrical
abdomen protected by expanded and hardened plates which represent those
found in a reduced condition in Cenobita. The species of Cenobita although
they inhabit shells and have normal branchiae, live on the shore, and have
not been seen to descend actually into the sea.
The Lithodidae, which are found in temperate seas, especially on the
Northern Pacific coasts (though Lithodes maia occurs in the North Sea, and
certain species inhabit deep water in the Indian Ocean), have a deceptively
Brachyuran appearance, the thorax being much shortened and the abdomen
being much reduced and carried tightly flexed on to the ventral surface of
the thorax. They live a free, unprotected existence, and are highly calcified.
They are, however, certainly Pagurids, as is evidenced by a number of
anatomical characters, but most clearly by the asymmetry of the abdomen,
especially in the female, which is not only markedly asymmetrical in the
arrangement of its dorsal plates (Fig. 121), but also in the presence of three
pleopods upon the left side only, as in Birgus. The male is without these
appendages, and the sixth pair of pleopods is absent in both sexes. The
remarkable calcified plates upon the abdomen bear a superficial
resemblance to those in Birgus, but their evolution is traced, not from a
Cenobite, but from an Eupagurine stock.[144]
fleshy abdomen of an ordinary
Pagurid, but it can easily be deduced
from that of the genus Cenobita,
ordinary Hermit-crabs found in the
Indo-Pacific Oceans, from which the
Robber-crab has evidently
descended. In Cenobita (Fig. 120, A)
we see the same system of plates
upon the dorsal surface of the
abdomen, but they are much smaller,
Fig. 120.—Dorsal view of abdomen, A, of and the lateral plates are not so
Cenobita, sp.; B, of Birgus latro. T, Telson; 1–6, numerous; indeed, the greater part of
1st–6th abdominal segments. the abdomen remains fleshy and
uncalcified. The under surface of the
abdomen shows the same rugosity as is found in Birgus, and from a number
of other anatomical characters it is evident that the Robber-crab is a highly
modified Cenobita that has deserted its shell and developed a symmetrical
abdomen protected by expanded and hardened plates which represent those
found in a reduced condition in Cenobita. The species of Cenobita although
they inhabit shells and have normal branchiae, live on the shore, and have
not been seen to descend actually into the sea.
The Lithodidae, which are found in temperate seas, especially on the
Northern Pacific coasts (though Lithodes maia occurs in the North Sea, and
certain species inhabit deep water in the Indian Ocean), have a deceptively
Brachyuran appearance, the thorax being much shortened and the abdomen
being much reduced and carried tightly flexed on to the ventral surface of
the thorax. They live a free, unprotected existence, and are highly calcified.
They are, however, certainly Pagurids, as is evidenced by a number of
anatomical characters, but most clearly by the asymmetry of the abdomen,
especially in the female, which is not only markedly asymmetrical in the
arrangement of its dorsal plates (Fig. 121), but also in the presence of three
pleopods upon the left side only, as in Birgus. The male is without these
appendages, and the sixth pair of pleopods is absent in both sexes. The
remarkable calcified plates upon the abdomen bear a superficial
resemblance to those in Birgus, but their evolution is traced, not from a
Cenobite, but from an Eupagurine stock.[144]
Page 224
Fig. 121.—Lithodes maia, ♀, in ventral view, × ¼. The abdomen is flexed on the
thorax, so that its dorsal surface is seen. l.3, Lateral plates of third abdominal
segment; l.5, left lateral plate of fifth abdominal segment; m, marginal plate; T,
brush-like last pereiopod; Te.6, telson and sixth abdominal segment.
In some of the Eupagurinae, e.g. Pylopagurus, feebly calcified plates are
present upon the segments of the abdomen (Fig. 122, A).
In the most primitive of the Lithodidae we witness the reduction (Fig.
122, B) and disappearance (C) of these original plates, their place being
taken first by a number of irregularly situated small spines and warts,
which, however, subsequently fuse up to form definite segmental plates. In
Lithodes maia, ♂ (D), there are a series of lateral and marginal plates, while
in Acantholithus (E) a number of median plates appear, presumably by the
fusion of the small spines present in the median line in Lithodes maia;
finally, a fusion of the marginal and lateral plates may take place, so that
each abdominal segment is covered by a median and two paired lateral
plates.
thorax, so that its dorsal surface is seen. l.3, Lateral plates of third abdominal
segment; l.5, left lateral plate of fifth abdominal segment; m, marginal plate; T,
brush-like last pereiopod; Te.6, telson and sixth abdominal segment.
In some of the Eupagurinae, e.g. Pylopagurus, feebly calcified plates are
present upon the segments of the abdomen (Fig. 122, A).
In the most primitive of the Lithodidae we witness the reduction (Fig.
122, B) and disappearance (C) of these original plates, their place being
taken first by a number of irregularly situated small spines and warts,
which, however, subsequently fuse up to form definite segmental plates. In
Lithodes maia, ♂ (D), there are a series of lateral and marginal plates, while
in Acantholithus (E) a number of median plates appear, presumably by the
fusion of the small spines present in the median line in Lithodes maia;
finally, a fusion of the marginal and lateral plates may take place, so that
each abdominal segment is covered by a median and two paired lateral
plates.
Page 225
Fig. 122.—Diagrams of abdomen: A, of Pylopagurus, sp.; B, of Hapalogaster
cavicauda; C, of Dermaturus hispidus; D, of Lithodes maia, ♂ ; E, of
Acantholithus hystrix. c, Central plates; l, lateral plates; m, marginal plates; T,
telson; 1–6, 1st–6th abdominal segments. (After Bouvier.)
It is to be noted that the males and females of the various species do not
follow a parallel course of development, the plates in the male being
symmetrical, while those of the female are often highly asymmetrical
(compare Figs. 122, D, and 121), thus giving the strongest evidence of a
Pagurid ancestry.
Birgus and the Lithodidae, then, are Pagurids which have given up living
in shells, and have become adapted to a free existence, protecting their soft
parts by the development of hard plates, and re-acquiring, to a greater or
less degree, a secondary symmetry of form. But the story of Pagurid
evolution does not apparently stop here. The genus Paralomis, from the
West Coast of America, superficially resembles Porcellana, and is held to
be descended from such forms as Pylocheles, while isolated species are
cavicauda; C, of Dermaturus hispidus; D, of Lithodes maia, ♂ ; E, of
Acantholithus hystrix. c, Central plates; l, lateral plates; m, marginal plates; T,
telson; 1–6, 1st–6th abdominal segments. (After Bouvier.)
It is to be noted that the males and females of the various species do not
follow a parallel course of development, the plates in the male being
symmetrical, while those of the female are often highly asymmetrical
(compare Figs. 122, D, and 121), thus giving the strongest evidence of a
Pagurid ancestry.
Birgus and the Lithodidae, then, are Pagurids which have given up living
in shells, and have become adapted to a free existence, protecting their soft
parts by the development of hard plates, and re-acquiring, to a greater or
less degree, a secondary symmetry of form. But the story of Pagurid
evolution does not apparently stop here. The genus Paralomis, from the
West Coast of America, superficially resembles Porcellana, and is held to
be descended from such forms as Pylocheles, while isolated species are
Page 226
known (though not well known), such as Tylaspis, described in the
Challenger Reports,[145] which appear to be Pagurids that have deserted their
shells.
Fig. 123.—Four stages in the development of Eupagurus longicarpus or E.
annulipes, × 20. A, Ventral view of Zoaea; B, lateral view of Metazoaea; C,
dorsal view of Glaucothoe; D, dorsal view of adolescent stage. Ab.6, 6th
abdominal appendage; Mxp.1, Mxp.3, 1st and 3rd maxillipedes. (After M. T.
Thompson.)
The metamorphosis of the Hermit-crabs has recently been studied by M.
T. Thompson.[146]
Challenger Reports,[145] which appear to be Pagurids that have deserted their
shells.
Fig. 123.—Four stages in the development of Eupagurus longicarpus or E.
annulipes, × 20. A, Ventral view of Zoaea; B, lateral view of Metazoaea; C,
dorsal view of Glaucothoe; D, dorsal view of adolescent stage. Ab.6, 6th
abdominal appendage; Mxp.1, Mxp.3, 1st and 3rd maxillipedes. (After M. T.
Thompson.)
The metamorphosis of the Hermit-crabs has recently been studied by M.
T. Thompson.[146]
Page 227
The Zoaea (Fig. 123, A) differs from that of the Galatheidea mainly in
the absence of the long spines. It possesses the usual appendages
characteristic of the Zoaea, namely, the first and second antennae,
mandibles, first and second maxillae, and two pairs of biramous swimming
maxillipedes and small third maxillipedes. In the Metazoaea (B), as in the
Anomura generally, the third maxillipedes develop into biramous
swimming organs, a thing they never do in the Brachyura, and the
rudiments of the thoracic segments put in a first appearance. The abdominal
segments are already fully formed in the Zoaea stage, so that here as in all
other Zoaeas, the order of development from in front backwards is
disturbed by the precocious differentiation of the abdominal segments. The
next stage is the “Glaucothoe” (Fig. 123, C), which corresponds to the
Megalopa of Brachyura (Fig. 125, p. 183). It differs from the adult Hermit-
crab in the perfect symmetry of its body, the segmented abdomen, and the
presence of five pairs of normal biramous pleopods. At this stage, which
lasts four or five days, it resembles closely a little Galatheid. The
asymmetry of the adult (Fig. 123, D) is now imposed upon this larva by the
migration of the liver, gonads, and green glands into the abdomen, and by
the shifting of the posterior lobes of the liver on to the left side of the
intestine, which is displaced dorsally and to the right. The gonad lies
entirely on the left side. The pleopods of the right side now degenerate,
more completely in the male than in the female, and this degeneration is not
completed until the little crab has found a shell and lived in it for some
time. If a shell is withheld from it, the degeneration of the pleopods is much
retarded, so that although the Hermit-crab assumes its asymmetry without
the stimulus of the spiral shell, yet this stimulus is necessary for the normal
completion of the later stages.
Fam. 1. Pylochelidae.—The abdomen is macrurous and symmetrical,
with all the limbs present. Pylocheles (Fig. 118, p. 173).
Fam. 2. Paguridae.—The abdomen is asymmetrical, with some of the
limbs lost. The antennal scale is well developed, and the flagella of the first
antennae end in a filament.
Sub-Fam. 1. Eupagurinae.—The third maxillipedes are wide apart at
the base, and the right chelipedes are much larger than the left.
Parapagurus from deep-sea, Eupagurus from temperate, especially north
temperate seas. Pylopagurus.
the absence of the long spines. It possesses the usual appendages
characteristic of the Zoaea, namely, the first and second antennae,
mandibles, first and second maxillae, and two pairs of biramous swimming
maxillipedes and small third maxillipedes. In the Metazoaea (B), as in the
Anomura generally, the third maxillipedes develop into biramous
swimming organs, a thing they never do in the Brachyura, and the
rudiments of the thoracic segments put in a first appearance. The abdominal
segments are already fully formed in the Zoaea stage, so that here as in all
other Zoaeas, the order of development from in front backwards is
disturbed by the precocious differentiation of the abdominal segments. The
next stage is the “Glaucothoe” (Fig. 123, C), which corresponds to the
Megalopa of Brachyura (Fig. 125, p. 183). It differs from the adult Hermit-
crab in the perfect symmetry of its body, the segmented abdomen, and the
presence of five pairs of normal biramous pleopods. At this stage, which
lasts four or five days, it resembles closely a little Galatheid. The
asymmetry of the adult (Fig. 123, D) is now imposed upon this larva by the
migration of the liver, gonads, and green glands into the abdomen, and by
the shifting of the posterior lobes of the liver on to the left side of the
intestine, which is displaced dorsally and to the right. The gonad lies
entirely on the left side. The pleopods of the right side now degenerate,
more completely in the male than in the female, and this degeneration is not
completed until the little crab has found a shell and lived in it for some
time. If a shell is withheld from it, the degeneration of the pleopods is much
retarded, so that although the Hermit-crab assumes its asymmetry without
the stimulus of the spiral shell, yet this stimulus is necessary for the normal
completion of the later stages.
Fam. 1. Pylochelidae.—The abdomen is macrurous and symmetrical,
with all the limbs present. Pylocheles (Fig. 118, p. 173).
Fam. 2. Paguridae.—The abdomen is asymmetrical, with some of the
limbs lost. The antennal scale is well developed, and the flagella of the first
antennae end in a filament.
Sub-Fam. 1. Eupagurinae.—The third maxillipedes are wide apart at
the base, and the right chelipedes are much larger than the left.
Parapagurus from deep-sea, Eupagurus from temperate, especially north
temperate seas. Pylopagurus.
Page 228
Sub-Fam. 2. Pagurinae.—The third maxillipedes are approximated at
the base; the chelipedes are equal or subequal, or the left is much larger.
Chiefly in the warm and tropical seas, but Clibanarius and Diogenes also in
the Mediterranean.
Fam. 3. Cenobitidae.—The abdomen is as in Paguridae. The antennal
scale is reduced, the flagella of the first antennae end bluntly. The members
of this family are characteristic of tropical beaches, where they live on the
land. Cenobita, with about six species, in the West Indies and Indo-Pacific,
living in Mollusc shells; Birgus (Fig. 119) on Indo-Pacific coral islands.
Fam. 4. Lithodidae.—The abdomen is bent under the thorax, and the
body is crab-like and calcified. The rostrum is spiniform, and the sixth
abdominal appendages are lost.
Sub-Fam. 1. Hapalogasterinae.—Abdomen not fully calcified, and
without complicated plates. Hapalogaster and Dermaturus in the North
Pacific littoral.
Sub-Fam. 2. Lithodinae.—Abdomen fully calcified, with a complicated
arrangement of plates. Lithodes (Fig. 121) practically universal distribution,
littoral and deep sea. Acantholithus, deep littoral of Japan; Paralomis, west
coast of America. This last genus should probably be placed in a separate
family.
Sub-Order 3. Brachyura.[147]
The abdomen is much reduced, especially in the male, and is carried
completely flexed on to the ventral face of the thorax so as to be invisible
from the dorsal surface. The pleopods in the male are only present on the
two anterior segments, and are highly modified as copulatory organs; the
pleopods in the female are four in number and are used simply for carrying
the eggs; the pleopods of the sixth pair are always absent in both sexes. The
first antennae and the stalked eyes can be retracted into special pits
excavated in the carapace.
the base; the chelipedes are equal or subequal, or the left is much larger.
Chiefly in the warm and tropical seas, but Clibanarius and Diogenes also in
the Mediterranean.
Fam. 3. Cenobitidae.—The abdomen is as in Paguridae. The antennal
scale is reduced, the flagella of the first antennae end bluntly. The members
of this family are characteristic of tropical beaches, where they live on the
land. Cenobita, with about six species, in the West Indies and Indo-Pacific,
living in Mollusc shells; Birgus (Fig. 119) on Indo-Pacific coral islands.
Fam. 4. Lithodidae.—The abdomen is bent under the thorax, and the
body is crab-like and calcified. The rostrum is spiniform, and the sixth
abdominal appendages are lost.
Sub-Fam. 1. Hapalogasterinae.—Abdomen not fully calcified, and
without complicated plates. Hapalogaster and Dermaturus in the North
Pacific littoral.
Sub-Fam. 2. Lithodinae.—Abdomen fully calcified, with a complicated
arrangement of plates. Lithodes (Fig. 121) practically universal distribution,
littoral and deep sea. Acantholithus, deep littoral of Japan; Paralomis, west
coast of America. This last genus should probably be placed in a separate
family.
Sub-Order 3. Brachyura.[147]
The abdomen is much reduced, especially in the male, and is carried
completely flexed on to the ventral face of the thorax so as to be invisible
from the dorsal surface. The pleopods in the male are only present on the
two anterior segments, and are highly modified as copulatory organs; the
pleopods in the female are four in number and are used simply for carrying
the eggs; the pleopods of the sixth pair are always absent in both sexes. The
first antennae and the stalked eyes can be retracted into special pits
excavated in the carapace.
Page 229
Fig. 124.—A, Zoaea, × 24, and B, Metazoaea, × 13, of Corystes cassivelaunus.
Ab, 3rd abdominal segment; An, 1st antenna; E, eye; G, gills; M, 1st maxillipede;
T.8, last thoracic appendage. (After Gurney.)
The larva hatches out as a Zoaea[148] (Fig. 124, A) very similar to that of
the Anomura; it is furnished with an anterior and posterior spine on the
carapace. It is characteristic of the Brachyuran Zoaea that the third
maxillipede is fashioned from the beginning in its definitive expanded form,
and is never a biramous swimming organ as in the Anomura. The only
exception to this rule is found in the Dromiacea, the most primitive of the
Brachyura, to be soon considered, in which not only the third maxillipede,
but also the first pair of pereiopods may be developed as biramous oars, a
condition taking one back to the Mysis stage of the Macrura. The
Metazoaea (Fig. 124, B) has the rudiments of the thoracic limbs developed
and crowded together at the back of the carapace; they are all laid down in
their definitive forms, and the abdomen has the pleopods precociously
Ab, 3rd abdominal segment; An, 1st antenna; E, eye; G, gills; M, 1st maxillipede;
T.8, last thoracic appendage. (After Gurney.)
The larva hatches out as a Zoaea[148] (Fig. 124, A) very similar to that of
the Anomura; it is furnished with an anterior and posterior spine on the
carapace. It is characteristic of the Brachyuran Zoaea that the third
maxillipede is fashioned from the beginning in its definitive expanded form,
and is never a biramous swimming organ as in the Anomura. The only
exception to this rule is found in the Dromiacea, the most primitive of the
Brachyura, to be soon considered, in which not only the third maxillipede,
but also the first pair of pereiopods may be developed as biramous oars, a
condition taking one back to the Mysis stage of the Macrura. The
Metazoaea (Fig. 124, B) has the rudiments of the thoracic limbs developed
and crowded together at the back of the carapace; they are all laid down in
their definitive forms, and the abdomen has the pleopods precociously
Page 230
developed. These Zoaeal stages are
of course pelagic, but the Metazoaea
next passes into the Megalopa stage
(Fig. 125), in which the little crab
forsakes its pelagic life and assumes
the ground-habits of the adult; the
Megalopa, which corresponds
exactly to the Glaucothoe of the
Pagurids, resembles a small Galathea
or Porcellana, the abdomen being
still large and unflexed and furnished
with normal pleopods. From this
stage the adult structure is soon
achieved, though, owing to the
continued growth of the Crustacea
even after maturity is reached, there
is often a slight progressive change in
structure, especially in the male, at
each successive moult of the
individual. The Megalopa of
Corystes cassivelaunus is peculiar in
the immense production of the
second antennae, which act as a
respiratory tube (Fig. 125).
The Brachyura must be considered
under the following subdivisions:— Fig. 125.—Later stage (Megalopa) in the
development of Corystes cassivelaunus, × 10. A,
Antenna; Ab, 3rd abdominal segment; C, great
chela; T.8, last thoracic appendage. (After
Gurney.)
Tribe 1. Dromiacea.
All authorities are agreed that these[149] are the most primitive of the
Brachyura. In them the abdomen is much less reduced in both sexes than in
other Brachyura; there is a common orbitoantennary fossa, into which eyes
and antennae are withdrawn, instead of a separate one on each side for each
organ; the carapace is often much elongated as in the Macrura and
of course pelagic, but the Metazoaea
next passes into the Megalopa stage
(Fig. 125), in which the little crab
forsakes its pelagic life and assumes
the ground-habits of the adult; the
Megalopa, which corresponds
exactly to the Glaucothoe of the
Pagurids, resembles a small Galathea
or Porcellana, the abdomen being
still large and unflexed and furnished
with normal pleopods. From this
stage the adult structure is soon
achieved, though, owing to the
continued growth of the Crustacea
even after maturity is reached, there
is often a slight progressive change in
structure, especially in the male, at
each successive moult of the
individual. The Megalopa of
Corystes cassivelaunus is peculiar in
the immense production of the
second antennae, which act as a
respiratory tube (Fig. 125).
The Brachyura must be considered
under the following subdivisions:— Fig. 125.—Later stage (Megalopa) in the
development of Corystes cassivelaunus, × 10. A,
Antenna; Ab, 3rd abdominal segment; C, great
chela; T.8, last thoracic appendage. (After
Gurney.)
Tribe 1. Dromiacea.
All authorities are agreed that these[149] are the most primitive of the
Brachyura. In them the abdomen is much less reduced in both sexes than in
other Brachyura; there is a common orbitoantennary fossa, into which eyes
and antennae are withdrawn, instead of a separate one on each side for each
organ; the carapace is often much elongated as in the Macrura and
Page 231
Anomura, and a number of other anatomical characters might be mentioned
which characterise the Dromiacea as intermediate between the true
Brachyura and the lower forms. There are, however, two views as to the
relationship of the Dromiacea; Claus held that they proceeded from a
Galatheid stock, and hence that the development of the Brachyura ran
through an Anomurous strain; but Huxley, and latterly Bouvier,[150] adopt
the view that the Dromiacea are descended, not from the Galatheidae, but
direct from the Macrura, and especially from the Nephropsidea. Special
resemblances are found between the Jurassic Nephropsidae and certain
present day Dromiacea, e.g. Homolodromia paradoxa, the detailed form of
the carapace in the two cases being very similar. It is, however, a little
strange that in the Dromiacea we meet with the same reduction and dorsal
position of the last, or last two pairs of thoracic limbs which we saw to be
such a characteristic feature of the Anomura, especially of the Galatheidae.
In the Dromiacea these limbs may be chelate, and they are used for
attaching shells and other bodies temporarily to the back. Must we suppose
that this resemblance to the Anomura is due to convergence, or that the
Nephropsidae, which gave rise to perhaps both Galatheidae and Dromiacea,
had this character, and that it has been subsequently lost in the Macruran
stock? We have already mentioned that the Metazoaea of Dromia has not
only a well-developed swimming third maxillipede, but also a biramous
first pereiopod, a character which speaks strongly for Macruran affinities.
Fam. 1. Dromiidae.—The eyes
and antennules are retractile into
orbits. The last two pairs of thoracic
limbs are small, and held dorsally.
The sixth pair of pleopods are
rudimentary or absent.
Homolodromia from West Indies,
deep-sea. Dromia, widely dispersed.
D. vulgaris (Fig. 126) occurs on the
Fig. 126.—Dromia vulgaris, × 1. (After Milne
Edwards and Bouvier.) English coasts.
Fam. 2. Dynomenidae.—Similar
to the preceding family, but only the last pair of thoracic limbs is small, and
held dorsally. The sixth pair of pleopods are reduced, but always present.
Dynomene in the Indo-Pacific.
which characterise the Dromiacea as intermediate between the true
Brachyura and the lower forms. There are, however, two views as to the
relationship of the Dromiacea; Claus held that they proceeded from a
Galatheid stock, and hence that the development of the Brachyura ran
through an Anomurous strain; but Huxley, and latterly Bouvier,[150] adopt
the view that the Dromiacea are descended, not from the Galatheidae, but
direct from the Macrura, and especially from the Nephropsidea. Special
resemblances are found between the Jurassic Nephropsidae and certain
present day Dromiacea, e.g. Homolodromia paradoxa, the detailed form of
the carapace in the two cases being very similar. It is, however, a little
strange that in the Dromiacea we meet with the same reduction and dorsal
position of the last, or last two pairs of thoracic limbs which we saw to be
such a characteristic feature of the Anomura, especially of the Galatheidae.
In the Dromiacea these limbs may be chelate, and they are used for
attaching shells and other bodies temporarily to the back. Must we suppose
that this resemblance to the Anomura is due to convergence, or that the
Nephropsidae, which gave rise to perhaps both Galatheidae and Dromiacea,
had this character, and that it has been subsequently lost in the Macruran
stock? We have already mentioned that the Metazoaea of Dromia has not
only a well-developed swimming third maxillipede, but also a biramous
first pereiopod, a character which speaks strongly for Macruran affinities.
Fam. 1. Dromiidae.—The eyes
and antennules are retractile into
orbits. The last two pairs of thoracic
limbs are small, and held dorsally.
The sixth pair of pleopods are
rudimentary or absent.
Homolodromia from West Indies,
deep-sea. Dromia, widely dispersed.
D. vulgaris (Fig. 126) occurs on the
Fig. 126.—Dromia vulgaris, × 1. (After Milne
Edwards and Bouvier.) English coasts.
Fam. 2. Dynomenidae.—Similar
to the preceding family, but only the last pair of thoracic limbs is small, and
held dorsally. The sixth pair of pleopods are reduced, but always present.
Dynomene in the Indo-Pacific.
Page 232
Fam. 3. Homolidae.—The eyes and antennules are not retractile into
orbits. Only the last pair of thoracic limbs are reduced, the sixth pair of
pleopods altogether absent. Homola and Latreillia, widely distributed,
occur in the Mediterranean. Latreillopsis from the Pacific. L. petterdi,[151] a
magnificent species, with the carapace nearly a foot long, and with very
long legs like a Spider-crab, has been dredged from 800 fathoms east of
Sydney, New South Wales.
Tribe 2. Oxystomata.
This group comprises Crabs whose carapace is more or less circular,
while the mouth, instead of being square as in the remaining Brachyura, is
triangular with the apex pointing forward, and the third maxillipedes are not
expanded into the flattened, lid-like structures found in other Crabs. There
is the same tendency in some of the genera for the posterior thoracic limbs
to be reduced and carried dorsally, as in the Galatheidae and Dromiacea.
The well-known Dorippe from the Mediterranean has this feature, and
frequently carries an empty shell upon its back, and Cymonomus[152]
presents the same peculiarity.
orbits. Only the last pair of thoracic limbs are reduced, the sixth pair of
pleopods altogether absent. Homola and Latreillia, widely distributed,
occur in the Mediterranean. Latreillopsis from the Pacific. L. petterdi,[151] a
magnificent species, with the carapace nearly a foot long, and with very
long legs like a Spider-crab, has been dredged from 800 fathoms east of
Sydney, New South Wales.
Tribe 2. Oxystomata.
This group comprises Crabs whose carapace is more or less circular,
while the mouth, instead of being square as in the remaining Brachyura, is
triangular with the apex pointing forward, and the third maxillipedes are not
expanded into the flattened, lid-like structures found in other Crabs. There
is the same tendency in some of the genera for the posterior thoracic limbs
to be reduced and carried dorsally, as in the Galatheidae and Dromiacea.
The well-known Dorippe from the Mediterranean has this feature, and
frequently carries an empty shell upon its back, and Cymonomus[152]
presents the same peculiarity.
Page 233
Fig. 127.—Cymonomus granulatus, × 1. A.1, A.2, 1st and 2nd antennae; E, eye-
stalk; S, extra-orbital spine of carapace. (After Lankester.)
Cymonomus granulatus (Fig. 127) is an abyssal form that has been
dredged from the Mediterranean and North Atlantic, in which the eye-stalks
are curiously tuberculated, and the ommatidia of the eye are entirely
unpigmented and degenerate, though a few corneal facets are still
recognisable. This species is replaced by C. quadratus in the Caribbean Sea
and by C. normani on the East African coast, in which the alteration of the
eye-stalks into thorny, beak-like projections becomes progressively marked,
and all traces even of the corneal facets disappear. This remarkable genus
was mentioned in the excursus on Crustacean eyes on p. 149.
The Oxystomata, like the Cyclometopa, to be considered later, live in
sandy and gravelly regions, and burrow to a greater or less extent, and we
find in both groups admirable adaptations for securing a pure stream of
water, uncontaminated by particles of sand, for flushing the gills. Perhaps
the most remarkable of these adaptations is afforded by Calappa.[153] This
animal has the chelipedes wonderfully modified in structure, and when it is
reposing in the sand it holds them apposed to the front of the carapace, as
shown in Fig. 128, so that the spines upon their edges, together with the
stalk; S, extra-orbital spine of carapace. (After Lankester.)
Cymonomus granulatus (Fig. 127) is an abyssal form that has been
dredged from the Mediterranean and North Atlantic, in which the eye-stalks
are curiously tuberculated, and the ommatidia of the eye are entirely
unpigmented and degenerate, though a few corneal facets are still
recognisable. This species is replaced by C. quadratus in the Caribbean Sea
and by C. normani on the East African coast, in which the alteration of the
eye-stalks into thorny, beak-like projections becomes progressively marked,
and all traces even of the corneal facets disappear. This remarkable genus
was mentioned in the excursus on Crustacean eyes on p. 149.
The Oxystomata, like the Cyclometopa, to be considered later, live in
sandy and gravelly regions, and burrow to a greater or less extent, and we
find in both groups admirable adaptations for securing a pure stream of
water, uncontaminated by particles of sand, for flushing the gills. Perhaps
the most remarkable of these adaptations is afforded by Calappa.[153] This
animal has the chelipedes wonderfully modified in structure, and when it is
reposing in the sand it holds them apposed to the front of the carapace, as
shown in Fig. 128, so that the spines upon their edges, together with the
Page 234
hairy margin of the carapace, form a
most efficient filter for straining off
sand and grit from the stream of
water which is sucked down between
the closely-fitting chelipedes and
carapace, to enter the branchial
chambers at their sides. The exhaled
current of water passes out anteriorly
Fig. 128.—Calappa granulata, from in front, × through a tube formed by a
½. C, Hand of chelipede; T, walking legs. (After prolongation of the endopodites of
Garstang.)
the first maxillipedes. The exhalant
aperture is shown in Fig. 128 by the
two black cavities below the snout in the middle line.
A similar method is pursued by the related Matuta banksii[153] (Fig. 129),
a swimming and fossorial Crab found in the Indo-Pacific. In this Crab the
chelipedes also fit against the carapace to form a strainer, and their function
is assisted by the enlargement of the posterior spine, which acts as a kind of
elbow-rest to keep the chelipedes properly in position. The inhalant
openings are situated just in front of the chelipedes. It is a most remarkable
fact that among the Cyclometopa, Lupa hastata (Fig. 131) has an exactly
similar arrangement. Apparently we have here another instance of
convergence, similar to that of Corystes and Albunea, but the case is
complicated by the fact that some of the Oxystomata, and among them
Matuta, show a certain amount of relationship to the Cyclometopous
Portunids, so that it is just conceivable that the resemblances in the
respiratory arrangement are due to a common descent and not to
convergence.
most efficient filter for straining off
sand and grit from the stream of
water which is sucked down between
the closely-fitting chelipedes and
carapace, to enter the branchial
chambers at their sides. The exhaled
current of water passes out anteriorly
Fig. 128.—Calappa granulata, from in front, × through a tube formed by a
½. C, Hand of chelipede; T, walking legs. (After prolongation of the endopodites of
Garstang.)
the first maxillipedes. The exhalant
aperture is shown in Fig. 128 by the
two black cavities below the snout in the middle line.
A similar method is pursued by the related Matuta banksii[153] (Fig. 129),
a swimming and fossorial Crab found in the Indo-Pacific. In this Crab the
chelipedes also fit against the carapace to form a strainer, and their function
is assisted by the enlargement of the posterior spine, which acts as a kind of
elbow-rest to keep the chelipedes properly in position. The inhalant
openings are situated just in front of the chelipedes. It is a most remarkable
fact that among the Cyclometopa, Lupa hastata (Fig. 131) has an exactly
similar arrangement. Apparently we have here another instance of
convergence, similar to that of Corystes and Albunea, but the case is
complicated by the fact that some of the Oxystomata, and among them
Matuta, show a certain amount of relationship to the Cyclometopous
Portunids, so that it is just conceivable that the resemblances in the
respiratory arrangement are due to a common descent and not to
convergence.
Page 235
Fig. 129.—Dorsal view of Matuta banksii, × 1. (From an original drawing
prepared for Professor Weldon.)
In the Leucosiidae, of which the Mediterranean Ilia nucleus (Fig. 130) is
an example, the inhalant aperture is situated between the orbits, and leads
into gutters excavated in the “pterygostomial plates” flanking the mouth,
which are furnished with filtering hairs and are converted into closed canals
by expansions of the exopodites of the third maxillipedes. Thus these Crabs
possess a filtering apparatus independent of the chelipedes and of the
margin of the carapace.
Fam. 1. Calappidae.—Cephalothorax rounded and crab-like. The
abdomen is hidden under the thorax, the antennae are small, and the legs
normal in position. The afferent openings to the gill-chambers lie in front of
the chelipedes. Male openings on coxae of last pair of legs. Calappa (Fig.
128) circumtropical, and extending into the warmer temperate seas. Matuta
(Fig. 129) from the Indo-Pacific.
Fam. 2. Leucosiidae.—Similar to the above, but the afferent openings to
the gill-chambers lie at the bases of the third maxillipedes. Male openings
on the sternum. This family contains a great number of forms, with
prepared for Professor Weldon.)
In the Leucosiidae, of which the Mediterranean Ilia nucleus (Fig. 130) is
an example, the inhalant aperture is situated between the orbits, and leads
into gutters excavated in the “pterygostomial plates” flanking the mouth,
which are furnished with filtering hairs and are converted into closed canals
by expansions of the exopodites of the third maxillipedes. Thus these Crabs
possess a filtering apparatus independent of the chelipedes and of the
margin of the carapace.
Fam. 1. Calappidae.—Cephalothorax rounded and crab-like. The
abdomen is hidden under the thorax, the antennae are small, and the legs
normal in position. The afferent openings to the gill-chambers lie in front of
the chelipedes. Male openings on coxae of last pair of legs. Calappa (Fig.
128) circumtropical, and extending into the warmer temperate seas. Matuta
(Fig. 129) from the Indo-Pacific.
Fam. 2. Leucosiidae.—Similar to the above, but the afferent openings to
the gill-chambers lie at the bases of the third maxillipedes. Male openings
on the sternum. This family contains a great number of forms, with
Page 236
headquarters in the tropical littoral,
but extending into the temperate seas.
Ilia in the European seas. I. nucleus
(Fig. 130) common in the
Mediterranean. Ebalia in the
Atlantic, North Sea, and Indo-
Pacific. Leucosia in Indo-Pacific.
Fam. 3. Dorippidae.—
Cephalothorax short and square. The
abdomen is not hidden under the
thorax; the antennae are large, and
the last two pairs of legs are held
dorsally, and have terminal hooked
claws. Dorippe, littoral in
Mediterranean and Indo-Pacific.
Fig. 130.—Dorsal view of Ilia nucleus, × 1.
(From an original drawing prepared for Cymonomus (Fig. 127) from deep-
Professor Weldon.) sea of Atlantic and Mediterranean.
Fam. 4. Raninidae.—Similar to
Dorippidae, but the cephalothorax is elongated, and the legs usually have
the last two joints very broad. Several genera, chiefly in the deeper littoral
zone. Ranina dentata in the Indo-Pacific.
Tribe 3. Cyclometopa.
In these Crabs the carapace is circular rather than square; its frontal and
lateral margins are produced into spines and there is no pointed rostrum.
The mouth is square, and the third maxillipedes are greatly flattened and
form a lid-like expansion over the other oral appendages. This group
includes the common Shore-crab of our coasts (Carcinus maenas), the
swimming Crabs with expanded pereiopods (Portunus, Lupa, etc.), the
Edible Crab (Cancer pagurus), and many others.
Corystes cassivelaunus is a Crab of doubtful affinities. It is sometimes
placed among the Oxyrhyncha, but, as Gurney[154] has pointed out, the
Megalopa shows Portunid characters, and the resemblance to the
Oxystomata in the front of the carapace and in the mouth may be secondary.
The respiratory arrangement of this Crab has already been mentioned in
but extending into the temperate seas.
Ilia in the European seas. I. nucleus
(Fig. 130) common in the
Mediterranean. Ebalia in the
Atlantic, North Sea, and Indo-
Pacific. Leucosia in Indo-Pacific.
Fam. 3. Dorippidae.—
Cephalothorax short and square. The
abdomen is not hidden under the
thorax; the antennae are large, and
the last two pairs of legs are held
dorsally, and have terminal hooked
claws. Dorippe, littoral in
Mediterranean and Indo-Pacific.
Fig. 130.—Dorsal view of Ilia nucleus, × 1.
(From an original drawing prepared for Cymonomus (Fig. 127) from deep-
Professor Weldon.) sea of Atlantic and Mediterranean.
Fam. 4. Raninidae.—Similar to
Dorippidae, but the cephalothorax is elongated, and the legs usually have
the last two joints very broad. Several genera, chiefly in the deeper littoral
zone. Ranina dentata in the Indo-Pacific.
Tribe 3. Cyclometopa.
In these Crabs the carapace is circular rather than square; its frontal and
lateral margins are produced into spines and there is no pointed rostrum.
The mouth is square, and the third maxillipedes are greatly flattened and
form a lid-like expansion over the other oral appendages. This group
includes the common Shore-crab of our coasts (Carcinus maenas), the
swimming Crabs with expanded pereiopods (Portunus, Lupa, etc.), the
Edible Crab (Cancer pagurus), and many others.
Corystes cassivelaunus is a Crab of doubtful affinities. It is sometimes
placed among the Oxyrhyncha, but, as Gurney[154] has pointed out, the
Megalopa shows Portunid characters, and the resemblance to the
Oxystomata in the front of the carapace and in the mouth may be secondary.
The respiratory arrangement of this Crab has already been mentioned in
Page 237
comparing its structure with that of the Mole-crab Albunea. The form of the
antennal tube can be gathered from the figure of the Megalopa stage (Fig.
125, p. 183). It should be noted that when the Crab is buried in the sand
with only the tip of the antennal tube projecting, the water is sucked down
and enters the branchial cavities anteriorly, the antennal tube being
continued by a tube formed from the third maxillipedes and the forehead;
the water is exhaled at the sides of the branchial cavities beneath the
branchiostegites. Thus in Corystes the normal direction of the current is
reversed, but when the Crab is not buried, and is moving over the surface, it
breathes in the usual manner, taking in the water at the sides of the
branchiostegites and exhaling it anteriorly by the tube. The related
Atelecyclus, found like Corystes very commonly at Plymouth, uses two
methods of breathing: when it is in the surface-layers of sand it makes use
of its antennal tube, which is, however, much shorter than in Corystes; but
when it burrows deeper, where the antennal tube is no use, it folds its
chelipedes and also its other legs, which are densely covered with bristles,
so as to form a reservoir of pure water underneath it free from sand, which
it passes through the gill-chambers in the usual manner (see Garstang, loc.
cit. p. 186).
The respiratory adaptations in Lupa hastata and their convergence
towards those of the Oxystomatous Matuta have been already touched upon
(pp. 186, 187).
In this connexion must be mentioned the interesting experiments of W. F.
R. Weldon[155] upon the respiratory functions of Carcinus maenas at
Plymouth, since these were the first noteworthy observations directed
towards the exact measurement of the action of natural selection upon any
animal, a field of observation in which Weldon will always be looked upon
as a pioneer. An extended series of measurements by Weldon and
Thompson on male specimens of Carcinus maenas of various sizes between
the years 1893 and 1898 showed a steady decrease in the ratio of carapace
breadth to length; the Crabs appeared to be becoming steadily narrower
across the frontal margin, and the same thing, though not to the same extent,
was happening in female Crabs. Weldon supposed that this change might be
correlated with the silting up of Plymouth Sound and the consequent
fouling of the water. To test this hypothesis he kept a very large number of
male Crabs in water to which fine porcelain clay was added and kept in
continual motion. In the course of the experiments the survivors and the
antennal tube can be gathered from the figure of the Megalopa stage (Fig.
125, p. 183). It should be noted that when the Crab is buried in the sand
with only the tip of the antennal tube projecting, the water is sucked down
and enters the branchial cavities anteriorly, the antennal tube being
continued by a tube formed from the third maxillipedes and the forehead;
the water is exhaled at the sides of the branchial cavities beneath the
branchiostegites. Thus in Corystes the normal direction of the current is
reversed, but when the Crab is not buried, and is moving over the surface, it
breathes in the usual manner, taking in the water at the sides of the
branchiostegites and exhaling it anteriorly by the tube. The related
Atelecyclus, found like Corystes very commonly at Plymouth, uses two
methods of breathing: when it is in the surface-layers of sand it makes use
of its antennal tube, which is, however, much shorter than in Corystes; but
when it burrows deeper, where the antennal tube is no use, it folds its
chelipedes and also its other legs, which are densely covered with bristles,
so as to form a reservoir of pure water underneath it free from sand, which
it passes through the gill-chambers in the usual manner (see Garstang, loc.
cit. p. 186).
The respiratory adaptations in Lupa hastata and their convergence
towards those of the Oxystomatous Matuta have been already touched upon
(pp. 186, 187).
In this connexion must be mentioned the interesting experiments of W. F.
R. Weldon[155] upon the respiratory functions of Carcinus maenas at
Plymouth, since these were the first noteworthy observations directed
towards the exact measurement of the action of natural selection upon any
animal, a field of observation in which Weldon will always be looked upon
as a pioneer. An extended series of measurements by Weldon and
Thompson on male specimens of Carcinus maenas of various sizes between
the years 1893 and 1898 showed a steady decrease in the ratio of carapace
breadth to length; the Crabs appeared to be becoming steadily narrower
across the frontal margin, and the same thing, though not to the same extent,
was happening in female Crabs. Weldon supposed that this change might be
correlated with the silting up of Plymouth Sound and the consequent
fouling of the water. To test this hypothesis he kept a very large number of
male Crabs in water to which fine porcelain clay was added and kept in
continual motion. In the course of the experiments the survivors and the
Page 238
dead were measured, and it was found that the mean carapace breadth of the
survivors was less than that of those that succumbed. The experiment was
repeated with the fine sand that is deposited and left at low water upon the
stones on Plymouth beach, and the same result was observed. It was also
noticed that the individuals which died had their gills clogged with the sand,
while those that survived had not. As a further confirmation, a great many
young male Crabs were isolated and kept in pure filtered water, and they
were measured before and after moulting; these measurements, when
compared with measurements of the frontal breadth in Crabs of the same
size taken at random upon the beach, were found to show a greater breadth
than the wild Crabs, thus indicating that a selection of narrow Crabs was
taking place in Nature which did not take place when the Crabs were
protected from the effects of fine sand in the water.
The whole chain of evidence goes to show that the carapace breadth in
Carcinus maenas in Plymouth Sound is being influenced by the rapid
change of conditions occurring in the locality. Various objections have been
urged against this conclusion, but, though they merit further investigation,
they do not appear very weighty.
The fresh-water Crab, Thelphusa fluviatilis, common in the South of
Europe and on the North coast of Africa, belongs to the Cyclometopa, and
is interesting from its direct mode of development without metamorphosis.
Fam. 1. Corystidae.—The orbits are formed, but, unlike all the other
families of the Cyclometopa, are incomplete. The body is elongate and oval,
and the rostrum and front edge of the mouth rather as in the Oxyrhyncha, in
which Tribe they are sometimes included. Corystes, with a few species in
European seas. C. cassivelaunus at Plymouth.
Fam. 2. Atelecyclidae.—Perhaps related to the foregoing. The carapace
is sub-circular, and the rostrum short and toothed. Atelecyclus, European
seas.
Fam. 3. Cancridae.—The carapace is broadly oval or hexagonal, and the
flagella of the second antennae are short and not hairy as in the foregoing.
The first antennae fold lengthwise. Carcinus maenas on English and North
European coasts. This crab has become naturalised in some unexplained
manner in Port Phillip, Melbourne. Cancer in North Atlantic, North Pacific,
and along the west coast of America into the Antarctic regions. C. pagurus
is the British Edible Crab.
survivors was less than that of those that succumbed. The experiment was
repeated with the fine sand that is deposited and left at low water upon the
stones on Plymouth beach, and the same result was observed. It was also
noticed that the individuals which died had their gills clogged with the sand,
while those that survived had not. As a further confirmation, a great many
young male Crabs were isolated and kept in pure filtered water, and they
were measured before and after moulting; these measurements, when
compared with measurements of the frontal breadth in Crabs of the same
size taken at random upon the beach, were found to show a greater breadth
than the wild Crabs, thus indicating that a selection of narrow Crabs was
taking place in Nature which did not take place when the Crabs were
protected from the effects of fine sand in the water.
The whole chain of evidence goes to show that the carapace breadth in
Carcinus maenas in Plymouth Sound is being influenced by the rapid
change of conditions occurring in the locality. Various objections have been
urged against this conclusion, but, though they merit further investigation,
they do not appear very weighty.
The fresh-water Crab, Thelphusa fluviatilis, common in the South of
Europe and on the North coast of Africa, belongs to the Cyclometopa, and
is interesting from its direct mode of development without metamorphosis.
Fam. 1. Corystidae.—The orbits are formed, but, unlike all the other
families of the Cyclometopa, are incomplete. The body is elongate and oval,
and the rostrum and front edge of the mouth rather as in the Oxyrhyncha, in
which Tribe they are sometimes included. Corystes, with a few species in
European seas. C. cassivelaunus at Plymouth.
Fam. 2. Atelecyclidae.—Perhaps related to the foregoing. The carapace
is sub-circular, and the rostrum short and toothed. Atelecyclus, European
seas.
Fam. 3. Cancridae.—The carapace is broadly oval or hexagonal, and the
flagella of the second antennae are short and not hairy as in the foregoing.
The first antennae fold lengthwise. Carcinus maenas on English and North
European coasts. This crab has become naturalised in some unexplained
manner in Port Phillip, Melbourne. Cancer in North Atlantic, North Pacific,
and along the west coast of America into the Antarctic regions. C. pagurus
is the British Edible Crab.
Page 239
Fam. 4. Portunidae.—The legs
are flattened and adapted for
swimming. The first antennae fold
back transversely. Portunus, Atlantic
and Mediterranean. Neptunus, Indo-
Pacific. Callinectes, C. sapidus, the
edible blue Crab of the Atlantic
coasts of America. Lupa (Fig. 131).
Fam. 5. Xanthidae.—The first
antennae fold transversely, but the
legs are not adapted for swimming;
the body is usually transversely oval. F(From
ig. 131.—Dorsal view of Lupa hastata, × 1.
an original drawing prepared for
This family is especially Professor Weldon.)
characteristic of the tropical littoral,
where it is very widely represented. Xantho, Actaea, Chlorodius, Pilumnus,
Eriphia, with E. spinifrons, common in the Mediterranean.
Fam. 6. Thelphusidae (Potamonidae).—Fresh-water crabs, with the
branchial region very much swollen. Thelphusa (or Potamon) has nearly a
hundred species distributed from North Australia, through Asia, Japan, the
Mediterranean region, and throughout Africa. Potamocarcinus in tropical
America.
Tribe 4. Oxyrhyncha.
This section includes the Spider-crabs and related genera, in which the
carapace is triangular, with the apex in front formed by a sharply-pointed
rostrum. There are two chief series, the one comprising the Spider-crabs,
with much elongated walking legs, e.g. the huge Maia squinado of
European seas, the yet more enormous Macrocheira kämpferi from Japan,
supposed to be the largest Crustacean in existence, and sometimes spanning
from outstretched chela to chela as much as eleven feet, and the smaller
forms, such as Inachus, Hyas, and Stenorhynchus, which are so common in
moderate depths off the English coasts. The other series is represented by
genera like Lambrus (Fig. 133), in which the legs are not much elongated,
but the chelipedes are enormous.
are flattened and adapted for
swimming. The first antennae fold
back transversely. Portunus, Atlantic
and Mediterranean. Neptunus, Indo-
Pacific. Callinectes, C. sapidus, the
edible blue Crab of the Atlantic
coasts of America. Lupa (Fig. 131).
Fam. 5. Xanthidae.—The first
antennae fold transversely, but the
legs are not adapted for swimming;
the body is usually transversely oval. F(From
ig. 131.—Dorsal view of Lupa hastata, × 1.
an original drawing prepared for
This family is especially Professor Weldon.)
characteristic of the tropical littoral,
where it is very widely represented. Xantho, Actaea, Chlorodius, Pilumnus,
Eriphia, with E. spinifrons, common in the Mediterranean.
Fam. 6. Thelphusidae (Potamonidae).—Fresh-water crabs, with the
branchial region very much swollen. Thelphusa (or Potamon) has nearly a
hundred species distributed from North Australia, through Asia, Japan, the
Mediterranean region, and throughout Africa. Potamocarcinus in tropical
America.
Tribe 4. Oxyrhyncha.
This section includes the Spider-crabs and related genera, in which the
carapace is triangular, with the apex in front formed by a sharply-pointed
rostrum. There are two chief series, the one comprising the Spider-crabs,
with much elongated walking legs, e.g. the huge Maia squinado of
European seas, the yet more enormous Macrocheira kämpferi from Japan,
supposed to be the largest Crustacean in existence, and sometimes spanning
from outstretched chela to chela as much as eleven feet, and the smaller
forms, such as Inachus, Hyas, and Stenorhynchus, which are so common in
moderate depths off the English coasts. The other series is represented by
genera like Lambrus (Fig. 133), in which the legs are not much elongated,
but the chelipedes are enormous.
Page 240
The Spider-crabs do not burrow, and their respiratory mechanism is
simple; but since they are forms that clamber about among weeds, etc.,
upon the sea-bottom, they often show remarkable protective resemblances
to their surroundings, which are not found in the burrowing Cyclometopa.
Alcock[156] gives a good account and figure of Parthenope investigatoris,
one of the short-legged Oxyrhyncha, the whole of whose dorsal surface is
wonderfully sculptured to resemble a piece of the old corroded coral among
which it lives.
But besides this, the long-legged forms, such as Inachus, Hyas, etc., have
the habit of planting out Zoophytes, Sponges, and Algae upon their spiny
carapaces, so that they literally become part and parcel of the organic
surroundings among which they live. It may, perhaps, be wondered what
are the enemies which these armoured Crustacea fear. Predaceous fish, such
as the Cod, devour large quantities of Crabs, which are often found in their
stomachs; and Octopuses of all sorts live specially upon Crabs, which they
first of all paralyse by injecting them with the secretion of poison-glands
situated in their mouth. The poison has been recently found by Dr. Martin
Henze at Naples to be an alkaloid, minute quantities of which, when
injected into a Crab, completely paralyse it. When the Crab is rendered
helpless the Octopus cuts out a hole in the carapace with its beak, and sucks
all the internal organs, and then leaves the empty shell.
Many of the Oxyrhyncha are found in the abysses; among them are
Encephaloides armstrongi (Fig. 132), dredged by Alcock from below the
100–fathom line in the Indian Ocean, which has the gill-chambers (G)
greatly swollen and enlarged to make up for the scarcity of oxygen in these
deep regions.
Fam. 1. Maiidae.—The chelipedes are not much larger than the other
legs, but are very mobile. Orbits incomplete. A very large family, including
all the true Spider-crabs, very common in the Atlantic and Mediterranean
littoral. Inachus, Pisa, Hyas, Stenorhynchus, Maia, Encephaloides (Fig.
132).
Fam. 2. Parthenopidae.—The chelipedes are much larger than the other
legs. Orbits complete. Lambrus (Fig. 133), Parthenope.
Fam. 3. Hymenosomatidae. The carapace is thin and flat; the chelipedes
are neither very long nor especially mobile. There are no orbits, and the
simple; but since they are forms that clamber about among weeds, etc.,
upon the sea-bottom, they often show remarkable protective resemblances
to their surroundings, which are not found in the burrowing Cyclometopa.
Alcock[156] gives a good account and figure of Parthenope investigatoris,
one of the short-legged Oxyrhyncha, the whole of whose dorsal surface is
wonderfully sculptured to resemble a piece of the old corroded coral among
which it lives.
But besides this, the long-legged forms, such as Inachus, Hyas, etc., have
the habit of planting out Zoophytes, Sponges, and Algae upon their spiny
carapaces, so that they literally become part and parcel of the organic
surroundings among which they live. It may, perhaps, be wondered what
are the enemies which these armoured Crustacea fear. Predaceous fish, such
as the Cod, devour large quantities of Crabs, which are often found in their
stomachs; and Octopuses of all sorts live specially upon Crabs, which they
first of all paralyse by injecting them with the secretion of poison-glands
situated in their mouth. The poison has been recently found by Dr. Martin
Henze at Naples to be an alkaloid, minute quantities of which, when
injected into a Crab, completely paralyse it. When the Crab is rendered
helpless the Octopus cuts out a hole in the carapace with its beak, and sucks
all the internal organs, and then leaves the empty shell.
Many of the Oxyrhyncha are found in the abysses; among them are
Encephaloides armstrongi (Fig. 132), dredged by Alcock from below the
100–fathom line in the Indian Ocean, which has the gill-chambers (G)
greatly swollen and enlarged to make up for the scarcity of oxygen in these
deep regions.
Fam. 1. Maiidae.—The chelipedes are not much larger than the other
legs, but are very mobile. Orbits incomplete. A very large family, including
all the true Spider-crabs, very common in the Atlantic and Mediterranean
littoral. Inachus, Pisa, Hyas, Stenorhynchus, Maia, Encephaloides (Fig.
132).
Fam. 2. Parthenopidae.—The chelipedes are much larger than the other
legs. Orbits complete. Lambrus (Fig. 133), Parthenope.
Fam. 3. Hymenosomatidae. The carapace is thin and flat; the chelipedes
are neither very long nor especially mobile. There are no orbits, and the
Page 241
male openings are on the sternum.
Characteristic of the Antarctic seas.
Hymenosoma, Trigonoplax.
Fig. 132.—Encephaloides armstrongi, × 1. The
long walking legs are omitted. C, Great chela;
G, one of the greatly swollen gill-chambers.
(After Alcock.)
Fig. 133.—Lambrus miersi, × 1. (After Milne
Edwards and Bouvier.)
Tribe 5. Catometopa.
These Crabs resemble the Cyclometopa in general appearance, but the
carapace is very square in outline, and its margins are never so well
provided with spines as in the Cyclometopa. The position of the male
Characteristic of the Antarctic seas.
Hymenosoma, Trigonoplax.
Fig. 132.—Encephaloides armstrongi, × 1. The
long walking legs are omitted. C, Great chela;
G, one of the greatly swollen gill-chambers.
(After Alcock.)
Fig. 133.—Lambrus miersi, × 1. (After Milne
Edwards and Bouvier.)
Tribe 5. Catometopa.
These Crabs resemble the Cyclometopa in general appearance, but the
carapace is very square in outline, and its margins are never so well
provided with spines as in the Cyclometopa. The position of the male
Page 242
genital openings is peculiar, since they lie upon the sternum, and are
connected with the copulatory appendages upon the abdomen by means of
furrows excavated in the sternum. The Catometopa are either littoral or
shallow water forms, or else they live entirely on land. The Grapsidae are
marine Crabs, Pachygrapsus marmoratus (Fig. 134) at Naples being
exceedingly common on rocks at high-water mark, over which it scuttles at
a great rate; in the Mediterranean it takes the place of our common
Garcinus maenas, which is not found there.
Among the land genera are
Ocypoda, Gelasimus, and Gecarcinus
of tropical lagoons and coastal
swamps. Ocypoda often occurs in
vast crowds in these regions, and
digs burrows in the sand.
Gelasimus (Fig. 135) is
remarkable for the enormous size of
one of the chelipedes, generally the
right, in the male, which may
Fig. 134.—Dorsal view of Pachygrapsus actually exceed in size the rest of the
marmoratus, × ⅓. (From an original drawing
prepared for Professor Weldon.) body. It is not known what purpose
this organ serves in the various
species. In Gelasimus it is supposed
that the male stops up the mouth of the burrow with it when he and the
female are safely inside. It is also used as a weapon in sexual combats with
other males; but Alcock, from observations made in the Indian Ocean,
believes that the males use it for exciting the admiration of the females in
courtship, as the huge chela is bright red in colour, and the males brandish it
about before the females as if displaying its florid beauty.
The species of Ocypoda are exclusively terrestrial, and cannot live for a
day in water. The gills have entirely disappeared, and the branchial
chambers are converted into air-breathing lungs with highly vascular walls,
the entrances into which are situated as round holes between the bases of
the third and fourth pairs of walking legs. As their name implies, they can
run with astonishing rapidity, and they seem to be always on the alert,
directing their eyes, which are placed on exceedingly long stalks, in all
directions.
connected with the copulatory appendages upon the abdomen by means of
furrows excavated in the sternum. The Catometopa are either littoral or
shallow water forms, or else they live entirely on land. The Grapsidae are
marine Crabs, Pachygrapsus marmoratus (Fig. 134) at Naples being
exceedingly common on rocks at high-water mark, over which it scuttles at
a great rate; in the Mediterranean it takes the place of our common
Garcinus maenas, which is not found there.
Among the land genera are
Ocypoda, Gelasimus, and Gecarcinus
of tropical lagoons and coastal
swamps. Ocypoda often occurs in
vast crowds in these regions, and
digs burrows in the sand.
Gelasimus (Fig. 135) is
remarkable for the enormous size of
one of the chelipedes, generally the
right, in the male, which may
Fig. 134.—Dorsal view of Pachygrapsus actually exceed in size the rest of the
marmoratus, × ⅓. (From an original drawing
prepared for Professor Weldon.) body. It is not known what purpose
this organ serves in the various
species. In Gelasimus it is supposed
that the male stops up the mouth of the burrow with it when he and the
female are safely inside. It is also used as a weapon in sexual combats with
other males; but Alcock, from observations made in the Indian Ocean,
believes that the males use it for exciting the admiration of the females in
courtship, as the huge chela is bright red in colour, and the males brandish it
about before the females as if displaying its florid beauty.
The species of Ocypoda are exclusively terrestrial, and cannot live for a
day in water. The gills have entirely disappeared, and the branchial
chambers are converted into air-breathing lungs with highly vascular walls,
the entrances into which are situated as round holes between the bases of
the third and fourth pairs of walking legs. As their name implies, they can
run with astonishing rapidity, and they seem to be always on the alert,
directing their eyes, which are placed on exceedingly long stalks, in all
directions.
Page 243
Some of the Grapsidae, e.g. Aratus
pisonii, are partially adapted for life
on land. Fritz Müller, in his Facts for
Darwin, alludes to this creature as “a
charming lively crab which ascends
mangrove bushes and gnaws their
leaves.” The carapace can be
elevated and depressed posteriorly,
apparently by means of a
membranous sac, which can be
inflated by the body-fluids. This Crab
retains its gills and can breathe under
water in the ordinary way.
A great many other Catometopa
are land-crabs; but we may specially
mention the genus Gecarcinus,
related to the marine Grapsidae,
which has representatives in the West
Indies and West Africa. The Crabs of
this genus may live in sheltered
situations several miles from the sea,
but in spring the whole adult
population rushes down in immense
troops to the shore, where breeding
and spawning take place; and when
this is completed they migrate back
again to the land. The young pass
through the normal larval stages in
Fig. 135.—Gelasimus annulipes, × 1. A,
the sea and then migrate inland.[157] Female; B, male. (After Alcock.)
Fam. 1. Carcinoplacidae.—The
carapace is rounded and broader than
long, usually with toothed front margin. The orbits and eyes are normal, and
not much enlarged. Geryon, in the deep littoral of the northern hemisphere.
Euryplax, Panoplax, etc., in the American coastal waters. Typhlocarcinus,
etc., in the Indo-Pacific.
pisonii, are partially adapted for life
on land. Fritz Müller, in his Facts for
Darwin, alludes to this creature as “a
charming lively crab which ascends
mangrove bushes and gnaws their
leaves.” The carapace can be
elevated and depressed posteriorly,
apparently by means of a
membranous sac, which can be
inflated by the body-fluids. This Crab
retains its gills and can breathe under
water in the ordinary way.
A great many other Catometopa
are land-crabs; but we may specially
mention the genus Gecarcinus,
related to the marine Grapsidae,
which has representatives in the West
Indies and West Africa. The Crabs of
this genus may live in sheltered
situations several miles from the sea,
but in spring the whole adult
population rushes down in immense
troops to the shore, where breeding
and spawning take place; and when
this is completed they migrate back
again to the land. The young pass
through the normal larval stages in
Fig. 135.—Gelasimus annulipes, × 1. A,
the sea and then migrate inland.[157] Female; B, male. (After Alcock.)
Fam. 1. Carcinoplacidae.—The
carapace is rounded and broader than
long, usually with toothed front margin. The orbits and eyes are normal, and
not much enlarged. Geryon, in the deep littoral of the northern hemisphere.
Euryplax, Panoplax, etc., in the American coastal waters. Typhlocarcinus,
etc., in the Indo-Pacific.
Page 244
Fam. 2. Gonoplacidae.—The carapace is square, with the antero-lateral
corners produced into spines. The orbits are transversely widened, and the
eye-stalks long. Gonoplax, widely distributed in the littoral zone. G.
rhomboides in British and European seas.
Fam. 3. Pinnotheridae.—Carapace round, with indistinct frontal margin.
Orbits and eyes very small, often rudimentary. The members of this family
live symbiotically or parasitically in the shells of living Bivalve Molluscs,
corals, and wormtubes in all seas except the Arctic. Pinnotheres pisum is
fairly commonly met with off the English coasts in the mantle-cavity of
Cardium norwegicum.
Fam. 4. Grapsidae.[158]—Carapace square, the lateral margins either
strictly parallel or slightly arched. The orbits and eyes are moderately large,
but the eye-stalks are not much lengthened. Littoral, fresh-water, and land.
Pachygrapsus marmoratus (Fig. 134), the common shore-crab of the
Mediterranean. Sesarma, with fresh-water and land representatives in the
tropics of both hemispheres. Cyclograpsus, marine in the tropical littoral.
Fam. 5. Gecarcinidae.—Carapace square, but much swollen in the
branchial region. Orbits and eyes moderately large. Typically land forms,
which only occasionally visit the sea or fresh water. Cardisoma is a
completely circumtropical genus, with species in tropical America, West
and East Africa, and throughout the Indo-Pacific. Gecarcinus in West Indies
and West Africa.
Fam. 6. Ocypodidae.—Carapace square or rounded, generally without
teeth on the lateral margins. The orbits transversely lengthened, eye-stalks
usually very long. The members of this family generally inhabit the mud-
flats and sands of tropical coasts; in the southern hemisphere they extend
far into the temperate regions. Macrophthalmus, with numerous species, in
Indo-Pacific. Gelasimus (Fig. 135), in the tropics of both hemispheres.
Ocypoda, with similar distribution.
corners produced into spines. The orbits are transversely widened, and the
eye-stalks long. Gonoplax, widely distributed in the littoral zone. G.
rhomboides in British and European seas.
Fam. 3. Pinnotheridae.—Carapace round, with indistinct frontal margin.
Orbits and eyes very small, often rudimentary. The members of this family
live symbiotically or parasitically in the shells of living Bivalve Molluscs,
corals, and wormtubes in all seas except the Arctic. Pinnotheres pisum is
fairly commonly met with off the English coasts in the mantle-cavity of
Cardium norwegicum.
Fam. 4. Grapsidae.[158]—Carapace square, the lateral margins either
strictly parallel or slightly arched. The orbits and eyes are moderately large,
but the eye-stalks are not much lengthened. Littoral, fresh-water, and land.
Pachygrapsus marmoratus (Fig. 134), the common shore-crab of the
Mediterranean. Sesarma, with fresh-water and land representatives in the
tropics of both hemispheres. Cyclograpsus, marine in the tropical littoral.
Fam. 5. Gecarcinidae.—Carapace square, but much swollen in the
branchial region. Orbits and eyes moderately large. Typically land forms,
which only occasionally visit the sea or fresh water. Cardisoma is a
completely circumtropical genus, with species in tropical America, West
and East Africa, and throughout the Indo-Pacific. Gecarcinus in West Indies
and West Africa.
Fam. 6. Ocypodidae.—Carapace square or rounded, generally without
teeth on the lateral margins. The orbits transversely lengthened, eye-stalks
usually very long. The members of this family generally inhabit the mud-
flats and sands of tropical coasts; in the southern hemisphere they extend
far into the temperate regions. Macrophthalmus, with numerous species, in
Indo-Pacific. Gelasimus (Fig. 135), in the tropics of both hemispheres.
Ocypoda, with similar distribution.
Page 245
CHAPTER VII
REMARKS ON THE DISTRIBUTION OF MARINE AND
FRESH-WATER CRUSTACEA
A. Marine.
The great majority of the Crustacea are inhabitants of the sea. From a
Zoogeographical point of view we divide the sea into three chief regions,
each of which is characterised by a special kind of fauna—the littoral, the
pelagic, and the abyssal regions.
The littoral region, which comprises all the shallow coastal waters down
to about 100 fathoms, varies very greatly in its physical character according
to the nature of the coast, its geological constitution, latitude, etc., but, on
the whole, it is characterised by variability of temperature and salinity, by
the presence of sunlight, and by the continuous motion of its waves. On the
shores of the large oceans this region is also greatly affected by the tides. It
is inhabited by a vast assemblage of Crustacea, all of which are dependent
upon a solid substratum, either of rock or sand, or of vegetable or animal
growth, upon which they may wander in search of food, or in which they
may hide themselves. In consequence, the character of the Crustacea on any
shore is largely determined by its geological nature.
Although a certain number of Entomostraca such as Copepoda
(Harpacticidae and Cyclopidae), Ostracoda (Cypridae and Cytheridae), and
a few Operculata are littoral in habit, it is the Malacostraca, from their
larger size and variety of form, which give the character to coastal waters.
On rocky coasts, especially those affected by tides, a great many kinds of
Shore-crab are found, which hide at low tide in the rock-pools and under
stones. Carcinus maenas is characteristic of the rocky coasts of the North
Sea, while it is replaced in warmer seas and all round the tropics by Crabs
of the family Grapsidae, which are typical rock-livers, and exceedingly
agile in clambering over tide-washed rocks. Porcellanidae are also very
REMARKS ON THE DISTRIBUTION OF MARINE AND
FRESH-WATER CRUSTACEA
A. Marine.
The great majority of the Crustacea are inhabitants of the sea. From a
Zoogeographical point of view we divide the sea into three chief regions,
each of which is characterised by a special kind of fauna—the littoral, the
pelagic, and the abyssal regions.
The littoral region, which comprises all the shallow coastal waters down
to about 100 fathoms, varies very greatly in its physical character according
to the nature of the coast, its geological constitution, latitude, etc., but, on
the whole, it is characterised by variability of temperature and salinity, by
the presence of sunlight, and by the continuous motion of its waves. On the
shores of the large oceans this region is also greatly affected by the tides. It
is inhabited by a vast assemblage of Crustacea, all of which are dependent
upon a solid substratum, either of rock or sand, or of vegetable or animal
growth, upon which they may wander in search of food, or in which they
may hide themselves. In consequence, the character of the Crustacea on any
shore is largely determined by its geological nature.
Although a certain number of Entomostraca such as Copepoda
(Harpacticidae and Cyclopidae), Ostracoda (Cypridae and Cytheridae), and
a few Operculata are littoral in habit, it is the Malacostraca, from their
larger size and variety of form, which give the character to coastal waters.
On rocky coasts, especially those affected by tides, a great many kinds of
Shore-crab are found, which hide at low tide in the rock-pools and under
stones. Carcinus maenas is characteristic of the rocky coasts of the North
Sea, while it is replaced in warmer seas and all round the tropics by Crabs
of the family Grapsidae, which are typical rock-livers, and exceedingly
agile in clambering over tide-washed rocks. Porcellanidae are also very
Page 246
common under stones at low tide on rocky beaches. Such typical Shore-
crabs as these are remarkably resistant to desiccation, and can live out of
water for an astonishing time; nor do they require a change of water
provided they have access to the air. The edible crab (Cancer pagurus) and
the lobsters (Homarus and Palinurus) are dependent on rocks, but they
rarely come close in-shore, preferring depths of a few fathoms.
Sandy coasts are preferred by Shrimps and Prawns, which haunt the
shallow coastal waters in shoals; and in the sand are found all the Crabs
whose respiratory mechanism is specially adapted for life in these regions,
e.g. Hippidea or Mole-crabs, Corystes, Matuta, Calappa, etc.
Characteristic of sandy bottoms are also the Thalassinidea, such as
Callianassa, which excavate galleries in the sand. On tropical sandy shores
various species of Ocypoda and Gelasimus are conspicuous, which have
deserted the sea, and live in burrows which they excavate on the shore.
Gelasimus is especially abundant in the muddy sand of tropical mangrove
swamps.
Besides the rocky and sandy coasts we must distinguish the muddy
shores and bottoms which support a large amount of vegetable and animal
growth. These, besides harbouring the greater number of Amphipods and
Isopods, are also the natural home of the Dromiacea and Oxyrhyncha, or
Spider-crabs, among which the habit is common of decking themselves out
with pieces of weed or animal growth in order to harmonise better with
their surroundings. Pagurids are also especially abundant in the deeper
waters of these coasts.
Coral-reefs support a characteristic Crustacean fauna. In the growing
coral at the reef-edge a number of small Cyclometopa are found, e.g.
Chlorodius, Actaea, Xantho, which are finely sculptured and often coloured
so as to harmonise with the coral. Alpheidae also, Shrimp-like Macrura with
highly asymmetrical claws, which can emit a sharp cracking sound with the
larger claw, are commonly found in pools on the reef. In the coralshingle
formed by abrasion from the reef-edge at a few fathoms depth, Leucosiidae
are found, in which, again, respiratory mechanisms for filtering sand from
the gills are present.
Besides the geological nature of the coast, latitude has a very important
bearing upon the distribution of littoral Crustacea. Indeed, the present
distribution of littoral Crustacea appears to be far more determined by the
crabs as these are remarkably resistant to desiccation, and can live out of
water for an astonishing time; nor do they require a change of water
provided they have access to the air. The edible crab (Cancer pagurus) and
the lobsters (Homarus and Palinurus) are dependent on rocks, but they
rarely come close in-shore, preferring depths of a few fathoms.
Sandy coasts are preferred by Shrimps and Prawns, which haunt the
shallow coastal waters in shoals; and in the sand are found all the Crabs
whose respiratory mechanism is specially adapted for life in these regions,
e.g. Hippidea or Mole-crabs, Corystes, Matuta, Calappa, etc.
Characteristic of sandy bottoms are also the Thalassinidea, such as
Callianassa, which excavate galleries in the sand. On tropical sandy shores
various species of Ocypoda and Gelasimus are conspicuous, which have
deserted the sea, and live in burrows which they excavate on the shore.
Gelasimus is especially abundant in the muddy sand of tropical mangrove
swamps.
Besides the rocky and sandy coasts we must distinguish the muddy
shores and bottoms which support a large amount of vegetable and animal
growth. These, besides harbouring the greater number of Amphipods and
Isopods, are also the natural home of the Dromiacea and Oxyrhyncha, or
Spider-crabs, among which the habit is common of decking themselves out
with pieces of weed or animal growth in order to harmonise better with
their surroundings. Pagurids are also especially abundant in the deeper
waters of these coasts.
Coral-reefs support a characteristic Crustacean fauna. In the growing
coral at the reef-edge a number of small Cyclometopa are found, e.g.
Chlorodius, Actaea, Xantho, which are finely sculptured and often coloured
so as to harmonise with the coral. Alpheidae also, Shrimp-like Macrura with
highly asymmetrical claws, which can emit a sharp cracking sound with the
larger claw, are commonly found in pools on the reef. In the coralshingle
formed by abrasion from the reef-edge at a few fathoms depth, Leucosiidae
are found, in which, again, respiratory mechanisms for filtering sand from
the gills are present.
Besides the geological nature of the coast, latitude has a very important
bearing upon the distribution of littoral Crustacea. Indeed, the present
distribution of littoral Crustacea appears to be far more determined by the
Page 247
temperature of the coastal waters than by the presence of any land-barriers,
however formidable. We may distinguish an Arctic, Antarctic, and
Circumtropical zone.
The Arctic zone includes the true Arctic seas, and stretches right down
through boreal regions towards the sub-tropical seas. Almost all the truly
Arctic forms penetrate fairly far south, the Arctic seas being characterised
more by the absence of temperate forms than by the presence of forms
peculiar to itself. At the same time it must be noted that the individuals from
the coldest regions often grow to an enormous size, a characteristic which is
physiologically unexplained.
A great many of the Crustacea characteristic of this region are
circumpolar, i.e. they are not restricted in range to either the Atlantic or
Pacific. This is especially true of the extremely northern types, e.g.
Crangonidae and Hippolytidae, but it is also true of a number of Crustacea
which do not now occur as far north as Greenland or Bering Strait, so that
there is no longer any free communication for them between Pacific and
Atlantic. This gives rise to a discontinuous distribution in the two oceans,
exemplified in the common Shrimp, Crangon vulgaris, which is found on
the temperate European coasts and on the Pacific coasts of Japan and
Eastern America. The same is true of Eupagurus pubescens and E.
bernhardus.
At the same time the boreal Atlantic and Pacific have their peculiar
forms. Thus the European and American Lobsters are confined to the
Atlantic, while the North Pacific possesses a very rich array of Lithodinae,
which cannot be paralleled in the Atlantic.
We may explain the community of many littoral forms to both the North
Atlantic and Pacific coasts by the continuous coast-line uniting them, which
in former times possibly did not lie so far north, or else was not subjected to
so rigorous a climate as now.
In the Antarctic zone we are presented with very different relations,
since the great continents are drawn out to points towards the south, and are
isolated by vast tracts of intervening deep sea. Nevertheless, certain littoral
forms are circumpolar, e.g. the Palinurid Iasus and the Crabs Cyclograpsus
and Hymenosoma. The genus Dromidia is common to Australia and South
Africa, though it is apparently absent from South America.
however formidable. We may distinguish an Arctic, Antarctic, and
Circumtropical zone.
The Arctic zone includes the true Arctic seas, and stretches right down
through boreal regions towards the sub-tropical seas. Almost all the truly
Arctic forms penetrate fairly far south, the Arctic seas being characterised
more by the absence of temperate forms than by the presence of forms
peculiar to itself. At the same time it must be noted that the individuals from
the coldest regions often grow to an enormous size, a characteristic which is
physiologically unexplained.
A great many of the Crustacea characteristic of this region are
circumpolar, i.e. they are not restricted in range to either the Atlantic or
Pacific. This is especially true of the extremely northern types, e.g.
Crangonidae and Hippolytidae, but it is also true of a number of Crustacea
which do not now occur as far north as Greenland or Bering Strait, so that
there is no longer any free communication for them between Pacific and
Atlantic. This gives rise to a discontinuous distribution in the two oceans,
exemplified in the common Shrimp, Crangon vulgaris, which is found on
the temperate European coasts and on the Pacific coasts of Japan and
Eastern America. The same is true of Eupagurus pubescens and E.
bernhardus.
At the same time the boreal Atlantic and Pacific have their peculiar
forms. Thus the European and American Lobsters are confined to the
Atlantic, while the North Pacific possesses a very rich array of Lithodinae,
which cannot be paralleled in the Atlantic.
We may explain the community of many littoral forms to both the North
Atlantic and Pacific coasts by the continuous coast-line uniting them, which
in former times possibly did not lie so far north, or else was not subjected to
so rigorous a climate as now.
In the Antarctic zone we are presented with very different relations,
since the great continents are drawn out to points towards the south, and are
isolated by vast tracts of intervening deep sea. Nevertheless, certain littoral
forms are circumpolar, e.g. the Palinurid Iasus and the Crabs Cyclograpsus
and Hymenosoma. The genus Dromidia is common to Australia and South
Africa, though it is apparently absent from South America.
Page 248
The Isopod genus Serolis is confined to Antarctic seas. The majority are
littoral species, and they are distributed round the coasts of Patagonia,
Australia, and Kerguelen in a manner that certainly suggests a closer
connection between these shores in the past. These facts are, on the whole,
evidence in favour of the former existence of an Antarctic continent
stretching farther north and connecting Australia, Africa, and S. America—a
supposition that has been put forward to account for the distribution of the
Penguins, Struthious birds, Oligochaets, Crayfishes, etc., in these regions
(see pp. 215–217).
In considering the Arctic and Antarctic faunas the supposed phenomenon
of bipolarity must be mentioned, i.e. the occurrence of particular species in
Arctic and Antarctic seas, but not in the intermediate regions. This
discontinuous type of distribution was upheld for a variety of marine
animals by Pfeffer, Murray, and others, but it has been very adversely
criticised by Ortmann.[159] As far as the Arctic and Antarctic Decapod fauna
in general are concerned, the north polar forms are quite distinct from the
south polar. Typical of the former are Hippolyte, Sclerocrangon, Hyas,
Homarus, etc.; of the latter, Hymenosoma, Dromidia, Iasus. It appears,
however, that in certain special cases, bipolarity of distribution may be
produced owing to the operation of peculiar causes. Two such cases seem to
be fairly well established. Crangon antarcticus occurs at the two poles, and
apparently not in the intermediate regions; but, as Ortmann points out, it is
represented right down the West American coast by a very closely related
form, C. franciscorum. The waters on the tropical western coasts both of
Africa and America are exceedingly cool, and it appears that in this way the
Crangon may have migrated across the tropical belt, leaving a slightly
modified race to represent it in this intermediate region. The other case of
bipolarity is afforded by the “Schizopod,” Boreomysis scyphops, which
occurs at both poles, but is not known from the tropics. This is a pelagic
species, and we know that the Mysidae often descend to considerable
depths. We also know that the Mysidae are dependent on cold water, only
occurring in boreal or temperate waters. We may safely suppose, therefore,
that the migration of this species has taken place by their forsaking the
surface-waters as the tropics were approached, and passing down into the
depths where the temperature is constantly low even in the tropics.
The dependence of Crustacea upon the temperature of the water is also
illustrated by the distribution of the Lithodinae. The headquarters of this
littoral species, and they are distributed round the coasts of Patagonia,
Australia, and Kerguelen in a manner that certainly suggests a closer
connection between these shores in the past. These facts are, on the whole,
evidence in favour of the former existence of an Antarctic continent
stretching farther north and connecting Australia, Africa, and S. America—a
supposition that has been put forward to account for the distribution of the
Penguins, Struthious birds, Oligochaets, Crayfishes, etc., in these regions
(see pp. 215–217).
In considering the Arctic and Antarctic faunas the supposed phenomenon
of bipolarity must be mentioned, i.e. the occurrence of particular species in
Arctic and Antarctic seas, but not in the intermediate regions. This
discontinuous type of distribution was upheld for a variety of marine
animals by Pfeffer, Murray, and others, but it has been very adversely
criticised by Ortmann.[159] As far as the Arctic and Antarctic Decapod fauna
in general are concerned, the north polar forms are quite distinct from the
south polar. Typical of the former are Hippolyte, Sclerocrangon, Hyas,
Homarus, etc.; of the latter, Hymenosoma, Dromidia, Iasus. It appears,
however, that in certain special cases, bipolarity of distribution may be
produced owing to the operation of peculiar causes. Two such cases seem to
be fairly well established. Crangon antarcticus occurs at the two poles, and
apparently not in the intermediate regions; but, as Ortmann points out, it is
represented right down the West American coast by a very closely related
form, C. franciscorum. The waters on the tropical western coasts both of
Africa and America are exceedingly cool, and it appears that in this way the
Crangon may have migrated across the tropical belt, leaving a slightly
modified race to represent it in this intermediate region. The other case of
bipolarity is afforded by the “Schizopod,” Boreomysis scyphops, which
occurs at both poles, but is not known from the tropics. This is a pelagic
species, and we know that the Mysidae often descend to considerable
depths. We also know that the Mysidae are dependent on cold water, only
occurring in boreal or temperate waters. We may safely suppose, therefore,
that the migration of this species has taken place by their forsaking the
surface-waters as the tropics were approached, and passing down into the
depths where the temperature is constantly low even in the tropics.
The dependence of Crustacea upon the temperature of the water is also
illustrated by the distribution of the Lithodinae. The headquarters of this
Page 249
family are in the boreal Pacific, with a few scattered representatives in the
boreal Atlantic. The cool currents on the western coasts of America,
however, have permitted certain forms to migrate as far south as Patagonia,
where they still have a littoral habit. In the tropical Indo-Pacific, where a
few species occur, they are only found in deep waters. Thus at these various
latitudes, by following cool currents or migrating into deep water, they are
always subjected to similar conditions of temperature. The same kind of
thing is observed in Arctic seas, where deep-sea forms are apt to take on
secondarily a littoral habit owing to the temperature of the depths and of the
shore being the same.
Despite the impassable barriers of land which now sever the tropical
oceans, we can yet speak of a circumtropical zone possessing many
species common to its most widely separated parts. Such circumtropical
species, occurring on both the Atlantic and Pacific coasts of tropical
America, on the West African coast, and in the Indo-Pacific, are various
Grapsidae, Calappa granulata and its allies, and certain Albunea. The most
striking instance of all is that of the Land-crabs. Of Ocypoda, the greater
number of species occur in the Indo-Pacific, but representatives are also
found on the tropical Eastern and Western American coasts and on the West
African coast, and the same is true of Gelasimus. The genus Cardisoma,
belonging to a different group of Land-crabs, is also typically
circumtropical.
For this community of the circumtropical species we may certainly
advance in explanation the comparatively recent formation of the Isthmus
of Panama. Besides the resemblance of the Crustacea on the east and west
coasts of the isthmus, we have an actual identity of species in several cases,
e.g. Pachycheles panamensis and Hippa emerita, and the same thing has
been observed for the marine fish.
Another connexion, at any rate during early tertiary times, which
probably existed between now isolated tropical coasts, was across the
Atlantic from the West Indies to the Mediterranean and West African coasts.
Numerous facts speak for this connexion. Species of Palinurus and Dromia
occur in the West Indies and the Mediterranean, which only differ from one
another in detail, and a connexion between these two regions has been
urged from the minute resemblances of the late Cretaceous Corals of the
West Indies with those of the Gosau beds of S. Europe, and also of the
boreal Atlantic. The cool currents on the western coasts of America,
however, have permitted certain forms to migrate as far south as Patagonia,
where they still have a littoral habit. In the tropical Indo-Pacific, where a
few species occur, they are only found in deep waters. Thus at these various
latitudes, by following cool currents or migrating into deep water, they are
always subjected to similar conditions of temperature. The same kind of
thing is observed in Arctic seas, where deep-sea forms are apt to take on
secondarily a littoral habit owing to the temperature of the depths and of the
shore being the same.
Despite the impassable barriers of land which now sever the tropical
oceans, we can yet speak of a circumtropical zone possessing many
species common to its most widely separated parts. Such circumtropical
species, occurring on both the Atlantic and Pacific coasts of tropical
America, on the West African coast, and in the Indo-Pacific, are various
Grapsidae, Calappa granulata and its allies, and certain Albunea. The most
striking instance of all is that of the Land-crabs. Of Ocypoda, the greater
number of species occur in the Indo-Pacific, but representatives are also
found on the tropical Eastern and Western American coasts and on the West
African coast, and the same is true of Gelasimus. The genus Cardisoma,
belonging to a different group of Land-crabs, is also typically
circumtropical.
For this community of the circumtropical species we may certainly
advance in explanation the comparatively recent formation of the Isthmus
of Panama. Besides the resemblance of the Crustacea on the east and west
coasts of the isthmus, we have an actual identity of species in several cases,
e.g. Pachycheles panamensis and Hippa emerita, and the same thing has
been observed for the marine fish.
Another connexion, at any rate during early tertiary times, which
probably existed between now isolated tropical coasts, was across the
Atlantic from the West Indies to the Mediterranean and West African coasts.
Numerous facts speak for this connexion. Species of Palinurus and Dromia
occur in the West Indies and the Mediterranean, which only differ from one
another in detail, and a connexion between these two regions has been
urged from the minute resemblances of the late Cretaceous Corals of the
West Indies with those of the Gosau beds of S. Europe, and also of the
Page 250
Miocene land-molluscs of S. Europe with those at the present time found in
the West Indies.
To account, then, for the present distribution of littoral Crustacea we
must imagine that great changes have taken place during comparatively
recent times in the coast-lines of the ocean, but the guiding principle in both
the past and present has been temperature, and this factor enables us,
despite the immense changes in the configuration of the globe that must
have taken place, to divide the coasts latitudinally into Arctic, Antarctic,
and Circumtropical zones.
Pelagic Crustacea belong chiefly to the Copepoda (Calanidae,
Centropagidae, Candacidae, Pontellidae, Corycaeidae), a few Ostracoda
(Halocypridae and Cypridinae), and among Malacostraca a few Amphipoda
(Hyperina), some “Schizopoda,” and among Decapoda only the
Sergestidae, if we except the few special forms which live on the floating
weeds of the Sargasso Sea, e.g. the Prawns Virbius acuminatus and
Latreutes ensiferus, and the Brachyura Neptunus sayi and Planes minutus.
Besides these Crustacea which are pelagic as adults, there is an enormous
host of larval forms, both among Entomostraca and Malacostraca, which
are taken in the surface-plankton.
In dealing with the Copepoda we have already mentioned the vast pelagic
shoals of these organisms which occur at particular times of the year, and
have an important influence on fishing industries. Anomalocera pattersoni
(Fig. 27, p. 60) is a good instance of this. It is a large Heterarthrandrian,
about 3 mm. long, with the body of a fine bluish green colour; it has a
remarkable power of springing out of the water, so that a shoal has the
appearance of fine rain upon the surface of the sea. It occurs in the open
Atlantic and Mediterranean, but comes into the coasts during violent
storms; the Norwegian fishermen hail its presence in the fjords as the sign
of the approach of the summer herring.
It was Haeckel[160] who first clearly distinguished between “neritic”
plankton, the species of which have their centres of distribution in shallow
coastal waters and die out gradually as the open ocean is approached, and
“oceanic” plankton which is habitually found in the open sea, and though it
may invade the coasts is not dependent on the sea-bottom in any way. It
appears that although these two kinds of plankton may get mixed up by
the West Indies.
To account, then, for the present distribution of littoral Crustacea we
must imagine that great changes have taken place during comparatively
recent times in the coast-lines of the ocean, but the guiding principle in both
the past and present has been temperature, and this factor enables us,
despite the immense changes in the configuration of the globe that must
have taken place, to divide the coasts latitudinally into Arctic, Antarctic,
and Circumtropical zones.
Pelagic Crustacea belong chiefly to the Copepoda (Calanidae,
Centropagidae, Candacidae, Pontellidae, Corycaeidae), a few Ostracoda
(Halocypridae and Cypridinae), and among Malacostraca a few Amphipoda
(Hyperina), some “Schizopoda,” and among Decapoda only the
Sergestidae, if we except the few special forms which live on the floating
weeds of the Sargasso Sea, e.g. the Prawns Virbius acuminatus and
Latreutes ensiferus, and the Brachyura Neptunus sayi and Planes minutus.
Besides these Crustacea which are pelagic as adults, there is an enormous
host of larval forms, both among Entomostraca and Malacostraca, which
are taken in the surface-plankton.
In dealing with the Copepoda we have already mentioned the vast pelagic
shoals of these organisms which occur at particular times of the year, and
have an important influence on fishing industries. Anomalocera pattersoni
(Fig. 27, p. 60) is a good instance of this. It is a large Heterarthrandrian,
about 3 mm. long, with the body of a fine bluish green colour; it has a
remarkable power of springing out of the water, so that a shoal has the
appearance of fine rain upon the surface of the sea. It occurs in the open
Atlantic and Mediterranean, but comes into the coasts during violent
storms; the Norwegian fishermen hail its presence in the fjords as the sign
of the approach of the summer herring.
It was Haeckel[160] who first clearly distinguished between “neritic”
plankton, the species of which have their centres of distribution in shallow
coastal waters and die out gradually as the open ocean is approached, and
“oceanic” plankton which is habitually found in the open sea, and though it
may invade the coasts is not dependent on the sea-bottom in any way. It
appears that although these two kinds of plankton may get mixed up by
Page 251
currents and storms, they are always recruited by new generations from the
neritic or oceanic stations proper to each kind.
Common oceanic species, found chiefly in the open Atlantic and in the
North Sea, are Anomalocera pattersoni, Calanus finmarchicus, Centropages
typicus, Metridia lucens, Oithona plumifera, etc. Common neritic species in
the Channel and other coastal waters are Centropages hamatus, Euterpe
acutifrons, Oithona nana, Temora longicornis, etc. It was found by
Gough[161] that although the true oceanic species invade the Channel from
the open Atlantic to the west, they become rarer and rarer as they advance
up the Channel. Thus the plankton midway between the Lizard and Ushant
at all times of year is about 70 per cent. oceanic, while at the line drawn
from Portland to the Cap de la Hague it is about 35 per cent. Seasonal
changes in the salinity of the Channel water, chiefly due to the influx of
oceanic water from the Atlantic, as observed by Matthews,[162] do not clearly
influence the distribution of oceanic and neritic forms. The influx of highly
saline water from the Atlantic was most marked during the winter months
up to February. From February to May the highly saline water receded, and
during the summer months at the line drawn between Portland and the Cap
de la Hague the salinity was rather low. This was increased in November by
a patch of oceanic water being cut off from the main mass and passing up
Channel, and it is noteworthy that during this month the highest percentage
of oceanic forms was taken in the plankton of this region.
Calanus finmarchicus affords a clear instance of the way in which the
plankton may be carried about for great distances by means of currents.
This species has its home in the subarctic seas, but is carried down in the
spring by the East Icelandic Polar stream to its spawning-place south of
Iceland; the enormous shoals produced here are carried back, continually
multiplying, along the coasts of Norway during the summer and autumn.
Besides these great migrations, the plankton organisms perform daily
movements, the majority of the Crustacea avoiding the surface during the
day, and often going down to as much as seventy fathoms or more, and only
coming up to the surface at night. Others, however, e.g. Calanus
finmarchicus, behave in the converse manner, preferring the sunlit surface
to swim in.
Owing to their dispersal by means of oceanic currents the pelagic
Crustacea do not offer any very striking features in regard to their
neritic or oceanic stations proper to each kind.
Common oceanic species, found chiefly in the open Atlantic and in the
North Sea, are Anomalocera pattersoni, Calanus finmarchicus, Centropages
typicus, Metridia lucens, Oithona plumifera, etc. Common neritic species in
the Channel and other coastal waters are Centropages hamatus, Euterpe
acutifrons, Oithona nana, Temora longicornis, etc. It was found by
Gough[161] that although the true oceanic species invade the Channel from
the open Atlantic to the west, they become rarer and rarer as they advance
up the Channel. Thus the plankton midway between the Lizard and Ushant
at all times of year is about 70 per cent. oceanic, while at the line drawn
from Portland to the Cap de la Hague it is about 35 per cent. Seasonal
changes in the salinity of the Channel water, chiefly due to the influx of
oceanic water from the Atlantic, as observed by Matthews,[162] do not clearly
influence the distribution of oceanic and neritic forms. The influx of highly
saline water from the Atlantic was most marked during the winter months
up to February. From February to May the highly saline water receded, and
during the summer months at the line drawn between Portland and the Cap
de la Hague the salinity was rather low. This was increased in November by
a patch of oceanic water being cut off from the main mass and passing up
Channel, and it is noteworthy that during this month the highest percentage
of oceanic forms was taken in the plankton of this region.
Calanus finmarchicus affords a clear instance of the way in which the
plankton may be carried about for great distances by means of currents.
This species has its home in the subarctic seas, but is carried down in the
spring by the East Icelandic Polar stream to its spawning-place south of
Iceland; the enormous shoals produced here are carried back, continually
multiplying, along the coasts of Norway during the summer and autumn.
Besides these great migrations, the plankton organisms perform daily
movements, the majority of the Crustacea avoiding the surface during the
day, and often going down to as much as seventy fathoms or more, and only
coming up to the surface at night. Others, however, e.g. Calanus
finmarchicus, behave in the converse manner, preferring the sunlit surface
to swim in.
Owing to their dispersal by means of oceanic currents the pelagic
Crustacea do not offer any very striking features in regard to their
Page 252
distribution, and the possibility of always finding congenial temperatures by
passing into the upper or under strata of water enables them to live in
almost all seas. The tropical species of Sergestidae are mostly
circumtropical, i.e. unhindered by the present barriers of land.
The Abyssal regions of the sea contain many of the most interesting
Crustacea. Families entirely confined to the abyss are the Eryonidae,
Pylochelidae, and certain Caridean Prawns (Psalidopodidae, etc.), but there
are a great number of normally littoral genera which have representatives in
deep water. If we draw the limit between the littoral and abyssal regions at
about 200 metres, we can characterise the latter as absolutely dark except
for the presence of phosphorescent organisms, with the temperature at a
little above zero, and with a comparative lack of dissolved oxygen in the
water. These conditions bring about remarkable modifications in the
structure and life-histories of the inhabitants of the deep sea; we have
already touched on the modifications of the visual organs and on the
presence of phosphorescence in many of the animals; other points to be
noticed are the usually uniform yellowish or bright red coloration, the
frequent delicacy of the tissues without much calcification, variations in the
structure of the breathing organs, e.g. in Bathynomus giganteus and
Encephaloides armstrongi, and the loss of the larval development. Owing to
the similarity of conditions in the deep sea all over the globe most of its
inhabitants are universally distributed. It is also a striking fact that species
are found in the deep sea of the tropics whose nearest allies occur, not in the
littoral seas of the tropics, but in those of the temperate region. This fact has
already been alluded to in dealing with the distribution of the Lithodinae.
Alcock[163] remarks that between 50–500 fathoms in the Indian Ocean are
found Crabs such as Maia, Latreillia, and Homola, regarded as
characteristic of the north temperate seas; the lobster Nephrops
andamanica, taken at 150–400 fathoms, is closely allied to the Norwegian
N. norwegica; and nine species of “Schizopoda,” which are certainly
temperate forms, occur in the Indian Ocean at depths of 500–1750 fathoms.
B. Fresh-Water.[164]
If we except the Crayfishes and River-crabs, the Crustacean fauna of
running water is exceedingly poor, but in all standing fresh-water, from the
passing into the upper or under strata of water enables them to live in
almost all seas. The tropical species of Sergestidae are mostly
circumtropical, i.e. unhindered by the present barriers of land.
The Abyssal regions of the sea contain many of the most interesting
Crustacea. Families entirely confined to the abyss are the Eryonidae,
Pylochelidae, and certain Caridean Prawns (Psalidopodidae, etc.), but there
are a great number of normally littoral genera which have representatives in
deep water. If we draw the limit between the littoral and abyssal regions at
about 200 metres, we can characterise the latter as absolutely dark except
for the presence of phosphorescent organisms, with the temperature at a
little above zero, and with a comparative lack of dissolved oxygen in the
water. These conditions bring about remarkable modifications in the
structure and life-histories of the inhabitants of the deep sea; we have
already touched on the modifications of the visual organs and on the
presence of phosphorescence in many of the animals; other points to be
noticed are the usually uniform yellowish or bright red coloration, the
frequent delicacy of the tissues without much calcification, variations in the
structure of the breathing organs, e.g. in Bathynomus giganteus and
Encephaloides armstrongi, and the loss of the larval development. Owing to
the similarity of conditions in the deep sea all over the globe most of its
inhabitants are universally distributed. It is also a striking fact that species
are found in the deep sea of the tropics whose nearest allies occur, not in the
littoral seas of the tropics, but in those of the temperate region. This fact has
already been alluded to in dealing with the distribution of the Lithodinae.
Alcock[163] remarks that between 50–500 fathoms in the Indian Ocean are
found Crabs such as Maia, Latreillia, and Homola, regarded as
characteristic of the north temperate seas; the lobster Nephrops
andamanica, taken at 150–400 fathoms, is closely allied to the Norwegian
N. norwegica; and nine species of “Schizopoda,” which are certainly
temperate forms, occur in the Indian Ocean at depths of 500–1750 fathoms.
B. Fresh-Water.[164]
If we except the Crayfishes and River-crabs, the Crustacean fauna of
running water is exceedingly poor, but in all standing fresh-water, from the
Page 253
smallest pond to the large lakes and inland seas, Crustacea, especially
Entomostraca, are abundant and characteristic, and form an important item
in the food of fresh-water fishes. In small ponds a vast assemblage of
Cladocera is met with; these animals multiply with great rapidity by
parthenogenesis, especially during spring and summer, but on the advent of
untoward conditions sexual individuals are produced, which lay fertilised
winter-eggs which lie dormant until favourable conditions again arise. As
Weismann first pointed out, the frequency with which sexual individuals are
produced in the various species is closely correlated with the liability of the
water in which they live to dry up; so that the Cladocera which inhabit
small ponds usually have at least two “epidemics” of sexual individuals,
one during early summer and the other before the onset of winter.
Besides Cladocera, the Phyllopoda (e.g. Apus, Artemia, etc.) inhabit
small pools; and also a great number of Cyclopidae. Of the other fresh-
water families of Copepoda, viz. Centropagidae and Harpacticidae,
inhabitants of small pieces of water are Diaptomus castor, as opposed to the
other species of Diaptomus which are pelagic, and a number of
Harpacticidae (Canthocamptus), the members of this family living in the
weed or mud of either small ponds or else on the shores of the larger lakes.
The greater number of Ostracoda are found in similar situations.
A district like the Broads of Norfolk, which consists partly of slowly-
moving streams and partly of extensive stretches of shallow water, supports
a Crustacean fauna intermediate in character between that found in small
ponds and the truly pelagic fauna characteristic of deep lakes. A very
complete list of the Crustacea of the Norfolk Broads, with an interesting
commentary on their distribution, is given by Mr. Robert Gurney.[165] We
miss here the pelagic Cladocera, such as Leptodora, Bythotrephes,
Holopedium, etc., which form so characteristic a feature of large lakes; at
the same time, besides a rich development of the Cladocera, Cyclopidae,
and Harpacticidae, which haunt the weeds and mud of shallow waters, we
find such species as Polyphemus pediculus and Bosmina longirostris among
Cladocera, which are otherwise confined to large bodies of water, and a few
pelagic Diaptomus, e.g. D. gracilis. The fauna is also complicated in this
district by the proximity to the sea and the frequently high salinity of the
water, which allows a number of typically marine Copepods to pass up the
estuaries and intermingle with typically fresh-water species; such are
Entomostraca, are abundant and characteristic, and form an important item
in the food of fresh-water fishes. In small ponds a vast assemblage of
Cladocera is met with; these animals multiply with great rapidity by
parthenogenesis, especially during spring and summer, but on the advent of
untoward conditions sexual individuals are produced, which lay fertilised
winter-eggs which lie dormant until favourable conditions again arise. As
Weismann first pointed out, the frequency with which sexual individuals are
produced in the various species is closely correlated with the liability of the
water in which they live to dry up; so that the Cladocera which inhabit
small ponds usually have at least two “epidemics” of sexual individuals,
one during early summer and the other before the onset of winter.
Besides Cladocera, the Phyllopoda (e.g. Apus, Artemia, etc.) inhabit
small pools; and also a great number of Cyclopidae. Of the other fresh-
water families of Copepoda, viz. Centropagidae and Harpacticidae,
inhabitants of small pieces of water are Diaptomus castor, as opposed to the
other species of Diaptomus which are pelagic, and a number of
Harpacticidae (Canthocamptus), the members of this family living in the
weed or mud of either small ponds or else on the shores of the larger lakes.
The greater number of Ostracoda are found in similar situations.
A district like the Broads of Norfolk, which consists partly of slowly-
moving streams and partly of extensive stretches of shallow water, supports
a Crustacean fauna intermediate in character between that found in small
ponds and the truly pelagic fauna characteristic of deep lakes. A very
complete list of the Crustacea of the Norfolk Broads, with an interesting
commentary on their distribution, is given by Mr. Robert Gurney.[165] We
miss here the pelagic Cladocera, such as Leptodora, Bythotrephes,
Holopedium, etc., which form so characteristic a feature of large lakes; at
the same time, besides a rich development of the Cladocera, Cyclopidae,
and Harpacticidae, which haunt the weeds and mud of shallow waters, we
find such species as Polyphemus pediculus and Bosmina longirostris among
Cladocera, which are otherwise confined to large bodies of water, and a few
pelagic Diaptomus, e.g. D. gracilis. The fauna is also complicated in this
district by the proximity to the sea and the frequently high salinity of the
water, which allows a number of typically marine Copepods to pass up the
estuaries and intermingle with typically fresh-water species; such are
Page 254
Eurytemora affinis among the Centropagidae, and several species of
Harpacticidae (see p. 62).
The large lakes of the world, such as the continental lakes of Europe and
America, or of our own Lake District, reproduce on a small scale the varied
conditions which appertain to the ocean—as in the ocean, we can recognise
in these lakes a littoral, a pelagic, and an abyssal region. Our knowledge of
the physiography of lakes is largely due to the classical work of Forel,[166]
and the following account of the physical conditions in the various regions
is condensed from his book.
The littoral region is sharply marked off from the others by the relative
instability of its physical conditions, owing to the agitation of its waters, the
affluence of streams and drainage, and the constant changes of temperature.
The water in this region generally contains a good deal of solid matter in
suspension, while the shelving banks of the lake support a wealth of
vegetable growth, both of Algae and of Phanerogams, down to about 20–25
metres. At this depth the daylight does not penetrate sufficiently to admit of
the growth of green plants, so that this region marks the limit, both physical
and biological, between the littoral and the abyssal zones. In this littoral
region there flourish a great quantity of Entomostraca, most of which are
also found in small ponds where similar conditions of life prevail—the
pelagic species only penetrating rarely, and by accident, into its waters. At
the beginning of July Mr. H. O. S. Gibson and myself found that the weedy
littoral region of Grasmere contained almost entirely large quantities of the
Cladoceran Eurycercus lamellatus, and a number of Cyclops fuscus and C.
strenuus. In the littoral zone of large lakes, Amphipods, Isopods, and fresh-
water shrimps may also be met with, but this applies more to the lakes of
the Tropics and of the Southern Hemisphere.
The pelagic[167] region is distinguished from the littoral by the greater
purity and transparency of its waters, and by the relative stability of the
temperature, the annual range, even at the surface, in Geneva being from
4°–20° C., while at 100 metres the water has a uniform temperature of 4° or
5° C. The upper strata are, of course, brightly illuminated, but at 20 metres
there is hardly sufficient light for green plants to grow, and at 100 metres it
is completely dark. The inhabitants of this region, known collectively as
plankton, spend their whole life swimming freely in the water, sometimes at
the surface and sometimes in the deeper strata. They consist chiefly of
Harpacticidae (see p. 62).
The large lakes of the world, such as the continental lakes of Europe and
America, or of our own Lake District, reproduce on a small scale the varied
conditions which appertain to the ocean—as in the ocean, we can recognise
in these lakes a littoral, a pelagic, and an abyssal region. Our knowledge of
the physiography of lakes is largely due to the classical work of Forel,[166]
and the following account of the physical conditions in the various regions
is condensed from his book.
The littoral region is sharply marked off from the others by the relative
instability of its physical conditions, owing to the agitation of its waters, the
affluence of streams and drainage, and the constant changes of temperature.
The water in this region generally contains a good deal of solid matter in
suspension, while the shelving banks of the lake support a wealth of
vegetable growth, both of Algae and of Phanerogams, down to about 20–25
metres. At this depth the daylight does not penetrate sufficiently to admit of
the growth of green plants, so that this region marks the limit, both physical
and biological, between the littoral and the abyssal zones. In this littoral
region there flourish a great quantity of Entomostraca, most of which are
also found in small ponds where similar conditions of life prevail—the
pelagic species only penetrating rarely, and by accident, into its waters. At
the beginning of July Mr. H. O. S. Gibson and myself found that the weedy
littoral region of Grasmere contained almost entirely large quantities of the
Cladoceran Eurycercus lamellatus, and a number of Cyclops fuscus and C.
strenuus. In the littoral zone of large lakes, Amphipods, Isopods, and fresh-
water shrimps may also be met with, but this applies more to the lakes of
the Tropics and of the Southern Hemisphere.
The pelagic[167] region is distinguished from the littoral by the greater
purity and transparency of its waters, and by the relative stability of the
temperature, the annual range, even at the surface, in Geneva being from
4°–20° C., while at 100 metres the water has a uniform temperature of 4° or
5° C. The upper strata are, of course, brightly illuminated, but at 20 metres
there is hardly sufficient light for green plants to grow, and at 100 metres it
is completely dark. The inhabitants of this region, known collectively as
plankton, spend their whole life swimming freely in the water, sometimes at
the surface and sometimes in the deeper strata. They consist chiefly of
Page 255
Diatoms, Protozoa, Rotifera, and Crustacea. The pelagic Crustacea,
especially the Cladocera, are often the most curiously and delicately built
creatures. Leptodora hyalina, which is quite transparent, is the largest of
them, attaining to three-quarters of an inch in length, though Bythotrephes
longimanus is nearly as large if we include the immense spine which
terminates the body. Holopedium gibberum, which is the commonest of all
in Grasmere lake, but not so frequently met with in the other English lakes,
is peculiar in that its body is enveloped in a spherical mass of transparent
jelly, sometimes a quarter of an inch in diameter, so that the contents of a
tow-net jar full of Holopedium have something of the consistency of boiled
sago. The enormous quantities in which these animals often occur during
summer is very astonishing; but to be truly appreciated tow-nettings should
be taken at the surface of the lake either during night-time when there is not
much moonlight, or else on a dark still day when there is a quiet drizzle
falling on the surface of the water. In bright sunshine the plankton passes
below the surface into the lower strata, and can be usually taken by sinking
the tow-net some 10–20 feet, or to even greater depths in the water. The
exact reason of these periodic migrations out of the light, and their
dependence on other physical conditions, such as temperature and the
agitation of the water, is not clearly understood. It appears, however, that
when the water is rough, plankton always passes into the deeper regions.
Besides the species mentioned, the minute Bosminidae, whose trunked
heads are suggestive under the microscope of elephants, and Polyphemus
pediculus are among the commonest pelagic Cladocera, though neither
Polyphemus nor Bythotrephes ever form shoals. The above-mentioned
genera are characteristic of the larger lakes in the Northern Hemisphere.
Our knowledge of the Crustacean plankton of tropical lakes and of those of
the Southern Hemisphere is limited (but see p. 216).
A very important constituent of lake-plankton is furnished by the
Copepoda, especially of the genus Diaptomus. With the exception of
Holopedium, by far the commonest Crustacean in Grasmere during July
was found by Mr. Gibson and myself to be D. caeruleus.
At the same time a number of Cyclopidae, e.g. Cyclops strenuus, may
occur in the pelagic region in considerable quantities, though they were
never found by us in such numbers as Diaptomus.
especially the Cladocera, are often the most curiously and delicately built
creatures. Leptodora hyalina, which is quite transparent, is the largest of
them, attaining to three-quarters of an inch in length, though Bythotrephes
longimanus is nearly as large if we include the immense spine which
terminates the body. Holopedium gibberum, which is the commonest of all
in Grasmere lake, but not so frequently met with in the other English lakes,
is peculiar in that its body is enveloped in a spherical mass of transparent
jelly, sometimes a quarter of an inch in diameter, so that the contents of a
tow-net jar full of Holopedium have something of the consistency of boiled
sago. The enormous quantities in which these animals often occur during
summer is very astonishing; but to be truly appreciated tow-nettings should
be taken at the surface of the lake either during night-time when there is not
much moonlight, or else on a dark still day when there is a quiet drizzle
falling on the surface of the water. In bright sunshine the plankton passes
below the surface into the lower strata, and can be usually taken by sinking
the tow-net some 10–20 feet, or to even greater depths in the water. The
exact reason of these periodic migrations out of the light, and their
dependence on other physical conditions, such as temperature and the
agitation of the water, is not clearly understood. It appears, however, that
when the water is rough, plankton always passes into the deeper regions.
Besides the species mentioned, the minute Bosminidae, whose trunked
heads are suggestive under the microscope of elephants, and Polyphemus
pediculus are among the commonest pelagic Cladocera, though neither
Polyphemus nor Bythotrephes ever form shoals. The above-mentioned
genera are characteristic of the larger lakes in the Northern Hemisphere.
Our knowledge of the Crustacean plankton of tropical lakes and of those of
the Southern Hemisphere is limited (but see p. 216).
A very important constituent of lake-plankton is furnished by the
Copepoda, especially of the genus Diaptomus. With the exception of
Holopedium, by far the commonest Crustacean in Grasmere during July
was found by Mr. Gibson and myself to be D. caeruleus.
At the same time a number of Cyclopidae, e.g. Cyclops strenuus, may
occur in the pelagic region in considerable quantities, though they were
never found by us in such numbers as Diaptomus.
Page 256
The life-cycle of the pelagic Entomostraca has been studied in both the
Cladocera and the Copepoda. In some of the Cladocera Weismann at first
supposed that males had altogether disappeared, and that reproduction was
entirely parthenogenetic. It appears, however, that all the pelagic species
have at least one sexual period, namely, in the autumn, when resting eggs
are produced which lie dormant during the winter. The pelagic Copepods
may either produce resting eggs for the winter (Diaptomus), or else the
winter is passed through in the Nauplius stage, the larvae hibernating in the
mud until the spring (Cyclopidae).
We have so far only dealt with fresh-water Entomostraca. There are, in
addition, a number of Malacostraca which inhabit fresh water, and some of
these are found in the abyssal region of the great lakes, which must now be
considered.
The physical conditions of the abyssal region are still more stable than
those of the pelagic region, since the water is never disturbed, the bottom is
always composed of a fine mud, the temperature is constant at 4°–5° C.,
and there is a total absence of light. It was hardly expected that animals
would inhabit this region, until Forel discovered Asellus aquaticus in a
depth of forty metres in the Lake of Geneva, and subsequently showed that
quite a number of animals, including a Hydra, several worms, Molluscs,
Crustacea, and larval Insects, may be found in these or even much greater
depths.
The Crustacea of the abyssal region are two in number, and these have
been found in a number of European lakes; Niphargus puteanus, a blind
Amphipod closely allied to Gammarus; and Asellus forelii, allied to A.
aquaticus and A. cavaticus, which may be either quite blind or else retain
the rudiments of eyes.
These two Crustacea, under a practically identical form, are also found in
the subterranean waters of Europe, and Forel considers that they have
arrived in the abysses of the lakes from the subterranean channels, and are
not derivatives of the littoral fauna.[168]
Having completed our short review of lacustrine Crustacea, we may deal
with the subterranean and cave Crustacea,[169] which, as far as light and
temperature are concerned, are subjected to very similar conditions to those
dwelling at the bottom of deep lakes. The inhabitants of the subterranean
waters have been chiefly brought to light in Artesian wells, etc., while the
Cladocera and the Copepoda. In some of the Cladocera Weismann at first
supposed that males had altogether disappeared, and that reproduction was
entirely parthenogenetic. It appears, however, that all the pelagic species
have at least one sexual period, namely, in the autumn, when resting eggs
are produced which lie dormant during the winter. The pelagic Copepods
may either produce resting eggs for the winter (Diaptomus), or else the
winter is passed through in the Nauplius stage, the larvae hibernating in the
mud until the spring (Cyclopidae).
We have so far only dealt with fresh-water Entomostraca. There are, in
addition, a number of Malacostraca which inhabit fresh water, and some of
these are found in the abyssal region of the great lakes, which must now be
considered.
The physical conditions of the abyssal region are still more stable than
those of the pelagic region, since the water is never disturbed, the bottom is
always composed of a fine mud, the temperature is constant at 4°–5° C.,
and there is a total absence of light. It was hardly expected that animals
would inhabit this region, until Forel discovered Asellus aquaticus in a
depth of forty metres in the Lake of Geneva, and subsequently showed that
quite a number of animals, including a Hydra, several worms, Molluscs,
Crustacea, and larval Insects, may be found in these or even much greater
depths.
The Crustacea of the abyssal region are two in number, and these have
been found in a number of European lakes; Niphargus puteanus, a blind
Amphipod closely allied to Gammarus; and Asellus forelii, allied to A.
aquaticus and A. cavaticus, which may be either quite blind or else retain
the rudiments of eyes.
These two Crustacea, under a practically identical form, are also found in
the subterranean waters of Europe, and Forel considers that they have
arrived in the abysses of the lakes from the subterranean channels, and are
not derivatives of the littoral fauna.[168]
Having completed our short review of lacustrine Crustacea, we may deal
with the subterranean and cave Crustacea,[169] which, as far as light and
temperature are concerned, are subjected to very similar conditions to those
dwelling at the bottom of deep lakes. The inhabitants of the subterranean
waters have been chiefly brought to light in Artesian wells, etc., while the
Page 257
cavedwellers have been investigated especially at Carniola and in the
American caves.
A number of species of Cyclopidae and Cypridae, many of which are
blind and colourless, have been brought up in well-water. The Amphipod
Niphargus puteanus has long been known from a similar source in
England[170] and all over Europe, and several other blind Gammarids inhabit
the subterranean waters and caves in various parts of the world. Among
Isopods, Asellus cavaticus is recorded from wells and caves in various parts
of Europe, Caecidotea stygia and C. nickajackensis from the Mammoth and
Nickajack Caves in America, and two very remarkable blind Isopods are
described by Chilton from the subterranean waters of New Zealand, viz.
Cruregens fontanus, whose nearest allies are the marine Anthuridae, and the
Isopods Phreatoicus typicus and P. assimilis, which bear an extraordinary
resemblance superficially to Amphipods. Besides these, a small number of
subterranean Decapoda are known which retain the eye-stalks but are
without functional ommatidia. These are Troglocaris schmidtii, in Hungary,
related to the fresh-water Atyid Xiphocaris of East Indian and East Asiatic
fresh waters rather than to the South European Atyephyra; Palaemonetes
antrorum, from artesian wells in Texas; and several species of Cambarus
from the Eastern United States. A blind species of Cambarus, C. stygius,
has been described from the caves of Carniola, and if this determination is
correct, is the sole Cambarus occurring outside America.
It will be seen from the above account that the subterranean Crustacea
are an exceedingly interesting and, in many respects, archaic group, many
of which have survived in these isolated and probably uncompetitive
districts, while many secular changes were going on in the quick world
overhead.
The remaining fresh water Malacostraca may be mentioned under the
headings of the groups to which they belong.
Only one “Schizopod,” apart from Paranaspides, is known from fresh-
water lakes, viz. Mysis relicta, which was discovered in 1861 by Lovén in
the Scandinavian lakes, and has since been found in the Finnish lakes, the
Caspian Sea, Lake Michigan, and other localities in N. America, and Lough
Erne in Ireland. This species is closely related to Mysis oculata of
Greenlandic seas.
American caves.
A number of species of Cyclopidae and Cypridae, many of which are
blind and colourless, have been brought up in well-water. The Amphipod
Niphargus puteanus has long been known from a similar source in
England[170] and all over Europe, and several other blind Gammarids inhabit
the subterranean waters and caves in various parts of the world. Among
Isopods, Asellus cavaticus is recorded from wells and caves in various parts
of Europe, Caecidotea stygia and C. nickajackensis from the Mammoth and
Nickajack Caves in America, and two very remarkable blind Isopods are
described by Chilton from the subterranean waters of New Zealand, viz.
Cruregens fontanus, whose nearest allies are the marine Anthuridae, and the
Isopods Phreatoicus typicus and P. assimilis, which bear an extraordinary
resemblance superficially to Amphipods. Besides these, a small number of
subterranean Decapoda are known which retain the eye-stalks but are
without functional ommatidia. These are Troglocaris schmidtii, in Hungary,
related to the fresh-water Atyid Xiphocaris of East Indian and East Asiatic
fresh waters rather than to the South European Atyephyra; Palaemonetes
antrorum, from artesian wells in Texas; and several species of Cambarus
from the Eastern United States. A blind species of Cambarus, C. stygius,
has been described from the caves of Carniola, and if this determination is
correct, is the sole Cambarus occurring outside America.
It will be seen from the above account that the subterranean Crustacea
are an exceedingly interesting and, in many respects, archaic group, many
of which have survived in these isolated and probably uncompetitive
districts, while many secular changes were going on in the quick world
overhead.
The remaining fresh water Malacostraca may be mentioned under the
headings of the groups to which they belong.
Only one “Schizopod,” apart from Paranaspides, is known from fresh-
water lakes, viz. Mysis relicta, which was discovered in 1861 by Lovén in
the Scandinavian lakes, and has since been found in the Finnish lakes, the
Caspian Sea, Lake Michigan, and other localities in N. America, and Lough
Erne in Ireland. This species is closely related to Mysis oculata of
Greenlandic seas.
Page 258
In the Southern Hemisphere we have a species of Anaspides, A.
tasmaniae, occurring in mountain streams and tarns in Tasmania, a related
form which haunts the littoral zone of the Great Lake in Tasmania, and a
small species, Koonunga cursor, occurs in a little stream near Melbourne.
Of the Isopoda certain genera, viz. Asellus and Monolistra, are confined
to fresh water, others, such as Sphaeroma, Idothea, Alitropus, and
Cymothoa, have occasional fresh-water representatives. Packard[171]
describes a remarkable blind Isopod, Caecidotea, from the Mammoth Cave
of Kentucky, which occupies a very isolated position, and in the same work
gives a very complete exposition of the cave-fauna of North America and
Europe.
The Phreatoicidae are a curious family of Isopods confined to the fresh
waters of Australia and New Zealand, which bear a remarkable resemblance
to Amphipods, being laterally compressed and possessing a subchelate hand
on the anterior thoracic leg. These Isopods are exceedingly common in
small mountain pools and in streams in Tasmania, and in the Great Lake in
that country I have recently found a number of species which, together with
some species of Amphipods, make up the dominant feature in the
Crustacean fauna. One of these species may grow to fully an inch in length.
The family is confined to the temperate regions, and is usually found on
mountains. A number of species are known from the mainland of Australia,
one coming from a high elevation on Mount Kosciusko, and another
(Phreatoicopsis) from the forests of Gippsland attaining a great size, and
living among damp leaves, etc.
The fresh-water Amphipoda all belong to the families Talitridae,
Gammaridae, and Haustoriidae (see p. 137).
Among the Talitridae, or Sand-hoppers, Orchestia and Talitrus have
marine as well as fresh-water and land representatives, while the American
Hyalella is entirely from fresh water, most of the species being peculiar to
Lake Titicaca. Many of these animals are partly emancipated from an
aquatic life. Thus Orchestia gammarellus, which is common on the sea-
shore of the Mediterranean, frequently penetrates far inland, and was found
in large numbers by Kotschy near a spring 4000 feet up on Mount Olympus.
Talitrus sylvaticus is very common among fallen leaves and decaying
timber in Tasmania and Southern Australia, many miles from the sea, and
often at an elevation of several thousand feet.
tasmaniae, occurring in mountain streams and tarns in Tasmania, a related
form which haunts the littoral zone of the Great Lake in Tasmania, and a
small species, Koonunga cursor, occurs in a little stream near Melbourne.
Of the Isopoda certain genera, viz. Asellus and Monolistra, are confined
to fresh water, others, such as Sphaeroma, Idothea, Alitropus, and
Cymothoa, have occasional fresh-water representatives. Packard[171]
describes a remarkable blind Isopod, Caecidotea, from the Mammoth Cave
of Kentucky, which occupies a very isolated position, and in the same work
gives a very complete exposition of the cave-fauna of North America and
Europe.
The Phreatoicidae are a curious family of Isopods confined to the fresh
waters of Australia and New Zealand, which bear a remarkable resemblance
to Amphipods, being laterally compressed and possessing a subchelate hand
on the anterior thoracic leg. These Isopods are exceedingly common in
small mountain pools and in streams in Tasmania, and in the Great Lake in
that country I have recently found a number of species which, together with
some species of Amphipods, make up the dominant feature in the
Crustacean fauna. One of these species may grow to fully an inch in length.
The family is confined to the temperate regions, and is usually found on
mountains. A number of species are known from the mainland of Australia,
one coming from a high elevation on Mount Kosciusko, and another
(Phreatoicopsis) from the forests of Gippsland attaining a great size, and
living among damp leaves, etc.
The fresh-water Amphipoda all belong to the families Talitridae,
Gammaridae, and Haustoriidae (see p. 137).
Among the Talitridae, or Sand-hoppers, Orchestia and Talitrus have
marine as well as fresh-water and land representatives, while the American
Hyalella is entirely from fresh water, most of the species being peculiar to
Lake Titicaca. Many of these animals are partly emancipated from an
aquatic life. Thus Orchestia gammarellus, which is common on the sea-
shore of the Mediterranean, frequently penetrates far inland, and was found
in large numbers by Kotschy near a spring 4000 feet up on Mount Olympus.
Talitrus sylvaticus is very common among fallen leaves and decaying
timber in Tasmania and Southern Australia, many miles from the sea, and
often at an elevation of several thousand feet.
Page 259
Among the Gammaridae, certain genera, e.g. Macrohectopus
(Constantia), from Lake Baikal, are purely fresh-water. An enormous
development of Gammaridae was discovered by Dybowsky in Lake Baikal,
comprising 116 species, and lately a number more have been found by
Korotneff.[172] The majority of these were originally placed in the genus
Gammarus, but Stebbing has rightly created a number of peculiar genera
for them. Certain species are, however, placed in more widely distributed
genera, e.g. Gammarus and Carinogammarus, which is also represented in
the Caspian Sea. Korotneff found some remarkable transparent pelagic
forms (Constantia) swimming in the abyssal regions at about 600 metres
depth, the majority of them being blind, but some possessing rudimentary
eyes, often on one side only.
Besides various species of Gammarus, a number of other Gammaridae
are frequently found in brackish water. Among Haustoriidae Pontoporeia
has representatives in both the oceans and inland lakes of the northern
hemispheres (see p. 137).
Of the Decapoda, seven families are typically fresh-water in habitat—the
Aegleidae, containing the single species Aeglea laevis, related to the
Galatheidae, which inhabits streams in temperate S. America; the Atyidae, a
family of Prawns from the tropical rivers and lakes of the New and Old
World, and in the Mediterranean region. A number of Palaemonidae are
found in fresh water, e.g. Palaemonetes varians in Europe and N. America,
while several species of Palaemon occur in lakes, streams, and estuaries of
the tropical Old and New World.
The expeditions of Moore and Cunnington to Lake Tanganyika brought
back an exceedingly rich collection of Prawns, comprising twelve species,
all of which are peculiar to the lake,[173] and this is all the more surprising
since Lakes Nyasa and Victoria Nyanza are only known to contain one
species, Caridina nilotica, which ranges all over Africa and into
Queensland and New Caledonia. The Tanganyika species, however, all
belong to purely fresh-water genera, and do not afford any suggestion that
they are part of a relict marine fauna. It would appear that they have been
differentiated in the lake itself during a long period of isolation.
Two groups of Brachyura, viz. the Thelphusidae and the Sesarminae (a
sub-family of the Grapsidae), are fresh-water. Thelphusa fluviatilis is an
inhabitant of North Africa, and penetrates into the temperate regions of the
(Constantia), from Lake Baikal, are purely fresh-water. An enormous
development of Gammaridae was discovered by Dybowsky in Lake Baikal,
comprising 116 species, and lately a number more have been found by
Korotneff.[172] The majority of these were originally placed in the genus
Gammarus, but Stebbing has rightly created a number of peculiar genera
for them. Certain species are, however, placed in more widely distributed
genera, e.g. Gammarus and Carinogammarus, which is also represented in
the Caspian Sea. Korotneff found some remarkable transparent pelagic
forms (Constantia) swimming in the abyssal regions at about 600 metres
depth, the majority of them being blind, but some possessing rudimentary
eyes, often on one side only.
Besides various species of Gammarus, a number of other Gammaridae
are frequently found in brackish water. Among Haustoriidae Pontoporeia
has representatives in both the oceans and inland lakes of the northern
hemispheres (see p. 137).
Of the Decapoda, seven families are typically fresh-water in habitat—the
Aegleidae, containing the single species Aeglea laevis, related to the
Galatheidae, which inhabits streams in temperate S. America; the Atyidae, a
family of Prawns from the tropical rivers and lakes of the New and Old
World, and in the Mediterranean region. A number of Palaemonidae are
found in fresh water, e.g. Palaemonetes varians in Europe and N. America,
while several species of Palaemon occur in lakes, streams, and estuaries of
the tropical Old and New World.
The expeditions of Moore and Cunnington to Lake Tanganyika brought
back an exceedingly rich collection of Prawns, comprising twelve species,
all of which are peculiar to the lake,[173] and this is all the more surprising
since Lakes Nyasa and Victoria Nyanza are only known to contain one
species, Caridina nilotica, which ranges all over Africa and into
Queensland and New Caledonia. The Tanganyika species, however, all
belong to purely fresh-water genera, and do not afford any suggestion that
they are part of a relict marine fauna. It would appear that they have been
differentiated in the lake itself during a long period of isolation.
Two groups of Brachyura, viz. the Thelphusidae and the Sesarminae (a
sub-family of the Grapsidae), are fresh-water. Thelphusa fluviatilis is an
inhabitant of North Africa, and penetrates into the temperate regions of the
Page 260
Mediterranean, and is said to be exceedingly common in the Alban Lake
near Rome. Both these families have representatives on land, e.g.
Potamocarcinus in Central and South America, and certain species of
Sesarma, and the closely related Gecarcinidae of the West Indies.
The remaining families to be dealt with are the two Crayfish families—
the Astacidae and the Parastacidae—which live in rapidly moving rivers
and streams, and occasionally in lakes. A few species of both families have
taken to a subterranean mode of life, and excavate burrows in the earth, e.g.
the Tasmanian Crayfish, Engaeus fossor. The distribution of the Crayfishes
has long engaged the attention of naturalists. It was first seriously studied
by Huxley,[174] and has subsequently been followed up, especially in North
America, by Faxon[175] and Ortmann,[176] but our knowledge of the South
American and Australian forms is still very incomplete. The Astacidae
inhabit the northern temperate hemisphere, the Parastacidae the southern
temperate hemisphere, the tropical belt being practically destitute of
Crayfishes. Of the Astacidae the genus Astacus (Potamobius), including the
common Crayfishes of Europe, occurs in Europe and in North America
west of the Rockies. The genus Cambaroides, which in certain respects
approaches Cambarus, is found in Japan and Eastern Asia. The very large
genus Cambarus, on the other hand, only occurs in North America east of
the Rockies, so that Cambaroides occupies a very isolated position. The
occurrence of a Cambarus, C. stygius, in the caves of Carniola, has been
recorded by Joseph, so that it would appear that this genus had a much
wider range formerly than now.
Of the southern temperate Parastacidae, Australia and Tasmania have the
genera Astacopsis and Engaeus; New Zealand has Paranephrops, South
America Parastacus, and Madagascar Astacoides. The last named genus is
rather isolated in its characters, possessing a truncated rostrum and a highly
modified branchial system, but it agrees with all the other Parastacine
genera, and differs from the Astacidae in the absence of sexual appendages
on the first abdominal segment, and in the absence of a distinct lamina on
the podobranchiae. The largest crayfish in the world is Astacopsis franklinii,
found in quite small streams on the north and west coast of Tasmania.
Specimens have been caught weighing eight or nine pounds, and rivalling
the European Lobster in size. Crayfishes appear to be entirely absent from
Africa.
near Rome. Both these families have representatives on land, e.g.
Potamocarcinus in Central and South America, and certain species of
Sesarma, and the closely related Gecarcinidae of the West Indies.
The remaining families to be dealt with are the two Crayfish families—
the Astacidae and the Parastacidae—which live in rapidly moving rivers
and streams, and occasionally in lakes. A few species of both families have
taken to a subterranean mode of life, and excavate burrows in the earth, e.g.
the Tasmanian Crayfish, Engaeus fossor. The distribution of the Crayfishes
has long engaged the attention of naturalists. It was first seriously studied
by Huxley,[174] and has subsequently been followed up, especially in North
America, by Faxon[175] and Ortmann,[176] but our knowledge of the South
American and Australian forms is still very incomplete. The Astacidae
inhabit the northern temperate hemisphere, the Parastacidae the southern
temperate hemisphere, the tropical belt being practically destitute of
Crayfishes. Of the Astacidae the genus Astacus (Potamobius), including the
common Crayfishes of Europe, occurs in Europe and in North America
west of the Rockies. The genus Cambaroides, which in certain respects
approaches Cambarus, is found in Japan and Eastern Asia. The very large
genus Cambarus, on the other hand, only occurs in North America east of
the Rockies, so that Cambaroides occupies a very isolated position. The
occurrence of a Cambarus, C. stygius, in the caves of Carniola, has been
recorded by Joseph, so that it would appear that this genus had a much
wider range formerly than now.
Of the southern temperate Parastacidae, Australia and Tasmania have the
genera Astacopsis and Engaeus; New Zealand has Paranephrops, South
America Parastacus, and Madagascar Astacoides. The last named genus is
rather isolated in its characters, possessing a truncated rostrum and a highly
modified branchial system, but it agrees with all the other Parastacine
genera, and differs from the Astacidae in the absence of sexual appendages
on the first abdominal segment, and in the absence of a distinct lamina on
the podobranchiae. The largest crayfish in the world is Astacopsis franklinii,
found in quite small streams on the north and west coast of Tasmania.
Specimens have been caught weighing eight or nine pounds, and rivalling
the European Lobster in size. Crayfishes appear to be entirely absent from
Africa.
Page 261
It seems reasonable to suppose that the two families of Crayfishes
characteristic respectively of the northern and southern hemispheres have
been independently derived from marine ancestors, which have
subsequently become extinct. Their complete absence in the tropics is
striking, and Huxley drew attention to the fact that it is exactly in those
regions where the Crayfishes are absent that the other large fresh-water
Malacostraca are particularly well developed, and vice versa. Thus the large
fresh-water Prawns are typically circumtropical in distribution, while the
South African rivers abound with River-crabs, which, in general, are found
wherever Crayfishes do not occur.
A few of the more interesting features in connection with the distribution
of fresh-water Crustacea have now been touched upon. With regard to the
origin of this fauna, we can see that a number of the species are
comparatively recent immigrants from the sea, working their way up the
estuaries of rivers, a proceeding which can be observed to be taking place
to-day in a district like the Broads of Norfolk. Others, again, but these are
few, appear to be true relict marine animals left stranded in arms of the sea
that have been cut off from the main ocean, and have been gradually
converted into fresh-water lakes and seas. Such are, perhaps, Mysis relicta
and the rich Gammarid fauna of Lake Baikal, a lake that, in the presence of
Seals, Sponges, and other marine forms, has clearly retained some of the
characters of the ocean from which it was derived. The majority of the
fresh-water species, however, have probably been evolved in situ, and their
origin from marine ancestors is lost in an obscure past. The Crustacean
fauna of the Caspian Sea[177] shows us in an interesting manner the effects of
isolation and changes in salinity, etc., on the inhabitants of a basin which
once formed part of the ocean. The waters of the Caspian Sea are not fresh,
but they are on the average about one-third as salt as that of the open ocean.
The Crustacea, described by Sars, belong to undoubtedly marine groups,
e.g. the Mysidae, Cumacea, and Amphipoda Crevettina, but the remarkable
feature of these Caspian Crustacea is the great variety of peculiar species
representing marine genera which are very poorly represented in the sea,
thus indicating that the variety of the fauna is not due to a great variety of
species having been shut up in the Caspian Sea to begin with, but rather
that, after the separation from the sea, the isolated species began to vary and
branch out in the most luxuriant way—whether from lack of competition or
owing to the changing conditions of salinity it is difficult to say. As an
characteristic respectively of the northern and southern hemispheres have
been independently derived from marine ancestors, which have
subsequently become extinct. Their complete absence in the tropics is
striking, and Huxley drew attention to the fact that it is exactly in those
regions where the Crayfishes are absent that the other large fresh-water
Malacostraca are particularly well developed, and vice versa. Thus the large
fresh-water Prawns are typically circumtropical in distribution, while the
South African rivers abound with River-crabs, which, in general, are found
wherever Crayfishes do not occur.
A few of the more interesting features in connection with the distribution
of fresh-water Crustacea have now been touched upon. With regard to the
origin of this fauna, we can see that a number of the species are
comparatively recent immigrants from the sea, working their way up the
estuaries of rivers, a proceeding which can be observed to be taking place
to-day in a district like the Broads of Norfolk. Others, again, but these are
few, appear to be true relict marine animals left stranded in arms of the sea
that have been cut off from the main ocean, and have been gradually
converted into fresh-water lakes and seas. Such are, perhaps, Mysis relicta
and the rich Gammarid fauna of Lake Baikal, a lake that, in the presence of
Seals, Sponges, and other marine forms, has clearly retained some of the
characters of the ocean from which it was derived. The majority of the
fresh-water species, however, have probably been evolved in situ, and their
origin from marine ancestors is lost in an obscure past. The Crustacean
fauna of the Caspian Sea[177] shows us in an interesting manner the effects of
isolation and changes in salinity, etc., on the inhabitants of a basin which
once formed part of the ocean. The waters of the Caspian Sea are not fresh,
but they are on the average about one-third as salt as that of the open ocean.
The Crustacea, described by Sars, belong to undoubtedly marine groups,
e.g. the Mysidae, Cumacea, and Amphipoda Crevettina, but the remarkable
feature of these Caspian Crustacea is the great variety of peculiar species
representing marine genera which are very poorly represented in the sea,
thus indicating that the variety of the fauna is not due to a great variety of
species having been shut up in the Caspian Sea to begin with, but rather
that, after the separation from the sea, the isolated species began to vary and
branch out in the most luxuriant way—whether from lack of competition or
owing to the changing conditions of salinity it is difficult to say. As an
Page 262
example, the Cumacea of the Caspian Sea are ten in number, all belonging
to peculiar genera related to Pseudocuma, except one species which is
included in that genus. These Caspian forms make up the Family
Pseudocumidae, which contains in addition only two marine forms of the
genus Pseudocuma (see p. 121). A very similar condition is found in the
numerous Amphipods of the Caspian Sea. Considering the enormous
changes that must have taken place in the distribution of land and water
even during Tertiary times, it is astonishing that the fresh waters of the
world do not contain more species in common with the ocean, but it must
be considered that the limited area and comparatively uniform conditions of
fresh-water lakes and streams would only permit a limited number of these
forms to survive which could most easily adapt themselves to the changed
conditions. And these would in all probability be the littoral species that
were in the habit of passing up into the brackish waters of estuaries and
lagoons, so that the uniform and limited nature of the fresh-water fauna can
be accounted for to a certain extent by this hypothesis.
We have seen in dealing with the marine Crustacea of the littoral zone
that the chief condition determining their distribution is temperature, and
that the world may be divided into three chief areas of distribution for these
animals, viz. the north temperate hemisphere, the tropics, and the south
temperate hemisphere. It seems that the same division holds good for fresh-
water Crustacea. We have already seen that the Crayfishes follow this rule,
being practically absent from the tropics, and represented in the two
temperate hemispheres by two distinct families, the Astacidae in the north
and the Parastacidae in the south. Characteristic of the tropical belt are the
absence of Crayfishes and the great development of Prawns and River-
crabs. In the case of Entomostraca the great majority of the genera are
cosmopolitan, especially those which live in small bodies of water liable to
dry up, because these forms always have special means of dissemination in
the shape of resting eggs which can be transported in a dry state by water-
birds and other agencies to great distances; but those genera which inhabit
large lakes are more confined in their distribution. The Copepod genus
Diaptomus, characteristic of lake-plankton, ranges all over the northern
hemisphere and into the tropics, but it is almost entirely replaced in the
southern hemisphere by the related but distinct genus Boeckella,[178] which
occurs in temperate South America, New Zealand, and southern Australia,
and was found by the author to be the chief inhabitant in the highland lakes
to peculiar genera related to Pseudocuma, except one species which is
included in that genus. These Caspian forms make up the Family
Pseudocumidae, which contains in addition only two marine forms of the
genus Pseudocuma (see p. 121). A very similar condition is found in the
numerous Amphipods of the Caspian Sea. Considering the enormous
changes that must have taken place in the distribution of land and water
even during Tertiary times, it is astonishing that the fresh waters of the
world do not contain more species in common with the ocean, but it must
be considered that the limited area and comparatively uniform conditions of
fresh-water lakes and streams would only permit a limited number of these
forms to survive which could most easily adapt themselves to the changed
conditions. And these would in all probability be the littoral species that
were in the habit of passing up into the brackish waters of estuaries and
lagoons, so that the uniform and limited nature of the fresh-water fauna can
be accounted for to a certain extent by this hypothesis.
We have seen in dealing with the marine Crustacea of the littoral zone
that the chief condition determining their distribution is temperature, and
that the world may be divided into three chief areas of distribution for these
animals, viz. the north temperate hemisphere, the tropics, and the south
temperate hemisphere. It seems that the same division holds good for fresh-
water Crustacea. We have already seen that the Crayfishes follow this rule,
being practically absent from the tropics, and represented in the two
temperate hemispheres by two distinct families, the Astacidae in the north
and the Parastacidae in the south. Characteristic of the tropical belt are the
absence of Crayfishes and the great development of Prawns and River-
crabs. In the case of Entomostraca the great majority of the genera are
cosmopolitan, especially those which live in small bodies of water liable to
dry up, because these forms always have special means of dissemination in
the shape of resting eggs which can be transported in a dry state by water-
birds and other agencies to great distances; but those genera which inhabit
large lakes are more confined in their distribution. The Copepod genus
Diaptomus, characteristic of lake-plankton, ranges all over the northern
hemisphere and into the tropics, but it is almost entirely replaced in the
southern hemisphere by the related but distinct genus Boeckella,[178] which
occurs in temperate South America, New Zealand, and southern Australia,
and was found by the author to be the chief inhabitant in the highland lakes
Page 263
and tarns of Tasmania, Diaptomus being entirely absent. Of the Cladocera
there are a number of pelagic genera (e.g. Leptodora, Holopedium,
Bythotrephes) entirely confined to the lakes of the northern hemisphere. The
distribution of Bosmina is interesting. This genus is distributed all over the
north temperate hemisphere in lakes and ponds of considerable size, not
liable to desiccation; in the New World it passes right through the tropics
into Patagonia,[179] the chain of the Andes doubtless permitting its migration.
In the tropics of the Old World it is unknown, but it turns up again, as the
author recently found, as a common constituent in the plankton of the
Tasmanian lakes. There is another instance of a group of Crustacea,
characteristic of the north temperate hemisphere, being entirely absent from
the tropics, at any rate of the Old World, but reappearing in the temperate
regions of Australasia. The commonest fresh-water Amphipods in this
region belong to the genus Neoniphargus, intermediate in its characters
between the northern Niphargus and Gammarus, but grading almost
completely into the latter. Both Niphargus and Gammarus are absolutely
unknown from the tropics, but whether, like Bosmina, they occur in the
Andes and temperate South America is not known; it seems, however,
probable that they have reached Southern Australia by way of South
America rather than through the tropics of Asia and Australia, where there
is no range of mountains to permit the migration of a group of animals
apparently dependent on a temperate climate. The other common fresh-
water Amphipod in temperate Australia and New Zealand is Chiltonia,
whose nearest ally is Hyalella from Lake Titicaca on the Andes, and
temperate South America.
The Anaspidacea and Phreatoicidae, which are so characteristic of
temperate Australia, and are generally of an Alpine habit, have never been
found in South America, but the Anaspidacea are represented by numerous
marine forms in the Permian and Carboniferous strata of the northern
hemisphere, so that it is probable that this group reached the southern
hemisphere from the north through America.
The distribution of the fresh-water Crustacea, therefore, in the temperate
southern hemisphere affords strong evidence in favour of the view that the
chief land-masses of this hemisphere, which are at present separated by
such vast stretches of deep ocean, were at no very remote epoch connected
in such a way as to permit of an intermixture of the temperate fauna of New
Zealand, Australia, and South America. While this connexion existed, a
there are a number of pelagic genera (e.g. Leptodora, Holopedium,
Bythotrephes) entirely confined to the lakes of the northern hemisphere. The
distribution of Bosmina is interesting. This genus is distributed all over the
north temperate hemisphere in lakes and ponds of considerable size, not
liable to desiccation; in the New World it passes right through the tropics
into Patagonia,[179] the chain of the Andes doubtless permitting its migration.
In the tropics of the Old World it is unknown, but it turns up again, as the
author recently found, as a common constituent in the plankton of the
Tasmanian lakes. There is another instance of a group of Crustacea,
characteristic of the north temperate hemisphere, being entirely absent from
the tropics, at any rate of the Old World, but reappearing in the temperate
regions of Australasia. The commonest fresh-water Amphipods in this
region belong to the genus Neoniphargus, intermediate in its characters
between the northern Niphargus and Gammarus, but grading almost
completely into the latter. Both Niphargus and Gammarus are absolutely
unknown from the tropics, but whether, like Bosmina, they occur in the
Andes and temperate South America is not known; it seems, however,
probable that they have reached Southern Australia by way of South
America rather than through the tropics of Asia and Australia, where there
is no range of mountains to permit the migration of a group of animals
apparently dependent on a temperate climate. The other common fresh-
water Amphipod in temperate Australia and New Zealand is Chiltonia,
whose nearest ally is Hyalella from Lake Titicaca on the Andes, and
temperate South America.
The Anaspidacea and Phreatoicidae, which are so characteristic of
temperate Australia, and are generally of an Alpine habit, have never been
found in South America, but the Anaspidacea are represented by numerous
marine forms in the Permian and Carboniferous strata of the northern
hemisphere, so that it is probable that this group reached the southern
hemisphere from the north through America.
The distribution of the fresh-water Crustacea, therefore, in the temperate
southern hemisphere affords strong evidence in favour of the view that the
chief land-masses of this hemisphere, which are at present separated by
such vast stretches of deep ocean, were at no very remote epoch connected
in such a way as to permit of an intermixture of the temperate fauna of New
Zealand, Australia, and South America. While this connexion existed, a
Page 264
certain number of forms characteristic of the northern hemisphere, which
had worked through the tropics by means of the Andes, were enabled to
reach temperate Australia and New Zealand. The existence of a coast-line
connecting the various isolated parts of the southern hemisphere would, of
course, also account for the community which exists between their littoral
marine fauna. It is impossible to enter here into the nature of this land-
connexion which is becoming more and more a necessary hypothesis for the
student of geographical distribution, whatever group of animals he may
choose, but it may be remarked that the connexion was probably by means
of rays of land passing up from an Antarctic continent to join the
southernmost projections of Tierra del Fuego, Tasmania, and New Zealand.
had worked through the tropics by means of the Andes, were enabled to
reach temperate Australia and New Zealand. The existence of a coast-line
connecting the various isolated parts of the southern hemisphere would, of
course, also account for the community which exists between their littoral
marine fauna. It is impossible to enter here into the nature of this land-
connexion which is becoming more and more a necessary hypothesis for the
student of geographical distribution, whatever group of animals he may
choose, but it may be remarked that the connexion was probably by means
of rays of land passing up from an Antarctic continent to join the
southernmost projections of Tierra del Fuego, Tasmania, and New Zealand.
Page 265
TRILOBITA
BY
HENRY WOODS, M.A.
St. John’s College, Cambridge, University Lecturer in Palaeozoology
BY
HENRY WOODS, M.A.
St. John’s College, Cambridge, University Lecturer in Palaeozoology
Page 266
CHAPTER VIII
TRILOBITA
Among the many interesting groups of fossils found in the Palaeozoic
deposits there is none which has attracted more attention than the Trilobites.
As early as 1698, Edward Lhwyd, Curator of the Ashmolean Museum in
Oxford, recorded in the Philosophical Transactions the discovery of
Trilobites in the neighbourhood of Llandeilo in South Wales; and of one of
his specimens he remarked that “it must be the Sceleton of a flat Fish.” In
the following year the same writer gave in his Lithophylacii Britannici
Ichnographia descriptions and figures of two Trilobites which are evidently
examples of the species now known as Ogygia buchi and Trinucleus
fimbriatus.
Although Trilobites differ so much from living Arthropods that it was
difficult to determine even whether they belonged to the Crustacea or the
Arachnida, yet one of the earliest writers, Dr. Cromwell Mortimer,
Secretary of the Royal Society (1753), recognised their resemblance to
Apus (see pp. 19–36). This view of their affinities was adopted by Linnaeus,
and has been supported by many later writers. Another early author,
Emanuel Mendez da Costa, thought that the Trilobites were related to the
Isopods, an opinion which has been held by some few zoologists of more
recent times.
The Trilobites form the only known Order of the Crustacea which has no
living representatives. They are found in the oldest known fossiliferous
deposits—the Lower Cambrian or Olenellus beds, where they are
represented by 19 genera belonging to the families Agnostidae,
Paradoxidae, Olenidae, and Conocephalidae. From the variety of forms
found and the state of development which they have reached, it is evident
that even at that remote period the group must have been of considerable
antiquity; but of its pre-Cambrian ancestors nothing is yet known;
consequently there is no direct evidence of the origin of the group.
TRILOBITA
Among the many interesting groups of fossils found in the Palaeozoic
deposits there is none which has attracted more attention than the Trilobites.
As early as 1698, Edward Lhwyd, Curator of the Ashmolean Museum in
Oxford, recorded in the Philosophical Transactions the discovery of
Trilobites in the neighbourhood of Llandeilo in South Wales; and of one of
his specimens he remarked that “it must be the Sceleton of a flat Fish.” In
the following year the same writer gave in his Lithophylacii Britannici
Ichnographia descriptions and figures of two Trilobites which are evidently
examples of the species now known as Ogygia buchi and Trinucleus
fimbriatus.
Although Trilobites differ so much from living Arthropods that it was
difficult to determine even whether they belonged to the Crustacea or the
Arachnida, yet one of the earliest writers, Dr. Cromwell Mortimer,
Secretary of the Royal Society (1753), recognised their resemblance to
Apus (see pp. 19–36). This view of their affinities was adopted by Linnaeus,
and has been supported by many later writers. Another early author,
Emanuel Mendez da Costa, thought that the Trilobites were related to the
Isopods, an opinion which has been held by some few zoologists of more
recent times.
The Trilobites form the only known Order of the Crustacea which has no
living representatives. They are found in the oldest known fossiliferous
deposits—the Lower Cambrian or Olenellus beds, where they are
represented by 19 genera belonging to the families Agnostidae,
Paradoxidae, Olenidae, and Conocephalidae. From the variety of forms
found and the state of development which they have reached, it is evident
that even at that remote period the group must have been of considerable
antiquity; but of its pre-Cambrian ancestors nothing is yet known;
consequently there is no direct evidence of the origin of the group.
Page 267
Trilobites form an important part of all the faunas of the Cambrian
system; they attain their greatest development in the Ordovician period,
after which they become less numerous; their decline is very marked in the
Devonian, in which nearly all the genera are but survivals from the Silurian
period; in the Carboniferous, evidence of approaching extinction is seen in
the small number of genera represented, all of which belong to one family
—the Proëtidae, in the relatively few species in each genus and in the small
size of the individuals of those species. In Europe no representatives of the
group appear to have survived the Carboniferous period, but in America one
form has been recorded from deposits of Permian age.
Trilobites seem to have been exclusively marine, since they are found
only in association with the remains of marine animals. Their range in depth
was evidently considerable, for they occur in many different kinds of
sediment, and were apparently able to live regardless of the nature of the
sea-floor—whether muddy, sandy, calcareous, or rocky. In some cases they
occur in deposits containing reef-building corals and other shallow water
animals; in others they are associated with organisms which lived at greater
depths. The group appears to have had a world-wide distribution, for the
remains of Trilobites are found in the Palaeozoic rocks of all countries.
Their range in size is considerable; for whilst a large proportion of the
species are about two or three inches in length, some, like Agnostus, are
only a quarter of an inch long, others are from ten to twenty inches long, the
largest forms including species of Paradoxides, Asaphus, Megalaspis,
Lichas, and Homalonotus.
The feature in a Trilobite which first attracts attention is the marked
division of the dorso-ventrally flattened body into a median or axial part,
and a lateral or pleural part on each side. It was this character that led
Walch, in 1771, to give the name by which the group is now known. The
axial part of the body contained the alimentary canal, as is shown by the
position of the mouth and anus, as well as by casts in mud of the canal
which are found in some specimens. The trilobation of the body is quite
distinct in the majority of Trilobites, but in a few genera belonging to the
Asaphidae and Calymenidae (Fig. 136) it becomes more or less completely
obsolete.
In most cases the only part of the Trilobite which is preserved is the
exoskeleton which covered the dorsal surface of the body. That skeleton
system; they attain their greatest development in the Ordovician period,
after which they become less numerous; their decline is very marked in the
Devonian, in which nearly all the genera are but survivals from the Silurian
period; in the Carboniferous, evidence of approaching extinction is seen in
the small number of genera represented, all of which belong to one family
—the Proëtidae, in the relatively few species in each genus and in the small
size of the individuals of those species. In Europe no representatives of the
group appear to have survived the Carboniferous period, but in America one
form has been recorded from deposits of Permian age.
Trilobites seem to have been exclusively marine, since they are found
only in association with the remains of marine animals. Their range in depth
was evidently considerable, for they occur in many different kinds of
sediment, and were apparently able to live regardless of the nature of the
sea-floor—whether muddy, sandy, calcareous, or rocky. In some cases they
occur in deposits containing reef-building corals and other shallow water
animals; in others they are associated with organisms which lived at greater
depths. The group appears to have had a world-wide distribution, for the
remains of Trilobites are found in the Palaeozoic rocks of all countries.
Their range in size is considerable; for whilst a large proportion of the
species are about two or three inches in length, some, like Agnostus, are
only a quarter of an inch long, others are from ten to twenty inches long, the
largest forms including species of Paradoxides, Asaphus, Megalaspis,
Lichas, and Homalonotus.
The feature in a Trilobite which first attracts attention is the marked
division of the dorso-ventrally flattened body into a median or axial part,
and a lateral or pleural part on each side. It was this character that led
Walch, in 1771, to give the name by which the group is now known. The
axial part of the body contained the alimentary canal, as is shown by the
position of the mouth and anus, as well as by casts in mud of the canal
which are found in some specimens. The trilobation of the body is quite
distinct in the majority of Trilobites, but in a few genera belonging to the
Asaphidae and Calymenidae (Fig. 136) it becomes more or less completely
obsolete.
In most cases the only part of the Trilobite which is preserved is the
exoskeleton which covered the dorsal surface of the body. That skeleton
Page 268
consists largely of calcareous
material, and shows in sections a
finely perforated structure. Generally
it is arched above, but in some cases
is only slightly convex; in outline it
is more or less oval. Three regions
can always be distinguished in the
body of a Trilobite—the head, the
thorax, and the abdomen or
pygidium.
The carapace which covers the
head is known as the cephalic shield
(Fig. 137, A, 1), and is commonly
more or less semicircular in outline,
but varies considerably in different
genera. Only in a few cases, as in
some species of Agnostus (Fig. 146),
is its length greater than its breadth.
The axial part of the cephalic shield,
called the “glabella” (Fig. 137, A, a),
is usually more convex than the
lateral parts (“cheeks” or “genae”),
and is separated from them by
longitudinal or axial furrows (b). The
shape of the glabella varies greatly; it
may be oblong, circular, semi-
Fig. 136.—Homalonotus delphinocephalus, cylindrical, pyriform, spherical, etc.
Green, × 1. Silurian. (After Zittel.) Its relative size likewise varies; thus
in Phacops cephalotes it expands in
front and forms the larger part of the head, whilst in Arethusina (Fig. 151,
B) it is narrow and short, being only about one-half of the length of the
head.
material, and shows in sections a
finely perforated structure. Generally
it is arched above, but in some cases
is only slightly convex; in outline it
is more or less oval. Three regions
can always be distinguished in the
body of a Trilobite—the head, the
thorax, and the abdomen or
pygidium.
The carapace which covers the
head is known as the cephalic shield
(Fig. 137, A, 1), and is commonly
more or less semicircular in outline,
but varies considerably in different
genera. Only in a few cases, as in
some species of Agnostus (Fig. 146),
is its length greater than its breadth.
The axial part of the cephalic shield,
called the “glabella” (Fig. 137, A, a),
is usually more convex than the
lateral parts (“cheeks” or “genae”),
and is separated from them by
longitudinal or axial furrows (b). The
shape of the glabella varies greatly; it
may be oblong, circular, semi-
Fig. 136.—Homalonotus delphinocephalus, cylindrical, pyriform, spherical, etc.
Green, × 1. Silurian. (After Zittel.) Its relative size likewise varies; thus
in Phacops cephalotes it expands in
front and forms the larger part of the head, whilst in Arethusina (Fig. 151,
B) it is narrow and short, being only about one-half of the length of the
head.
Page 269
Fig. 137.—Calymene tuberculata, Brünn. × 1. Silurian, Dudley. A, Dorsal
surface: 1, head; 2, thorax; 3, pygidium or abdomen. a, Glabella; b, axial furrow;
c, glabella-furrow; d, neck-furrow; e, fixed cheek; f, free cheek; g, facial suture;
h, eye; i, genal angle; k, axis of thorax; l, pleura. B, Ventral surface of head (after
Barrande): a, hypostome; b, doublure; c, c′, facial sutures; d, rostral suture; e,
rostral plate. C, One segment of the thorax: a, ring of axis; b, groove; c, articular
portion; d, axial furrow; d-f, pleura; d-e, internal part of pleura; e-f, external part
of pleura; e, fulcrum; g, groove. D, Coiled specimen: a, glabella; b, eye; c, facial
suture; d, pygidium; e, rostral suture; f, continuation of facial suture.
The segmentation of the head is indicated by transverse furrows on the
glabella (Fig. 137, A, c, d). In some cases these furrows extend quite across
the glabella (Fig. 147), but commonly they are found on the sides only and
divide the glabella into lateral lobes. Only the posterior or “neck-furrow”
(Fig. 137, A, d) is continued on to the cheeks, and the segment which it
limits anteriorly on the glabella[180] is known as the occipital or neck-ring. In
front of the neck-furrow there may be three other furrows, so that altogether
five cephalic segments are indicated by the furrows of the glabella.
Commonly all the furrows are distinct in the primitive types; but in the
more modified forms some, especially the anterior, become either reduced
in size or obsolete. The actual number of furrows present consequently
surface: 1, head; 2, thorax; 3, pygidium or abdomen. a, Glabella; b, axial furrow;
c, glabella-furrow; d, neck-furrow; e, fixed cheek; f, free cheek; g, facial suture;
h, eye; i, genal angle; k, axis of thorax; l, pleura. B, Ventral surface of head (after
Barrande): a, hypostome; b, doublure; c, c′, facial sutures; d, rostral suture; e,
rostral plate. C, One segment of the thorax: a, ring of axis; b, groove; c, articular
portion; d, axial furrow; d-f, pleura; d-e, internal part of pleura; e-f, external part
of pleura; e, fulcrum; g, groove. D, Coiled specimen: a, glabella; b, eye; c, facial
suture; d, pygidium; e, rostral suture; f, continuation of facial suture.
The segmentation of the head is indicated by transverse furrows on the
glabella (Fig. 137, A, c, d). In some cases these furrows extend quite across
the glabella (Fig. 147), but commonly they are found on the sides only and
divide the glabella into lateral lobes. Only the posterior or “neck-furrow”
(Fig. 137, A, d) is continued on to the cheeks, and the segment which it
limits anteriorly on the glabella[180] is known as the occipital or neck-ring. In
front of the neck-furrow there may be three other furrows, so that altogether
five cephalic segments are indicated by the furrows of the glabella.
Commonly all the furrows are distinct in the primitive types; but in the
more modified forms some, especially the anterior, become either reduced
in size or obsolete. The actual number of furrows present consequently
Page 270
varies in different genera, and may even differ in different species of the
same genus. In a few genera all the furrows are either indistinct or absent,
as for example in Ellipsocephalus (Fig. 150, B). In some cases four furrows
are present in addition to the neck-furrow; this is due to the division of the
anterior lobe of the glabella by fulcra which are developed for the
attachment of muscles.
When the glabella reaches the front border of the head the two cheeks are
separated (Fig. 150, I); but in other cases they unite in front of the glabella
(Fig. 150, C). The outer posterior angle of the cheeks or genae (“genal
angle,” Fig. 137, A, i) may be rounded, pointed, or produced into
backwardly directed spines (Fig. 140). The marginal part of the cephalic
shield is often flattened or concave; this border may be quite a narrow rim
as in Calymene (Fig. 137, A), but in some genera (e.g. Trinucleus, Fig. 140,
B; Harpes, Fig. 150, A; Asaphus) it attains a great development. Each cheek
is usually divided by a suture—the “facial suture” (Fig. 137, A, g)—into an
inner and an outer part; the former is the “fixed cheek” (e), and the latter the
“free cheek” (f). The course of the facial suture varies in different genera:
on the posterior part of the head it begins either at the posterior margin (Fig.
150, C) or at the posterior part of the lateral margin (Fig. 151, C, D); at first
it is directed inwards, and then bends forward, forming an angle. In front it
may (a) end at the front margin (Fig. 147), or (b) be united beneath the front
margin by a rostral suture (Fig. 137, B, d, D, e), or (c) unite with the other
suture on the dorsal surface in front of the glabella (Fig. 151, C). In the last
case the free cheeks also unite in front of the glabella.
The facial suture is one of the distinguishing features of the Trilobites,
and may have been of some use in ecdysis. In only a few forms is it absent,
as for example in Agnostus (Fig. 146) and Microdiscus. In the former,
however, Beecher states that a suture is really present, but, unlike that of
most other Trilobites, it is situated at the margin of the cephalic shield, and
consequently the free cheek, if present, must be on the ventral surface.
Lindström and Holm, after a re-examination of well-preserved specimens,
deny the existence of a suture in Agnostus. By most authors Olenellus is
said to be without a suture, but Beecher maintains that although the fixed
and free cheeks have coalesced, yet a raised line passing from the eye-lobe
to the posterior margin marks the position of the suture; this view is not
accepted by Lindström.
same genus. In a few genera all the furrows are either indistinct or absent,
as for example in Ellipsocephalus (Fig. 150, B). In some cases four furrows
are present in addition to the neck-furrow; this is due to the division of the
anterior lobe of the glabella by fulcra which are developed for the
attachment of muscles.
When the glabella reaches the front border of the head the two cheeks are
separated (Fig. 150, I); but in other cases they unite in front of the glabella
(Fig. 150, C). The outer posterior angle of the cheeks or genae (“genal
angle,” Fig. 137, A, i) may be rounded, pointed, or produced into
backwardly directed spines (Fig. 140). The marginal part of the cephalic
shield is often flattened or concave; this border may be quite a narrow rim
as in Calymene (Fig. 137, A), but in some genera (e.g. Trinucleus, Fig. 140,
B; Harpes, Fig. 150, A; Asaphus) it attains a great development. Each cheek
is usually divided by a suture—the “facial suture” (Fig. 137, A, g)—into an
inner and an outer part; the former is the “fixed cheek” (e), and the latter the
“free cheek” (f). The course of the facial suture varies in different genera:
on the posterior part of the head it begins either at the posterior margin (Fig.
150, C) or at the posterior part of the lateral margin (Fig. 151, C, D); at first
it is directed inwards, and then bends forward, forming an angle. In front it
may (a) end at the front margin (Fig. 147), or (b) be united beneath the front
margin by a rostral suture (Fig. 137, B, d, D, e), or (c) unite with the other
suture on the dorsal surface in front of the glabella (Fig. 151, C). In the last
case the free cheeks also unite in front of the glabella.
The facial suture is one of the distinguishing features of the Trilobites,
and may have been of some use in ecdysis. In only a few forms is it absent,
as for example in Agnostus (Fig. 146) and Microdiscus. In the former,
however, Beecher states that a suture is really present, but, unlike that of
most other Trilobites, it is situated at the margin of the cephalic shield, and
consequently the free cheek, if present, must be on the ventral surface.
Lindström and Holm, after a re-examination of well-preserved specimens,
deny the existence of a suture in Agnostus. By most authors Olenellus is
said to be without a suture, but Beecher maintains that although the fixed
and free cheeks have coalesced, yet a raised line passing from the eye-lobe
to the posterior margin marks the position of the suture; this view is not
accepted by Lindström.
Page 271
The existence of a facial suture in Trinucleus has likewise been disputed.
But Emmerich, Salter, and M‘Coy[181] have maintained that a suture is
present in a normal position on the dorsal surface, extending from the
posterior margin just within the genal angle to the eye (when present), and
from thence bending forward and ending on the front margin near the
glabella. It must be admitted that no indications of the suture are seen in the
majority of specimens, perhaps owing to the fact that most examples of
Trinucleus are in the form of internal casts; perhaps also to the more or less
complete coalescence of the fixed and free cheeks, since in no specimen has
the free cheek been found separated from the rest of the head, as occurs not
uncommonly in many other Trilobites. The probability of the existence of a
suture receives some support from the fact that one is found in the allied
genera Orometopus and Ampyx (Fig. 140). Barrande and Oehlert deny its
existence in Trinucleus. There is, however, in that genus a suture running
close to the margin of the cephalic border,[182] and joining the genal angle so
as to cut off the genal spine. Lovén and Oehlert claim that this suture
represents the facial suture, but in an abnormal position; this view, however,
is not accepted by Beyrich. In this connection it should be noted that in
Acidaspis, whilst the majority of the species possess a facial suture, there
are two in which it has disappeared owing to the fusion of the fixed and free
cheeks. Such being the case, it seems not improbable that the curved line
passing backwards from the eye in Harpes may mark the position of the
suture; but it is stated that the only suture present in that form runs at the
margin of the cephalic border, and is similar to that of Trinucleus. This
matter will be referred to again when discussing the nature of the eyes in
Trinucleus and Harpes.
The relative sizes of the fixed and free cheeks obviously depend on the
position of the facial suture; when this starts on the lateral margin of the
cephalic shield and passes forward to the outer part of the front margin, the
free cheek will be a narrow strip; when, on the other hand, the suture starts
from the posterior margin and runs close to the glabella, the free cheek will
be relatively large and the fixed cheek narrow. The fixed cheek is small in
Phacops, Cheirurus, and Illaenus; relatively large in Remopleurides,
Phillipsia, and Stygina. It was suggested by M‘Coy[183] that the free cheek
represents the pleura of an anterior segment which has not become fused
with the other cephalic pleurae. The fixed cheek appears to be formed of the
coalesced pleurae of the other cephalic segments, but of those pleurae the
But Emmerich, Salter, and M‘Coy[181] have maintained that a suture is
present in a normal position on the dorsal surface, extending from the
posterior margin just within the genal angle to the eye (when present), and
from thence bending forward and ending on the front margin near the
glabella. It must be admitted that no indications of the suture are seen in the
majority of specimens, perhaps owing to the fact that most examples of
Trinucleus are in the form of internal casts; perhaps also to the more or less
complete coalescence of the fixed and free cheeks, since in no specimen has
the free cheek been found separated from the rest of the head, as occurs not
uncommonly in many other Trilobites. The probability of the existence of a
suture receives some support from the fact that one is found in the allied
genera Orometopus and Ampyx (Fig. 140). Barrande and Oehlert deny its
existence in Trinucleus. There is, however, in that genus a suture running
close to the margin of the cephalic border,[182] and joining the genal angle so
as to cut off the genal spine. Lovén and Oehlert claim that this suture
represents the facial suture, but in an abnormal position; this view, however,
is not accepted by Beyrich. In this connection it should be noted that in
Acidaspis, whilst the majority of the species possess a facial suture, there
are two in which it has disappeared owing to the fusion of the fixed and free
cheeks. Such being the case, it seems not improbable that the curved line
passing backwards from the eye in Harpes may mark the position of the
suture; but it is stated that the only suture present in that form runs at the
margin of the cephalic border, and is similar to that of Trinucleus. This
matter will be referred to again when discussing the nature of the eyes in
Trinucleus and Harpes.
The relative sizes of the fixed and free cheeks obviously depend on the
position of the facial suture; when this starts on the lateral margin of the
cephalic shield and passes forward to the outer part of the front margin, the
free cheek will be a narrow strip; when, on the other hand, the suture starts
from the posterior margin and runs close to the glabella, the free cheek will
be relatively large and the fixed cheek narrow. The fixed cheek is small in
Phacops, Cheirurus, and Illaenus; relatively large in Remopleurides,
Phillipsia, and Stygina. It was suggested by M‘Coy[183] that the free cheek
represents the pleura of an anterior segment which has not become fused
with the other cephalic pleurae. The fixed cheek appears to be formed of the
coalesced pleurae of the other cephalic segments, but of those pleurae the
Page 272
only indication seen in adult specimens is in the neck-ring; in young
specimens of Olenellus, however, the presence of other pleurae is indicated
by furrows on the cheeks in front of the neck-furrow.
A pair of compound eyes are
present in the majority of Trilobites.
Each eye is situated on the free
cheek, at that part of its inner margin
where the facial suture bends to form
an angle (Figs. 137, A, h, 138). The
position of the eye is consequently
determined by the position of the
facial suture; it may be near the
glabella or near the lateral margin of
the head, and either as far forward as Fig. 138.—Phacops latifrons, Bronn, × 1.
the first segment of the glabella or Devonian. Showing large compound eye. (After
Zittel.)
nearly as far back as the neck-furrow.
In many Trilobites the eye is more or
less conical, with its summit truncated or rounded, but in some genera it is
ovoid, or crescentic. In Aeglina (Fig. 150, H) the eye is flattened and
scarcely raised above the general level of the cheek. The eye of a Trilobite
is oriented so that its longer axis is parallel or nearly parallel to the axis of
the body (Fig. 150, G); but in one case (Encrinurus intercostatus) it is
placed at right angles to this axis. The size of the eye varies considerably; it
is largest in Aeglina, in which it covers nearly the whole of the free cheek; it
is small in Acidaspis and Encrinurus.
Though the eye is always entirely on the free cheek, the adjoining part of
the fixed cheek is raised to form a buttress on which the eye rests; this
buttress, which is known as the “palpebral lobe,” is seen clearly when the
fixed cheek is removed. The eyes of Trilobites are always sessile; for
although in some species, such as Asaphus cornigerus, A. kowalewskii, and
Encrinurus punctatus, they are on the summits of prominent stalks, yet
those stalks are immovable.
Three types of compound eye have been recognised in Trilobites[184]—
holochroal, prismatic, and schizochroal.
specimens of Olenellus, however, the presence of other pleurae is indicated
by furrows on the cheeks in front of the neck-furrow.
A pair of compound eyes are
present in the majority of Trilobites.
Each eye is situated on the free
cheek, at that part of its inner margin
where the facial suture bends to form
an angle (Figs. 137, A, h, 138). The
position of the eye is consequently
determined by the position of the
facial suture; it may be near the
glabella or near the lateral margin of
the head, and either as far forward as Fig. 138.—Phacops latifrons, Bronn, × 1.
the first segment of the glabella or Devonian. Showing large compound eye. (After
Zittel.)
nearly as far back as the neck-furrow.
In many Trilobites the eye is more or
less conical, with its summit truncated or rounded, but in some genera it is
ovoid, or crescentic. In Aeglina (Fig. 150, H) the eye is flattened and
scarcely raised above the general level of the cheek. The eye of a Trilobite
is oriented so that its longer axis is parallel or nearly parallel to the axis of
the body (Fig. 150, G); but in one case (Encrinurus intercostatus) it is
placed at right angles to this axis. The size of the eye varies considerably; it
is largest in Aeglina, in which it covers nearly the whole of the free cheek; it
is small in Acidaspis and Encrinurus.
Though the eye is always entirely on the free cheek, the adjoining part of
the fixed cheek is raised to form a buttress on which the eye rests; this
buttress, which is known as the “palpebral lobe,” is seen clearly when the
fixed cheek is removed. The eyes of Trilobites are always sessile; for
although in some species, such as Asaphus cornigerus, A. kowalewskii, and
Encrinurus punctatus, they are on the summits of prominent stalks, yet
those stalks are immovable.
Three types of compound eye have been recognised in Trilobites[184]—
holochroal, prismatic, and schizochroal.
Page 273
Fig. 139.—Eyes of Trilobites. (After Lindström.) A, B, Sphaerophthalmus
alatus, Ang. Upper Cambrian. Vertical and horizontal sections, × 100. C,
Asaphus fallax, Dalm. Horizontal section, × 60. D, Nileus armadillo, Dalm.
Vertical section, × 60, a, prismatic lenses; b, cuticle; c, part of free cheek. E,
Dalmanites vulgaris, Salt. Part of eye, × 30. F, Dalmanites imbricatulus, Ang.
Vertical section of eye, with a part of the free cheek on the left, × 60. G, H,
Harpes vittatus, Barr. G, The two lenses of one eye, × 8; H, vertical section of
the same, × 60.
1. In the holochroal eye (Fig. 139, A, B) the lenses are globular or
biconvex and close together, so that the cornea is continuous over the entire
eye. Examples of this are seen in Bronteus and Sphaerophthalmus.
2. In the prismatic type (Fig. 139, C, D) the lenses are prismatic and
plano-convex, and the entire surface of the eye is covered by a smooth
cuticle. The lenses are close together and usually hexagonal, but
occasionally rhombic or square. Near the margin of the eye the lenses may
alatus, Ang. Upper Cambrian. Vertical and horizontal sections, × 100. C,
Asaphus fallax, Dalm. Horizontal section, × 60. D, Nileus armadillo, Dalm.
Vertical section, × 60, a, prismatic lenses; b, cuticle; c, part of free cheek. E,
Dalmanites vulgaris, Salt. Part of eye, × 30. F, Dalmanites imbricatulus, Ang.
Vertical section of eye, with a part of the free cheek on the left, × 60. G, H,
Harpes vittatus, Barr. G, The two lenses of one eye, × 8; H, vertical section of
the same, × 60.
1. In the holochroal eye (Fig. 139, A, B) the lenses are globular or
biconvex and close together, so that the cornea is continuous over the entire
eye. Examples of this are seen in Bronteus and Sphaerophthalmus.
2. In the prismatic type (Fig. 139, C, D) the lenses are prismatic and
plano-convex, and the entire surface of the eye is covered by a smooth
cuticle. The lenses are close together and usually hexagonal, but
occasionally rhombic or square. Near the margin of the eye the lenses may
Page 274
become irregular, giving rise to a border in which the prismatic structure is
more or less indistinct. The prismatic type of eye is found in the genera
Asaphus, Nileus, Illaenus, etc.
3. The schizochroal eye occurs only in the family Phacopidae (Fig. 139,
E, F). The lenses are biconvex and are separated by portions of the cephalic
shield, so that each lens appears to rest in a separate socket, and the cornea
is not continuous for the entire eye. The lenses are circular in outline, but
owing to the upward and inward growth of the interstitial test they may
appear, on the surface, to be hexagonal. The diameter of a lens may be as
much as 0·5 mm. The crystalline cones have not been preserved. In
specimens of Phacops rana, in which the inner face of the lens is more
convex than the outer, J. M. Clarke[185] has obtained evidence of a posterior
spheroidal cavity in addition to the anterior corneal cavity. The complete
separation of the lenses in this type of eye has led to the suggestion that the
schizochroal eye is an aggregate rather than a compound eye. But the
difference between this and the holochroal eye is probably less than appears
at first sight if the statement made by Clarke is confirmed, namely, that in
young specimens of Calymene senaria the lenses are relatively large and
similar to those of Phacops, whereas in the adult the eye is holochroal.
These three types of eye, according to Lindström, have appeared
successively in chronological order: the prismatic occurring first in the
Olenus beds (Upper Cambrian), the holochroal first in the Ceratopyge
Limestone (Uppermost Cambrian), and the schizochroal first in the
Ordovician. The number of lenses in the eye varies greatly. For example, in
Trimerocephalus volborthi there are 14 only, whilst in Remopleurides
radians there are as many as 15,000. Even in different species of the same
genus there may be considerable differences. Thus Bronteus brongniarti
possesses 1000, B. palifer 4000, lenses in each eye. The number increases
from the young up to the adult, but decreases in old age. The lenses are
usually arranged in alternating rows. In Trilobites with a conical eye the
outer segment of the cone bears the visual surface. It has been stated that
the eyes of Trilobites resemble those of Isopods,[186] but close comparison is
difficult to make, since in Trilobites no part of the eye beneath the lenses is
preserved. In some genera a threadlike ridge, called the “eye-line,” passes
from the glabella, generally from the front segment, to the eye, where it
often ends in the palpebral lobe; this eye-line is found in nearly all genera
which are confined to the Cambrian period, and persists in a few of later
more or less indistinct. The prismatic type of eye is found in the genera
Asaphus, Nileus, Illaenus, etc.
3. The schizochroal eye occurs only in the family Phacopidae (Fig. 139,
E, F). The lenses are biconvex and are separated by portions of the cephalic
shield, so that each lens appears to rest in a separate socket, and the cornea
is not continuous for the entire eye. The lenses are circular in outline, but
owing to the upward and inward growth of the interstitial test they may
appear, on the surface, to be hexagonal. The diameter of a lens may be as
much as 0·5 mm. The crystalline cones have not been preserved. In
specimens of Phacops rana, in which the inner face of the lens is more
convex than the outer, J. M. Clarke[185] has obtained evidence of a posterior
spheroidal cavity in addition to the anterior corneal cavity. The complete
separation of the lenses in this type of eye has led to the suggestion that the
schizochroal eye is an aggregate rather than a compound eye. But the
difference between this and the holochroal eye is probably less than appears
at first sight if the statement made by Clarke is confirmed, namely, that in
young specimens of Calymene senaria the lenses are relatively large and
similar to those of Phacops, whereas in the adult the eye is holochroal.
These three types of eye, according to Lindström, have appeared
successively in chronological order: the prismatic occurring first in the
Olenus beds (Upper Cambrian), the holochroal first in the Ceratopyge
Limestone (Uppermost Cambrian), and the schizochroal first in the
Ordovician. The number of lenses in the eye varies greatly. For example, in
Trimerocephalus volborthi there are 14 only, whilst in Remopleurides
radians there are as many as 15,000. Even in different species of the same
genus there may be considerable differences. Thus Bronteus brongniarti
possesses 1000, B. palifer 4000, lenses in each eye. The number increases
from the young up to the adult, but decreases in old age. The lenses are
usually arranged in alternating rows. In Trilobites with a conical eye the
outer segment of the cone bears the visual surface. It has been stated that
the eyes of Trilobites resemble those of Isopods,[186] but close comparison is
difficult to make, since in Trilobites no part of the eye beneath the lenses is
preserved. In some genera a threadlike ridge, called the “eye-line,” passes
from the glabella, generally from the front segment, to the eye, where it
often ends in the palpebral lobe; this eye-line is found in nearly all genera
which are confined to the Cambrian period, and persists in a few of later
Page 275
date, as for example in Triarthrus, Euloma, and some species of Calymene
from the Ordovician; in Arethusina and Acidaspis from the Silurian; and in
Harpes from the Devonian (Fig. 150, A).
In Harpes and in some species of
Trinucleus eyes are present, but have
been stated to be of a different type.
They are described as simple eyes,
and have been compared with ocelli;
they are never found in Trilobites
which possess the compound eyes
described above. In Harpes (Fig.
150, A) the eye is near the middle of
the cheek, in the position where
compound eyes occur in other
genera; it appears to consist of two or
three granules or tubercles which are
Fig. 140.—Trinucleidae. A, Orometopus really lenses, and is connected with
elatifrons, Ang. × 5. Restoration based on
specimens from the Upper Cambrian the front of the glabella by an eye-
(Tremadoc) of Shineton, Shropshire. B, line. No facial suture can be seen,
Trinucleus bucklandi, Barr. Ordovician, consequently the whole of the cheek
Bohemia. A complete but not fully-grown [187]
individual showing eyes. Natural size. (After is stated to be the fixed cheek. In
Barrande.) C, Ampyx rouaulti, Barr. × 3. Trinucleus (Fig. 140, B) a single
Ordovician, Bohemia. (After Barrande.) tubercle is found on the middle of the
cheek in the young of some species,
and is sometimes connected with the glabella by an eye-line; the latter
disappears before the adult state is reached, and in some species the tubercle
also disappears, but in others (such as T. seticornis, T. bucklandi) it persists
in the adult individuals.
From the lateral position of these eyes they can hardly be compared with
the median simple eye of other Crustacea. In Harpes it is more probable
that, as suggested by J. M. Clarke, they are schizochroal eyes imperfectly
developed. Their structure (Fig. 139, G, H) is somewhat similar to that of
schizochroal eyes, and moreover, in one species, H. macrocephalus,[188]
there are, in addition to the three main tubercles, other smaller tubercles in
regular rows. Further, the eye-line occupies the same position as in other
Trilobites which have undoubted compound eyes. The absence of a facial
suture cannot be taken as evidence against these eyes being of the ordinary
from the Ordovician; in Arethusina and Acidaspis from the Silurian; and in
Harpes from the Devonian (Fig. 150, A).
In Harpes and in some species of
Trinucleus eyes are present, but have
been stated to be of a different type.
They are described as simple eyes,
and have been compared with ocelli;
they are never found in Trilobites
which possess the compound eyes
described above. In Harpes (Fig.
150, A) the eye is near the middle of
the cheek, in the position where
compound eyes occur in other
genera; it appears to consist of two or
three granules or tubercles which are
Fig. 140.—Trinucleidae. A, Orometopus really lenses, and is connected with
elatifrons, Ang. × 5. Restoration based on
specimens from the Upper Cambrian the front of the glabella by an eye-
(Tremadoc) of Shineton, Shropshire. B, line. No facial suture can be seen,
Trinucleus bucklandi, Barr. Ordovician, consequently the whole of the cheek
Bohemia. A complete but not fully-grown [187]
individual showing eyes. Natural size. (After is stated to be the fixed cheek. In
Barrande.) C, Ampyx rouaulti, Barr. × 3. Trinucleus (Fig. 140, B) a single
Ordovician, Bohemia. (After Barrande.) tubercle is found on the middle of the
cheek in the young of some species,
and is sometimes connected with the glabella by an eye-line; the latter
disappears before the adult state is reached, and in some species the tubercle
also disappears, but in others (such as T. seticornis, T. bucklandi) it persists
in the adult individuals.
From the lateral position of these eyes they can hardly be compared with
the median simple eye of other Crustacea. In Harpes it is more probable
that, as suggested by J. M. Clarke, they are schizochroal eyes imperfectly
developed. Their structure (Fig. 139, G, H) is somewhat similar to that of
schizochroal eyes, and moreover, in one species, H. macrocephalus,[188]
there are, in addition to the three main tubercles, other smaller tubercles in
regular rows. Further, the eye-line occupies the same position as in other
Trilobites which have undoubted compound eyes. The absence of a facial
suture cannot be taken as evidence against these eyes being of the ordinary
Page 276
type, since in some species of Acidaspis (e.g. A. verneuili, A. vesiculosa)
which possess compound eyes there is, in consequence of the coalescence
of the fixed and free cheeks, no suture.
In some species of Trinucleus (Fig. 140, B) the simple eye is found in the
same position as the eye in Harpes, and if, as some writers have
maintained, there is evidence of the existence of a suture in that genus, then
there is no reason for regarding the eye as other than a degenerate form of
compound eye. The probability of its being such is supported by the
existence of a compound eye in a similar position in the allied form
Orometopus (Fig. 140, A) which possesses a facial suture.
In some species of Trinucleus (Fig. 140, B) and Ampyx there is a small
median tubercle on the front part of the glabella, which from its position
may be a simple unpaired eye, but its structure appears to be unknown.
Some Trilobites possess no eyes. Well-known examples of such are
Agnostus, Microdiscus, Ampyx, Conocoryphe, and some species of Illaenus
and Trinucleus; such blind Trilobites are almost confined to the Cambrian
and Ordovician periods. All the forms of later periods, with the exception of
a species of Ampyx, and possibly one or two other species, possess eyes. In
addition to those undoubtedly blind forms Lindström considers that most of
the Olenidae and Paradoxidae were without eyes. Many of the members of
these families possess a lobe closely resembling a palpebral lobe, and a
corresponding excavation in the free cheek; such forms have been generally
regarded as possessing eyes; and the absence of any indication of lenses in
those cases, on which Lindström lays stress, has been explained by the
comparatively imperfect preservation of these early Trilobites. The
development of the supposed eye-lobe in some of the Paradoxidae and
Olenidae differs from that of the eyes in other families of Trilobites. In the
latter the eye appears first at the margin of the head and always in
connexion with the facial suture. But in Olenellus, in which there is said to
be no facial suture, development shows that the crescentic eye-like lobe
(Fig. 145, E) is really of the nature of a pleura coming off from the base of
the first segment of the glabella. In Paradoxides, which resembles
Olenellus in many respects, a facial suture is present and forms the outer
boundary of the eye-like lobe, but it is developed subsequently to the
appearance of the latter, which seems to be similar to that of Olenellus. In
some genera of the Olenidae the eye-line, which comes off from the first
which possess compound eyes there is, in consequence of the coalescence
of the fixed and free cheeks, no suture.
In some species of Trinucleus (Fig. 140, B) the simple eye is found in the
same position as the eye in Harpes, and if, as some writers have
maintained, there is evidence of the existence of a suture in that genus, then
there is no reason for regarding the eye as other than a degenerate form of
compound eye. The probability of its being such is supported by the
existence of a compound eye in a similar position in the allied form
Orometopus (Fig. 140, A) which possesses a facial suture.
In some species of Trinucleus (Fig. 140, B) and Ampyx there is a small
median tubercle on the front part of the glabella, which from its position
may be a simple unpaired eye, but its structure appears to be unknown.
Some Trilobites possess no eyes. Well-known examples of such are
Agnostus, Microdiscus, Ampyx, Conocoryphe, and some species of Illaenus
and Trinucleus; such blind Trilobites are almost confined to the Cambrian
and Ordovician periods. All the forms of later periods, with the exception of
a species of Ampyx, and possibly one or two other species, possess eyes. In
addition to those undoubtedly blind forms Lindström considers that most of
the Olenidae and Paradoxidae were without eyes. Many of the members of
these families possess a lobe closely resembling a palpebral lobe, and a
corresponding excavation in the free cheek; such forms have been generally
regarded as possessing eyes; and the absence of any indication of lenses in
those cases, on which Lindström lays stress, has been explained by the
comparatively imperfect preservation of these early Trilobites. The
development of the supposed eye-lobe in some of the Paradoxidae and
Olenidae differs from that of the eyes in other families of Trilobites. In the
latter the eye appears first at the margin of the head and always in
connexion with the facial suture. But in Olenellus, in which there is said to
be no facial suture, development shows that the crescentic eye-like lobe
(Fig. 145, E) is really of the nature of a pleura coming off from the base of
the first segment of the glabella. In Paradoxides, which resembles
Olenellus in many respects, a facial suture is present and forms the outer
boundary of the eye-like lobe, but it is developed subsequently to the
appearance of the latter, which seems to be similar to that of Olenellus. In
some genera of the Olenidae the eye-line, which comes off from the first
Page 277
segment of the glabella, ends in some cases in a swelling or knob which has
hitherto been regarded as a palpebral lobe, but according to Lindström’s
view no trace of an eye has been found in connexion with that lobe, nor is
there any space between the lobe and the free cheek in which the eye could
have occurred. If this view is correct it follows that the majority of the
Cambrian Trilobites were blind. The earliest genus with eyes would then be
Eurycare found in the Olenus beds of the Upper Cambrian.
Sphaerophthalmus and Ctenopyge, found in the higher beds of the
Cambrian, also possessed eyes, but Olenus and Parabolina were probably
blind.
On the ventral surface of the head there is a flat rim around the margin
(Fig. 137, B, b); this rim or “doublure” is the reflexed border of the cephalic
shield. In many Trilobites its median part in front is cut off by sutures so as
to form a separate plate (e); such is the case when the two facial sutures (c,
c′) cut the anterior margin of the cephalic shield and are continued across
the doublure, where they are joined by a transverse or rostral suture (d) just
below the margin. When, however, as in Phacops and Remopleurides, the
two facial sutures unite on the dorsal surface, in front of the glabella, the
median part of the doublure is not separated from the lateral parts, or from
the dorsal part of the cephalic shield.
Fig. 141.—A, Hypostome of Bronteus polyactin, Ang. showing maculae, × 4. B,
Left macula of Bronteus irradians, Lindst. × 12. (After Lindström.)
The “labrum” or “hypostome” is attached to the doublure in front (Fig.
137, B, a); it is commonly an oval or shield-shaped plate, but is
occasionally nearly square. Its surface is sometimes divided into two or
hitherto been regarded as a palpebral lobe, but according to Lindström’s
view no trace of an eye has been found in connexion with that lobe, nor is
there any space between the lobe and the free cheek in which the eye could
have occurred. If this view is correct it follows that the majority of the
Cambrian Trilobites were blind. The earliest genus with eyes would then be
Eurycare found in the Olenus beds of the Upper Cambrian.
Sphaerophthalmus and Ctenopyge, found in the higher beds of the
Cambrian, also possessed eyes, but Olenus and Parabolina were probably
blind.
On the ventral surface of the head there is a flat rim around the margin
(Fig. 137, B, b); this rim or “doublure” is the reflexed border of the cephalic
shield. In many Trilobites its median part in front is cut off by sutures so as
to form a separate plate (e); such is the case when the two facial sutures (c,
c′) cut the anterior margin of the cephalic shield and are continued across
the doublure, where they are joined by a transverse or rostral suture (d) just
below the margin. When, however, as in Phacops and Remopleurides, the
two facial sutures unite on the dorsal surface, in front of the glabella, the
median part of the doublure is not separated from the lateral parts, or from
the dorsal part of the cephalic shield.
Fig. 141.—A, Hypostome of Bronteus polyactin, Ang. showing maculae, × 4. B,
Left macula of Bronteus irradians, Lindst. × 12. (After Lindström.)
The “labrum” or “hypostome” is attached to the doublure in front (Fig.
137, B, a); it is commonly an oval or shield-shaped plate, but is
occasionally nearly square. Its surface is sometimes divided into two or
Page 278
three areas by shallow transverse grooves (Fig. 141, A), Just behind the
middle of the hypostome, or when transverse grooves are present either in
or near the anterior groove, there are often found a pair of small patches or
“maculae” which are more or less oval or elliptical in outline (Fig. 141).
The maculae may be (1) surrounded by a raised border, or (2) in the form of
pits, or (3) raised like tubercles. In some cases the entire surface of a
macula is smooth and glossy; in others either the whole or a part is covered
with granules, and in the latter case the granules may be limited to the
internal third (Fig. 141, B) or to the central portion. Sections of a macula
show that the granules are really globular lenses similar to those of the
compound eyes on the dorsal surface of the head. Some of the maculae
which are without lenses show no structure, but in others there is a spongy
or irregularly polyhedric structure with prisms, resembling the marginal
zone of the prismatic eyes of some genera. There seems no doubt that the
maculae with lenses are visual organs, and those without are degenerate
eyes. They occur in some genera which, according to Lindström, are
without eyes on the dorsal surface. Maculae do not appear to be present in
other Crustacea, but they have been compared with a median organ, found
just in front of the hypostome in Branchipus.[189] Maculae, have so far been
found in 136 species of Trilobites belonging to 39 genera ranging from
Lower Cambrian to Carboniferous.
A “metastoma” or lower lip plate (Fig. 142, Ep) is found just behind the
hypostome in Triarthrus, but has not been noticed in any other genus.
Between the hypostome and the metastoma lies the mouth.
The segments of the thorax are free, and their number varies from two in
Agnostus (Fig. 146) to twenty-six in Harpes (Fig. 150, A). In the Trilobites
confined to the Cambrian period the number (except in the Agnostidae) is
usually larger than in the genera found in the Ordovician and later periods.
Owing to the free thoracic segments many Trilobites were able to curl up
somewhat after the manner of a Wood-louse (Figs. 137, D, 138). The axial
part of each thoracic segment is more or less considerably arched. Usually it
consists of three parts: (i.) the largest part (Fig. 137, C, a), called the ring, is
band-like in form, and is always visible whether the Trilobite is extended or
coiled up; (ii.) in front of the ring is a depressed, groove-like part (Fig. 137,
C, b) separating it from (iii.) the articular portion (c) which is convex in
front and extends beneath the ring of the preceding segment; this part is
only visible when the Trilobite is coiled up or when the segments are
middle of the hypostome, or when transverse grooves are present either in
or near the anterior groove, there are often found a pair of small patches or
“maculae” which are more or less oval or elliptical in outline (Fig. 141).
The maculae may be (1) surrounded by a raised border, or (2) in the form of
pits, or (3) raised like tubercles. In some cases the entire surface of a
macula is smooth and glossy; in others either the whole or a part is covered
with granules, and in the latter case the granules may be limited to the
internal third (Fig. 141, B) or to the central portion. Sections of a macula
show that the granules are really globular lenses similar to those of the
compound eyes on the dorsal surface of the head. Some of the maculae
which are without lenses show no structure, but in others there is a spongy
or irregularly polyhedric structure with prisms, resembling the marginal
zone of the prismatic eyes of some genera. There seems no doubt that the
maculae with lenses are visual organs, and those without are degenerate
eyes. They occur in some genera which, according to Lindström, are
without eyes on the dorsal surface. Maculae do not appear to be present in
other Crustacea, but they have been compared with a median organ, found
just in front of the hypostome in Branchipus.[189] Maculae, have so far been
found in 136 species of Trilobites belonging to 39 genera ranging from
Lower Cambrian to Carboniferous.
A “metastoma” or lower lip plate (Fig. 142, Ep) is found just behind the
hypostome in Triarthrus, but has not been noticed in any other genus.
Between the hypostome and the metastoma lies the mouth.
The segments of the thorax are free, and their number varies from two in
Agnostus (Fig. 146) to twenty-six in Harpes (Fig. 150, A). In the Trilobites
confined to the Cambrian period the number (except in the Agnostidae) is
usually larger than in the genera found in the Ordovician and later periods.
Owing to the free thoracic segments many Trilobites were able to curl up
somewhat after the manner of a Wood-louse (Figs. 137, D, 138). The axial
part of each thoracic segment is more or less considerably arched. Usually it
consists of three parts: (i.) the largest part (Fig. 137, C, a), called the ring, is
band-like in form, and is always visible whether the Trilobite is extended or
coiled up; (ii.) in front of the ring is a depressed, groove-like part (Fig. 137,
C, b) separating it from (iii.) the articular portion (c) which is convex in
front and extends beneath the ring of the preceding segment; this part is
only visible when the Trilobite is coiled up or when the segments are
Page 279
separated. In some few genera the axial part consists of a simple arched
band without either a groove or a specially modified articular portion. The
pleurae (Fig. 137, A, l, C, d-f) are fixed firmly to the axis, and have the
form of narrow bands with the ends rounded, obtuse, pointed, or spinose. In
a few cases the pleurae have a plain surface; but usually they possess either
a ridge or a groove (Fig. 137, C, g); the former is generally parallel to the
margins of the pleura, the latter is generally oblique, being inclined
backwards from the axis. Sometimes in front of the ridge there is a small
groove. On the ventral surface each pleura shows, at its outer extremity, a
reflexed margin or doublure. At some distance from the axis the pleurae are
bent downwards and backwards. The point where this bend occurs is called
the “fulcrum” (e); it divides the pleura into an internal and an external part:
the internal part (d-e) is flat or slightly convex, and just touches the front
and back margins of the adjacent pleurae; the external part (e-f) may be (i.)
narrower than the internal part, so that it is separated from the previous and
succeeding pleurae; such occurs principally in pleurae with ridges, as in
Cheirurus and Bronteus; or (ii.) it may be in the form of a long cylindrical
process, as in many species of Acidaspis; or (iii.) the external part may be
of the same width, either throughout or in part, as the internal part, and may
overlap the next pleura behind; this type is found principally in pleurae with
a groove such as in Phacops, Calymene, Sao, Asaphus, Ellipsocephalus.
In some Trilobites there is beyond the fulcrum a smooth, flat, triangular
part at the front margin of the pleura; this part is known as the “facet,” and
forms a surface articulating with the preceding segment which overlaps it.
In the remarkable form Deiphon (Fig. 151, E) the pleurae are separate
throughout their entire length.
In some Trilobites broad and narrow forms of the same species occur—
the difference being seen especially in the axis. The former are regarded as
females, the latter as males.[190]
The segments of the abdomen or pygidium (Fig. 137, A, 3) are similar
to those of the thorax, except that they are fused together. In a few forms,
such as Illaenus (Fig. 150, F) and Bumastus, the fusion is so complete that
no trace of segmentation can be seen on the dorsal surface. Usually,
however, the segments are easily distinguishable; the number seen on the
axis is commonly greater than on the lateral parts of the pygidium; this
difference is particularly well shown in Encrinurus. In Trilobites which
band without either a groove or a specially modified articular portion. The
pleurae (Fig. 137, A, l, C, d-f) are fixed firmly to the axis, and have the
form of narrow bands with the ends rounded, obtuse, pointed, or spinose. In
a few cases the pleurae have a plain surface; but usually they possess either
a ridge or a groove (Fig. 137, C, g); the former is generally parallel to the
margins of the pleura, the latter is generally oblique, being inclined
backwards from the axis. Sometimes in front of the ridge there is a small
groove. On the ventral surface each pleura shows, at its outer extremity, a
reflexed margin or doublure. At some distance from the axis the pleurae are
bent downwards and backwards. The point where this bend occurs is called
the “fulcrum” (e); it divides the pleura into an internal and an external part:
the internal part (d-e) is flat or slightly convex, and just touches the front
and back margins of the adjacent pleurae; the external part (e-f) may be (i.)
narrower than the internal part, so that it is separated from the previous and
succeeding pleurae; such occurs principally in pleurae with ridges, as in
Cheirurus and Bronteus; or (ii.) it may be in the form of a long cylindrical
process, as in many species of Acidaspis; or (iii.) the external part may be
of the same width, either throughout or in part, as the internal part, and may
overlap the next pleura behind; this type is found principally in pleurae with
a groove such as in Phacops, Calymene, Sao, Asaphus, Ellipsocephalus.
In some Trilobites there is beyond the fulcrum a smooth, flat, triangular
part at the front margin of the pleura; this part is known as the “facet,” and
forms a surface articulating with the preceding segment which overlaps it.
In the remarkable form Deiphon (Fig. 151, E) the pleurae are separate
throughout their entire length.
In some Trilobites broad and narrow forms of the same species occur—
the difference being seen especially in the axis. The former are regarded as
females, the latter as males.[190]
The segments of the abdomen or pygidium (Fig. 137, A, 3) are similar
to those of the thorax, except that they are fused together. In a few forms,
such as Illaenus (Fig. 150, F) and Bumastus, the fusion is so complete that
no trace of segmentation can be seen on the dorsal surface. Usually,
however, the segments are easily distinguishable; the number seen on the
axis is commonly greater than on the lateral parts of the pygidium; this
difference is particularly well shown in Encrinurus. In Trilobites which
Page 280
have grooved pleurae the conspicuous grooves seen on the lateral parts of
the pygidium are the grooves of the pleurae, the sutures between the pleurae
being less distinct. The shape of the pygidium may be semicircular, a
segment of a circle, trapezoidal, triangular, semi-parabolic, etc.; its size
varies considerably; in the Cambrian forms it is usually small, but in the
Trilobites of later periods it becomes relatively larger. The number of
segments in the pygidium varies from two to twenty-eight. The axis of the
pygidium tapers more rapidly than that of the thorax; sometimes it reaches
quite to the posterior end of the body, but is commonly shorter than the
pygidium; in Bronteus it is extremely short, and the grooves on the lateral
parts of the pygidium radiate from it in a fan-like manner. Occasionally, as
in Bumastus, the axis cannot be distinguished from the lateral parts. In a
few early Trilobites (Olenellus, Holmia, Fig. 148, Paradoxides, Fig. 147)
the lateral parts of the pygidium are very small. In some genera, such as
Asaphus, the marginal part of the pygidium forms a flattened or concave
border. The margin may be entire or produced into spines, and sometimes
(Fig. 151, C) a caudal spine comes off from the end of the axis. On the
ventral surface of the pygidium there is a marginal rim similar to the
doublure of the cephalic shield. The anus is on the ventral surface of the last
segment of the pygidium.
Although Trilobites are often found in abundance and in an excellent
state of preservation, it is only in very rare cases that anything is seen of the
ventral surface except the hypostome and the reflexed borders of the
cephalic shield, of the thoracic segments, and of the pygidium. The usual
absence of appendages is probably due to their tenuity. Billings, in 1870,
first obtained clear evidence of the presence of pairs of appendages, in
Asaphus platycephalus. Soon afterwards Walcott[191] showed their existence
in American specimens of Asaphus megistos, Calymene senaria, and
Cheirurus pleurexacanthus. In the two latter species the appendages were
found by cutting sections of curled-up specimens obtained from the Trenton
Limestone; 2200 examples were sliced, of which 270 showed evidence of
the existence of appendages. They were seen to be present on the head,
thorax, and pygidium; a ventral uncalcified cuticle with transverse arches
was also found. By means of sections of curled-up specimens it was
difficult to determine satisfactorily the form and position of the appendages.
Subsequently extended specimens of Triarthrus (Fig. 142) and Trinucleus,
showing the ventral surface and appendages clearly, were discovered in the
the pygidium are the grooves of the pleurae, the sutures between the pleurae
being less distinct. The shape of the pygidium may be semicircular, a
segment of a circle, trapezoidal, triangular, semi-parabolic, etc.; its size
varies considerably; in the Cambrian forms it is usually small, but in the
Trilobites of later periods it becomes relatively larger. The number of
segments in the pygidium varies from two to twenty-eight. The axis of the
pygidium tapers more rapidly than that of the thorax; sometimes it reaches
quite to the posterior end of the body, but is commonly shorter than the
pygidium; in Bronteus it is extremely short, and the grooves on the lateral
parts of the pygidium radiate from it in a fan-like manner. Occasionally, as
in Bumastus, the axis cannot be distinguished from the lateral parts. In a
few early Trilobites (Olenellus, Holmia, Fig. 148, Paradoxides, Fig. 147)
the lateral parts of the pygidium are very small. In some genera, such as
Asaphus, the marginal part of the pygidium forms a flattened or concave
border. The margin may be entire or produced into spines, and sometimes
(Fig. 151, C) a caudal spine comes off from the end of the axis. On the
ventral surface of the pygidium there is a marginal rim similar to the
doublure of the cephalic shield. The anus is on the ventral surface of the last
segment of the pygidium.
Although Trilobites are often found in abundance and in an excellent
state of preservation, it is only in very rare cases that anything is seen of the
ventral surface except the hypostome and the reflexed borders of the
cephalic shield, of the thoracic segments, and of the pygidium. The usual
absence of appendages is probably due to their tenuity. Billings, in 1870,
first obtained clear evidence of the presence of pairs of appendages, in
Asaphus platycephalus. Soon afterwards Walcott[191] showed their existence
in American specimens of Asaphus megistos, Calymene senaria, and
Cheirurus pleurexacanthus. In the two latter species the appendages were
found by cutting sections of curled-up specimens obtained from the Trenton
Limestone; 2200 examples were sliced, of which 270 showed evidence of
the existence of appendages. They were seen to be present on the head,
thorax, and pygidium; a ventral uncalcified cuticle with transverse arches
was also found. By means of sections of curled-up specimens it was
difficult to determine satisfactorily the form and position of the appendages.
Subsequently extended specimens of Triarthrus (Fig. 142) and Trinucleus,
showing the ventral surface and appendages clearly, were discovered in the
Page 281
Utica Slate (Ordovician) near Rome, New York. A full account of the
appendages in those specimens has been given by Beecher.[192]
In Triarthrus each segment, except
the anal, bears a pair of appendages,
all of which, except the first, are
biramous. There are five pairs of
cephalic appendages; the first pair
are attached at each side of the
hypostome, and have the structure of
antennae, each consisting of a single
flagellum formed of short conical
joints. The other cephalic appendages
increase in size successively. At
present the second and third pairs are
not satisfactorily known, but appear
to have been similar to the fourth and
fifth pairs. The second pair is
attached at the level of the posterior
end of the hypostome. The fourth and
fifth pairs have large, triangular
coxopodites which served as
gnathobases, their inner edges being
denticulate; the endopodites consist
of stout joints; the exopodites are
slender, and bear setae which are
often arranged in a fan-like manner.
The first pair of appendages
appear to be antennules, whilst the
second pair probably represent the
antennae, the third pair the
mandibles, and the fourth and fifth FSlate
ig. 142.—Triarthrus becki, Green, × 2½. Utica
(Ordovician), near Rome, New York. A,
pairs the maxillae of other Crustacea. Ventral surface with appendages; Ep,
The appendages of the thorax and metastome; Hy, hypostome. B, second thoracic
pygidium do not differ essentially appendage; en, endopodite; ex, exopodite, × 12.
(After Beecher.)
from the two posterior cephalic
appendages. Those on the anterior
part of the thorax are the longest; the others gradually decrease in size in
appendages in those specimens has been given by Beecher.[192]
In Triarthrus each segment, except
the anal, bears a pair of appendages,
all of which, except the first, are
biramous. There are five pairs of
cephalic appendages; the first pair
are attached at each side of the
hypostome, and have the structure of
antennae, each consisting of a single
flagellum formed of short conical
joints. The other cephalic appendages
increase in size successively. At
present the second and third pairs are
not satisfactorily known, but appear
to have been similar to the fourth and
fifth pairs. The second pair is
attached at the level of the posterior
end of the hypostome. The fourth and
fifth pairs have large, triangular
coxopodites which served as
gnathobases, their inner edges being
denticulate; the endopodites consist
of stout joints; the exopodites are
slender, and bear setae which are
often arranged in a fan-like manner.
The first pair of appendages
appear to be antennules, whilst the
second pair probably represent the
antennae, the third pair the
mandibles, and the fourth and fifth FSlate
ig. 142.—Triarthrus becki, Green, × 2½. Utica
(Ordovician), near Rome, New York. A,
pairs the maxillae of other Crustacea. Ventral surface with appendages; Ep,
The appendages of the thorax and metastome; Hy, hypostome. B, second thoracic
pygidium do not differ essentially appendage; en, endopodite; ex, exopodite, × 12.
(After Beecher.)
from the two posterior cephalic
appendages. Those on the anterior
part of the thorax are the longest; the others gradually decrease in size in
Page 282
passing posteriorly. Each thoracic leg (Fig. 142, B) consists of a short
coxopodite with an inward cylindrical prolongation forming a gnathobase
which is best developed on the anterior legs; the endopodite and exopodite
are long and nearly equal; the former consists of six joints tapering
gradually to the end; the latter, of a long proximal joint with a denticulate
edge and a distal part of ten or more joints, and it bears a row of setae along
the whole of the posterior edge.
The anterior appendages of the pygidium differ but little from the
posterior thoracic legs; but the phyllopodous character, which appears in the
latter, becomes more distinct in the appendages of the pygidium, especially
those near its posterior end, and is due to the broad, flat, laminar joints of
the endopodite.
The more striking features of the appendages of Triarthrus are the small
amount of differentiation which they show in different parts of the body,
especially the want of specialisation in the cephalic region; the distinctly
biramous character of all except the first pair; and the presence of one pair
of functional antennae only, and the occurrence of thoracic gnathobases.
In Trinucleus the appendages are not so well known, but they are
considerably shorter than in Triarthrus.
In the Palaeozoic rocks of Bohemia, where Trilobites are very perfectly
preserved, Barrande[193] discovered the larval forms of several species, and
in some cases was able to trace out the development very completely, but
in others the earliest stages were not found. In the strata in which Trilobites
occur Barrande found minute spheroidal bodies, usually of a black colour,
and only a little smaller than the youngest larval stages; those bodies are
probably the eggs of Trilobites. Since the publication of Barrande’s work
the development of some species found in North America has been studied
by Ford, Matthew, Walcott, and Beecher. But even now the development is
known in only a very small proportion of the total number of genera of
Trilobites. The early larval form (Fig. 143, A) is similar in general character
in the various species in which it has been found. It is circular or ovoid in
outline, with a length of from 0·4 to 1 mm., and consists of a large cephalic
and a small pygidial portion; the axis is distinct and usually shows more or
less clear indications of five cephalic segments; the eyes, when present, are
found at or near the front margin, and the free cheeks, if visible at all on the
dorsal surface, are narrow. For this early larval form Beecher has proposed
coxopodite with an inward cylindrical prolongation forming a gnathobase
which is best developed on the anterior legs; the endopodite and exopodite
are long and nearly equal; the former consists of six joints tapering
gradually to the end; the latter, of a long proximal joint with a denticulate
edge and a distal part of ten or more joints, and it bears a row of setae along
the whole of the posterior edge.
The anterior appendages of the pygidium differ but little from the
posterior thoracic legs; but the phyllopodous character, which appears in the
latter, becomes more distinct in the appendages of the pygidium, especially
those near its posterior end, and is due to the broad, flat, laminar joints of
the endopodite.
The more striking features of the appendages of Triarthrus are the small
amount of differentiation which they show in different parts of the body,
especially the want of specialisation in the cephalic region; the distinctly
biramous character of all except the first pair; and the presence of one pair
of functional antennae only, and the occurrence of thoracic gnathobases.
In Trinucleus the appendages are not so well known, but they are
considerably shorter than in Triarthrus.
In the Palaeozoic rocks of Bohemia, where Trilobites are very perfectly
preserved, Barrande[193] discovered the larval forms of several species, and
in some cases was able to trace out the development very completely, but
in others the earliest stages were not found. In the strata in which Trilobites
occur Barrande found minute spheroidal bodies, usually of a black colour,
and only a little smaller than the youngest larval stages; those bodies are
probably the eggs of Trilobites. Since the publication of Barrande’s work
the development of some species found in North America has been studied
by Ford, Matthew, Walcott, and Beecher. But even now the development is
known in only a very small proportion of the total number of genera of
Trilobites. The early larval form (Fig. 143, A) is similar in general character
in the various species in which it has been found. It is circular or ovoid in
outline, with a length of from 0·4 to 1 mm., and consists of a large cephalic
and a small pygidial portion; the axis is distinct and usually shows more or
less clear indications of five cephalic segments; the eyes, when present, are
found at or near the front margin, and the free cheeks, if visible at all on the
dorsal surface, are narrow. For this early larval form Beecher has proposed
Page 283
the name “protaspis”; he regards it as the representative of the Nauplius of
other Crustacea, but that view is not accepted by Professor J. S. Kingsley.
[194]
The general changes which occur in the course of development are:
modifications in the shape and relative size of the glabella, and of the
number and depth of the glabella-furrows; the growth of the free cheeks and
the consequent inward movement of the facial sutures and eyes; the
introduction of and gradual increase in number of the thoracic segments,
and the relative decrease in size of the head.
Sao hirsuta is a species found in
the Cambrian, the development of
which was fully described by
Barrande. Its earliest protaspis stage
(Fig. 143, A) is circular in outline;
the glabella expands in front and
reaches the anterior margin; the
pygidial region is not distinctly
separated from the cephalic region;
Fig. 143.—Development of Sao hirsuta, Barr. segmentation is indicated in the
Cambrian. A, Protaspis; B-F, later stages; G, former, and the neck-ring is present
adult. The small outlines below each figure
show the actual size of each specimen. (After in the latter; the eye-line is seen on
Barrande.) each side of the glabella near the
anterior margin. In a later stage (Fig.
143, C) the segmentation of the glabella becomes more distinct, indicating
the existence of five cephalic segments, and the facial suture appears near
the margin limiting a very narrow free cheek. Subsequently (Fig. 143, D-F)
the thoracic segments develop, and increase in number until the adult stage
(G) is reached; also the eyes appear at the margin of the cephalic shield, and
gradually move inwards, and the glabella becomes narrower and rounded in
front, and ceases to reach the anterior margin. In this species the eye-line is
present in the adult.
In the protaspis of Triarthrus (Fig. 144), found in the Ordovician, the
glabella does not reach the front margin nor expand in front as it does in
Sao; an eye-line is present, but disappears before the adult stage is reached.
other Crustacea, but that view is not accepted by Professor J. S. Kingsley.
[194]
The general changes which occur in the course of development are:
modifications in the shape and relative size of the glabella, and of the
number and depth of the glabella-furrows; the growth of the free cheeks and
the consequent inward movement of the facial sutures and eyes; the
introduction of and gradual increase in number of the thoracic segments,
and the relative decrease in size of the head.
Sao hirsuta is a species found in
the Cambrian, the development of
which was fully described by
Barrande. Its earliest protaspis stage
(Fig. 143, A) is circular in outline;
the glabella expands in front and
reaches the anterior margin; the
pygidial region is not distinctly
separated from the cephalic region;
Fig. 143.—Development of Sao hirsuta, Barr. segmentation is indicated in the
Cambrian. A, Protaspis; B-F, later stages; G, former, and the neck-ring is present
adult. The small outlines below each figure
show the actual size of each specimen. (After in the latter; the eye-line is seen on
Barrande.) each side of the glabella near the
anterior margin. In a later stage (Fig.
143, C) the segmentation of the glabella becomes more distinct, indicating
the existence of five cephalic segments, and the facial suture appears near
the margin limiting a very narrow free cheek. Subsequently (Fig. 143, D-F)
the thoracic segments develop, and increase in number until the adult stage
(G) is reached; also the eyes appear at the margin of the cephalic shield, and
gradually move inwards, and the glabella becomes narrower and rounded in
front, and ceases to reach the anterior margin. In this species the eye-line is
present in the adult.
In the protaspis of Triarthrus (Fig. 144), found in the Ordovician, the
glabella does not reach the front margin nor expand in front as it does in
Sao; an eye-line is present, but disappears before the adult stage is reached.
Page 284
Fig. 144.—Triarthrus becki, Green. Ordovician.
A, B, Two successive stages of the protaspis, ×
45. (After Beecher.)
Fig. 145.—Larval stages of Trilobites. A-D, Dalmanites socialis, Barr.
Ordovician, Bohemia. The small figures below show the natural size of each
specimen. (After Barrande.) E, Mesonacis asaphoides, Emmons, × 10. Lower
Cambrian, North America. (After Walcott.) F, Acidaspis tuberculata, Conrad, ×
20. Lower Helderberg Group (Lower Devonian or Upper Silurian), Albany
County. (After Beecher.)
Dalmanites (Fig. 151, C) is a more advanced type than Sao and
Triarthrus, and is found in later deposits. In the earliest stage (Fig. 145, A)
the head and pygidium are quite distinct, and there is no eye-line present at
A, B, Two successive stages of the protaspis, ×
45. (After Beecher.)
Fig. 145.—Larval stages of Trilobites. A-D, Dalmanites socialis, Barr.
Ordovician, Bohemia. The small figures below show the natural size of each
specimen. (After Barrande.) E, Mesonacis asaphoides, Emmons, × 10. Lower
Cambrian, North America. (After Walcott.) F, Acidaspis tuberculata, Conrad, ×
20. Lower Helderberg Group (Lower Devonian or Upper Silurian), Albany
County. (After Beecher.)
Dalmanites (Fig. 151, C) is a more advanced type than Sao and
Triarthrus, and is found in later deposits. In the earliest stage (Fig. 145, A)
the head and pygidium are quite distinct, and there is no eye-line present at
Page 285
this or any stage in development, but large ovoid eyes are found on the front
margin, and have their long axes placed transversely to the axis of the body;
the glabella is strongly segmented and is rounded in front. In later stages (C,
D) the pygidium increases in size relatively, and the thoracic segments are
successively introduced; the facial sutures and free cheeks appear on the
dorsal surface, and as the free cheeks grow the eyes move inwards and
backwards, and gradually swing round until their long axes become parallel
with the axis of the body.
The larval form of Acidaspis (Fig. 145, F) is of interest since even in the
earliest stage it shows the spiny character which forms such a striking
feature of the adult (Fig. 151, F).
Before the discovery of the ventral surface of Trilobites it was thought by
some zoologists that their affinities were with the Xiphosura rather than
with the Crustacea. But the presence of antennae, and of five pairs of
cephalic appendages; the biramous thoracic and pygidial appendages, the
hypostome, and the character of the larval form, as well as the absence of a
genital operculum, separate the Trilobites from the Xiphosura and connect
them with the Crustacea.
The position of the Trilobites in the Crustacea is, however, difficult to
determine. Already in the Cambrian period, at least five main groups of the
Crustacea were clearly differentiated, namely, the Phyllopoda, Ostracoda,
Cirripedia, Trilobita, and Leptostraca (Phyllocarida), and probably also the
Copepoda, but of the last no remains have been preserved as fossils.
Palaeontology, therefore, furnishes no connecting links between any two of
these orders.
The Crustacea to which the Trilobites show some resemblance are the
families Apodidae and Branchipodidae of the Order Phyllopoda (see pp.
19–36). The Trilobita agree with those families in having a large but
variable number of trunk-segments, in the possession of a large labrum
(hypostome), and in the occurrence of gnathobases on the thoracic
appendages; also the foliation of some of the trunk-appendages is somewhat
similar. The points of difference, however, are considerable; thus the
cephalic appendages are much more specialised in the Apodidae and
Branchipodidae than in the Trilobita; in the latter all, with the exception of
the antennae, are distinctly biramous, and whilst the basal joints were
masticatory the distal parts appear to have been locomotor organs. The
margin, and have their long axes placed transversely to the axis of the body;
the glabella is strongly segmented and is rounded in front. In later stages (C,
D) the pygidium increases in size relatively, and the thoracic segments are
successively introduced; the facial sutures and free cheeks appear on the
dorsal surface, and as the free cheeks grow the eyes move inwards and
backwards, and gradually swing round until their long axes become parallel
with the axis of the body.
The larval form of Acidaspis (Fig. 145, F) is of interest since even in the
earliest stage it shows the spiny character which forms such a striking
feature of the adult (Fig. 151, F).
Before the discovery of the ventral surface of Trilobites it was thought by
some zoologists that their affinities were with the Xiphosura rather than
with the Crustacea. But the presence of antennae, and of five pairs of
cephalic appendages; the biramous thoracic and pygidial appendages, the
hypostome, and the character of the larval form, as well as the absence of a
genital operculum, separate the Trilobites from the Xiphosura and connect
them with the Crustacea.
The position of the Trilobites in the Crustacea is, however, difficult to
determine. Already in the Cambrian period, at least five main groups of the
Crustacea were clearly differentiated, namely, the Phyllopoda, Ostracoda,
Cirripedia, Trilobita, and Leptostraca (Phyllocarida), and probably also the
Copepoda, but of the last no remains have been preserved as fossils.
Palaeontology, therefore, furnishes no connecting links between any two of
these orders.
The Crustacea to which the Trilobites show some resemblance are the
families Apodidae and Branchipodidae of the Order Phyllopoda (see pp.
19–36). The Trilobita agree with those families in having a large but
variable number of trunk-segments, in the possession of a large labrum
(hypostome), and in the occurrence of gnathobases on the thoracic
appendages; also the foliation of some of the trunk-appendages is somewhat
similar. The points of difference, however, are considerable; thus the
cephalic appendages are much more specialised in the Apodidae and
Branchipodidae than in the Trilobita; in the latter all, with the exception of
the antennae, are distinctly biramous, and whilst the basal joints were
masticatory the distal parts appear to have been locomotor organs. The
Page 286
appendages of the trunk also differ considerably; in the Trilobita all are
clearly biramous, those of the thorax having a schizopodal form. In the
possession of a single pair of antennae the Trilobita differ from other
Crustacea; but in some forms of Apus the second pair of antennae may be
rudimentary or even absent.
There are still other features which characterise the Trilobita: thus the
eyes are borne on free cheeks, and differ in structure from those of
Phyllopods. The broad pygidium formed of fused segments and without
terminal fulcra is quite unlike the slender-jointed abdomen of Apus and
Branchipus; and whilst in the Trilobites all the segments bear appendages,
in the Phyllopods some, at any rate, of the posterior segments are devoid of
appendages. The distinct division of the body into an axial and pleural
region is not seen in Phyllopods, and is probably a character of some
importance, since it occurs in the great majority of Trilobites, including all
the early forms.
The existence of some relationship between the Trilobita and the
Leptostraca (Phyllocarida) has been maintained by Professor G. H.
Carpenter.[195] He points out that some of the earliest Trilobites, such as
Holmia kjerulfi (Fig. 148), possess nearly the same number of segments as
Nebalia (Fig. 76, p. 111), and that in the latter genus the cephalic
appendages, especially the mandibles and maxillae, are less specialised than
in Apus, and consequently differ less from those of Trilobites than do the
appendages of the Apodidae. Further, in another genus of the Leptostraca,
Paranebalia, the biramous thoracic legs, in which both endopodite and
exopodite are elongate, approach those of Trilobites more nearly than do the
thoracic legs of Apus.
The view[196] that some connexion may exist between the Isopoda and the
Trilobita seems to have been based on the similar dorso-ventral flattening of
the body, its division into three regions—head, thorax, and abdomen—and
the presence of sessile eyes. Beyond this it is difficult to find any
resemblance; whilst the differences, such as the variable number of thoracic
segments and their biramous appendages in Trilobites, are important.
At present, then, we can only conclude that the Trilobita are more
primitive than any other Crustacea, and that their resemblance to some of
the Phyllopoda is sufficient to make it probable that they had some ancestral
connexion;[197] the possibility of such a relationship receives some support
clearly biramous, those of the thorax having a schizopodal form. In the
possession of a single pair of antennae the Trilobita differ from other
Crustacea; but in some forms of Apus the second pair of antennae may be
rudimentary or even absent.
There are still other features which characterise the Trilobita: thus the
eyes are borne on free cheeks, and differ in structure from those of
Phyllopods. The broad pygidium formed of fused segments and without
terminal fulcra is quite unlike the slender-jointed abdomen of Apus and
Branchipus; and whilst in the Trilobites all the segments bear appendages,
in the Phyllopods some, at any rate, of the posterior segments are devoid of
appendages. The distinct division of the body into an axial and pleural
region is not seen in Phyllopods, and is probably a character of some
importance, since it occurs in the great majority of Trilobites, including all
the early forms.
The existence of some relationship between the Trilobita and the
Leptostraca (Phyllocarida) has been maintained by Professor G. H.
Carpenter.[195] He points out that some of the earliest Trilobites, such as
Holmia kjerulfi (Fig. 148), possess nearly the same number of segments as
Nebalia (Fig. 76, p. 111), and that in the latter genus the cephalic
appendages, especially the mandibles and maxillae, are less specialised than
in Apus, and consequently differ less from those of Trilobites than do the
appendages of the Apodidae. Further, in another genus of the Leptostraca,
Paranebalia, the biramous thoracic legs, in which both endopodite and
exopodite are elongate, approach those of Trilobites more nearly than do the
thoracic legs of Apus.
The view[196] that some connexion may exist between the Isopoda and the
Trilobita seems to have been based on the similar dorso-ventral flattening of
the body, its division into three regions—head, thorax, and abdomen—and
the presence of sessile eyes. Beyond this it is difficult to find any
resemblance; whilst the differences, such as the variable number of thoracic
segments and their biramous appendages in Trilobites, are important.
At present, then, we can only conclude that the Trilobita are more
primitive than any other Crustacea, and that their resemblance to some of
the Phyllopoda is sufficient to make it probable that they had some ancestral
connexion;[197] the possibility of such a relationship receives some support
Page 287
from the presence in the Lower Cambrian rocks of Protocaris, a genus of
the Phyllopoda which resembles Apus.[198] The primitive characters of
Trilobites are the variable and often large number of segments in the thorax
and pygidium; the presence of a pair of appendages on every segment
except the anal; the biramous form of all except the first pair of appendages;
and the lack of specialisation shown by the appendages, especially those of
the head.
The classification of Trilobites is due largely to the work of Barrande
and Salter, and the families defined by those authors have been, in the main,
generally adopted. But the phylogenetic relationship of the families has
still, to a large extent, to be established. Salter[199] arranged the families in
four groups, but did not claim that that classification was entirely natural.
His groups with the families included in each are:—
1. Agnostini. Without eyes or facial suture. Agnostidae.
2. Ampycini. Facial sutures obscure, or submarginal, or absent. Eyes
often absent. Trinucleidae.
3. Asaphini. Facial sutures ending on the posterior margin. Acidaspidae,
Lichadidae, Harpedidae, Calymenidae, Paradoxidae, Conocephalidae,
Olenidae, Asaphidae, Bronteidae, and Proëtidae.
4. Phacopini. Facial sutures ending on the lateral margins. Eyes well
developed. Phacopidae, Cheiruridae, and Encrinuridae.
A modification of Salter’s classification has been brought forward by
Beecher[200] who divides the Trilobita into three main groups:—
1. Hypoparia. Facial sutures at or near the margin, or ventral. Compound
eyes absent. This is equivalent to Salter’s Agnostini and Ampycini with the
addition of the Harpedidae.
2. Opisthoparia. Facial sutures extending from the posterior margin to
the front margin, but occasionally uniting in front of the glabella. Eyes
holochroal or prismatic, but sometimes absent. This comprises the same
families as Salter’s Asaphini with the exclusion of the Harpedidae and
Calymenidae.
3. Proparia. Facial sutures extending from the lateral margins, and either
cutting the anterior margin or uniting in front of the glabella. Eyes
holochroal or schizochroal; occasionally absent. This is equivalent to
Salter’s Phacopini with the addition of the Calymenidae.
the Phyllopoda which resembles Apus.[198] The primitive characters of
Trilobites are the variable and often large number of segments in the thorax
and pygidium; the presence of a pair of appendages on every segment
except the anal; the biramous form of all except the first pair of appendages;
and the lack of specialisation shown by the appendages, especially those of
the head.
The classification of Trilobites is due largely to the work of Barrande
and Salter, and the families defined by those authors have been, in the main,
generally adopted. But the phylogenetic relationship of the families has
still, to a large extent, to be established. Salter[199] arranged the families in
four groups, but did not claim that that classification was entirely natural.
His groups with the families included in each are:—
1. Agnostini. Without eyes or facial suture. Agnostidae.
2. Ampycini. Facial sutures obscure, or submarginal, or absent. Eyes
often absent. Trinucleidae.
3. Asaphini. Facial sutures ending on the posterior margin. Acidaspidae,
Lichadidae, Harpedidae, Calymenidae, Paradoxidae, Conocephalidae,
Olenidae, Asaphidae, Bronteidae, and Proëtidae.
4. Phacopini. Facial sutures ending on the lateral margins. Eyes well
developed. Phacopidae, Cheiruridae, and Encrinuridae.
A modification of Salter’s classification has been brought forward by
Beecher[200] who divides the Trilobita into three main groups:—
1. Hypoparia. Facial sutures at or near the margin, or ventral. Compound
eyes absent. This is equivalent to Salter’s Agnostini and Ampycini with the
addition of the Harpedidae.
2. Opisthoparia. Facial sutures extending from the posterior margin to
the front margin, but occasionally uniting in front of the glabella. Eyes
holochroal or prismatic, but sometimes absent. This comprises the same
families as Salter’s Asaphini with the exclusion of the Harpedidae and
Calymenidae.
3. Proparia. Facial sutures extending from the lateral margins, and either
cutting the anterior margin or uniting in front of the glabella. Eyes
holochroal or schizochroal; occasionally absent. This is equivalent to
Salter’s Phacopini with the addition of the Calymenidae.
Page 288
In each of the groups proposed Beecher regards as the more primitive
forms those which possess characters similar to those of the early larval
stages, such as narrow free cheeks, the absence of compound eyes, and a
glabella which is broad in front and reaches the anterior margin of the head.
The modifications introduced by Beecher can scarcely be regarded as
making Salter’s classification more natural. For instance, the Agnostidae
differ so much from all other families that, at present, there is no evidence
to show that they have any close phylogenetic relationship with the
Trinucleidae and Harpedidae. Further, the Calymenidae, which Salter
recognised as related to the Olenidae, have been shown by the careful work
of Professor Pompeckj[201] to have descended from the latter family, and to
have no genetic connexion with the Phacopidae with which they are
grouped by Beecher. Then in the Trinucleidae the earliest genus,
Orometopus[202] (Fig. 140, A), possesses compound eyes and facial sutures
which begin at the posterior margin and unite in front of the glabella; so
that, according to Beecher’s classification, that genus would belong to the
Opisthoparia, whereas the later genera (Trinucleus, etc.) of the same family
would be placed in the Hypoparia. At present, therefore, the only
classification of Trilobites which can be adopted is a division into families,
of which a short account is given below.
Fam. 1. Agnostidae (Fig. 146).—Small Trilobites, in which the head and
pygidium are of nearly the same size and shape. The thorax is shorter than
the head or pygidium, and consists of from two to four segments with
grooved pleurae. The length and width of the head are commonly nearly
equal, but sometimes the length is greater. Eyes are absent. Facial sutures
appear to be absent, but are stated by Beecher to be at the margin of the
cephalic shield. From the absence of eyes, the probable absence of facial
sutures, the few or indistinct furrows on the glabella, and the smaller
number of thoracic segments, the Agnostidae appear to be degenerate
forms. Microdiscus is apparently less modified than Agnostus, on account
of the larger number of thoracic segments, the more distinct segmentation
of the pygidium, and, in some species, the larger number of furrows on the
glabella. Cambrian and Ordovician. Genera: Agnostus, Microdiscus.
Fam. 2. Shumardiidae.—The body is very small and oval. The cephalic
shield is nearly semicircular and very convex, with a broad glabella which
expands in front, and in which the furrows, except the neck-furrow, are
forms those which possess characters similar to those of the early larval
stages, such as narrow free cheeks, the absence of compound eyes, and a
glabella which is broad in front and reaches the anterior margin of the head.
The modifications introduced by Beecher can scarcely be regarded as
making Salter’s classification more natural. For instance, the Agnostidae
differ so much from all other families that, at present, there is no evidence
to show that they have any close phylogenetic relationship with the
Trinucleidae and Harpedidae. Further, the Calymenidae, which Salter
recognised as related to the Olenidae, have been shown by the careful work
of Professor Pompeckj[201] to have descended from the latter family, and to
have no genetic connexion with the Phacopidae with which they are
grouped by Beecher. Then in the Trinucleidae the earliest genus,
Orometopus[202] (Fig. 140, A), possesses compound eyes and facial sutures
which begin at the posterior margin and unite in front of the glabella; so
that, according to Beecher’s classification, that genus would belong to the
Opisthoparia, whereas the later genera (Trinucleus, etc.) of the same family
would be placed in the Hypoparia. At present, therefore, the only
classification of Trilobites which can be adopted is a division into families,
of which a short account is given below.
Fam. 1. Agnostidae (Fig. 146).—Small Trilobites, in which the head and
pygidium are of nearly the same size and shape. The thorax is shorter than
the head or pygidium, and consists of from two to four segments with
grooved pleurae. The length and width of the head are commonly nearly
equal, but sometimes the length is greater. Eyes are absent. Facial sutures
appear to be absent, but are stated by Beecher to be at the margin of the
cephalic shield. From the absence of eyes, the probable absence of facial
sutures, the few or indistinct furrows on the glabella, and the smaller
number of thoracic segments, the Agnostidae appear to be degenerate
forms. Microdiscus is apparently less modified than Agnostus, on account
of the larger number of thoracic segments, the more distinct segmentation
of the pygidium, and, in some species, the larger number of furrows on the
glabella. Cambrian and Ordovician. Genera: Agnostus, Microdiscus.
Fam. 2. Shumardiidae.—The body is very small and oval. The cephalic
shield is nearly semicircular and very convex, with a broad glabella which
expands in front, and in which the furrows, except the neck-furrow, are
Page 289
indistinct. The facial suture is
marginal and eyes are absent. There
are six thoracic segments with ridged
pleurae; the axis is broader than the
pleurae. The pygidium is large, and is
formed of about four segments
similar to those of the thorax. Upper
Cambrian and Ordovician. Genus:
Shumardia.
Fam. 3. Trinucleidae (Fig. 140).
—The head is large and has a flat
border (except in Ampyx), and long
genal spines. In the earliest genus
(Orometopus) the facial sutures start
from the posterior margin (near the
genal angle) and pass obliquely
inwards to the compound eye, from
whence they continue forward and
unite in front of the glabella. In
Ampyx the suture starts from just
within the genal angle and passes to
the front border, cutting off a narrow
free cheek; eyes are absent. In most
specimens of Trinucleus no sutures
are seen, but some examples show
indications of what may be a facial
suture (see p. 226), and a suture is
sometimes found at the margin of the
cephalic border; eyes may occur (see Fig. 146.—Agnostus integer, Beyr., × 8.
p. 230). The thorax consists of from Cambrian. (After Barrande.)
five to eight segments, with grooved
pleurae. The pygidium is triangular. Principally Ordovician. Genera:
Orometopus (Upper Cambrian), Ampyx, Trinucleus, Dionide.
Fam. 4. Harpedidae (Figs. 139, G, H; 150, A).—The head is large and
has a broad, flat border which is finely punctate, and extends backwards on
each side in the form of a horn-like projection nearly as far as the posterior
end of the thorax. The glabella is convex and does not reach the front
marginal and eyes are absent. There
are six thoracic segments with ridged
pleurae; the axis is broader than the
pleurae. The pygidium is large, and is
formed of about four segments
similar to those of the thorax. Upper
Cambrian and Ordovician. Genus:
Shumardia.
Fam. 3. Trinucleidae (Fig. 140).
—The head is large and has a flat
border (except in Ampyx), and long
genal spines. In the earliest genus
(Orometopus) the facial sutures start
from the posterior margin (near the
genal angle) and pass obliquely
inwards to the compound eye, from
whence they continue forward and
unite in front of the glabella. In
Ampyx the suture starts from just
within the genal angle and passes to
the front border, cutting off a narrow
free cheek; eyes are absent. In most
specimens of Trinucleus no sutures
are seen, but some examples show
indications of what may be a facial
suture (see p. 226), and a suture is
sometimes found at the margin of the
cephalic border; eyes may occur (see Fig. 146.—Agnostus integer, Beyr., × 8.
p. 230). The thorax consists of from Cambrian. (After Barrande.)
five to eight segments, with grooved
pleurae. The pygidium is triangular. Principally Ordovician. Genera:
Orometopus (Upper Cambrian), Ampyx, Trinucleus, Dionide.
Fam. 4. Harpedidae (Figs. 139, G, H; 150, A).—The head is large and
has a broad, flat border which is finely punctate, and extends backwards on
each side in the form of a horn-like projection nearly as far as the posterior
end of the thorax. The glabella is convex and does not reach the front
Page 290
margin. The cheeks are less convex than the glabella, and bear eyes which
usually consist of two or three lenses. An eye-line connects the eye with the
anterior part of the glabella. A suture is stated to occur at the external
margin of the flat border. The thorax consists of from twenty-five to twenty-
nine segments; its axis is narrow, and the pleurae are long and grooved. The
pygidium is very small, and consists of three or four segments. Ordovician
to Devonian. Genus: Harpes.
Fam. 5. Paradoxidae (Figs. 147,
148, 149).—The cephalic shield is
large, and bears long genal spines.
The glabella is more or less swollen
in front. The facial sutures appear to
be absent in some genera, and when
present extend from the posterior to
the anterior margin. The palpebral
lobes are long, and often more or less
semicircular or kidney-shaped. The
thorax is long, and consists of from
sixteen to twenty segments with their
pleurae produced into spines. The
pygidium is very small, and plate-
like, or sometimes in the form of a
long spine. Cambrian. Genera:
Olenellus, Holmia, Mesonacis,
Olenelloides, Paradoxides,
Zacanthoides, Centropleura
(Anopolenus). Remopleurides (Fig.
150, D) from the Ordovician is
usually included in the Paradoxidae,
but probably belongs to a separate
family.
Fig. 147.—Paradoxides bohemicus, Barr. × ½.
Fam. 6. Conocephalidae
Middle Cambrian. (After Zittel.) (Conocoryphidae) (Fig. 150, E).—
The cephalic shield is semicircular,
and larger than the pygidium. The
glabella narrows in front. The facial suture passes from near the genal angle
on the posterior border to the antero-lateral margin, and limits a large fixed
usually consist of two or three lenses. An eye-line connects the eye with the
anterior part of the glabella. A suture is stated to occur at the external
margin of the flat border. The thorax consists of from twenty-five to twenty-
nine segments; its axis is narrow, and the pleurae are long and grooved. The
pygidium is very small, and consists of three or four segments. Ordovician
to Devonian. Genus: Harpes.
Fam. 5. Paradoxidae (Figs. 147,
148, 149).—The cephalic shield is
large, and bears long genal spines.
The glabella is more or less swollen
in front. The facial sutures appear to
be absent in some genera, and when
present extend from the posterior to
the anterior margin. The palpebral
lobes are long, and often more or less
semicircular or kidney-shaped. The
thorax is long, and consists of from
sixteen to twenty segments with their
pleurae produced into spines. The
pygidium is very small, and plate-
like, or sometimes in the form of a
long spine. Cambrian. Genera:
Olenellus, Holmia, Mesonacis,
Olenelloides, Paradoxides,
Zacanthoides, Centropleura
(Anopolenus). Remopleurides (Fig.
150, D) from the Ordovician is
usually included in the Paradoxidae,
but probably belongs to a separate
family.
Fig. 147.—Paradoxides bohemicus, Barr. × ½.
Fam. 6. Conocephalidae
Middle Cambrian. (After Zittel.) (Conocoryphidae) (Fig. 150, E).—
The cephalic shield is semicircular,
and larger than the pygidium. The
glabella narrows in front. The facial suture passes from near the genal angle
on the posterior border to the antero-lateral margin, and limits a large fixed
Page 291
cheek and a narrow free cheek. Eyes
are absent or rudimentary, but an eye-
line is usually present. The thorax
consists of from fourteen to
seventeen segments with grooved
pleurae, which may be pointed, but
are not usually produced into spines.
The pygidium is small, and formed
of few segments. Cambrian. Genera:
Conocoryphe, Atops, Ctenocephalus,
Bathynotus.
Fam. 7. Olenidae (Figs. 142, 143;
150, B, C).—The cephalic shield is
larger than the pygidium. The
glabella is either rectangular or
parabolic. The facial suture passes
from the posterior to the anterior
margin. The palpebral lobes are of
Fig. 148.—Holmia kjerulfi, Linnars. × 1. Lower
moderate or rather large size, and are Cambrian. (After Holm.)
connected by an eye-line with the
front part of the glabella. The thorax
includes from eleven (occasionally fewer) to eighteen segments with
grooved pleurae. The pygidium is usually small, with from two to eight
segments. Principally Cambrian. Genera: Ptychoparia, Angelina,
Solenopleura, Sao, Agraulos (Arionellus), Ellipsocephalus, Protolenus,
Olenus, Peltura, Acerocare, Eurycare, Ctenopyge, Leptoplastus, Triarthrus,
Parabolina, Sphaerophthalmus, Parabolinella, Ceratopyge (position
doubtful). Dikelocephalus is usually placed in the Olenidae, but perhaps
belongs to a distinct family.
Fam. 8. Calymenidae (Figs. 136, 137).—The glabella is broadest
behind. The facial suture starts at or near the genal angle—sometimes on
the posterior border just inside the angle, sometimes on the lateral border
just in front of the angle; the suture may be continuous with the other suture
in front of the glabella, or may cut the anterior margin, beneath which it is
connected with the other suture by means of a transverse suture (Fig. 137,
B, D). The eyes are rather small. The thorax consists of thirteen segments
with grooved pleurae; the pygidium of from six to fourteen segments.
are absent or rudimentary, but an eye-
line is usually present. The thorax
consists of from fourteen to
seventeen segments with grooved
pleurae, which may be pointed, but
are not usually produced into spines.
The pygidium is small, and formed
of few segments. Cambrian. Genera:
Conocoryphe, Atops, Ctenocephalus,
Bathynotus.
Fam. 7. Olenidae (Figs. 142, 143;
150, B, C).—The cephalic shield is
larger than the pygidium. The
glabella is either rectangular or
parabolic. The facial suture passes
from the posterior to the anterior
margin. The palpebral lobes are of
Fig. 148.—Holmia kjerulfi, Linnars. × 1. Lower
moderate or rather large size, and are Cambrian. (After Holm.)
connected by an eye-line with the
front part of the glabella. The thorax
includes from eleven (occasionally fewer) to eighteen segments with
grooved pleurae. The pygidium is usually small, with from two to eight
segments. Principally Cambrian. Genera: Ptychoparia, Angelina,
Solenopleura, Sao, Agraulos (Arionellus), Ellipsocephalus, Protolenus,
Olenus, Peltura, Acerocare, Eurycare, Ctenopyge, Leptoplastus, Triarthrus,
Parabolina, Sphaerophthalmus, Parabolinella, Ceratopyge (position
doubtful). Dikelocephalus is usually placed in the Olenidae, but perhaps
belongs to a distinct family.
Fam. 8. Calymenidae (Figs. 136, 137).—The glabella is broadest
behind. The facial suture starts at or near the genal angle—sometimes on
the posterior border just inside the angle, sometimes on the lateral border
just in front of the angle; the suture may be continuous with the other suture
in front of the glabella, or may cut the anterior margin, beneath which it is
connected with the other suture by means of a transverse suture (Fig. 137,
B, D). The eyes are rather small. The thorax consists of thirteen segments
with grooved pleurae; the pygidium of from six to fourteen segments.
Page 292
Ordovician to Devonian. Genera:
Calymene, Synhomalonotus,
Homalonotus.
Fig. 149.—Clenelloides armatus, Peach. Lower
Cambrian, × 3. (After Peach.)
Calymene, Synhomalonotus,
Homalonotus.
Fig. 149.—Clenelloides armatus, Peach. Lower
Cambrian, × 3. (After Peach.)
Page 293
Fig. 150.—A, Harpes ungula, Sternb., Ordovician. B, Ellipsocephalus hoffi,
Scloth., Cambrian. C, Olenus truncatus, Brünn., Cambrian. (After Angelin.) D,
Remopleurides radians, Barr., Ordovician. E, Conocoryphe sulzeri, Barr.,
Cambrian. F, Illaenus dalmanni, Volb., Ordovician. G, Proëtus bohemicus,
Corda, Silurian, × 1½. H, Aeglina prisca, Barr., Ordovician, × 3. I, Phacops
sternbergi, Barr., Devonian. (A, D, E, G, H, I, after Barrande; B, F, from Zittel;
natural size except G, H.)
Fam. 9. Asaphidae (Fig. 150, F).—The body is oval and commonly
rather large. The cephalic shield is large, with its glabella often indistinctly
limited and the glabella-furrows often obscure. The facial suture starts from
Scloth., Cambrian. C, Olenus truncatus, Brünn., Cambrian. (After Angelin.) D,
Remopleurides radians, Barr., Ordovician. E, Conocoryphe sulzeri, Barr.,
Cambrian. F, Illaenus dalmanni, Volb., Ordovician. G, Proëtus bohemicus,
Corda, Silurian, × 1½. H, Aeglina prisca, Barr., Ordovician, × 3. I, Phacops
sternbergi, Barr., Devonian. (A, D, E, G, H, I, after Barrande; B, F, from Zittel;
natural size except G, H.)
Fam. 9. Asaphidae (Fig. 150, F).—The body is oval and commonly
rather large. The cephalic shield is large, with its glabella often indistinctly
limited and the glabella-furrows often obscure. The facial suture starts from
Page 294
the posterior margin and usually cuts the anterior margin, but is sometimes
continued in front of the glabella. The relative size of the fixed and free
cheeks varies greatly. The eyes are of variable size. The thorax consists of
eight or ten (sometimes fewer) segments; the pleurae are generally grooved,
but sometimes plane. The pygidium is large, often being similar in form and
size to the head; it consists of numerous segments which, however, may be
indistinctly shown; the axis in some forms is obsolete. Upper Cambrian
(Tremadoc) to Silurian; common in the Ordovician. Genera: Asaphus (sub-
genera, Megalaspis, Asaphellus, Symphysurus, etc.), Ogygia, Barrandia,
Niobe, Nileus, Illaenus, Bumastus, Stygina. Aeglina (Fig. 150, H) is usually
placed in this family, but its systematic position is doubtful.
Fam. 10. Bronteidae.—The general form is similar to that of the
Asaphidae. The glabella broadens rapidly in front, and is marked with
furrows on each side, which are usually short, and may be indistinct. The
facial suture passes from the posterior margin to the crescentic eye which is
situated rather near the posterior border, and from thence to the anterior
margin. There are ten thoracic segments with ridged pleurae. The pygidium
is longer than the head, and has a very short axis, from which the furrows
on the pleural part radiate. Ordovician to Devonian. Genus: Bronteus.
Fam. 11. Phacopidae (Figs. 138; 150, I; 151, C).—The head and
pygidium are of about the same size. The glabella is distinctly limited, and
wider in front than behind, with a neck-furrow and three other furrows, of
which some of the anterior may be indistinct or obsolete. The eyes are
schizochroal and usually large. The facial suture begins at the lateral margin
and unites with the suture of the other side in front of the glabella. There are
eleven thoracic segments with grooved pleurae. The pygidium is usually
large, with a distinct axis and many segments. Ordovician to Devonian.
Genera: Phacops, Trimerocephalus, Acaste, Pterygometopus, Chasmops,
Dalmanites, Cryphaeus.
continued in front of the glabella. The relative size of the fixed and free
cheeks varies greatly. The eyes are of variable size. The thorax consists of
eight or ten (sometimes fewer) segments; the pleurae are generally grooved,
but sometimes plane. The pygidium is large, often being similar in form and
size to the head; it consists of numerous segments which, however, may be
indistinctly shown; the axis in some forms is obsolete. Upper Cambrian
(Tremadoc) to Silurian; common in the Ordovician. Genera: Asaphus (sub-
genera, Megalaspis, Asaphellus, Symphysurus, etc.), Ogygia, Barrandia,
Niobe, Nileus, Illaenus, Bumastus, Stygina. Aeglina (Fig. 150, H) is usually
placed in this family, but its systematic position is doubtful.
Fam. 10. Bronteidae.—The general form is similar to that of the
Asaphidae. The glabella broadens rapidly in front, and is marked with
furrows on each side, which are usually short, and may be indistinct. The
facial suture passes from the posterior margin to the crescentic eye which is
situated rather near the posterior border, and from thence to the anterior
margin. There are ten thoracic segments with ridged pleurae. The pygidium
is longer than the head, and has a very short axis, from which the furrows
on the pleural part radiate. Ordovician to Devonian. Genus: Bronteus.
Fam. 11. Phacopidae (Figs. 138; 150, I; 151, C).—The head and
pygidium are of about the same size. The glabella is distinctly limited, and
wider in front than behind, with a neck-furrow and three other furrows, of
which some of the anterior may be indistinct or obsolete. The eyes are
schizochroal and usually large. The facial suture begins at the lateral margin
and unites with the suture of the other side in front of the glabella. There are
eleven thoracic segments with grooved pleurae. The pygidium is usually
large, with a distinct axis and many segments. Ordovician to Devonian.
Genera: Phacops, Trimerocephalus, Acaste, Pterygometopus, Chasmops,
Dalmanites, Cryphaeus.
Page 295
Fig. 151.—A, Phillipsia gemmulifera, Phill., Carboniferous. B, Arethusina
konincki, Barr., Ordovician. C, Dalmanites limulurus, Green, Silurian. (After
Hall.) D, Cheirurus insignis, Beyr., Silurian. E, Deiphon forbesi, Barr., Silurian.
F, Acidaspis dufrenoyi, Barr., Silurian. (A, B, from Zittel; D, E, F, after
Barrande; natural size.)
Fam. 12. Cheiruridae (Fig. 151, D, E).—The glabella is convex or
inflated, and distinctly defined. The facial suture passes from the lateral to
the front margin. The free cheeks are small, and the eyes usually rather
small. There are from nine to eighteen (usually eleven) thoracic segments;
konincki, Barr., Ordovician. C, Dalmanites limulurus, Green, Silurian. (After
Hall.) D, Cheirurus insignis, Beyr., Silurian. E, Deiphon forbesi, Barr., Silurian.
F, Acidaspis dufrenoyi, Barr., Silurian. (A, B, from Zittel; D, E, F, after
Barrande; natural size.)
Fam. 12. Cheiruridae (Fig. 151, D, E).—The glabella is convex or
inflated, and distinctly defined. The facial suture passes from the lateral to
the front margin. The free cheeks are small, and the eyes usually rather
small. There are from nine to eighteen (usually eleven) thoracic segments;
Page 296
the pleurae have ridges or grooves and free ends. The pygidium is small,
consisting of from three to five segments often produced into spines. Upper
Cambrian to Devonian. Genera: Cheirurus, Deiphon, Placoparia,
Sphaerexochus, Amphion, Staurocephalus.
Fam. 13. Proëtidae (Figs. 150, G; 151, A, B).—The body is rather small,
and the head forms about a third of its entire length. The glabella is sharply
defined, and its furrows are sometimes indistinct; the posterior furrow
curves backward to the neck-furrow, thus limiting a basal lobe on each side
of the glabella. The eyes are often large (Fig. 150, G); but in Arethusina
(Fig. 151, B), in which an eye-line is present, they are small. The facial
sutures pass from the posterior to the anterior margin. The free cheeks are
large. There are from eight to twenty-two thoracic segments with grooved
pleurae. The pygidium is usually formed of numerous segments, and its
margin is usually entire. Ordovician to Permian. Genera: Proëtus,
Arethusina, Cyphaspis, Phillipsia, Griffithides, Brachymetopus,
[203]
Dechenella.
Fam. 14. Encrinuridae.—The cephalic shield is ornamented with
tubercles. The free cheeks are narrow, and the eyes very small. The facial
suture extends from the lateral margin (or from the genal angle) to the
anterior margin. There are from ten to twelve thoracic segments with ridged
pleurae. On the axis of the pygidium numerous segments are seen, but
usually fewer are indicated on the lateral parts. Ordovician and Silurian.
Genera: Encrinurus, Cybele, Dindymene.
Fam. 15. Acidaspidae (Fig. 151, F).—The cephalic shield is broad, with
a spinose margin, genal spines, and sometimes spines on the neck-ring. The
glabella has a longitudinal furrow on each side, due to the backward
bending of the lateral furrows. The facial suture passes from the posterior
border (near the genal angle) to the anterior border. The free cheeks are
large; the eyes small. There are from eight to ten thoracic segments with
ridged pleurae, which are produced into long backwardly directed spines.
The pygidium is short, and is formed of two or three segments with long
spines at the margin. Ordovician to Devonian. Genus: Acidaspis.
Fam. 16. Lichadidae.—The body is broad, with a granular dorsal
surface. The cephalic shield is small and short, with spinose genal angles.
The glabella is broad, and its anterior furrows are directed backwards,
limiting a convex median lobe and some lateral lobes. The facial suture
consisting of from three to five segments often produced into spines. Upper
Cambrian to Devonian. Genera: Cheirurus, Deiphon, Placoparia,
Sphaerexochus, Amphion, Staurocephalus.
Fam. 13. Proëtidae (Figs. 150, G; 151, A, B).—The body is rather small,
and the head forms about a third of its entire length. The glabella is sharply
defined, and its furrows are sometimes indistinct; the posterior furrow
curves backward to the neck-furrow, thus limiting a basal lobe on each side
of the glabella. The eyes are often large (Fig. 150, G); but in Arethusina
(Fig. 151, B), in which an eye-line is present, they are small. The facial
sutures pass from the posterior to the anterior margin. The free cheeks are
large. There are from eight to twenty-two thoracic segments with grooved
pleurae. The pygidium is usually formed of numerous segments, and its
margin is usually entire. Ordovician to Permian. Genera: Proëtus,
Arethusina, Cyphaspis, Phillipsia, Griffithides, Brachymetopus,
[203]
Dechenella.
Fam. 14. Encrinuridae.—The cephalic shield is ornamented with
tubercles. The free cheeks are narrow, and the eyes very small. The facial
suture extends from the lateral margin (or from the genal angle) to the
anterior margin. There are from ten to twelve thoracic segments with ridged
pleurae. On the axis of the pygidium numerous segments are seen, but
usually fewer are indicated on the lateral parts. Ordovician and Silurian.
Genera: Encrinurus, Cybele, Dindymene.
Fam. 15. Acidaspidae (Fig. 151, F).—The cephalic shield is broad, with
a spinose margin, genal spines, and sometimes spines on the neck-ring. The
glabella has a longitudinal furrow on each side, due to the backward
bending of the lateral furrows. The facial suture passes from the posterior
border (near the genal angle) to the anterior border. The free cheeks are
large; the eyes small. There are from eight to ten thoracic segments with
ridged pleurae, which are produced into long backwardly directed spines.
The pygidium is short, and is formed of two or three segments with long
spines at the margin. Ordovician to Devonian. Genus: Acidaspis.
Fam. 16. Lichadidae.—The body is broad, with a granular dorsal
surface. The cephalic shield is small and short, with spinose genal angles.
The glabella is broad, and its anterior furrows are directed backwards,
limiting a convex median lobe and some lateral lobes. The facial suture
Page 297
extends from the posterior to the anterior margin. There are nine or ten
thoracic segments with grooved pleurae, which have pointed ends. The
pygidium is large and triangular, with a short axis and a toothed margin.
Ordovician to Devonian. Genus: Lichas (sub-genera, Arges, Dicranogmus,
Conolichas, Ceratolichas).
thoracic segments with grooved pleurae, which have pointed ends. The
pygidium is large and triangular, with a short axis and a toothed margin.
Ordovician to Devonian. Genus: Lichas (sub-genera, Arges, Dicranogmus,
Conolichas, Ceratolichas).
Page 298
INTRODUCTION TO ARACHNIDA,
AND
XIPHOSURA
BY
A. E. SHIPLEY, M.A., F.R.S.
Fellow of Christ’s College, Cambridge, and Reader in Zoology in the University
AND
XIPHOSURA
BY
A. E. SHIPLEY, M.A., F.R.S.
Fellow of Christ’s College, Cambridge, and Reader in Zoology in the University
Page 299
CHAPTER IX
ARACHNIDA—INTRODUCTION
The Arachnida, together with the Crustacea, Insecta, Myriapoda, and
Peripatus, make up the great phylum Arthropoda, a phylum which, from the
point of view of numbers of species and of individuals, is the dominant one
on this planet, and from the point of view of intelligence and power of co-
operating in the formation of social communities is surpassed but by the
Vertebrata. The Arachnida form a more diverse class than the Insecta; they
differ, perhaps, as much inter se as do the Crustacea, and in structure as in
size and habit they cover a wide range.
Lankester in his article upon the Arthropoda, in the tenth edition of the
Encyclopaedia Britannica, dwells upon the fact that whereas the adult
Peripatus has but one persisting segment in front of the head, and its mouth
is between the second persisting appendages, in Arachnids the mouth has
receded and lies between the bases of the appendages (pedipalpi) of the
third persisting segment, while two of the persisting segments, those of the
eyes and chelicerae, have passed in front of the mouth. This process has
continued in the Crustacea and in the Insecta; in both of these classes there
are three embryonic segments in front of the adult mouth, which lies
between the appendages of the fourth segment.
In the larger and more complex Arachnida the number of segments is
fixed and constant, and though possibly no adult member of the group,
owing to the suppression of one or more segments during the ontogeny,
ever shows the full number at any one time, the body can be analysed into
twenty-one segments. It is interesting to note that the same number of
segments occurs in Insecta and in the higher Crustacea.[204] The significance
of this fact is not perhaps apparent, but it seems to indicate “a sort of
general oneness, if I may be allowed to use so strong an expression,” as Mr.
Curdle said when discussing the unities of the drama with Nicholas
Nickleby.
ARACHNIDA—INTRODUCTION
The Arachnida, together with the Crustacea, Insecta, Myriapoda, and
Peripatus, make up the great phylum Arthropoda, a phylum which, from the
point of view of numbers of species and of individuals, is the dominant one
on this planet, and from the point of view of intelligence and power of co-
operating in the formation of social communities is surpassed but by the
Vertebrata. The Arachnida form a more diverse class than the Insecta; they
differ, perhaps, as much inter se as do the Crustacea, and in structure as in
size and habit they cover a wide range.
Lankester in his article upon the Arthropoda, in the tenth edition of the
Encyclopaedia Britannica, dwells upon the fact that whereas the adult
Peripatus has but one persisting segment in front of the head, and its mouth
is between the second persisting appendages, in Arachnids the mouth has
receded and lies between the bases of the appendages (pedipalpi) of the
third persisting segment, while two of the persisting segments, those of the
eyes and chelicerae, have passed in front of the mouth. This process has
continued in the Crustacea and in the Insecta; in both of these classes there
are three embryonic segments in front of the adult mouth, which lies
between the appendages of the fourth segment.
In the larger and more complex Arachnida the number of segments is
fixed and constant, and though possibly no adult member of the group,
owing to the suppression of one or more segments during the ontogeny,
ever shows the full number at any one time, the body can be analysed into
twenty-one segments. It is interesting to note that the same number of
segments occurs in Insecta and in the higher Crustacea.[204] The significance
of this fact is not perhaps apparent, but it seems to indicate “a sort of
general oneness, if I may be allowed to use so strong an expression,” as Mr.
Curdle said when discussing the unities of the drama with Nicholas
Nickleby.
Page 300
These segments are arranged in higher categories or “tagmata,” of which
we can recognise three: (i.) the prosoma, (ii.) the mesosoma, and (iii.) the
metasoma. The prosoma, sometimes termed the “cephalothorax,” includes
all the segments in front of the genital pore. According to this definition the
prosoma includes the segment which bears the chilaria in Limulus (the
King-crab) and the pregenital but evanescent segment in Scorpions. The
mesosoma begins with the segment bearing the genital pore, and ends with
the last segment which bears free appendages, six segments in all. The
metasoma also consists of six segments which have no appendages;
together with the mesosoma it forms the abdomen of some writers. The
anus lies posteriorly on the last segment, and behind it comes in the higher
forms a post-anal “telson,” taking in Scorpions the form of the sting, in
King-crabs that of the spine.
As we have seen, it is only in the more typical and perhaps higher forms
that we can find our twenty-one segments, and then they are never present
all at once. In many groups of Arachnids the number is reduced at the
hinder end, and obscured by the fusion of neighbouring segments. Also
segments are dropped as a stitch is dropped when knitting; for instance, in
the rostral segment which has a neuromere, and in the Spider Trochosa
vestigial antennae, or in Scorpions the pregenital segment.
Primitive Arachnids appear to have lived in the sea and to have breathed
by gill-books borne on appendages; when their descendants took to living
on land and to breathing air instead of water, the gill-books sank into the
body and became lung-books, to which the air was admitted by slit-like
stigmata. In other terrestrial forms the lung-books are replaced by tracheae
which in their structure and arrangement resemble those of Peripatus rather
than those of the Insecta. The circulation, as is usual in Arthropods, is
largely lacunar, but in Scorpions and Limulus the arteries form definite
channels, and are in fact better developed than in any other Arthropod.
As a rule the alimentary canal in Arachnids is no longer than the distance
between the mouth and the anus; but in the King-crab, where the mouth is
pushed back almost to the centre of the body, there is a flexure in the
median vertical plane. Paired glands, usually called the liver, open into the
mesenteron; food passes into the lumen of these glands, and is probably
digested there. In many Arachnids these glands extend into the limbs. In
those members of the group that have become terrestrial the nitrogenous
we can recognise three: (i.) the prosoma, (ii.) the mesosoma, and (iii.) the
metasoma. The prosoma, sometimes termed the “cephalothorax,” includes
all the segments in front of the genital pore. According to this definition the
prosoma includes the segment which bears the chilaria in Limulus (the
King-crab) and the pregenital but evanescent segment in Scorpions. The
mesosoma begins with the segment bearing the genital pore, and ends with
the last segment which bears free appendages, six segments in all. The
metasoma also consists of six segments which have no appendages;
together with the mesosoma it forms the abdomen of some writers. The
anus lies posteriorly on the last segment, and behind it comes in the higher
forms a post-anal “telson,” taking in Scorpions the form of the sting, in
King-crabs that of the spine.
As we have seen, it is only in the more typical and perhaps higher forms
that we can find our twenty-one segments, and then they are never present
all at once. In many groups of Arachnids the number is reduced at the
hinder end, and obscured by the fusion of neighbouring segments. Also
segments are dropped as a stitch is dropped when knitting; for instance, in
the rostral segment which has a neuromere, and in the Spider Trochosa
vestigial antennae, or in Scorpions the pregenital segment.
Primitive Arachnids appear to have lived in the sea and to have breathed
by gill-books borne on appendages; when their descendants took to living
on land and to breathing air instead of water, the gill-books sank into the
body and became lung-books, to which the air was admitted by slit-like
stigmata. In other terrestrial forms the lung-books are replaced by tracheae
which in their structure and arrangement resemble those of Peripatus rather
than those of the Insecta. The circulation, as is usual in Arthropods, is
largely lacunar, but in Scorpions and Limulus the arteries form definite
channels, and are in fact better developed than in any other Arthropod.
As a rule the alimentary canal in Arachnids is no longer than the distance
between the mouth and the anus; but in the King-crab, where the mouth is
pushed back almost to the centre of the body, there is a flexure in the
median vertical plane. Paired glands, usually called the liver, open into the
mesenteron; food passes into the lumen of these glands, and is probably
digested there. In many Arachnids these glands extend into the limbs. In
those members of the group that have become terrestrial the nitrogenous
Page 301
excreta are separated out by Malpighian tubules which open into the
proctodaeum; but coxal glands, homologous with the green gland and shell-
glands of Crustacea, may coexist, and in the aquatic Limulus these alone are
found. They usually open on the base of one or more pairs of walking legs.
The endosternite, or internal skeletal plate to which muscles are attached,
reaches a higher development in the Arachnida than in the Crustacea. In
Scorpions it forms a kind of diaphragm incompletely separating the cavities
of the pro- and meso-soma.
The supra-oesophageal ganglion supplies the two existing segments
which have slipped before the mouth, i.e. those of the eyes and of the
chelicerae. The post-oral ganglia in the Acarina, the Pedipalpi, the
Solifugae, and the Araneae have fused into a central nerve-mass, from
which nerves radiate; but in Limulus the prosomatic appendages are all
supplied from the nerve-ring. The chief sense-organs are eyes of the
characteristic Arthropod type, and sensory hairs of a great variety of
complexity. Scorpions and Spiders have stridulating organs, and we may
assume that they have also some auditory apparatus; perhaps some of the
hairs just mentioned act as hearing organs.
Arachnids are male and female; they do not reproduce asexually, and
there is no satisfactory proof that they ever reproduce parthenogenetically.
As a rule there is little external difference between the two sexes, except in
Spiders, where the male is as a rule smaller than the female, and when adult
has the pedipalpi modified for use in depositing the spermatophores. The
ovaries and testes are annular, and with their ducts encircle the alimentary
canal in Mites and Phalangids; in Scorpions and King-crabs they have
become retiform. Mites, Scorpions, and Pedipalps are viviparous, their eggs
developing in the ovary or in a uterus. Other Arachnids lay eggs, and many
Spiders and Pseudoscorpions carry their eggs about with them. As a rule the
young is but a miniature of the parent, and the Arachnid, unlike the
Crustacean or Insect, undergoes little or no metamorphosis.
A certain number of Mites are parasitic in plants and in animals, and a
few, together with a few Spiders, have resumed the aquatic life of their
remote ancestors. The members of some Orders, such as the Solifugae and
Opiliones, are nocturnal, and many are provided with silk-glands and weave
webs which reach their highest pitch of perfection amongst the Spiders. At
times—especially is this the case with the Mites—enormous numbers of
proctodaeum; but coxal glands, homologous with the green gland and shell-
glands of Crustacea, may coexist, and in the aquatic Limulus these alone are
found. They usually open on the base of one or more pairs of walking legs.
The endosternite, or internal skeletal plate to which muscles are attached,
reaches a higher development in the Arachnida than in the Crustacea. In
Scorpions it forms a kind of diaphragm incompletely separating the cavities
of the pro- and meso-soma.
The supra-oesophageal ganglion supplies the two existing segments
which have slipped before the mouth, i.e. those of the eyes and of the
chelicerae. The post-oral ganglia in the Acarina, the Pedipalpi, the
Solifugae, and the Araneae have fused into a central nerve-mass, from
which nerves radiate; but in Limulus the prosomatic appendages are all
supplied from the nerve-ring. The chief sense-organs are eyes of the
characteristic Arthropod type, and sensory hairs of a great variety of
complexity. Scorpions and Spiders have stridulating organs, and we may
assume that they have also some auditory apparatus; perhaps some of the
hairs just mentioned act as hearing organs.
Arachnids are male and female; they do not reproduce asexually, and
there is no satisfactory proof that they ever reproduce parthenogenetically.
As a rule there is little external difference between the two sexes, except in
Spiders, where the male is as a rule smaller than the female, and when adult
has the pedipalpi modified for use in depositing the spermatophores. The
ovaries and testes are annular, and with their ducts encircle the alimentary
canal in Mites and Phalangids; in Scorpions and King-crabs they have
become retiform. Mites, Scorpions, and Pedipalps are viviparous, their eggs
developing in the ovary or in a uterus. Other Arachnids lay eggs, and many
Spiders and Pseudoscorpions carry their eggs about with them. As a rule the
young is but a miniature of the parent, and the Arachnid, unlike the
Crustacean or Insect, undergoes little or no metamorphosis.
A certain number of Mites are parasitic in plants and in animals, and a
few, together with a few Spiders, have resumed the aquatic life of their
remote ancestors. The members of some Orders, such as the Solifugae and
Opiliones, are nocturnal, and many are provided with silk-glands and weave
webs which reach their highest pitch of perfection amongst the Spiders. At
times—especially is this the case with the Mites—enormous numbers of
Page 302
individuals live together, but they never show the least adaptation to
communal life, and no individuals are ever specialised to perform certain
functions, as is the rule in communities of social Insects.
With the two exceptions that we regard the Trilobites as more nearly
allied to the Crustacea, and have therefore considered them apart, and have
treated the Pycnogonida independently of the Arachnida, we have followed
Lankester in his classification, though not always in his nomenclature:—
Sub-class 1. Delobranchiata[205] (Merostomata).
Order (i.) Xiphosura.
Order (ii.) Eurypterida (= Gigantostraca, Extinct).
Sub-class 2. Embolobranchiata.
Order (i.) Scorpionidea.
Order (ii.) Pedipalpi.
Order (iii.) Araneae.
Order (iv.) Palpigradi.
Order (v.) Solifugae.
Order (vi.) Chernetidea (= Pseudoscorpiones).
Order (vii.) Podogona.
Order (viii.) Phalangidea (= Opiliones).
Order (ix.) Acarina.
Appendices
(i.) Tardigrada.
(ii.) Pentastomida.
communal life, and no individuals are ever specialised to perform certain
functions, as is the rule in communities of social Insects.
With the two exceptions that we regard the Trilobites as more nearly
allied to the Crustacea, and have therefore considered them apart, and have
treated the Pycnogonida independently of the Arachnida, we have followed
Lankester in his classification, though not always in his nomenclature:—
Sub-class 1. Delobranchiata[205] (Merostomata).
Order (i.) Xiphosura.
Order (ii.) Eurypterida (= Gigantostraca, Extinct).
Sub-class 2. Embolobranchiata.
Order (i.) Scorpionidea.
Order (ii.) Pedipalpi.
Order (iii.) Araneae.
Order (iv.) Palpigradi.
Order (v.) Solifugae.
Order (vi.) Chernetidea (= Pseudoscorpiones).
Order (vii.) Podogona.
Order (viii.) Phalangidea (= Opiliones).
Order (ix.) Acarina.
Appendices
(i.) Tardigrada.
(ii.) Pentastomida.
Page 303
CHAPTER X
ARACHNIDA (CONTINUED)—DELOBRANCHIATA =
MEROSTOMATA—XIPHOSURA
SUB-CLASS I.—DELOBRANCHIATA = MEROSTOMATA.
Order I. Xiphosura.[206]
In his recent classification of the Arachnida, Lankester[207] has grouped
the Xiphosura or King-crabs with the extinct Eurypterids or Gigantostraca
under the name of Delobranchiata, better known under the name
Merostomata[208] of Dana. The chief character of this group, and one which
differentiates it from all the animals placed together by Lankester in the
group Embolobranchiata, is that they have gills patent and exposed. The
Xiphosura are, in fact, with the exception of a few marine Mites, the only
Arachnids which now live in the sea as did their allies the Eurypterids in
Palaeozoic times. With a few fresh-water exceptions, all other Arachnids
have taken to life on land, and with a change from water-breathing to air-
breathing came a change in the respiratory system, the gills becoming
“lung-books,” or possibly tracheae, or disappearing altogether.
A few years ago Pocock re-classified the Xiphosura, and his
classification will be found on pp. 276, 277. It will be noticed that in his
classification the generic name Limulus has disappeared. I have, however,
retained it in this article, partly because I regard the name as so well
established that every one knows what it denotes, and partly because in a
group which contains confessedly very few species, differing inter se
comparatively slightly, it seems unnecessary to complicate matters with
sub-families and new names.
Looked at from above a Limulus presents a horse-shoe-like outline, from
the posterior end of which projects a long spine. It is often called in
America the Horsefoot-crab, but its common or vulgar name is the King-
ARACHNIDA (CONTINUED)—DELOBRANCHIATA =
MEROSTOMATA—XIPHOSURA
SUB-CLASS I.—DELOBRANCHIATA = MEROSTOMATA.
Order I. Xiphosura.[206]
In his recent classification of the Arachnida, Lankester[207] has grouped
the Xiphosura or King-crabs with the extinct Eurypterids or Gigantostraca
under the name of Delobranchiata, better known under the name
Merostomata[208] of Dana. The chief character of this group, and one which
differentiates it from all the animals placed together by Lankester in the
group Embolobranchiata, is that they have gills patent and exposed. The
Xiphosura are, in fact, with the exception of a few marine Mites, the only
Arachnids which now live in the sea as did their allies the Eurypterids in
Palaeozoic times. With a few fresh-water exceptions, all other Arachnids
have taken to life on land, and with a change from water-breathing to air-
breathing came a change in the respiratory system, the gills becoming
“lung-books,” or possibly tracheae, or disappearing altogether.
A few years ago Pocock re-classified the Xiphosura, and his
classification will be found on pp. 276, 277. It will be noticed that in his
classification the generic name Limulus has disappeared. I have, however,
retained it in this article, partly because I regard the name as so well
established that every one knows what it denotes, and partly because in a
group which contains confessedly very few species, differing inter se
comparatively slightly, it seems unnecessary to complicate matters with
sub-families and new names.
Looked at from above a Limulus presents a horse-shoe-like outline, from
the posterior end of which projects a long spine. It is often called in
America the Horsefoot-crab, but its common or vulgar name is the King-
Page 304
crab. Across the middle of the body is a joint, and this joint separates the
prosoma from the meso- and metasoma which are in King-crabs fused
together. The prosoma comprises all the segments up to and including the
segment which carries the chilaria;[209] the mesosoma begins with the
segment bearing the genital pores, and ends with the last segment which
bears appendages; the metasoma comprises all the segments posterior to the
last segment which carries appendages. The prosoma corresponds with the
“cephalothorax” of some authors, and the meso-plus the metasoma are
equivalent to their “abdomen.”
Dorsally, then, the prosoma is a vaulted structure with a smooth, horse-
shoe-shaped anterior and lateral margin. Its posterior edge, the line where
the meso-plus the metasoma are hinged, is a re-entrant bay with three sides.
The meso- and metasoma are in the King-crabs fused together and form a
hexagon. Three sides of this hexagonal double region form the hinge, two
form the lateral margins and slope inwards; these bear six fused and six-
jointed spines which have a segmental value. The sixth or posterior side is
indented, and its concavity forms the area to which the large post-anal,
unsegmented tail or spine is hinged.
The whole body is covered by a smooth chitinous sheath varying from
sage-green to black in colour, and it is kept very clean, probably by some
excretion which hinders various sessile animals attaching themselves to it
as they do, for instance, on many Copepods. Burrowing animals like
Limulus are usually free from these messmates. King-crabs have a self-
respecting, well-groomed appearance. On the rounded dorsal surface the
chitinous covering is produced into a certain number of spines arranged in a
median and two lateral rows. The anterior median spine overhangs the
median eyes, and the anterior lateral spine on each side overshadows the
large lateral eyes.
prosoma from the meso- and metasoma which are in King-crabs fused
together. The prosoma comprises all the segments up to and including the
segment which carries the chilaria;[209] the mesosoma begins with the
segment bearing the genital pores, and ends with the last segment which
bears appendages; the metasoma comprises all the segments posterior to the
last segment which carries appendages. The prosoma corresponds with the
“cephalothorax” of some authors, and the meso-plus the metasoma are
equivalent to their “abdomen.”
Dorsally, then, the prosoma is a vaulted structure with a smooth, horse-
shoe-shaped anterior and lateral margin. Its posterior edge, the line where
the meso-plus the metasoma are hinged, is a re-entrant bay with three sides.
The meso- and metasoma are in the King-crabs fused together and form a
hexagon. Three sides of this hexagonal double region form the hinge, two
form the lateral margins and slope inwards; these bear six fused and six-
jointed spines which have a segmental value. The sixth or posterior side is
indented, and its concavity forms the area to which the large post-anal,
unsegmented tail or spine is hinged.
The whole body is covered by a smooth chitinous sheath varying from
sage-green to black in colour, and it is kept very clean, probably by some
excretion which hinders various sessile animals attaching themselves to it
as they do, for instance, on many Copepods. Burrowing animals like
Limulus are usually free from these messmates. King-crabs have a self-
respecting, well-groomed appearance. On the rounded dorsal surface the
chitinous covering is produced into a certain number of spines arranged in a
median and two lateral rows. The anterior median spine overhangs the
median eyes, and the anterior lateral spine on each side overshadows the
large lateral eyes.
Page 305
Fig. 152.—Dorsal view of the King-crab, Limulus polyphemus, × ½. From
Shipley and MacBride. 1, Carapace covering prosoma; 2, meso- and metasoma;
3, telson; 4, median eye; 5, lateral eye.
Shipley and MacBride. 1, Carapace covering prosoma; 2, meso- and metasoma;
3, telson; 4, median eye; 5, lateral eye.
Page 306
The vaulted carapace is turned in on the under side, where there is a flat
rim which widens anteriorly, and on the inner edge this rim borders a
sunken area, into the concavity of which the numerous appendages project.
Thus, although when viewed from above a Limulus looks as though it had a
solid body shaped something like half a pear, when viewed from below,
especially if the appendages be removed, it will be found that the body is
thin and hollowed, and almost leaf-like, as if most of the edible part of the
half-pear had been scooped out. Within the hollow thus formed the
appendages lie, and here they move about, seldom or never protruding
beyond the edge of the carapace,—in fact, all except the pedipalps and
ambulatory legs are too short to project beyond this limit.
rim which widens anteriorly, and on the inner edge this rim borders a
sunken area, into the concavity of which the numerous appendages project.
Thus, although when viewed from above a Limulus looks as though it had a
solid body shaped something like half a pear, when viewed from below,
especially if the appendages be removed, it will be found that the body is
thin and hollowed, and almost leaf-like, as if most of the edible part of the
half-pear had been scooped out. Within the hollow thus formed the
appendages lie, and here they move about, seldom or never protruding
beyond the edge of the carapace,—in fact, all except the pedipalps and
ambulatory legs are too short to project beyond this limit.
Page 307
Fig. 153.—Ventral view of the King-crab, Limulus polyphemus, × ½. From
Shipley and MacBride. 1, Carapace covering prosoma; 2, meso- and metasoma;
3, telson; 4, chelicera; 5, pedipalp; 6, 7, 8, 9, 3rd to 6th appendages, ambulatory
limbs; 10, genital operculum turned forward to show the genital apertures; 11,
12, 13, 14, 15, appendages bearing gill-books; 16, anus; 17, mouth; 18, chilaria.
Shipley and MacBride. 1, Carapace covering prosoma; 2, meso- and metasoma;
3, telson; 4, chelicera; 5, pedipalp; 6, 7, 8, 9, 3rd to 6th appendages, ambulatory
limbs; 10, genital operculum turned forward to show the genital apertures; 11,
12, 13, 14, 15, appendages bearing gill-books; 16, anus; 17, mouth; 18, chilaria.
Page 308
The body of a King-crab can be analysed into twenty-one segments, but
these do not all persist to the adult stage. They are grouped together in
higher aggregates, or “tagmata” as Lankester calls them, and most of the
segments bear paired appendages.
The segments with their respective appendages and their grouping into
tagmata are shown in the following scheme:—
Appendages.
I. Segment Median eyes Preoral Prosoma
II. „ Rostrum „
III. „ Chelicerae „
IV. „ Pedipalpi Lateral to mouth
V. „ 1st Walking Legs Postoral
VI. „ 2nd Walking Legs „
VII. „ 3rd Walking Legs „
VIII. „ 4th Walking Legs „
IX. „ Chilaria „
X. „ Genital operculum „ Mesosoma
XI. „ 1st Gill-books „
XII. „ 2nd Gill-books „
XIII. „ 3rd Gill-books „
XIV. „ 4th Gill-books „
XV. „ 5th Gill-books „
XVI. „ No appendages „ Metasoma
XVII. „ „ „
XVIII. „ „ „
XIX. „ „ „
XX. „ „ „
XXI. „ „ „
We have followed Carpenter[210] in inserting the rostral segment. This
corresponds with the segment that in Insects and Crustacea bears the
antennae or first antennae respectively, the absence of these organs being
one of the characteristic but negative features of all Arachnids. The
evidence for the existence of this evanescent segment rests partly upon the
observation of von Jaworowski[211] on the vestigial feelers in an embryo
Spider, Trochosa, and perhaps more securely on the fact that, according to
Korschelt and Heider, there is a distinct neuromere for this segment,
between the proto-cerebral neuromere which supplies the eyes and the trito-
these do not all persist to the adult stage. They are grouped together in
higher aggregates, or “tagmata” as Lankester calls them, and most of the
segments bear paired appendages.
The segments with their respective appendages and their grouping into
tagmata are shown in the following scheme:—
Appendages.
I. Segment Median eyes Preoral Prosoma
II. „ Rostrum „
III. „ Chelicerae „
IV. „ Pedipalpi Lateral to mouth
V. „ 1st Walking Legs Postoral
VI. „ 2nd Walking Legs „
VII. „ 3rd Walking Legs „
VIII. „ 4th Walking Legs „
IX. „ Chilaria „
X. „ Genital operculum „ Mesosoma
XI. „ 1st Gill-books „
XII. „ 2nd Gill-books „
XIII. „ 3rd Gill-books „
XIV. „ 4th Gill-books „
XV. „ 5th Gill-books „
XVI. „ No appendages „ Metasoma
XVII. „ „ „
XVIII. „ „ „
XIX. „ „ „
XX. „ „ „
XXI. „ „ „
We have followed Carpenter[210] in inserting the rostral segment. This
corresponds with the segment that in Insects and Crustacea bears the
antennae or first antennae respectively, the absence of these organs being
one of the characteristic but negative features of all Arachnids. The
evidence for the existence of this evanescent segment rests partly upon the
observation of von Jaworowski[211] on the vestigial feelers in an embryo
Spider, Trochosa, and perhaps more securely on the fact that, according to
Korschelt and Heider, there is a distinct neuromere for this segment,
between the proto-cerebral neuromere which supplies the eyes and the trito-
Page 309
cerebral neuromere which supplies the chelicerae. According to Brauer[212]
the chelicerae of Scorpions are also supplied by the third neuromere.
The bases of the chelicerae do not limit the mouth, but between and
behind them is a ridge or tubercle which has the same relationship to the
mouth of Limulus that the labrum has in Insects and some Crustacea.
Posteriorly the mouth is bounded by the “promesosternite,” a large median
plate which lies between the bases of the ambulatory limbs. The pedipalps
and all the ambulatory limbs have their bases directed towards the mouth,
their gnathobases or sterno-coxal processes are cushion-like structures
covered with spines—all pointing inwards—and with crushing teeth. They
form a very efficient manducatory apparatus. The boundary of the mouth is
finally completed by the chilaria.
Certain of the appendages which persist will be described with the
functions they subserve, the eyes with the sense-organs, the genital
operculum with the generative organs, the gill-books with the respiratory
system, but the chelicerae, pedipalpi, and walking limbs, which have
retained the functions of prehension and locomotion usual to limbs, merit a
little attention.[213] The chelicerae are short and composed of but three joints.
They are, like the succeeding segments, chelate, and the chelae of all are
fine and delicate like a pair of forceps rather than like a Lobster’s claw. In
the female L. polyphemus the pedipalp is remarkably like the three
ambulatory legs which succeed it, and all four are chelate, but in the adult
male the penultimate joint of the pedipalp is not prolonged to form one limb
of the chela, which is therefore absent, and the appendage is thicker and
heavier than in the other sex. In L. longispina and L. moluccanus the first
walking leg, as well as the pedipalp, ends in a claw and not in a chela; the
immature males resemble the females. The first three walking legs in both
sexes of L. polyphemus resemble the pedipalpi of the female, and like them
have six joints. The fourth and last pair of ambulatory appendages is not
chelate, but its distal joints carry a number of somewhat flattened structures,
which are capable of being alternately divaricated and approximated or
bunched together. This enables them to act as organs for clearing away sand
or mud from beneath the carapace as the creature lies prone on the bottom
of the sea. To quote Mr. Lloyd,[214] the “two limbs are, sometimes alternately
and sometimes simultaneously, thrust backward below the carapace, quite
beyond the hinder edge of the shell; and in the act of thrusting, the lobes or
plates on each leg encounter the sand, the resistance or pressure of which
the chelicerae of Scorpions are also supplied by the third neuromere.
The bases of the chelicerae do not limit the mouth, but between and
behind them is a ridge or tubercle which has the same relationship to the
mouth of Limulus that the labrum has in Insects and some Crustacea.
Posteriorly the mouth is bounded by the “promesosternite,” a large median
plate which lies between the bases of the ambulatory limbs. The pedipalps
and all the ambulatory limbs have their bases directed towards the mouth,
their gnathobases or sterno-coxal processes are cushion-like structures
covered with spines—all pointing inwards—and with crushing teeth. They
form a very efficient manducatory apparatus. The boundary of the mouth is
finally completed by the chilaria.
Certain of the appendages which persist will be described with the
functions they subserve, the eyes with the sense-organs, the genital
operculum with the generative organs, the gill-books with the respiratory
system, but the chelicerae, pedipalpi, and walking limbs, which have
retained the functions of prehension and locomotion usual to limbs, merit a
little attention.[213] The chelicerae are short and composed of but three joints.
They are, like the succeeding segments, chelate, and the chelae of all are
fine and delicate like a pair of forceps rather than like a Lobster’s claw. In
the female L. polyphemus the pedipalp is remarkably like the three
ambulatory legs which succeed it, and all four are chelate, but in the adult
male the penultimate joint of the pedipalp is not prolonged to form one limb
of the chela, which is therefore absent, and the appendage is thicker and
heavier than in the other sex. In L. longispina and L. moluccanus the first
walking leg, as well as the pedipalp, ends in a claw and not in a chela; the
immature males resemble the females. The first three walking legs in both
sexes of L. polyphemus resemble the pedipalpi of the female, and like them
have six joints. The fourth and last pair of ambulatory appendages is not
chelate, but its distal joints carry a number of somewhat flattened structures,
which are capable of being alternately divaricated and approximated or
bunched together. This enables them to act as organs for clearing away sand
or mud from beneath the carapace as the creature lies prone on the bottom
of the sea. To quote Mr. Lloyd,[214] the “two limbs are, sometimes alternately
and sometimes simultaneously, thrust backward below the carapace, quite
beyond the hinder edge of the shell; and in the act of thrusting, the lobes or
plates on each leg encounter the sand, the resistance or pressure of which
Page 310
causes them to open and fill with sand, a load of which at every thrusting
operation is pushed away from under the king-crab, and deposited outside
the carapace. The four plates then close and are withdrawn closed, previous
to being opened and charged with another load of sand; and at the deposit of
every load the whole animal sinks deeper into its bed, till it is hidden all
except the eyes.” There seems little doubt that the action of these
appendages in removing the sand from under the carapace is reinforced by
the fanning action of the respiratory appendages, which set up a current that
helps to wash the particles away. But the posterior walking legs are not the
only organs used in burrowing. The Rev. Dr. Lockwood,[215] who observed
the habits of L. polyphemus off the New Jersey coast, says, “The king-crab
delights in moderately deep water, say from two to six fathoms. It is
emphatically a burrowing animal, living literally in the mud, into which it
scoops or gouges its way with great facility. In the burrowing operation the
forward edge of the anterior shield is pressed downward and shoved
forward, the two shields being inflected, and the sharp point of the tail
presenting the fulcrum as it pierces the mud, whilst underneath the feet are
incessantly active scratching up and pushing out the earth on both sides.
There is a singular economy of force in this excavating action; for the
doubling up or inflecting and straightening out of the two carapaces, with
the pushing purchase exerted by the tail, accomplish both digging and
subterranean progression.”
At night-time Limulus is apt to leave the sand and progress by a series of
short swimming hops, the respiratory appendages giving the necessary
impetus, whilst between each two short flights the animal balances itself for
a moment on the tip of its tail. During this method of progressing the
carapace is slanting, forming an angle of about 45° with the ground. The
unsegmented tail is also used when a King-crab falls on its back. “The spine
is then bent, i.e. its point is planted in the sand so that it makes an acute
angle with the carapace, which is then so far raised that some of the feet are
enabled to grasp a projecting surface, either longitudinal or vertical, or at
some combination of the two; and the crab then turns over.”
operation is pushed away from under the king-crab, and deposited outside
the carapace. The four plates then close and are withdrawn closed, previous
to being opened and charged with another load of sand; and at the deposit of
every load the whole animal sinks deeper into its bed, till it is hidden all
except the eyes.” There seems little doubt that the action of these
appendages in removing the sand from under the carapace is reinforced by
the fanning action of the respiratory appendages, which set up a current that
helps to wash the particles away. But the posterior walking legs are not the
only organs used in burrowing. The Rev. Dr. Lockwood,[215] who observed
the habits of L. polyphemus off the New Jersey coast, says, “The king-crab
delights in moderately deep water, say from two to six fathoms. It is
emphatically a burrowing animal, living literally in the mud, into which it
scoops or gouges its way with great facility. In the burrowing operation the
forward edge of the anterior shield is pressed downward and shoved
forward, the two shields being inflected, and the sharp point of the tail
presenting the fulcrum as it pierces the mud, whilst underneath the feet are
incessantly active scratching up and pushing out the earth on both sides.
There is a singular economy of force in this excavating action; for the
doubling up or inflecting and straightening out of the two carapaces, with
the pushing purchase exerted by the tail, accomplish both digging and
subterranean progression.”
At night-time Limulus is apt to leave the sand and progress by a series of
short swimming hops, the respiratory appendages giving the necessary
impetus, whilst between each two short flights the animal balances itself for
a moment on the tip of its tail. During this method of progressing the
carapace is slanting, forming an angle of about 45° with the ground. The
unsegmented tail is also used when a King-crab falls on its back. “The spine
is then bent, i.e. its point is planted in the sand so that it makes an acute
angle with the carapace, which is then so far raised that some of the feet are
enabled to grasp a projecting surface, either longitudinal or vertical, or at
some combination of the two; and the crab then turns over.”
Page 311
Fig. 154.—A sagittal section of Limulus, seen from the right side, somewhat
smaller than natural size. After Patten and Redenbaugh.
All the prosomatic appendages, except the chelicera (4) and chilarium (33) of the
right side, are omitted. The genital operculum (32) and the five gills (28) are
represented.
The muscles are omitted except the fibres running from the occipital ring to the
posterior side of the oesophagus, the chilarial muscles, the sphincter ani (27),
and the levator ani (24).
The endosternite (34), with the occipital ring and the capsuliginous bar, is seen
from the side, and the positions of the abdominal endochondrites (31) are
indicated.
The mouth (1) leads into the oesophagus, which passes through the brain to the
proventriculus (12). A constriction, which marks the position of the pyloric
valve, separates the proventriculus from the intestine (23) which passes
posteriorly to the anus (26). A pair of hepatic ducts (15) enter the intestine
opposite the endocranium.
The heart (16) surrounded by the pericardial sinus lies above the intestine. The
pericardium is shown between the heart and the intestine. The ostia (17) of the
heart and the origins of the four lateral arteries (19) are indicated; the frontal
artery (13) and the aortic arches (14) curving down to the brain, arise from the
anterior end of the heart; the superior abdominal artery and the opening of the
collateral artery into it are shown.
The brain surrounding the oesophagus is seen in side view upon the neural side
of the endosternite (34). The ventral cord (35) passes through the occipital ring
into the abdominal region. The anterior commissure (3), with the three rostral
nerves (2) innervating the rostrum, or labrum, and four of the post-oral
commissures, are represented.
The cheliceral nerve with the small external pedal branch is shown entire, but the
next five neural nerves are cut off. The chilarial nerve, the opercular nerve, and
the five branchial nerves, enter their respective appendages, the two former
passing through the occipital ring.
From the fore-brain the three olfactory nerves (5) pass anteriorly to the olfactory
organ; the median eye-nerve (10) passes to the right of the proventriculus (12) to
the median eyes (11); the lateral eye-nerve (7) passes forward and is represented
smaller than natural size. After Patten and Redenbaugh.
All the prosomatic appendages, except the chelicera (4) and chilarium (33) of the
right side, are omitted. The genital operculum (32) and the five gills (28) are
represented.
The muscles are omitted except the fibres running from the occipital ring to the
posterior side of the oesophagus, the chilarial muscles, the sphincter ani (27),
and the levator ani (24).
The endosternite (34), with the occipital ring and the capsuliginous bar, is seen
from the side, and the positions of the abdominal endochondrites (31) are
indicated.
The mouth (1) leads into the oesophagus, which passes through the brain to the
proventriculus (12). A constriction, which marks the position of the pyloric
valve, separates the proventriculus from the intestine (23) which passes
posteriorly to the anus (26). A pair of hepatic ducts (15) enter the intestine
opposite the endocranium.
The heart (16) surrounded by the pericardial sinus lies above the intestine. The
pericardium is shown between the heart and the intestine. The ostia (17) of the
heart and the origins of the four lateral arteries (19) are indicated; the frontal
artery (13) and the aortic arches (14) curving down to the brain, arise from the
anterior end of the heart; the superior abdominal artery and the opening of the
collateral artery into it are shown.
The brain surrounding the oesophagus is seen in side view upon the neural side
of the endosternite (34). The ventral cord (35) passes through the occipital ring
into the abdominal region. The anterior commissure (3), with the three rostral
nerves (2) innervating the rostrum, or labrum, and four of the post-oral
commissures, are represented.
The cheliceral nerve with the small external pedal branch is shown entire, but the
next five neural nerves are cut off. The chilarial nerve, the opercular nerve, and
the five branchial nerves, enter their respective appendages, the two former
passing through the occipital ring.
From the fore-brain the three olfactory nerves (5) pass anteriorly to the olfactory
organ; the median eye-nerve (10) passes to the right of the proventriculus (12) to
the median eyes (11); the lateral eye-nerve (7) passes forward and is represented
Page 312
as cut off opposite the proventriculus. The lateral nerve (9) or first haemal nerve
is also cut off just beyond the point where it fuses with the second haemal nerve
(8). The stomodaeal nerve (6) ramifies over the oesophagus and proventriculus.
The second haemal nerve (8) passes to the anterior extremity of the carapace; its
haemal branch is cut off opposite the proventriculus. An intestinal branch arises
from near its base and disappears behind the anterior cornu of the endosternite.
The next three haemal nerves (36) are cut off close to the brain, and the
following nine haemal nerves are cut off beyond the cardiac branches. The
fifteenth haemal nerve (29) is cut off beyond its branch to the telson muscles.
Both branches of the haemal nerve are represented extending into the telson (25).
The intestinal nerves are shown arising from the haemal nerves and entering the
intestine. Those from the sixth and seventh neuromeres pass through foramina in
the endosternite, and communicate with a plexus in the longitudinal abdominal
muscles before entering the intestine. The eighth passes just posterior to the
endosternite and joins the same plexus. Those from the first four branchial
neuromeres arise very near the abdominal ganglia, and are double in their
origins, the anterior branches joining the above-mentioned plexus, and the
posterior branches entering the intestine. The fifteenth extends far back towards
the rectum and anastomoses with the sixteenth, which arises from the caudal
branch of the sixteenth haemal nerve, and innervates the rectum and anal
muscles.
The segmental cardiac nerves (18) arise from the haemal nerves of the sixth to
the thirteenth neuromeres respectively. The most anterior one passes to the inter-
tergal muscles and the epidermis in the median line, but the connections with the
cardiac plexus have not been made out. The next two (18) fuse to form a large
nerve, which passes to the inter-tergal muscles and epidermis, but has not been
observed to connect directly with the cardiac plexus. It, however, sends
posteriorly a branch, the pericardial nerve (20), which in turn gives a branch to
each of the cardiac nerves of the branchial neuromeres, and then continues
onward to the posterior margin of the abdomen. This nerve lies in the epidermis.
The median and lateral cardiac nerves (22 and 21) are seen upon the walls of the
heart. The five cardiac nerves from the branchial neuromeres pass, in the
epidermis, to the median line, and dip down to the median nerve (22) of the heart
opposite the last five pairs of ostia (17). They communicate with the pericardial
nerve (20) and also with the lateral sympathetic nerve (30).
Two post-cardiac nerves pass from the first and second post-branchial nerves to
the epidermis posterior to the heart.
The last cardiac nerve and the two post-cardiac nerves give off branches which
anastomose with each other and innervate the extensors of the telson.
The lateral sympathetic nerve (30) receives branches from all the neuromeres
from the eighth to the fourteenth, either through the cardiac nerves or the haemal
nerves, and innervates the branchio-thoracic muscles, extending with these far
into the cephalothorax.
is also cut off just beyond the point where it fuses with the second haemal nerve
(8). The stomodaeal nerve (6) ramifies over the oesophagus and proventriculus.
The second haemal nerve (8) passes to the anterior extremity of the carapace; its
haemal branch is cut off opposite the proventriculus. An intestinal branch arises
from near its base and disappears behind the anterior cornu of the endosternite.
The next three haemal nerves (36) are cut off close to the brain, and the
following nine haemal nerves are cut off beyond the cardiac branches. The
fifteenth haemal nerve (29) is cut off beyond its branch to the telson muscles.
Both branches of the haemal nerve are represented extending into the telson (25).
The intestinal nerves are shown arising from the haemal nerves and entering the
intestine. Those from the sixth and seventh neuromeres pass through foramina in
the endosternite, and communicate with a plexus in the longitudinal abdominal
muscles before entering the intestine. The eighth passes just posterior to the
endosternite and joins the same plexus. Those from the first four branchial
neuromeres arise very near the abdominal ganglia, and are double in their
origins, the anterior branches joining the above-mentioned plexus, and the
posterior branches entering the intestine. The fifteenth extends far back towards
the rectum and anastomoses with the sixteenth, which arises from the caudal
branch of the sixteenth haemal nerve, and innervates the rectum and anal
muscles.
The segmental cardiac nerves (18) arise from the haemal nerves of the sixth to
the thirteenth neuromeres respectively. The most anterior one passes to the inter-
tergal muscles and the epidermis in the median line, but the connections with the
cardiac plexus have not been made out. The next two (18) fuse to form a large
nerve, which passes to the inter-tergal muscles and epidermis, but has not been
observed to connect directly with the cardiac plexus. It, however, sends
posteriorly a branch, the pericardial nerve (20), which in turn gives a branch to
each of the cardiac nerves of the branchial neuromeres, and then continues
onward to the posterior margin of the abdomen. This nerve lies in the epidermis.
The median and lateral cardiac nerves (22 and 21) are seen upon the walls of the
heart. The five cardiac nerves from the branchial neuromeres pass, in the
epidermis, to the median line, and dip down to the median nerve (22) of the heart
opposite the last five pairs of ostia (17). They communicate with the pericardial
nerve (20) and also with the lateral sympathetic nerve (30).
Two post-cardiac nerves pass from the first and second post-branchial nerves to
the epidermis posterior to the heart.
The last cardiac nerve and the two post-cardiac nerves give off branches which
anastomose with each other and innervate the extensors of the telson.
The lateral sympathetic nerve (30) receives branches from all the neuromeres
from the eighth to the fourteenth, either through the cardiac nerves or the haemal
nerves, and innervates the branchio-thoracic muscles, extending with these far
into the cephalothorax.
Page 313
1, Mouth; 2, rostral nerve in labrum; 3, anterior commissure; 4, chelicera; 5,
olfactory nerves; 6, stomodaeal nerve; 7, lateral eye-nerve; 8, 2nd haemal nerve;
9, lateral nerve; 10, median eye-nerve; 11, median eye; 12, proventriculus; 13,
frontal artery; 14, aortic arch; 15, anterior hepatic duct of liver; 16, heart; 17, 2nd
ostium; 18, 7th and 8th segmental cardiac nerves; 19, one of the lateral arteries;
20, pericardial nerve; 21, lateral cardiac nerve; 22, median cardiac nerve; 23,
intestine; 24, levator ani muscle; 25, telson; 26, anus; 27, sphincter ani muscle;
28, last branchial appendage; 29, 15th haemal nerve; 30, lateral sympathetic
nerve; 31, 8th abdominal endochondrite; 32, genital operculum; 33, chilarium;
34, endosternite; 35, ventral nerve-cord; 36, 6th haemal nerve; 37, origin of 6th
neural nerve.
Limulus feeds partly on bivalves, but mainly on worms, especially
Nereids, which it catches with its chelate limbs as it burrows through the
sand. The food is held immediately under the mouth by the chelicerae,
aided at times by the succeeding appendages; it is thus brought within range
of the gnathobases of the walking legs, and these by an alternate motion
“card” the food into fragments, which when sufficiently comminuted pass
into the mouth. At times its appendages are caught between the valves of
Venus mercenaria, a burrowing bivalve known in America as the “quahog”
or “round clam.” The Limulus has seized with its chelate claws the
protruding siphon of this mollusc, which, being rapidly drawn in, drags
with it the limb of the king-crab, and the valves of the clam are swiftly
snapped to.
As a rule in Arachnids the alimentary canal is no longer than the body,
and runs straight from mouth to anus, but in Limulus, the mouth being
pushed far backward, there is a median loop, and the narrow oesophagus
which leads from the mouth, having traversed the nerve-ring, passes
forward towards the anterior end of the carapace. Here it enters into a
somewhat ⸧ shaped and spacious proventriculus; posteriorly the
proventriculus opens by a funnel-shaped valve into the anterior end of the
narrow intestine. All these structures are derived from the stomodaeum, are
lined with chitin and are provided with very muscular walls whose internal
surface is thrown into longitudinal ridges. The intestine runs straight
backward, diminishing in its diameter, and ends in a short, chitin-lined, and
muscular rectum which is derived from the proctodaeum; the anus is a
longitudinal slit. A large gland, usually called the liver, consisting of
innumerable tubules, pours its secretions into the broader anterior end of the
intestine by two ducts upon each side; it extends into the meso- and
olfactory nerves; 6, stomodaeal nerve; 7, lateral eye-nerve; 8, 2nd haemal nerve;
9, lateral nerve; 10, median eye-nerve; 11, median eye; 12, proventriculus; 13,
frontal artery; 14, aortic arch; 15, anterior hepatic duct of liver; 16, heart; 17, 2nd
ostium; 18, 7th and 8th segmental cardiac nerves; 19, one of the lateral arteries;
20, pericardial nerve; 21, lateral cardiac nerve; 22, median cardiac nerve; 23,
intestine; 24, levator ani muscle; 25, telson; 26, anus; 27, sphincter ani muscle;
28, last branchial appendage; 29, 15th haemal nerve; 30, lateral sympathetic
nerve; 31, 8th abdominal endochondrite; 32, genital operculum; 33, chilarium;
34, endosternite; 35, ventral nerve-cord; 36, 6th haemal nerve; 37, origin of 6th
neural nerve.
Limulus feeds partly on bivalves, but mainly on worms, especially
Nereids, which it catches with its chelate limbs as it burrows through the
sand. The food is held immediately under the mouth by the chelicerae,
aided at times by the succeeding appendages; it is thus brought within range
of the gnathobases of the walking legs, and these by an alternate motion
“card” the food into fragments, which when sufficiently comminuted pass
into the mouth. At times its appendages are caught between the valves of
Venus mercenaria, a burrowing bivalve known in America as the “quahog”
or “round clam.” The Limulus has seized with its chelate claws the
protruding siphon of this mollusc, which, being rapidly drawn in, drags
with it the limb of the king-crab, and the valves of the clam are swiftly
snapped to.
As a rule in Arachnids the alimentary canal is no longer than the body,
and runs straight from mouth to anus, but in Limulus, the mouth being
pushed far backward, there is a median loop, and the narrow oesophagus
which leads from the mouth, having traversed the nerve-ring, passes
forward towards the anterior end of the carapace. Here it enters into a
somewhat ⸧ shaped and spacious proventriculus; posteriorly the
proventriculus opens by a funnel-shaped valve into the anterior end of the
narrow intestine. All these structures are derived from the stomodaeum, are
lined with chitin and are provided with very muscular walls whose internal
surface is thrown into longitudinal ridges. The intestine runs straight
backward, diminishing in its diameter, and ends in a short, chitin-lined, and
muscular rectum which is derived from the proctodaeum; the anus is a
longitudinal slit. A large gland, usually called the liver, consisting of
innumerable tubules, pours its secretions into the broader anterior end of the
intestine by two ducts upon each side; it extends into the meso- and
Page 314
metasoma, and, together with the reproductive organs, forms a “packing” in
which the other organs are embedded. The contents of the alimentary canal
are described as “pulpy and scanty,” and probably much of the actual
digestion goes on inside the lumen of the above-mentioned gland.
The vascular system of Limulus, like that of the Scorpions, is more
completely developed than is usually the case in Arthropods. For the most
part the blood runs in definite arteries, and when it passes as it does into
venous lacunae these are more definite in position and in their retaining
walls than in other members of the phylum.
The heart lies in a pericardial space with which it communicates by
eight[216] pairs of ostia. Eight paired bands of connective tissue, the “alary
muscles” of authors, sling the heart to the pericardial membrane. Posteriorly
the pericardial chamber receives five paired veins on each side coming from
the gills and returning the purified blood to the heart.
Eleven arteries arise from the heart. These are (i.) a median frontal artery
which, passing forward, divides into a right and left marginal artery. These
run round the edge of the carapace to its posterior angle, where each
receives a branch of the collateral artery mentioned below. (ii.) and (iii.) are
the aortic arches (Fig. 154), paired vessels running round and supplying the
proventriculus and oesophagus. These unite ventrally in a vascular ring
which encloses the nerve-ring, and is continued along the ventral nerve-
cord as the ventral artery and along some of the chief nerves. This vascular
ring supplies the lateral eyes and all the appendages mentioned on p. 263 up
to and including the genital operculum. The ventral artery supplies the
respiratory appendages, and gives branches to the rectum, caudal spine, etc.
Two of its branches encircle the rectum, and uniting open into the superior
abdominal artery. iv.–xi. are paired lateral arteries which leave the heart
beneath the anterior four ostia, and soon enter a longitudinal pair of
collateral arteries which unite behind in the just mentioned superior
abdominal artery; they also give off branches to the muscles and to the
intestine, and a stout branch mentioned above which passes into the
marginal artery posteriorly. The venous system is lacunar, and the blood is
collected from the irregular spaces between the various organs into a pair of
longitudinal sinuses, whence it passes into the operculum and the five pairs
of gills. A large branchio-cardiac canal returns the blood from each gill to
the cavity of the pericardium, and so through the ostia to the heart. Eight
which the other organs are embedded. The contents of the alimentary canal
are described as “pulpy and scanty,” and probably much of the actual
digestion goes on inside the lumen of the above-mentioned gland.
The vascular system of Limulus, like that of the Scorpions, is more
completely developed than is usually the case in Arthropods. For the most
part the blood runs in definite arteries, and when it passes as it does into
venous lacunae these are more definite in position and in their retaining
walls than in other members of the phylum.
The heart lies in a pericardial space with which it communicates by
eight[216] pairs of ostia. Eight paired bands of connective tissue, the “alary
muscles” of authors, sling the heart to the pericardial membrane. Posteriorly
the pericardial chamber receives five paired veins on each side coming from
the gills and returning the purified blood to the heart.
Eleven arteries arise from the heart. These are (i.) a median frontal artery
which, passing forward, divides into a right and left marginal artery. These
run round the edge of the carapace to its posterior angle, where each
receives a branch of the collateral artery mentioned below. (ii.) and (iii.) are
the aortic arches (Fig. 154), paired vessels running round and supplying the
proventriculus and oesophagus. These unite ventrally in a vascular ring
which encloses the nerve-ring, and is continued along the ventral nerve-
cord as the ventral artery and along some of the chief nerves. This vascular
ring supplies the lateral eyes and all the appendages mentioned on p. 263 up
to and including the genital operculum. The ventral artery supplies the
respiratory appendages, and gives branches to the rectum, caudal spine, etc.
Two of its branches encircle the rectum, and uniting open into the superior
abdominal artery. iv.–xi. are paired lateral arteries which leave the heart
beneath the anterior four ostia, and soon enter a longitudinal pair of
collateral arteries which unite behind in the just mentioned superior
abdominal artery; they also give off branches to the muscles and to the
intestine, and a stout branch mentioned above which passes into the
marginal artery posteriorly. The venous system is lacunar, and the blood is
collected from the irregular spaces between the various organs into a pair of
longitudinal sinuses, whence it passes into the operculum and the five pairs
of gills. A large branchio-cardiac canal returns the blood from each gill to
the cavity of the pericardium, and so through the ostia to the heart. Eight
Page 315
veno-pericardiac muscles run from the under surface of the pericardium to
be inserted into the upper surface of the longitudinal sinus; they occur
opposite the ostia, and play an important part in the mechanism of the
circulation. The blood is coloured blue by haemocyanin; amoeboid
corpuscles float in the plasma.
The respiratory organs are external gills borne on the posterior face of the
exopodite of the lamella-like posterior five mesosomatic limbs. Each gill
consists of a series of leaves like the leaves of a book, and some 150–200 in
number. Within the substance of each leaf the blood flows, while without
the oxygen-carrying water circulates between the leaves. These gillbearing
appendages can be flapped to and fro, and they seem to be at times held
apart by the flabellum, a spatulate process which Patten and Redenbaugh
regard as a development of the median sensory knob on the outer side of the
coxopodite of the last pair of walking limbs.
Limulus has no trace of Malpighian tubules, structures which seem often
to develop only when animals cease to live in water and come to live in air.
The Xiphosura have retained as organs of nitrogenous excretion the more
primitive nephridia, or coxal glands as they are called, in the Arachnida.
They are redbrick in colour, and consist of a longitudinal portion on each
side of the body, which gives off a lobe opposite the base of the pedipalps
and each of the first three walking legs—in the embryo also of the
chelicerae and last walking legs, but these latter disappear during
development. A duct leads from the interior of the gland and opens upon the
posterior face of the last pair of walking legs but one.
The nervous system has been very fully described by Patten and
Redenbaugh, and its complex nature plays a large part in the ingenious
speculations of Dr. Gaskell as to the origin of Vertebrates. It consists of a
stout ring surrounding the oesophagus and a ventral nerve-cord, composed
—if we omit the so-called fore-brain—of sixteen neuromeres. The fore-
brain supplies the median and the lateral eyes, and gives off a median nerve
which runs to an organ, described as olfactory by Patten, situated in front of
the chelicerae on the ventral face of the carapace. Patten distinguishes
behind the fore-brain a mid-brain, which consists solely of the cheliceral
neuromere, a hind-brain which supplies the pedipalps and four pair of
walking legs, and an accessory brain which supplies the chilaria and the
genital operculum. This is continued backward into a ventral nerve-cord
be inserted into the upper surface of the longitudinal sinus; they occur
opposite the ostia, and play an important part in the mechanism of the
circulation. The blood is coloured blue by haemocyanin; amoeboid
corpuscles float in the plasma.
The respiratory organs are external gills borne on the posterior face of the
exopodite of the lamella-like posterior five mesosomatic limbs. Each gill
consists of a series of leaves like the leaves of a book, and some 150–200 in
number. Within the substance of each leaf the blood flows, while without
the oxygen-carrying water circulates between the leaves. These gillbearing
appendages can be flapped to and fro, and they seem to be at times held
apart by the flabellum, a spatulate process which Patten and Redenbaugh
regard as a development of the median sensory knob on the outer side of the
coxopodite of the last pair of walking limbs.
Limulus has no trace of Malpighian tubules, structures which seem often
to develop only when animals cease to live in water and come to live in air.
The Xiphosura have retained as organs of nitrogenous excretion the more
primitive nephridia, or coxal glands as they are called, in the Arachnida.
They are redbrick in colour, and consist of a longitudinal portion on each
side of the body, which gives off a lobe opposite the base of the pedipalps
and each of the first three walking legs—in the embryo also of the
chelicerae and last walking legs, but these latter disappear during
development. A duct leads from the interior of the gland and opens upon the
posterior face of the last pair of walking legs but one.
The nervous system has been very fully described by Patten and
Redenbaugh, and its complex nature plays a large part in the ingenious
speculations of Dr. Gaskell as to the origin of Vertebrates. It consists of a
stout ring surrounding the oesophagus and a ventral nerve-cord, composed
—if we omit the so-called fore-brain—of sixteen neuromeres. The fore-
brain supplies the median and the lateral eyes, and gives off a median nerve
which runs to an organ, described as olfactory by Patten, situated in front of
the chelicerae on the ventral face of the carapace. Patten distinguishes
behind the fore-brain a mid-brain, which consists solely of the cheliceral
neuromere, a hind-brain which supplies the pedipalps and four pair of
walking legs, and an accessory brain which supplies the chilaria and the
genital operculum. This is continued backward into a ventral nerve-cord
Page 316
which bears five paired ganglia
supplying the five pairs of gills and
three pairs of post-branchial ganglia;
the latter are ill-defined and closely
fused together. As was mentioned
above, the whole of the central
nervous system is bathed in the blood
of the ventral sinus.
The sense-organs consist of the
olfactory organ of Patten, the median
and lateral eyes, and possibly of
certain gustatory hairs upon the
gnathobases. The lateral eyes in their
histology are not so differentiated as
the median eyes, but both fall well
within the limits of Arachnid eye-
structure, and their minute anatomy
Fig. 155.—Diagram of the first gill of Limulus,
has been advanced as one piece of
from the posterior side, showing the distribution evidence amongst many which tend
of the gill-nerve to the gill-book (about natural to demonstrate that Limulus is an
size). After Patten and Redenbaugh. 1, Inner
lobe of the appendage; 2, outer lobe of
Arachnid.
appendage; 3, median lobe of appendage; 4, gill- Both ovaries and testes take the
book; 5, neural nerve of the ninth neuromere; 6,
internal branchial nerve; 7, gill-nerve; 8, median
form of a tubular network which is
branchial nerve; 9, external branchial nerve. almost inextricably entangled with
the liver. From each side a duct
collects the reproductive cells which
are formed from cells lining the walls of the tubes, and discharges them by
a pore one on each side of the hinder surface of the genital operculum. As is
frequently the case in Arachnids the males are smaller than the females, and
after their last ecdysis the pedipalps and first two pairs of walking legs, or
some of these appendages, end in slightly bent claws and not in chelae. Off
the New Jersey coast the king-crabs (L. polyphemus) spawn during the
months of May, June, and July, Lockwood states at the periods of highest
tides, but Kingsley[217] was never “able to notice any connexion between the
hours when they frequent the shore and the state of the tide.” “When first
seen they come from the deeper water, the male, which is almost always the
smaller, grasping the hinder half of the carapace of the female with the
supplying the five pairs of gills and
three pairs of post-branchial ganglia;
the latter are ill-defined and closely
fused together. As was mentioned
above, the whole of the central
nervous system is bathed in the blood
of the ventral sinus.
The sense-organs consist of the
olfactory organ of Patten, the median
and lateral eyes, and possibly of
certain gustatory hairs upon the
gnathobases. The lateral eyes in their
histology are not so differentiated as
the median eyes, but both fall well
within the limits of Arachnid eye-
structure, and their minute anatomy
Fig. 155.—Diagram of the first gill of Limulus,
has been advanced as one piece of
from the posterior side, showing the distribution evidence amongst many which tend
of the gill-nerve to the gill-book (about natural to demonstrate that Limulus is an
size). After Patten and Redenbaugh. 1, Inner
lobe of the appendage; 2, outer lobe of
Arachnid.
appendage; 3, median lobe of appendage; 4, gill- Both ovaries and testes take the
book; 5, neural nerve of the ninth neuromere; 6,
internal branchial nerve; 7, gill-nerve; 8, median
form of a tubular network which is
branchial nerve; 9, external branchial nerve. almost inextricably entangled with
the liver. From each side a duct
collects the reproductive cells which
are formed from cells lining the walls of the tubes, and discharges them by
a pore one on each side of the hinder surface of the genital operculum. As is
frequently the case in Arachnids the males are smaller than the females, and
after their last ecdysis the pedipalps and first two pairs of walking legs, or
some of these appendages, end in slightly bent claws and not in chelae. Off
the New Jersey coast the king-crabs (L. polyphemus) spawn during the
months of May, June, and July, Lockwood states at the periods of highest
tides, but Kingsley[217] was never “able to notice any connexion between the
hours when they frequent the shore and the state of the tide.” “When first
seen they come from the deeper water, the male, which is almost always the
smaller, grasping the hinder half of the carapace of the female with the
Page 317
modified pincer of the second pair of feet. Thus fastened together the male
rides to shallow water. The couples will stop at intervals and then move on.
Usually a nest of eggs can be found at each of the stopping-places, and as
each nest is usually buried from one to two inches beneath the surface of
the sand, it appears probable that the female thrusts the genital plate into the
sand, while at the same time the male discharges the milt into the water. I
have not been able to watch the process more closely because the animals
lie so close to the sand, and all the appendages are concealed beneath the
carapace. If touched during the oviposition, they cease the operation and
wander to another spot or separate and return to deep water. I have never
seen the couples come entirely out of the water, although they frequently
come so close to the shore that portions of the carapace are uncovered.”[218]
rides to shallow water. The couples will stop at intervals and then move on.
Usually a nest of eggs can be found at each of the stopping-places, and as
each nest is usually buried from one to two inches beneath the surface of
the sand, it appears probable that the female thrusts the genital plate into the
sand, while at the same time the male discharges the milt into the water. I
have not been able to watch the process more closely because the animals
lie so close to the sand, and all the appendages are concealed beneath the
carapace. If touched during the oviposition, they cease the operation and
wander to another spot or separate and return to deep water. I have never
seen the couples come entirely out of the water, although they frequently
come so close to the shore that portions of the carapace are uncovered.”[218]
Page 318
Page 319
Fig. 156.—A view of the nervous system of Limulus from below. (About natural
size.) After Patten and Redenbaugh.
The carapace is represented as transparent. The appendages have been removed,
but the outlines of the left entocoxites (6) have been sketched in. The positions of
the abdominal appendages are indicated by the external branchial muscles (17),
the branchial cartilages (19), the tendinous stigmata (18), and the abdominal
endochondrites (21). In the cephalothorax (1) all the tergo-coxal and plastro-
coxal muscles have been dissected away, leaving the endosternite (11) with the
occipital ring exposed. One of the left tergo-proplastral muscles (4) and the left
branchio-thoracic muscles (16) are represented. The longitudinal abdominal
muscles are also seen. All the muscles of the right side have been omitted except
the haemo-neural muscles (23), of which the last two are represented upon the
left side also. At the base of the telson the flexors (29) and extensors (27) of the
caudal spine are represented as cut off near their insertions. The sphincter ani
(26), levator ani, and occludor ani (25), and their relations to the anus (28), are
shown.
The oesophagus runs forward to the proventriculus (3). From this the intestine
(20) passes posteriorly.
The brain lies upon the neural side of the endosternite, and the ventral cord (22)
passes back through the occipital ring. The neural nerves are cut off, but the left
haemal nerves and those from the fore-brain (12) are represented entire.
The first pair of neural nerves go to the chelicerae. The second to sixth pairs go
to the next five cephalothoracic appendages, which are represented by the
entocoxites (6). The seventh pair of neural nerves go to the chilaria, and the
eighth pair to the operculum. The neural nerves from the ninth to the thirteenth
arise from the abdominal ganglia and innervate the five pairs of gills.
From the fore-brain a median olfactory nerve (9) and two lateral ones (8) pass
forward to the olfactory organ; a median eye-nerve (2) passes anteriorly and
haemally upon the right of the proventriculus (3) to the median eyes; and a pair
of lateral eye-nerves pass to the lateral eyes (15).
The first haemal nerve, or lateral nerve, follows the general course of the lateral
eye-nerve, but continues posteriorly far back on to the neural side of the
abdomen.
The haemal nerves of the hind-brain radiate from the brain to the margins of the
carapace, and each one passes anterior to the appendage of its own metamere.
The integumentary portions divide into haemal and neural branches, of which the
haemal branches (5) are cut off. Each haemal branch gives off a small nerve
which turns back toward the median line upon the haemal side of the body.
The haemal nerves of the accessory brain pass through the occipital ring to the
sides of the body between the operculum and the sixth cephalothoracic
appendage. The seventh innervates the posterior angles of the cephalothorax, the
size.) After Patten and Redenbaugh.
The carapace is represented as transparent. The appendages have been removed,
but the outlines of the left entocoxites (6) have been sketched in. The positions of
the abdominal appendages are indicated by the external branchial muscles (17),
the branchial cartilages (19), the tendinous stigmata (18), and the abdominal
endochondrites (21). In the cephalothorax (1) all the tergo-coxal and plastro-
coxal muscles have been dissected away, leaving the endosternite (11) with the
occipital ring exposed. One of the left tergo-proplastral muscles (4) and the left
branchio-thoracic muscles (16) are represented. The longitudinal abdominal
muscles are also seen. All the muscles of the right side have been omitted except
the haemo-neural muscles (23), of which the last two are represented upon the
left side also. At the base of the telson the flexors (29) and extensors (27) of the
caudal spine are represented as cut off near their insertions. The sphincter ani
(26), levator ani, and occludor ani (25), and their relations to the anus (28), are
shown.
The oesophagus runs forward to the proventriculus (3). From this the intestine
(20) passes posteriorly.
The brain lies upon the neural side of the endosternite, and the ventral cord (22)
passes back through the occipital ring. The neural nerves are cut off, but the left
haemal nerves and those from the fore-brain (12) are represented entire.
The first pair of neural nerves go to the chelicerae. The second to sixth pairs go
to the next five cephalothoracic appendages, which are represented by the
entocoxites (6). The seventh pair of neural nerves go to the chilaria, and the
eighth pair to the operculum. The neural nerves from the ninth to the thirteenth
arise from the abdominal ganglia and innervate the five pairs of gills.
From the fore-brain a median olfactory nerve (9) and two lateral ones (8) pass
forward to the olfactory organ; a median eye-nerve (2) passes anteriorly and
haemally upon the right of the proventriculus (3) to the median eyes; and a pair
of lateral eye-nerves pass to the lateral eyes (15).
The first haemal nerve, or lateral nerve, follows the general course of the lateral
eye-nerve, but continues posteriorly far back on to the neural side of the
abdomen.
The haemal nerves of the hind-brain radiate from the brain to the margins of the
carapace, and each one passes anterior to the appendage of its own metamere.
The integumentary portions divide into haemal and neural branches, of which the
haemal branches (5) are cut off. Each haemal branch gives off a small nerve
which turns back toward the median line upon the haemal side of the body.
The haemal nerves of the accessory brain pass through the occipital ring to the
sides of the body between the operculum and the sixth cephalothoracic
appendage. The seventh innervates the posterior angles of the cephalothorax, the
Page 320
eighth the opercular portion of the abdomen. The next five haemal nerves arise
from the five branchial neuromeres, pass out anterior to the gills to the sides of
the abdominal carapace, and innervate the first five spines upon the sides of the
abdomen.
The first post-branchial nerve innervates the last abdominal spine; the second
post-branchial nerve and one branch of the third post-branchial innervate the
posterior angles of the abdomen and the muscles of the telson; and the caudal
branch of the third post-branchial nerve innervates the telson.
Intestinal branches arise from all the haemal nerves from the sixth to the
sixteenth, and pass to the longitudinal abdominal muscles and to the intestine.
Cardiac nerves arise from all the haemal nerves from the sixth to the thirteenth.
Six of the cardiac nerves communicate with the lateral sympathetic nerve (24),
which innervates the branchio-thoracic muscles (16).
Two post-cardiac nerves arise from the first two post-branchial nerves, and
passing to the haemal side anastomose with a branch from the last cardiac nerve,
and innervate the extensors (27) of the telson and the epidermis behind the heart.
1, Cephalothorax; 2, median eye-nerve; 3, proventriculus; 4, tergo-proplastral
muscles; 5, haemal branch of integumentary nerve; 6, entocoxites; 7, 2nd haemal
nerve; 8, right olfactory nerve; 9, median olfactory nerve; 10, intestine; 11,
endosternite; 12, fore-brain; 13, origin of 4th neural nerve; 14, lateral nerve; 15,
lateral eye; 16, branchio-thoracic muscles; 17, external branchial muscles; 18,
tendinous stigmata; 19, branchial cartilages; 20, intestine; 21, abdominal
endochondrites; 22, ventral cord; 23, haemo-neural muscles; 24, lateral
sympathetic nerve; 25, occludor ani; 26, sphincter ani; 27, extensors of telson;
28, anus; 29, flexors of telson; 30, lateral projections of abdomen; 31, nerves of
spines; 32, external branchial muscles.
The developing ova and young larvae are very hardy, and in a little sea-
water, or still better packed in sea-weed, will survive long journeys. In this
way they have been transported from the Atlantic to the Pacific coasts of the
United States, and for a time at any rate flourished in the western waters.
Three barrels full of them consigned from Woods Holl to Sir E. Ray
Lankester arrived in England with a large proportion of larvae alive and
apparently well.
According to Kishinouye, L. longispina spawns chiefly in August and
between tide-marks. “The female excavates a hole about 15 cm. deep, and
deposits eggs in it while the male fertilises them. The female afterwards
buries them, and begins to excavate the next hole.”[219] A line of nests (Fig.
157) is thus established which is always at right angles to the shore-line.
After a certain number of nests have been formed the female tires, and the
from the five branchial neuromeres, pass out anterior to the gills to the sides of
the abdominal carapace, and innervate the first five spines upon the sides of the
abdomen.
The first post-branchial nerve innervates the last abdominal spine; the second
post-branchial nerve and one branch of the third post-branchial innervate the
posterior angles of the abdomen and the muscles of the telson; and the caudal
branch of the third post-branchial nerve innervates the telson.
Intestinal branches arise from all the haemal nerves from the sixth to the
sixteenth, and pass to the longitudinal abdominal muscles and to the intestine.
Cardiac nerves arise from all the haemal nerves from the sixth to the thirteenth.
Six of the cardiac nerves communicate with the lateral sympathetic nerve (24),
which innervates the branchio-thoracic muscles (16).
Two post-cardiac nerves arise from the first two post-branchial nerves, and
passing to the haemal side anastomose with a branch from the last cardiac nerve,
and innervate the extensors (27) of the telson and the epidermis behind the heart.
1, Cephalothorax; 2, median eye-nerve; 3, proventriculus; 4, tergo-proplastral
muscles; 5, haemal branch of integumentary nerve; 6, entocoxites; 7, 2nd haemal
nerve; 8, right olfactory nerve; 9, median olfactory nerve; 10, intestine; 11,
endosternite; 12, fore-brain; 13, origin of 4th neural nerve; 14, lateral nerve; 15,
lateral eye; 16, branchio-thoracic muscles; 17, external branchial muscles; 18,
tendinous stigmata; 19, branchial cartilages; 20, intestine; 21, abdominal
endochondrites; 22, ventral cord; 23, haemo-neural muscles; 24, lateral
sympathetic nerve; 25, occludor ani; 26, sphincter ani; 27, extensors of telson;
28, anus; 29, flexors of telson; 30, lateral projections of abdomen; 31, nerves of
spines; 32, external branchial muscles.
The developing ova and young larvae are very hardy, and in a little sea-
water, or still better packed in sea-weed, will survive long journeys. In this
way they have been transported from the Atlantic to the Pacific coasts of the
United States, and for a time at any rate flourished in the western waters.
Three barrels full of them consigned from Woods Holl to Sir E. Ray
Lankester arrived in England with a large proportion of larvae alive and
apparently well.
According to Kishinouye, L. longispina spawns chiefly in August and
between tide-marks. “The female excavates a hole about 15 cm. deep, and
deposits eggs in it while the male fertilises them. The female afterwards
buries them, and begins to excavate the next hole.”[219] A line of nests (Fig.
157) is thus established which is always at right angles to the shore-line.
After a certain number of nests have been formed the female tires, and the
Page 321
heaped up sand is not so prominent.
In each “nest” there are about a
thousand eggs, placed first to the left
side of the nest and then to the right,
from which Kishinouye concludes
that the left ovary deposits its ova
first and then the right. Limulus
rotundicauda and L. moluccanus do
not bury their eggs, but carry them
about attached to their swimmerets.
The egg is covered by a leathery
egg-shell which bursts after a certain
time, and leaves the larva surrounded
only by the blastodermic cuticle;
when ripe it emerges in the condition
known as the “Trilobite larva” (Fig.
158), so-called from a superficial and
misleading resemblance to a
Trilobite. They are active little
larvae, burrowing in the sand like
their parents, and swimming
vigorously about by aid of their leaf-
like posterior limbs. Sometimes they
are taken in tow-nets. After the first
moult the segments of the meso- and
metasoma, which at first had been
free, showing affinities with
Prestwichia and Belinurus of
Palaeozoic times, become more
solidified, while the post-anal tail-
spine—absent in the Trilobite larva—
makes its first appearance. This
increases in size with successive
moults. We have already noted the
late appearance of the external sexual
characters, the chelate walking
In each “nest” there are about a
thousand eggs, placed first to the left
side of the nest and then to the right,
from which Kishinouye concludes
that the left ovary deposits its ova
first and then the right. Limulus
rotundicauda and L. moluccanus do
not bury their eggs, but carry them
about attached to their swimmerets.
The egg is covered by a leathery
egg-shell which bursts after a certain
time, and leaves the larva surrounded
only by the blastodermic cuticle;
when ripe it emerges in the condition
known as the “Trilobite larva” (Fig.
158), so-called from a superficial and
misleading resemblance to a
Trilobite. They are active little
larvae, burrowing in the sand like
their parents, and swimming
vigorously about by aid of their leaf-
like posterior limbs. Sometimes they
are taken in tow-nets. After the first
moult the segments of the meso- and
metasoma, which at first had been
free, showing affinities with
Prestwichia and Belinurus of
Palaeozoic times, become more
solidified, while the post-anal tail-
spine—absent in the Trilobite larva—
makes its first appearance. This
increases in size with successive
moults. We have already noted the
late appearance of the external sexual
characters, the chelate walking
Page 322
Fig. 157.—The markings on the sand made by appendages only being replaced by
the female Limulus when depositing eggs.
Towards the lower end the round “nests” cease hooks at the last moult.
to be apparent, the king-crab being apparently
exhausted. (From Kishinouye.) About natural
size.
Fig. 158.—Dorsal and ventral view of the last larval stage (the so-called Trilobite
stage) of Limulus polyphemus before the appearance of the telson. 1, Liver; 2,
median eye; 3, lateral eye; 4, last walking leg; 5, chilaria. (From Kingsley and
Takano.)
Limulus casts its cuticle several times during the first year—Lockwood
estimates five or six times between hatching out in June and the onset of the
cold weather. The cuticle splits along a “thin narrow rim” which “runs
round the under side of the anterior portion of the cephalic shield.”[220] This
extends until it reaches that level where the animal is widest. Through this
slit the body of the king-crab emerges, coming out, not as that of a beetle
anteriorly and dorsally, but anteriorly and ventrally, in such a way as to
induce the unobservant to exclaim “it is spewing itself out of its mouth.” In
one nearly full-sized animal the increase in the shorter diameter of the
cephalic shield after a moult was from 8 inches to 9½ inches, which is an
indication of very rapid growth. If after their first year they moult annually
Lockwood estimates it would take them eight years to attain their full size.
The only economic use I know to which Limulus is put is that of feeding
both poultry and pigs. The females are preferred on account of the eggs, of
the female Limulus when depositing eggs.
Towards the lower end the round “nests” cease hooks at the last moult.
to be apparent, the king-crab being apparently
exhausted. (From Kishinouye.) About natural
size.
Fig. 158.—Dorsal and ventral view of the last larval stage (the so-called Trilobite
stage) of Limulus polyphemus before the appearance of the telson. 1, Liver; 2,
median eye; 3, lateral eye; 4, last walking leg; 5, chilaria. (From Kingsley and
Takano.)
Limulus casts its cuticle several times during the first year—Lockwood
estimates five or six times between hatching out in June and the onset of the
cold weather. The cuticle splits along a “thin narrow rim” which “runs
round the under side of the anterior portion of the cephalic shield.”[220] This
extends until it reaches that level where the animal is widest. Through this
slit the body of the king-crab emerges, coming out, not as that of a beetle
anteriorly and dorsally, but anteriorly and ventrally, in such a way as to
induce the unobservant to exclaim “it is spewing itself out of its mouth.” In
one nearly full-sized animal the increase in the shorter diameter of the
cephalic shield after a moult was from 8 inches to 9½ inches, which is an
indication of very rapid growth. If after their first year they moult annually
Lockwood estimates it would take them eight years to attain their full size.
The only economic use I know to which Limulus is put is that of feeding
both poultry and pigs. The females are preferred on account of the eggs, of
Page 323
which half-a-pint may be crowded into the cephalic shield. The king-crab is
opened by running a knife round the thin line mentioned on p. 275. There is
a belief in New Jersey that this diet makes the poultry lay; undoubtedly it
fattens both fowls and pigs, but it gives a “shocking” flavour to the flesh of
both.
CLASSIFICATION.
But five species of existing King-crabs are known, and these are grouped
by Pocock into two sub-families: (i.) the Xiphosurinae, and (ii.) the
Tachypleinae. These together make up the single family Xiphosuridae
which is co-extensive with the Order. The following is Pocock’s
classification.[221] The names used in this article are printed in italic capitals.
Order Xiphosura.
Family 1. Xiphosuridae.
Sub-Fam. 1. Xiphosurinae.
This includes the single species Xiphosura polyphemus (Linn.) (=
Limulus polyphemus, Latreille), “which is said to range from the coast of
Maine to Yucatan.”
Sub-Fam. 2. Tachypleinae.
Genus A. Tachypleus includes three species: (i.) T. gigas, Müll. (=
Limulus gigas, Müll., and L. moluccanus, Latreille), widely distributed in
Malaysia; (ii.) T. tridentatus, Leach (= L. tridentatus, Leach, and L.
longispina, Van der Hoeven), extending from British North Borneo to China
and Southern Japan; and (iii.) T. hoeveni, Pocock (= L. moluccanus, Van der
Hoeven), found in the Moluccas.
Genus B. Carcinoscorpius with one species, C. rotundicauda (Latreille)
(= L. rotundicauda, Latreille). It occupies a more westerly area than T.
opened by running a knife round the thin line mentioned on p. 275. There is
a belief in New Jersey that this diet makes the poultry lay; undoubtedly it
fattens both fowls and pigs, but it gives a “shocking” flavour to the flesh of
both.
CLASSIFICATION.
But five species of existing King-crabs are known, and these are grouped
by Pocock into two sub-families: (i.) the Xiphosurinae, and (ii.) the
Tachypleinae. These together make up the single family Xiphosuridae
which is co-extensive with the Order. The following is Pocock’s
classification.[221] The names used in this article are printed in italic capitals.
Order Xiphosura.
Family 1. Xiphosuridae.
Sub-Fam. 1. Xiphosurinae.
This includes the single species Xiphosura polyphemus (Linn.) (=
Limulus polyphemus, Latreille), “which is said to range from the coast of
Maine to Yucatan.”
Sub-Fam. 2. Tachypleinae.
Genus A. Tachypleus includes three species: (i.) T. gigas, Müll. (=
Limulus gigas, Müll., and L. moluccanus, Latreille), widely distributed in
Malaysia; (ii.) T. tridentatus, Leach (= L. tridentatus, Leach, and L.
longispina, Van der Hoeven), extending from British North Borneo to China
and Southern Japan; and (iii.) T. hoeveni, Pocock (= L. moluccanus, Van der
Hoeven), found in the Moluccas.
Genus B. Carcinoscorpius with one species, C. rotundicauda (Latreille)
(= L. rotundicauda, Latreille). It occupies a more westerly area than T.
Page 324
gigas or than T. tridentatus, having been recorded from India and Bengal,
the Gulf of Siam, Penang, the Moluccas, and the Philippines.
With regard to the affinities of the group it is now almost universally
accepted that they are Arachnids. The chief features in which they differ
from other Arachnids are the presence of gills and the absence of
Malpighian tubules, both being features associated with aquatic life. As
long ago as 1829 Straus-Dürckheim emphasised the points of resemblance
between the two groups, and although the view was during the middle of
the last century by no means universally accepted, towards the end of that
epoch the painstaking researches of Lankester and his pupils, who
compared the King-crab and the Scorpion, segment with segment, organ
with organ, tissue with tissue, almost cell with cell, established the
connexion beyond doubt. Lankester would put the Trilobites in the same
phylum, but in this we do not follow him. With regard to the brilliant but, to
our mind, unconvincing speculations as to the connexion of some Limulus-
like ancestor with the Vertebrates, we must refer the reader to the ingenious
writings of Dr. Gaskell,[222] recently summarised in his volume on “The
Origin of Vertebrates,” and to those of Dr. Patten in his article “On the
Origin of Vertebrates from Arachnids.”[223]
Fossil Xiphosura.[224]
Limulus is an example of a persistent type. It appears first in deposits of
Triassic age, and is found again in the Jurassic, Cretaceous, and Oligocene.
In the lithographic limestone of Solenhofen in Bavaria, which is of Upper
Jurassic age, Limulus is common and is represented by several species. One
species is known from the Chalk of Lebanon, and another occurs in the
Oligocene of Saxony. No other genus of the Xiphosura appears to be
represented in the Mesozoic and Tertiary deposits, but in the Palaeozoic
formations (principally in the Upper Silurian, the Old Red Sandstone, and
the Coal Measures) several genera have been found, most of which differ
from Limulus in having some or all of the segments of the abdomen free; in
this respect they resemble the Eurypterida, but differ from them in the
number of segments. In Hemiaspis (Fig. 159, A), from the Silurian, the
segments of the abdomen are divisible into two groups (mesosoma and
metasoma) in the same way that they are in Eurypterids; the first six
the Gulf of Siam, Penang, the Moluccas, and the Philippines.
With regard to the affinities of the group it is now almost universally
accepted that they are Arachnids. The chief features in which they differ
from other Arachnids are the presence of gills and the absence of
Malpighian tubules, both being features associated with aquatic life. As
long ago as 1829 Straus-Dürckheim emphasised the points of resemblance
between the two groups, and although the view was during the middle of
the last century by no means universally accepted, towards the end of that
epoch the painstaking researches of Lankester and his pupils, who
compared the King-crab and the Scorpion, segment with segment, organ
with organ, tissue with tissue, almost cell with cell, established the
connexion beyond doubt. Lankester would put the Trilobites in the same
phylum, but in this we do not follow him. With regard to the brilliant but, to
our mind, unconvincing speculations as to the connexion of some Limulus-
like ancestor with the Vertebrates, we must refer the reader to the ingenious
writings of Dr. Gaskell,[222] recently summarised in his volume on “The
Origin of Vertebrates,” and to those of Dr. Patten in his article “On the
Origin of Vertebrates from Arachnids.”[223]
Fossil Xiphosura.[224]
Limulus is an example of a persistent type. It appears first in deposits of
Triassic age, and is found again in the Jurassic, Cretaceous, and Oligocene.
In the lithographic limestone of Solenhofen in Bavaria, which is of Upper
Jurassic age, Limulus is common and is represented by several species. One
species is known from the Chalk of Lebanon, and another occurs in the
Oligocene of Saxony. No other genus of the Xiphosura appears to be
represented in the Mesozoic and Tertiary deposits, but in the Palaeozoic
formations (principally in the Upper Silurian, the Old Red Sandstone, and
the Coal Measures) several genera have been found, most of which differ
from Limulus in having some or all of the segments of the abdomen free; in
this respect they resemble the Eurypterida, but differ from them in the
number of segments. In Hemiaspis (Fig. 159, A), from the Silurian, the
segments of the abdomen are divisible into two groups (mesosoma and
metasoma) in the same way that they are in Eurypterids; the first six
Page 325
segments have broad, short terga, the
lateral margins of the sixth being
divided into two lobes, probably
indicating the presence of two fused
segments; the last three segments are
narrower and longer than the
preceding, and at the end is a pointed
tail-spine. In Belinurus (Fig. 160)
from the Carboniferous, the two
regions of the abdomen are much less
Fig. 159.—A., Hemiaspis limuloides, Woodw., distinct; there are eight segments, the
Upper Silurian, Leintwardine, Shropshire. last three of which are fused together,
Natural size. (After Woodward.) B., Prestwichia
(Euroöps) danae (Meek), Carboniferous, and a long tail-spine. In Neolimulus,
Illinois, × ⅔. (After Packard.) from the Silurian, there seems to be
no division of the abdomen into two
regions, and apparently all the segments were free. On the other hand, in
Prestwichia (Carboniferous), all the segments of the abdomen, of which
there appear to be seven only, were fused together (Fig. 159, B).
In the Palaeozoic genera the median or axial part of the dorsal surface is
raised and distinctly limited on each side, so presenting a trilobed
appearance similar to that of Trilobites. In Neolimulus, Belinurus, and
Prestwichia, lateral eyes are present on the sides of the axial parts of the
carapace, and near its front margin median eyes have been found in the two
last-named genera.
In nearly all the specimens of Palaeozoic Xiphosura[225] which have been
found nothing is seen but the dorsal surface of the body; in only a very few
cases have any traces of the appendages been seen,[226] but, so far as known,
they appear to have the same general character as in Limulus.
Aglaspis, found in the Upper Cambrian of Wisconsin, has been regarded
as a Xiphosuran. If that view of its position is correct, then Aglaspis will be
the earliest representative of the group at present known. Other genera of
Palaeozoic Xiphosura are Bunodes, Bunodella, and Pseudoniscus in the
Silurian; Protolimulus in the Upper Devonian; and Prolimulus in the
Permian.
lateral margins of the sixth being
divided into two lobes, probably
indicating the presence of two fused
segments; the last three segments are
narrower and longer than the
preceding, and at the end is a pointed
tail-spine. In Belinurus (Fig. 160)
from the Carboniferous, the two
regions of the abdomen are much less
Fig. 159.—A., Hemiaspis limuloides, Woodw., distinct; there are eight segments, the
Upper Silurian, Leintwardine, Shropshire. last three of which are fused together,
Natural size. (After Woodward.) B., Prestwichia
(Euroöps) danae (Meek), Carboniferous, and a long tail-spine. In Neolimulus,
Illinois, × ⅔. (After Packard.) from the Silurian, there seems to be
no division of the abdomen into two
regions, and apparently all the segments were free. On the other hand, in
Prestwichia (Carboniferous), all the segments of the abdomen, of which
there appear to be seven only, were fused together (Fig. 159, B).
In the Palaeozoic genera the median or axial part of the dorsal surface is
raised and distinctly limited on each side, so presenting a trilobed
appearance similar to that of Trilobites. In Neolimulus, Belinurus, and
Prestwichia, lateral eyes are present on the sides of the axial parts of the
carapace, and near its front margin median eyes have been found in the two
last-named genera.
In nearly all the specimens of Palaeozoic Xiphosura[225] which have been
found nothing is seen but the dorsal surface of the body; in only a very few
cases have any traces of the appendages been seen,[226] but, so far as known,
they appear to have the same general character as in Limulus.
Aglaspis, found in the Upper Cambrian of Wisconsin, has been regarded
as a Xiphosuran. If that view of its position is correct, then Aglaspis will be
the earliest representative of the group at present known. Other genera of
Palaeozoic Xiphosura are Bunodes, Bunodella, and Pseudoniscus in the
Silurian; Protolimulus in the Upper Devonian; and Prolimulus in the
Permian.
Page 326
EURYPTERIDA
BY
HENRY WOODS, M.A.
St. John’s College, Cambridge, University Lecturer in Palaeozoology.
BY
HENRY WOODS, M.A.
St. John’s College, Cambridge, University Lecturer in Palaeozoology.
Page 327
CHAPTER XI
ARACHNIDA (CONTINUED)—DELOBRANCHIATA =
MEROSTOMATA (CONTINUED)—EURYPTERIDA
Order II. Eurypterida.
The Eurypterida or Gigantostraca are found only in the Palaeozoic
formations. Some species of Pterygotus, Slimonia, and Stylonurus have a
length of from five to six feet, and are not only the largest Invertebrates
which have been found fossil but do not seem to be surpassed in size at the
present day except by some of the Dibranchiate Cephalopods. All the
Eurypterids were aquatic, and, with the possible exception of forms found
in the Coal Measures, all were marine. The earliest examples occur in the
Cambrian deposits, and the latest in the Permian; but although the
Eurypterids have thus a considerable geological range, yet it is mainly in
the Silurian and the Old Red Sandstone that they are found, the principal
genera represented in those deposits being Eurypterus, Stylonurus,
Slimonia, Pterygotus, Hughmilleria, Dolichopterus, and Eusarcus. From the
Cambrian rocks the only form recorded is Strabops;[227] in the Ordovician
the imperfectly known Echinognathus[228] and some indeterminable
fragments have alone been found. In the Carboniferous deposits Eurypterus
and Glyptoscorpius occur, and the former survived into the Permian.[229]
ARACHNIDA (CONTINUED)—DELOBRANCHIATA =
MEROSTOMATA (CONTINUED)—EURYPTERIDA
Order II. Eurypterida.
The Eurypterida or Gigantostraca are found only in the Palaeozoic
formations. Some species of Pterygotus, Slimonia, and Stylonurus have a
length of from five to six feet, and are not only the largest Invertebrates
which have been found fossil but do not seem to be surpassed in size at the
present day except by some of the Dibranchiate Cephalopods. All the
Eurypterids were aquatic, and, with the possible exception of forms found
in the Coal Measures, all were marine. The earliest examples occur in the
Cambrian deposits, and the latest in the Permian; but although the
Eurypterids have thus a considerable geological range, yet it is mainly in
the Silurian and the Old Red Sandstone that they are found, the principal
genera represented in those deposits being Eurypterus, Stylonurus,
Slimonia, Pterygotus, Hughmilleria, Dolichopterus, and Eusarcus. From the
Cambrian rocks the only form recorded is Strabops;[227] in the Ordovician
the imperfectly known Echinognathus[228] and some indeterminable
fragments have alone been found. In the Carboniferous deposits Eurypterus
and Glyptoscorpius occur, and the former survived into the Permian.[229]
Page 328
Fig. 161.—Eurypterus fischeri, Eichw. Upper Silurian, Rootziküll, Oesel. Dorsal
surface. a, Ocellus; b, lateral eye; 2–6, appendages of prosoma; 7–12, segments
of mesosoma; 13–18, segments of metasoma; 19, tail-spine. (After Holm.)
surface. a, Ocellus; b, lateral eye; 2–6, appendages of prosoma; 7–12, segments
of mesosoma; 13–18, segments of metasoma; 19, tail-spine. (After Holm.)
Page 329
The Eurypterid which is best known is Eurypterus fischeri (Figs. 161,
162), which is found in the Upper Silurian rocks at Rootziküll in the Island
of Oesel (Gulf of Riga). In the Eurypterids from other deposits the chitinous
exoskeleton has been altered into a carbonaceous substance, but in the
specimens from Oesel the chitin is perfectly preserved in its original
condition; and since these specimens are found in a dolomitic rock which is
soluble in acid, it has been possible to separate the fossil completely from
the rock in which it is embedded, with the result that the structure can be
studied more easily and more thoroughly than in the case of specimens
from other localities. Consequently Eurypterus fischeri[230] may, with
advantage, be taken as a type of the Eurypterida.
The general form of the body (Fig. 161) is somewhat like that of a
Scorpion, but is relatively broader and shorter. On the surface of many parts
of the exoskeleton numerous scale-like markings are found (Figs. 162, 163).
[231]
The prosoma or cephalothorax consists of six fused segments covered
by a quadrate carapace with its front angles rounded. This bears on its
dorsal surface two pairs of eyes—large kidney-shaped lateral eyes and
median ocelli (Fig. 161, b, a). The margin of the dorsal part of the carapace
is bent underneath to form a rim which joins the ventral part of the
carapace.
On the ventral surface of the prosoma (Fig. 162) six pairs of appendages
are seen, of which only the first pair (the chelicerae) are in front of the
mouth. The chelicerae are small, and each consists of a basal joint and a
chela, the latter being found parallel to the axis of the body; they closely
resemble the chelicerae of Limulus. The remaining five pairs of appendages
are found at the sides of the elongate mouth, and in all these the
gnathobases of the coxae are provided with teeth at their inner margins and
were able to function in mastication, whilst the distal part of each
appendage served as an organ of locomotion. The posterior part of each
coxa is plate-like and is covered (except in the case of the sixth appendage)
by the coxa of the next appendage behind. A small process or “epicoxite” is
found at the posterior end of the toothed part of the coxae of the second,
third, fourth, and fifth pairs of appendages. The second appendage consists
of seven joints, whilst the remaining four consist of eight joints; none of
these appendages end in chelae. The second, third,[232] and fourth pairs of
appendages are similar to one another in structure, but become successively
larger from before backwards. These three pairs are directed radially
162), which is found in the Upper Silurian rocks at Rootziküll in the Island
of Oesel (Gulf of Riga). In the Eurypterids from other deposits the chitinous
exoskeleton has been altered into a carbonaceous substance, but in the
specimens from Oesel the chitin is perfectly preserved in its original
condition; and since these specimens are found in a dolomitic rock which is
soluble in acid, it has been possible to separate the fossil completely from
the rock in which it is embedded, with the result that the structure can be
studied more easily and more thoroughly than in the case of specimens
from other localities. Consequently Eurypterus fischeri[230] may, with
advantage, be taken as a type of the Eurypterida.
The general form of the body (Fig. 161) is somewhat like that of a
Scorpion, but is relatively broader and shorter. On the surface of many parts
of the exoskeleton numerous scale-like markings are found (Figs. 162, 163).
[231]
The prosoma or cephalothorax consists of six fused segments covered
by a quadrate carapace with its front angles rounded. This bears on its
dorsal surface two pairs of eyes—large kidney-shaped lateral eyes and
median ocelli (Fig. 161, b, a). The margin of the dorsal part of the carapace
is bent underneath to form a rim which joins the ventral part of the
carapace.
On the ventral surface of the prosoma (Fig. 162) six pairs of appendages
are seen, of which only the first pair (the chelicerae) are in front of the
mouth. The chelicerae are small, and each consists of a basal joint and a
chela, the latter being found parallel to the axis of the body; they closely
resemble the chelicerae of Limulus. The remaining five pairs of appendages
are found at the sides of the elongate mouth, and in all these the
gnathobases of the coxae are provided with teeth at their inner margins and
were able to function in mastication, whilst the distal part of each
appendage served as an organ of locomotion. The posterior part of each
coxa is plate-like and is covered (except in the case of the sixth appendage)
by the coxa of the next appendage behind. A small process or “epicoxite” is
found at the posterior end of the toothed part of the coxae of the second,
third, fourth, and fifth pairs of appendages. The second appendage consists
of seven joints, whilst the remaining four consist of eight joints; none of
these appendages end in chelae. The second, third,[232] and fourth pairs of
appendages are similar to one another in structure, but become successively
larger from before backwards. These three pairs are directed radially
Page 330
outwards; each consists of short joints tapering to the end of the limb, and
bearing spines at the sides and on the under surface, and also a spine at the
end of the last joint.
bearing spines at the sides and on the under surface, and also a spine at the
end of the last joint.
Page 331
Fig. 162.—Eurypterus fischeri, Eichw. Upper Silurian, Rootziküll, Oesel.
Restoration of ventral surface; 1–6, appendages of prosoma; m, metastoma.
Immediately posterior to the metastoma is the “median process” of the genital
operculum. (After Holm.)
Restoration of ventral surface; 1–6, appendages of prosoma; m, metastoma.
Immediately posterior to the metastoma is the “median process” of the genital
operculum. (After Holm.)
Page 332
The fifth appendage is longer than the fourth and is directed backwards;
its second and third joints are short and ring-like; the others (fourth to
eighth) are long and similar to one another, each being of uniform width
throughout; the last joint is produced into a spine on each side, and between
these two is the movable end-spine; the other joints do not bear long spines
as is the case in the three preceding pairs of appendages.
The sixth appendage is much larger and stronger than the others, and like
the fifth, is without long spines. The coxa is large and quadrate; the second
and third joints are short, like those of the fifth appendage; the fourth, fifth,
and sixth joints are longer and more or less bell-shaped; the seventh and
eighth joints are much larger than the others and are flattened.
The metastoma (Fig. 162, m) is an oval plate immediately behind the
mouth; it covers the inner parts of the coxae of the sixth pair of appendages,
and represents the chilaria of Limulus. But, unlike the latter, it is not a
paired structure; nevertheless the presence of a longitudinal groove on its
anterior part renders probable the view that it is derived from a paired
organ.[233] The front margin of the metastoma is indented and toothed. On its
inner side in front is a transverse plate, the endostoma, which is not seen
from the exterior, since the front margin of the metastoma extends a little
beyond it.
Behind the prosoma are twelve free segments, of which the first six form
the mesosoma (Fig. 161, 7–12). The tergum on the dorsal surface of each
segment is broad and short, the middle part being slightly convex and the
lateral parts slightly concave; the external margin is bent under, thus
forming a narrow rim on the ventral surface. The tergum of each segment
overlaps the one next behind. The segments increase in breadth slightly up
to the fourth segment, posterior to which they gradually become narrower.
On the ventral surface the segments of the mesosoma bear pairs of plate-
like appendages, each of which overlaps the one behind like the tiles on a
roof. On the posterior (or inner) surfaces of these appendages are found the
lamellar branchiae, which are oval in outline (Fig. 165, d). Between the two
appendages of the first pair is a median process which is genital in function;
this pair are larger than the other appendages, and cover both first and
second segments, the latter being without any appendages, and they
represent the genital operculum of Limulus (Fig. 153, 10). The form of the
operculum, more particularly of the median process, differs in the male and
its second and third joints are short and ring-like; the others (fourth to
eighth) are long and similar to one another, each being of uniform width
throughout; the last joint is produced into a spine on each side, and between
these two is the movable end-spine; the other joints do not bear long spines
as is the case in the three preceding pairs of appendages.
The sixth appendage is much larger and stronger than the others, and like
the fifth, is without long spines. The coxa is large and quadrate; the second
and third joints are short, like those of the fifth appendage; the fourth, fifth,
and sixth joints are longer and more or less bell-shaped; the seventh and
eighth joints are much larger than the others and are flattened.
The metastoma (Fig. 162, m) is an oval plate immediately behind the
mouth; it covers the inner parts of the coxae of the sixth pair of appendages,
and represents the chilaria of Limulus. But, unlike the latter, it is not a
paired structure; nevertheless the presence of a longitudinal groove on its
anterior part renders probable the view that it is derived from a paired
organ.[233] The front margin of the metastoma is indented and toothed. On its
inner side in front is a transverse plate, the endostoma, which is not seen
from the exterior, since the front margin of the metastoma extends a little
beyond it.
Behind the prosoma are twelve free segments, of which the first six form
the mesosoma (Fig. 161, 7–12). The tergum on the dorsal surface of each
segment is broad and short, the middle part being slightly convex and the
lateral parts slightly concave; the external margin is bent under, thus
forming a narrow rim on the ventral surface. The tergum of each segment
overlaps the one next behind. The segments increase in breadth slightly up
to the fourth segment, posterior to which they gradually become narrower.
On the ventral surface the segments of the mesosoma bear pairs of plate-
like appendages, each of which overlaps the one behind like the tiles on a
roof. On the posterior (or inner) surfaces of these appendages are found the
lamellar branchiae, which are oval in outline (Fig. 165, d). Between the two
appendages of the first pair is a median process which is genital in function;
this pair are larger than the other appendages, and cover both first and
second segments, the latter being without any appendages, and they
represent the genital operculum of Limulus (Fig. 153, 10). The form of the
operculum, more particularly of the median process, differs in the male and
Page 333
female. In that which is believed to be the female (Fig. 162) the median
process is long, and extends beyond the posterior margin of the operculum;
it is formed of two small five-sided parts at the base which are united at the
sides to the two plates of the operculum; behind this is a long, unpaired
part, which is pointed in front; this, together with the remaining parts, is not
joined to the side-plates of the operculum, so that the latter are here
separated from one another. The third part of the median process is shorter
than the second, and bears at its end a pair of small pointed and diverging
plates, the tips of which reach to the middle of the third plate-like
appendages. On the inner side of the operculum there are, in the female, a
pair of curved, tubular organs, attached to the anterior end of the median
process, where they open, the free ends being closed; the function of these
organs is not known, but was probably sexual.
In the male (Fig. 163, A, a) the median process is formed of two parts
only, and is very short, so that the two plates of the operculum unite behind
the process.
In the female a median process (Fig. 163, B) is also present between the
second pair of appendages (belonging to the third segment of the
mesosoma); it consists of a basal unpaired part, and of a pair of long
pointed pieces which project on to the next segment. Just as in the case of
the genital operculum the basal part is united in front to the appendages, the
remainder being free, and separating the greater part of the two plate-like
appendages. In the complete animal the median process of this segment is
covered by the median process of the genital operculum. The remaining
appendages of the female, and all the appendages behind the operculum in
the male, are without any median process, and the plates of each pair unite
by a suture in the middle line.
process is long, and extends beyond the posterior margin of the operculum;
it is formed of two small five-sided parts at the base which are united at the
sides to the two plates of the operculum; behind this is a long, unpaired
part, which is pointed in front; this, together with the remaining parts, is not
joined to the side-plates of the operculum, so that the latter are here
separated from one another. The third part of the median process is shorter
than the second, and bears at its end a pair of small pointed and diverging
plates, the tips of which reach to the middle of the third plate-like
appendages. On the inner side of the operculum there are, in the female, a
pair of curved, tubular organs, attached to the anterior end of the median
process, where they open, the free ends being closed; the function of these
organs is not known, but was probably sexual.
In the male (Fig. 163, A, a) the median process is formed of two parts
only, and is very short, so that the two plates of the operculum unite behind
the process.
In the female a median process (Fig. 163, B) is also present between the
second pair of appendages (belonging to the third segment of the
mesosoma); it consists of a basal unpaired part, and of a pair of long
pointed pieces which project on to the next segment. Just as in the case of
the genital operculum the basal part is united in front to the appendages, the
remainder being free, and separating the greater part of the two plate-like
appendages. In the complete animal the median process of this segment is
covered by the median process of the genital operculum. The remaining
appendages of the female, and all the appendages behind the operculum in
the male, are without any median process, and the plates of each pair unite
by a suture in the middle line.
Page 334
Fig. 163.—Eurypterus fischeri, Eichw. Upper Silurian. (After Holm.) A, Genital
operculum of male; a, median process. B, Middle part of second appendage of
the mesosoma in the female, showing the median process.
The metasoma (Fig. 161, 13–18) consists of six segments which become
longer and narrower from before backwards. Each segment is covered by a
ring-like sheath or sclerite, and bears no appendages. The posterior end of
the last segment is produced into a lobe on each side, and between these
lobes the long, narrow tail-spine arises (Fig. 161, 19).
The other genera of the Eurypterida do not differ in any important
morphological respects from the form just described, All the genera, of
which about thirteen have been recognised, are placed in one family.
Fam. Eurypteridae.—The carapace varies somewhat in outline; in
Slimonia it is more distinctly quadrate than in Eurypterus, whilst in
Pterygotus (Fig. 164) and Hughmilleria[234] it is semi-ovoid. The lateral eyes
are at the margin of the carapace in Pterygotus, Slimonia (Fig. 165, a), and
Hughmilleria, but in the other genera, including the earliest form, Strabops,
operculum of male; a, median process. B, Middle part of second appendage of
the mesosoma in the female, showing the median process.
The metasoma (Fig. 161, 13–18) consists of six segments which become
longer and narrower from before backwards. Each segment is covered by a
ring-like sheath or sclerite, and bears no appendages. The posterior end of
the last segment is produced into a lobe on each side, and between these
lobes the long, narrow tail-spine arises (Fig. 161, 19).
The other genera of the Eurypterida do not differ in any important
morphological respects from the form just described, All the genera, of
which about thirteen have been recognised, are placed in one family.
Fam. Eurypteridae.—The carapace varies somewhat in outline; in
Slimonia it is more distinctly quadrate than in Eurypterus, whilst in
Pterygotus (Fig. 164) and Hughmilleria[234] it is semi-ovoid. The lateral eyes
are at the margin of the carapace in Pterygotus, Slimonia (Fig. 165, a), and
Hughmilleria, but in the other genera, including the earliest form, Strabops,
Page 335
[235]
they are on the dorsal surface at a
greater or less distance from the
margin.
The pre-oral appendages of
Pterygotus (Fig. 164, 1) differ from
those of other genera in their much
greater length and in the large size of
the chelae; they probably consist of a
proximal joint and chelae only,
although, commonly, they are
represented as having a larger
number of joints. Unlike Eurypterus
and Pterygotus, the second pair of
appendages in Slimonia (Fig. 165, 2)
differ from the third, fourth, and fifth
pairs in being distinctly smaller and
more slender, and it is probable that
they were tactile. Whilst in
Eurypterus the fifth pair of
appendages are larger than the three
preceding pairs, and also differ from
them in structure, in the genus
Fig. 164.—Pterygotus osiliensis, Schmidt, Pterygotus (Fig. 164, 5) they agree
Upper Silurian, Rootziküll, Oesel. Ventral closely with the second, third, and
surface. Reduced. (After Schmidt.) 1–6, fourth pairs, and in Slimonia (Fig.
Appendages of the prosoma; 7–12, mesosoma;
7, 8, genital operculum; 13–18, metasoma; 19, 165, 5) they are nearly the same as
tail-plate; a, epistome; b, metastoma; c, coxae of the third and fourth pairs. The sixth
sixth pair of appendages.
pair of appendages are much larger
and more powerful than the fifth pair
in nearly all genera; in Stylonurus (Fig. 166), however, the sixth pair are
similar to the fifth, both being greatly elongated and slender; also in
Eusarcus (Drepanopterus) the sixth pair differ less from the preceding pair
of appendages than is usually the case.
In Pterygotus there is a well-developed epistome (Fig. 164, a) between
the mouth and the front margin of the carapace, thus occupying the same
position as the hypostome of Trilobites (p. 233). The metastoma is always
well developed and forms one of the distinguishing features of the
they are on the dorsal surface at a
greater or less distance from the
margin.
The pre-oral appendages of
Pterygotus (Fig. 164, 1) differ from
those of other genera in their much
greater length and in the large size of
the chelae; they probably consist of a
proximal joint and chelae only,
although, commonly, they are
represented as having a larger
number of joints. Unlike Eurypterus
and Pterygotus, the second pair of
appendages in Slimonia (Fig. 165, 2)
differ from the third, fourth, and fifth
pairs in being distinctly smaller and
more slender, and it is probable that
they were tactile. Whilst in
Eurypterus the fifth pair of
appendages are larger than the three
preceding pairs, and also differ from
them in structure, in the genus
Fig. 164.—Pterygotus osiliensis, Schmidt, Pterygotus (Fig. 164, 5) they agree
Upper Silurian, Rootziküll, Oesel. Ventral closely with the second, third, and
surface. Reduced. (After Schmidt.) 1–6, fourth pairs, and in Slimonia (Fig.
Appendages of the prosoma; 7–12, mesosoma;
7, 8, genital operculum; 13–18, metasoma; 19, 165, 5) they are nearly the same as
tail-plate; a, epistome; b, metastoma; c, coxae of the third and fourth pairs. The sixth
sixth pair of appendages.
pair of appendages are much larger
and more powerful than the fifth pair
in nearly all genera; in Stylonurus (Fig. 166), however, the sixth pair are
similar to the fifth, both being greatly elongated and slender; also in
Eusarcus (Drepanopterus) the sixth pair differ less from the preceding pair
of appendages than is usually the case.
In Pterygotus there is a well-developed epistome (Fig. 164, a) between
the mouth and the front margin of the carapace, thus occupying the same
position as the hypostome of Trilobites (p. 233). The metastoma is always
well developed and forms one of the distinguishing features of the
Page 336
Eurypterids; in form it varies from
oval in Eurypterus, to cordate in
Slimonia, and lyrate in
Dolichopterus.
The principal modifications seen
in the genital operculum are in the
form of its median process; in
Slimonia this either ends in three
sharp points posteriorly (Fig. 165, c),
or has the form of a truncated cone;
its form in Eurypterus has already
been described. Glyptoscorpius
differs from other Eurypterids in the
possession of comb-like organs
closely resembling the pectines of
Scorpions. Slimonia apparently
differs from other genera in that the
plate-like appendages on the
posterior three segments of the
mesosoma do not meet in the middle
line (Fig. 165, 10–12). In some
forms, such as Pterygotus (Fig. 164),
there is a nearly gradual decrease in
the width of the segments in passing
from the mesosoma to the metasoma;
but in some others, which in this
respect are less primitive, such as
Slimonia (Fig. 165), the posterior
five segments of the body (like those
of Scorpions) are distinctly narrower
and longer than the preceding
segments. The long tail-spine of
Eurypterus is represented in Slimonia
by an oval plate produced into a
spine at the end (Fig. 165, 19); whilst
in some species of Pterygotus the
plate is bi-lobed at the posterior end
oval in Eurypterus, to cordate in
Slimonia, and lyrate in
Dolichopterus.
The principal modifications seen
in the genital operculum are in the
form of its median process; in
Slimonia this either ends in three
sharp points posteriorly (Fig. 165, c),
or has the form of a truncated cone;
its form in Eurypterus has already
been described. Glyptoscorpius
differs from other Eurypterids in the
possession of comb-like organs
closely resembling the pectines of
Scorpions. Slimonia apparently
differs from other genera in that the
plate-like appendages on the
posterior three segments of the
mesosoma do not meet in the middle
line (Fig. 165, 10–12). In some
forms, such as Pterygotus (Fig. 164),
there is a nearly gradual decrease in
the width of the segments in passing
from the mesosoma to the metasoma;
but in some others, which in this
respect are less primitive, such as
Slimonia (Fig. 165), the posterior
five segments of the body (like those
of Scorpions) are distinctly narrower
and longer than the preceding
segments. The long tail-spine of
Eurypterus is represented in Slimonia
by an oval plate produced into a
spine at the end (Fig. 165, 19); whilst
in some species of Pterygotus the
plate is bi-lobed at the posterior end
Page 337
(Fig. 164, 19). In Hughmilleria the
tail-spine is lanceolate.
The Eurypterids resemble the
Xiphosura in many respects. In both
groups the prosoma consists of at
least six fused segments, and bears
two pairs of eyes—one pair simple,
the other grouped eyes—on the
dorsal surface of the carapace. The
number and position of the
appendages of the prosoma in
Eurypterids agree with those of
Limulus. The chelicerae are closely
similar in both cases. The coxae of
all five pairs of legs in Eurypterids
are toothed and function in
mastication; similarly in Limulus all
are spiny except the coxae of the last
pair of legs. In both a similar
epicoxite is present on the coxae. The
number of joints in the legs is
somewhat greater in the Eurypterids
than in Limulus, and in the former
none of the legs end in chelae,
whereas in the latter all the walking
legs, except the last, and also the first
in the male, may be chelate. The
metastoma of Eurypterids differs in
being a large unpaired plate, but is
represented in Limulus by the pair of
relatively small chilaria. On the
mesosoma the genital operculum and
plate-like appendages with branchial
lamellae are similar in both groups,
but in the Eurypterids the genital
operculum shows a greater
development and covers the second
tail-spine is lanceolate.
The Eurypterids resemble the
Xiphosura in many respects. In both
groups the prosoma consists of at
least six fused segments, and bears
two pairs of eyes—one pair simple,
the other grouped eyes—on the
dorsal surface of the carapace. The
number and position of the
appendages of the prosoma in
Eurypterids agree with those of
Limulus. The chelicerae are closely
similar in both cases. The coxae of
all five pairs of legs in Eurypterids
are toothed and function in
mastication; similarly in Limulus all
are spiny except the coxae of the last
pair of legs. In both a similar
epicoxite is present on the coxae. The
number of joints in the legs is
somewhat greater in the Eurypterids
than in Limulus, and in the former
none of the legs end in chelae,
whereas in the latter all the walking
legs, except the last, and also the first
in the male, may be chelate. The
metastoma of Eurypterids differs in
being a large unpaired plate, but is
represented in Limulus by the pair of
relatively small chilaria. On the
mesosoma the genital operculum and
plate-like appendages with branchial
lamellae are similar in both groups,
but in the Eurypterids the genital
operculum shows a greater
development and covers the second
Page 338
segment, which is without plate-like Fig. 165.—Slimonia acuminata, Salter. Upper
Silurian. Restoration of ventral surface, × ⅑. 1–
appendages. A striking difference 6, Appendages of prosoma; 7, 8, genital
between the two groups is seen in the operculum; 7–12, mesosoma; 13–18, segments
segments of the mesosoma and of metasoma; 19, tail-spine; a, lateral eye; b,
metastoma, covering the inner parts of the coxae
metasoma; in Eurypterids these are of the last pair of appendages; c, median process
all free, whilst in Limulus they are of genital operculum; d, branchial lamellae seen
fused together, but this difference is through the plate-like appendages. (After
Laurie.)
bridged over by some of the
Palaeozoic Xiphosura (Fig. 159, A)
in which those segments are free.
Silurian. Restoration of ventral surface, × ⅑. 1–
appendages. A striking difference 6, Appendages of prosoma; 7, 8, genital
between the two groups is seen in the operculum; 7–12, mesosoma; 13–18, segments
segments of the mesosoma and of metasoma; 19, tail-spine; a, lateral eye; b,
metastoma, covering the inner parts of the coxae
metasoma; in Eurypterids these are of the last pair of appendages; c, median process
all free, whilst in Limulus they are of genital operculum; d, branchial lamellae seen
fused together, but this difference is through the plate-like appendages. (After
Laurie.)
bridged over by some of the
Palaeozoic Xiphosura (Fig. 159, A)
in which those segments are free.
Page 339
Page 340
Fig. 166.—Stylonurus lacoanus, Claypole. Upper Devonian, Pennsylvania.
Restoration of dorsal surface. Length nearly five feet. (After Beecher.)
The Eurypterids present a striking resemblance to Scorpions. In both
groups the segments in the three regions of the body are the same in
number, and the appendages of the prosoma also agree in number and
position. The pre-oral appendages are chelate in both, but the second pair of
appendages are chelate in the Scorpions only. In Eurypterids the coxae of
the five pairs of legs are toothed and meet in the middle line, but in the
Scorpions the coxae of the last two pairs do not meet; this difference,
however, appears to be bridged over in the earliest known Scorpion—
Palaeophonus,[236] from the Silurian rocks. The Eurypterids are
distinguished from the Scorpions by the much greater development of the
last pair of legs. The large metastoma of the former is homologous with the
sternum of the Scorpion. The genital operculum is much smaller in
Scorpions than in Eurypterids, and in this respect the latter agree with
Thelyphonus (one of the Pedipalpi) more than with the Scorpions. The
pectines are absent in the Eurypterids except in Glyptoscorpius. Instead of
the lung-books of the Scorpions the Eurypterids possess branchial lamellae
on the plate-like appendages; but this difference between the two groups
appears to be bridged over by Palaeophonus, which was marine, and may
have possessed branchial lamellae since stigmata seem to be absent.
Glyptoscorpius,[237] which is found in the Lower Carboniferous of the
south of Scotland, is a form of considerable interest. It is about a foot in
length, and agrees in many respects with Eurypterida, but it may be
necessary to separate it from that group since it possesses pectines, and the
legs end in a double claw; it cannot, however, be regarded as a link between
Eurypterids and Scorpions, but must rather be considered as an offshoot
from the former, since the latter group was already in existence at a much
earlier period.
Restoration of dorsal surface. Length nearly five feet. (After Beecher.)
The Eurypterids present a striking resemblance to Scorpions. In both
groups the segments in the three regions of the body are the same in
number, and the appendages of the prosoma also agree in number and
position. The pre-oral appendages are chelate in both, but the second pair of
appendages are chelate in the Scorpions only. In Eurypterids the coxae of
the five pairs of legs are toothed and meet in the middle line, but in the
Scorpions the coxae of the last two pairs do not meet; this difference,
however, appears to be bridged over in the earliest known Scorpion—
Palaeophonus,[236] from the Silurian rocks. The Eurypterids are
distinguished from the Scorpions by the much greater development of the
last pair of legs. The large metastoma of the former is homologous with the
sternum of the Scorpion. The genital operculum is much smaller in
Scorpions than in Eurypterids, and in this respect the latter agree with
Thelyphonus (one of the Pedipalpi) more than with the Scorpions. The
pectines are absent in the Eurypterids except in Glyptoscorpius. Instead of
the lung-books of the Scorpions the Eurypterids possess branchial lamellae
on the plate-like appendages; but this difference between the two groups
appears to be bridged over by Palaeophonus, which was marine, and may
have possessed branchial lamellae since stigmata seem to be absent.
Glyptoscorpius,[237] which is found in the Lower Carboniferous of the
south of Scotland, is a form of considerable interest. It is about a foot in
length, and agrees in many respects with Eurypterida, but it may be
necessary to separate it from that group since it possesses pectines, and the
legs end in a double claw; it cannot, however, be regarded as a link between
Eurypterids and Scorpions, but must rather be considered as an offshoot
from the former, since the latter group was already in existence at a much
earlier period.
Page 341
ARACHNIDA EMBOLOBRANCHIATA
(SCORPIONS, SPIDERS, MITES, ETC.)
BY
CECIL WARBURTON, M.A.
Christ’s College, Cambridge; Zoologist to the Royal Agricultural Society
(SCORPIONS, SPIDERS, MITES, ETC.)
BY
CECIL WARBURTON, M.A.
Christ’s College, Cambridge; Zoologist to the Royal Agricultural Society
Page 342
CHAPTER XII
ARACHNIDA (CONTINUED)—EMBOLOBRANCHIATA—
SCORPIONIDEA—PEDIPALPI
SUB-CLASS II.—EMBOLOBRANCHIATA.[238]
Order I. Scorpionidea.
Segmented Arachnids with chelate chelicerae and pedipalpi. The
abdomen, which is broadly attached to the cephalothorax or prosoma, is
divided into two regions, a six-jointed mesosoma and a six-jointed tail-like
metasoma, ending in a poison-sting. There are four pairs of lung-books,
and the second mesosomatic segment bears a pair of comb-like organs, the
pectines.
The Scorpions include the largest tracheate Arachnid forms, and show in
some respects a high grade of organisation. It is impossible, however, to
arrange the Arachnida satisfactorily in an ascending series, for certain
primitive characteristics are often most marked in those Orders which on
other grounds would seem entitled to rank at the head of the group. Such a
primitive characteristic is the very complete segmentation exhibited by the
Scorpions. They are nocturnal animals of rapacious habit. In size they range
from scarcely more than half an inch to eight inches in length. In the
northern hemisphere they are not found above the fortieth parallel of
latitude in the Old World, though in the New World they extend as high as
the forty-fifth. A corresponding southward limit would practically include
all the land in the southern hemisphere, and here the Order is universally
represented except in New Zealand, South Patagonia, and the Antarctic
islands.
Fossil scorpions are rarely found. The earliest examples known occur in
the Silurian rocks, and belong to the genus Palaeophonus. In the
ARACHNIDA (CONTINUED)—EMBOLOBRANCHIATA—
SCORPIONIDEA—PEDIPALPI
SUB-CLASS II.—EMBOLOBRANCHIATA.[238]
Order I. Scorpionidea.
Segmented Arachnids with chelate chelicerae and pedipalpi. The
abdomen, which is broadly attached to the cephalothorax or prosoma, is
divided into two regions, a six-jointed mesosoma and a six-jointed tail-like
metasoma, ending in a poison-sting. There are four pairs of lung-books,
and the second mesosomatic segment bears a pair of comb-like organs, the
pectines.
The Scorpions include the largest tracheate Arachnid forms, and show in
some respects a high grade of organisation. It is impossible, however, to
arrange the Arachnida satisfactorily in an ascending series, for certain
primitive characteristics are often most marked in those Orders which on
other grounds would seem entitled to rank at the head of the group. Such a
primitive characteristic is the very complete segmentation exhibited by the
Scorpions. They are nocturnal animals of rapacious habit. In size they range
from scarcely more than half an inch to eight inches in length. In the
northern hemisphere they are not found above the fortieth parallel of
latitude in the Old World, though in the New World they extend as high as
the forty-fifth. A corresponding southward limit would practically include
all the land in the southern hemisphere, and here the Order is universally
represented except in New Zealand, South Patagonia, and the Antarctic
islands.
Fossil scorpions are rarely found. The earliest examples known occur in
the Silurian rocks, and belong to the genus Palaeophonus. In the
Page 343
Carboniferous Eoscorpius is found, and in the Oligocene Tityus.
Much remains to be discovered with regard to the habits of scorpions,
and most of the isolated observations which have been recorded lose much
of their value through the uncertainty as to the species concerned. The brief
accounts given by Lankester and by Pocock,[239] and the more recent and
elaborate studies of Fabre,[240] are free from this defect and contain almost
the only trustworthy information we possess.
All are viviparous, and the females carry the newly-hatched young on
their backs. They are predaceous, feeding for the most part on insects and
spiders. These are seized by the chelate pedipalps, and, if small, are simply
picked to pieces by the chelicerae and devoured, but if large the tail-sting is
brought into play and the victim quickly paralysed. The process of eating is
a slow one, and a Cape scorpion in captivity took two hours to devour a
cockroach.
In walking, scorpions carry their pedipalps horizontally in front, using
them partly as feelers and partly as raptorial organs. As regards the body the
attitude varies considerably. In some cases (Parabuthus, Prionurus, etc.) it
is raised high upon the legs, and the “tail” or metasoma is curved forward
over the back, but in others (Euscorpius) the body is held low, and the “tail”
is dragged along behind, the end only being slightly curled. In the daytime
they hide away under wood or stone, or in pits which they dig in the sand.
Parabuthus capensis was observed to dig a shallow pit by means of its
second and third ambulatory legs, resting on its first and fourth legs aided
by the chelae and the metasoma. Those that hide under wood are usually
found clinging to their shelter ventral side uppermost. In captivity the
creatures, though supplied with water, were never observed to drink;
indeed, they are characteristic inhabitants of arid steppes and parched
wastes. Like most Arachnids they can endure prolonged abstinence from
food.
The only sense well developed seems to be that of touch.
Notwithstanding the possession of several eyes their sight is poor. A moving
object within the range of a few inches is certainly perceived, but it has to
be touched before its nature is recognised. Some writers have attributed to
scorpions a keen sense of hearing, and so-called “auditory hairs” are
described on the tibia of the pedipalp, but Pocock came to the conclusion
that Parabuthus capensis and Euscorpius carpathicus were entirely deaf,
Much remains to be discovered with regard to the habits of scorpions,
and most of the isolated observations which have been recorded lose much
of their value through the uncertainty as to the species concerned. The brief
accounts given by Lankester and by Pocock,[239] and the more recent and
elaborate studies of Fabre,[240] are free from this defect and contain almost
the only trustworthy information we possess.
All are viviparous, and the females carry the newly-hatched young on
their backs. They are predaceous, feeding for the most part on insects and
spiders. These are seized by the chelate pedipalps, and, if small, are simply
picked to pieces by the chelicerae and devoured, but if large the tail-sting is
brought into play and the victim quickly paralysed. The process of eating is
a slow one, and a Cape scorpion in captivity took two hours to devour a
cockroach.
In walking, scorpions carry their pedipalps horizontally in front, using
them partly as feelers and partly as raptorial organs. As regards the body the
attitude varies considerably. In some cases (Parabuthus, Prionurus, etc.) it
is raised high upon the legs, and the “tail” or metasoma is curved forward
over the back, but in others (Euscorpius) the body is held low, and the “tail”
is dragged along behind, the end only being slightly curled. In the daytime
they hide away under wood or stone, or in pits which they dig in the sand.
Parabuthus capensis was observed to dig a shallow pit by means of its
second and third ambulatory legs, resting on its first and fourth legs aided
by the chelae and the metasoma. Those that hide under wood are usually
found clinging to their shelter ventral side uppermost. In captivity the
creatures, though supplied with water, were never observed to drink;
indeed, they are characteristic inhabitants of arid steppes and parched
wastes. Like most Arachnids they can endure prolonged abstinence from
food.
The only sense well developed seems to be that of touch.
Notwithstanding the possession of several eyes their sight is poor. A moving
object within the range of a few inches is certainly perceived, but it has to
be touched before its nature is recognised. Some writers have attributed to
scorpions a keen sense of hearing, and so-called “auditory hairs” are
described on the tibia of the pedipalp, but Pocock came to the conclusion
that Parabuthus capensis and Euscorpius carpathicus were entirely deaf,
Page 344
and Lankester could obtain no indication of auditory powers in the case of
Prionurus. The sense of touch is extremely delicate, and seems to reside in
the hairs with which the body and appendages are more or less thickly
clothed. The pectines are special tactile organs. That they are in some way
related to sex seems probable from the fact that they are larger in the male
and sometimes curiously modified in the female, but they appear to be of
use also in determining the nature of the ground traversed by the animal,
being long in such species as raise the body high on the legs, and short in
those that adopt a more grovelling posture. Pocock noticed that a scorpion
which had walked over a portion of a cockroach far enough for the pectines
to come in contact with it immediately backed and ate it.
As is the case with most poisonous
animals, their ferocity has been much
exaggerated; they never sting unless
molested, and their chief anxiety is to
slink off unobserved. The fables that
they kill their young, and that when
hard pressed they commit suicide by
stinging themselves to death, perhaps
hardly deserve serious consideration.
The latter accusation is disproved by
the fact that a scorpion’s poison has
Fig. 167.—Buthus occitanus in the mating no effect upon itself, or even upon a
period. (After Fabre.)
closely allied species. Some writers
think that in the frantic waving of the
“tail,” which is generally induced by strong excitement, a scorpion may
sometimes inadvertently wound itself with the sharp point of its telson.
Fabre gives a fascinating account of the habits of Buthus occitanus,
which occurs in the south of France. He found these scorpions plentifully in
arid, stony spots exposed to the sun. They were always solitary, and if two
were found under the same stone, one was engaged in eating the other.
Their sight is so poor that they do not recognise each other without absolute
contact.
Fabre established colonies in his garden and study, providing them with
suitable soil and sheltering stones. They dug holes by reducing the earth to
powder by means of the three anterior pairs of legs—never using their
Prionurus. The sense of touch is extremely delicate, and seems to reside in
the hairs with which the body and appendages are more or less thickly
clothed. The pectines are special tactile organs. That they are in some way
related to sex seems probable from the fact that they are larger in the male
and sometimes curiously modified in the female, but they appear to be of
use also in determining the nature of the ground traversed by the animal,
being long in such species as raise the body high on the legs, and short in
those that adopt a more grovelling posture. Pocock noticed that a scorpion
which had walked over a portion of a cockroach far enough for the pectines
to come in contact with it immediately backed and ate it.
As is the case with most poisonous
animals, their ferocity has been much
exaggerated; they never sting unless
molested, and their chief anxiety is to
slink off unobserved. The fables that
they kill their young, and that when
hard pressed they commit suicide by
stinging themselves to death, perhaps
hardly deserve serious consideration.
The latter accusation is disproved by
the fact that a scorpion’s poison has
Fig. 167.—Buthus occitanus in the mating no effect upon itself, or even upon a
period. (After Fabre.)
closely allied species. Some writers
think that in the frantic waving of the
“tail,” which is generally induced by strong excitement, a scorpion may
sometimes inadvertently wound itself with the sharp point of its telson.
Fabre gives a fascinating account of the habits of Buthus occitanus,
which occurs in the south of France. He found these scorpions plentifully in
arid, stony spots exposed to the sun. They were always solitary, and if two
were found under the same stone, one was engaged in eating the other.
Their sight is so poor that they do not recognise each other without absolute
contact.
Fabre established colonies in his garden and study, providing them with
suitable soil and sheltering stones. They dug holes by reducing the earth to
powder by means of the three anterior pairs of legs—never using their
Page 345
pedipalpi in the operation—and sweeping away the débris with the tail.
From October to March they ate nothing, rejecting all food offered to them,
though always awake and ready to resent disturbance. In April appetite
seemed to awaken, though a very trifling amount of food seemed to suffice.
At that time, too, they began to wander, and apparently without any
intention of returning, and they continued daily to escape from the garden
enclosure until the most stringent measures were taken to keep them in. Not
till they were surrounded by glass and the framework of their cages covered
with varnished paper were their attempts to climb out of their prison
frustrated. Fabre came to the conclusion that they took at least five years to
attain their full size.
His most interesting observations
were concerned with their mating
habits, in connection with which he
noted some extraordinary
phenomena. After some very curious
antics, in which the animals stood
face to face (Fig. 167) with raised
tails, which they intertwined— Fig. 168.—The “promenade à deux” of Buthus
evidently with no hostile intention— occitanus. (After Fabre.)
they always indulged in what Fabre
calls a “promenade à deux,” hand in hand, so to speak, the male seizing the
chelae of the female with its own, and walking backwards, while the female
followed, usually without any reluctance. This promenade occupied an hour
or more, during which the animals turned several times. At length, if in the
neighbourhood of a suitable stone, the male would dig a hole, without for a
moment entirely quitting its hold of the female, and presently both would
disappear into the newly-formed retreat.
After mating, the male was often devoured by the female. Moreover,
after any combat with an enemy, such as a Lycosa or a Scolopendra, it
appeared to be de rigueur to eat the vanquished, and on such occasions only
was any considerable amount of food consumed.
The scorpions were not, however, anxious to fight, greatly preferring to
retire if possible; but when incited to combat, their sting was quickly fatal
to any mature insect, to spiders and to centipedes. Curiously enough,
however, insect larvae, though badly wounded, did not succumb to the
From October to March they ate nothing, rejecting all food offered to them,
though always awake and ready to resent disturbance. In April appetite
seemed to awaken, though a very trifling amount of food seemed to suffice.
At that time, too, they began to wander, and apparently without any
intention of returning, and they continued daily to escape from the garden
enclosure until the most stringent measures were taken to keep them in. Not
till they were surrounded by glass and the framework of their cages covered
with varnished paper were their attempts to climb out of their prison
frustrated. Fabre came to the conclusion that they took at least five years to
attain their full size.
His most interesting observations
were concerned with their mating
habits, in connection with which he
noted some extraordinary
phenomena. After some very curious
antics, in which the animals stood
face to face (Fig. 167) with raised
tails, which they intertwined— Fig. 168.—The “promenade à deux” of Buthus
evidently with no hostile intention— occitanus. (After Fabre.)
they always indulged in what Fabre
calls a “promenade à deux,” hand in hand, so to speak, the male seizing the
chelae of the female with its own, and walking backwards, while the female
followed, usually without any reluctance. This promenade occupied an hour
or more, during which the animals turned several times. At length, if in the
neighbourhood of a suitable stone, the male would dig a hole, without for a
moment entirely quitting its hold of the female, and presently both would
disappear into the newly-formed retreat.
After mating, the male was often devoured by the female. Moreover,
after any combat with an enemy, such as a Lycosa or a Scolopendra, it
appeared to be de rigueur to eat the vanquished, and on such occasions only
was any considerable amount of food consumed.
The scorpions were not, however, anxious to fight, greatly preferring to
retire if possible; but when incited to combat, their sting was quickly fatal
to any mature insect, to spiders and to centipedes. Curiously enough,
however, insect larvae, though badly wounded, did not succumb to the
Page 346
poison. Newly-hatched scorpions mounted on the mother’s back, where
they remained motionless for a week, entirely unfed. They then underwent a
moult, after which they were able to forage for themselves.
External Structure.
The chitinous plates of the prosoma are fused to form a carapace. Six
segments are clearly indicated by the six pairs of appendages, but, though
the development of Scorpio affords little direct evidence of the fact, there is
reason to believe that there once existed a pre-cheliceral segment,[241] as has
been clearly proved in the case of the spiders. An embryonic pregenital
segment has also been recognised. The six prosomatic appendages are those
proper to the Arachnida, being the chelicerae, pedipalpi, and four pairs of
ambulatory legs. The mesosoma, which is broadly attached to the prosoma,
comprises six segments, indicated ventrally by the genital operculum, the
pectines, and the four pairs of pulmonary stigmata. The last of the broad
abdominal segments, which tapers abruptly, belongs to the metasoma,
which also comprises six segments, and is succeeded by the post-anal spine
or sting.
Prosoma.—Near the middle of the carapace are two median eyes, and on
its antero-lateral borders are usually to be found groups of smaller eyes,
numbering from two to five. All the eyes are simple. There is a difference,
however, in their development, the median eyes being diplostichous, or
involving two layers of hypoderm, while the lateral eyes are monostichous,
and pass through a stage strikingly like the permanent condition of the eyes
of Limulus. The arrangement of various slight longitudinal ridges on the
dorsal surface of the carapace is of systematic importance. On the ventral
surface, just in front of the genital operculum, is a sternum, never large, and
sometimes barely visible. Its shape and size constitute one of the principal
family characteristics.
they remained motionless for a week, entirely unfed. They then underwent a
moult, after which they were able to forage for themselves.
External Structure.
The chitinous plates of the prosoma are fused to form a carapace. Six
segments are clearly indicated by the six pairs of appendages, but, though
the development of Scorpio affords little direct evidence of the fact, there is
reason to believe that there once existed a pre-cheliceral segment,[241] as has
been clearly proved in the case of the spiders. An embryonic pregenital
segment has also been recognised. The six prosomatic appendages are those
proper to the Arachnida, being the chelicerae, pedipalpi, and four pairs of
ambulatory legs. The mesosoma, which is broadly attached to the prosoma,
comprises six segments, indicated ventrally by the genital operculum, the
pectines, and the four pairs of pulmonary stigmata. The last of the broad
abdominal segments, which tapers abruptly, belongs to the metasoma,
which also comprises six segments, and is succeeded by the post-anal spine
or sting.
Prosoma.—Near the middle of the carapace are two median eyes, and on
its antero-lateral borders are usually to be found groups of smaller eyes,
numbering from two to five. All the eyes are simple. There is a difference,
however, in their development, the median eyes being diplostichous, or
involving two layers of hypoderm, while the lateral eyes are monostichous,
and pass through a stage strikingly like the permanent condition of the eyes
of Limulus. The arrangement of various slight longitudinal ridges on the
dorsal surface of the carapace is of systematic importance. On the ventral
surface, just in front of the genital operculum, is a sternum, never large, and
sometimes barely visible. Its shape and size constitute one of the principal
family characteristics.
Page 347
Fig. 169.—Buthus occitanus. A, Dorsal view; B, ventral view. (After Kraepelin.)
Mesosoma.—The dorsal plates or terga are distinct, and are connected by
soft chitin with their corresponding sterna.
Beneath the second abdominal segments are borne the “pectines” or
comb-like organs. In their structure four portions are distinguishable, an
anterior lamella or shaft attaching them to the body, a middle lamella, the
teeth, and the fulcra, a series of small chitinous pieces intercalated between
the bases of the movable teeth.
Beneath the third, fourth, fifth, and sixth segments are the paired
openings of the lung-sacs.
Metasoma.—The first segment is usually and the remainder are
invariably enclosed in complete chitinous rings and show considerable
variations in their comparative size and shape, and in the arrangement of the
ridges and keels with which they are usually furnished. The post-anal
Mesosoma.—The dorsal plates or terga are distinct, and are connected by
soft chitin with their corresponding sterna.
Beneath the second abdominal segments are borne the “pectines” or
comb-like organs. In their structure four portions are distinguishable, an
anterior lamella or shaft attaching them to the body, a middle lamella, the
teeth, and the fulcra, a series of small chitinous pieces intercalated between
the bases of the movable teeth.
Beneath the third, fourth, fifth, and sixth segments are the paired
openings of the lung-sacs.
Metasoma.—The first segment is usually and the remainder are
invariably enclosed in complete chitinous rings and show considerable
variations in their comparative size and shape, and in the arrangement of the
ridges and keels with which they are usually furnished. The post-anal
Page 348
segment is more or less globular at its base, constituting a “vesicle,” and
terminates in a fine curved point, the “aculeus,” perforated for the passage
of the delicate poison-duct. With the abdomen fully extended the point is
directed downward, but in the attitude of attack or defence, when the “tail”
is carried horizontally over the back, the sting points forward in the
neighbourhood of the animal’s head.
Appendages.—The three-jointed
chelicerae are powerful and chelate.
The first joint is small, but the second
is strongly developed and bears at its
anterior end on the inner side a
projection which forms the
immovable finger of the chela. The
third joint, or movable finger, is
articulated on the outer side, and both
fingers are armed with teeth whose
arrangement is useful in
distinguishing the species. The
Fig. 170.—A, Diagram of a Scorpion’s leg; 1, pedipalpi consist of six joints. The
coxa; 2, trochanter; 3, femur; 4, patella; 5, tibia; coxa is small and has an inwardly
6, protarsus; 7, tarsus; p.s, pedal spur; t.s, tibial
spur. B, Fourth tarsus of Palamnaeus
directed lamella which assists in
swammerdami; l, lateral lobe. (After Pocock.) feeding. The trochanter is also a
small joint, bearing, normally at right
angles to the longitudinal axis, the
powerful humerus or femur. Then follows the brachium or tibia, again
directed forward, and the last two joints form the chela or “hand,” the
terminal joint or movable finger being on the outer side as in the chelicerae.
In systematic determination special attention is given to the “hand.” In
some forms the upper surface is uniformly rounded, while in others a
“finger-keel” divides it into two flattish surfaces almost at right angles. The
biting edges of the fingers are usually furnished with rows of minute teeth
arranged characteristically in the different genera. The ambulatory legs are
seven-jointed, though, unfortunately, authors are not agreed upon the
nomenclature of the joints. Kraepelin[242] names them coxa, trochanter,
femur, tibia, and three-jointed tarsus, and Simon[243] agrees with him.
Pocock’s names[244] are coxa, trochanter, femur, patella, tibia, protarsus, and
tarsus, and it is certainly convenient that each joint should have a separate
terminates in a fine curved point, the “aculeus,” perforated for the passage
of the delicate poison-duct. With the abdomen fully extended the point is
directed downward, but in the attitude of attack or defence, when the “tail”
is carried horizontally over the back, the sting points forward in the
neighbourhood of the animal’s head.
Appendages.—The three-jointed
chelicerae are powerful and chelate.
The first joint is small, but the second
is strongly developed and bears at its
anterior end on the inner side a
projection which forms the
immovable finger of the chela. The
third joint, or movable finger, is
articulated on the outer side, and both
fingers are armed with teeth whose
arrangement is useful in
distinguishing the species. The
Fig. 170.—A, Diagram of a Scorpion’s leg; 1, pedipalpi consist of six joints. The
coxa; 2, trochanter; 3, femur; 4, patella; 5, tibia; coxa is small and has an inwardly
6, protarsus; 7, tarsus; p.s, pedal spur; t.s, tibial
spur. B, Fourth tarsus of Palamnaeus
directed lamella which assists in
swammerdami; l, lateral lobe. (After Pocock.) feeding. The trochanter is also a
small joint, bearing, normally at right
angles to the longitudinal axis, the
powerful humerus or femur. Then follows the brachium or tibia, again
directed forward, and the last two joints form the chela or “hand,” the
terminal joint or movable finger being on the outer side as in the chelicerae.
In systematic determination special attention is given to the “hand.” In
some forms the upper surface is uniformly rounded, while in others a
“finger-keel” divides it into two flattish surfaces almost at right angles. The
biting edges of the fingers are usually furnished with rows of minute teeth
arranged characteristically in the different genera. The ambulatory legs are
seven-jointed, though, unfortunately, authors are not agreed upon the
nomenclature of the joints. Kraepelin[242] names them coxa, trochanter,
femur, tibia, and three-jointed tarsus, and Simon[243] agrees with him.
Pocock’s names[244] are coxa, trochanter, femur, patella, tibia, protarsus, and
tarsus, and it is certainly convenient that each joint should have a separate
Page 349
name, but it must be borne in mind that the tibia of different authors is not
always the same joint. Special attention must be directed to the three
terminal joints, which furnish highly important characteristics. The tibia (in
Pocock’s sense) is sometimes provided with a “tibial spur” at its lower
distal extremity. From the soft arthrodial membrane between the protarsus
and tarsus may proceed one or more dark-tipped claw-like spurs, the “pedal
spurs.” The terminal joint (tarsus of Pocock) is variously furnished with
hairs and teeth, and always ends in a pair of well-developed movable claws
beneath which a much reduced and sometimes almost obsolete third claw is
distinguishable. The tarsus generally projects in a “claw-lobe” over the base
of the superior claws, and sometimes lateral lobes are present. The first and
second coxae have triangular maxillary lobes directed towards the mouth.
The third and fourth coxae are fused together on each side, and those on one
side are separated from those on the other by the sternum. In other respects
the four pairs of legs are usually similar.
Internal Anatomy.
The alimentary canal is a fairly uniform tube, nowhere greatly dilated.
The very small mouth leads into a small suctorial chamber, and this is
connected by a narrow oesophagus, which pierces the cerebral nerve-mass,
with a slightly dilated portion which receives the ducts of the first pair of
gastric glands, often called salivary glands. The succeeding portion in the
prosoma receives four or five more pairs of ducts from the well-developed
gastric glands. In the rapidly narrowing first metasomatic segment the
intestine receives one or two pairs of Malpighian tubes, and thence
proceeds to the anus, situated ventrally in the last segment.
The vascular system is of the usual Arachnid type, the heart being a
seven-chambered dorsal longitudinal vessel lying in a pericardium, with
which it communicates by seven pairs of valvular ostia. Lankester[245] has
demonstrated several pairs of superficial lateral veins connecting two deep-
seated ventral venous trunks with the pericardium. The lung-books are, so
to speak, pushed in to dilatations of these trunks, so that some of the lateral
veins carry blood newly aerated by the lung-books directly to the
pericardium.
always the same joint. Special attention must be directed to the three
terminal joints, which furnish highly important characteristics. The tibia (in
Pocock’s sense) is sometimes provided with a “tibial spur” at its lower
distal extremity. From the soft arthrodial membrane between the protarsus
and tarsus may proceed one or more dark-tipped claw-like spurs, the “pedal
spurs.” The terminal joint (tarsus of Pocock) is variously furnished with
hairs and teeth, and always ends in a pair of well-developed movable claws
beneath which a much reduced and sometimes almost obsolete third claw is
distinguishable. The tarsus generally projects in a “claw-lobe” over the base
of the superior claws, and sometimes lateral lobes are present. The first and
second coxae have triangular maxillary lobes directed towards the mouth.
The third and fourth coxae are fused together on each side, and those on one
side are separated from those on the other by the sternum. In other respects
the four pairs of legs are usually similar.
Internal Anatomy.
The alimentary canal is a fairly uniform tube, nowhere greatly dilated.
The very small mouth leads into a small suctorial chamber, and this is
connected by a narrow oesophagus, which pierces the cerebral nerve-mass,
with a slightly dilated portion which receives the ducts of the first pair of
gastric glands, often called salivary glands. The succeeding portion in the
prosoma receives four or five more pairs of ducts from the well-developed
gastric glands. In the rapidly narrowing first metasomatic segment the
intestine receives one or two pairs of Malpighian tubes, and thence
proceeds to the anus, situated ventrally in the last segment.
The vascular system is of the usual Arachnid type, the heart being a
seven-chambered dorsal longitudinal vessel lying in a pericardium, with
which it communicates by seven pairs of valvular ostia. Lankester[245] has
demonstrated several pairs of superficial lateral veins connecting two deep-
seated ventral venous trunks with the pericardium. The lung-books are, so
to speak, pushed in to dilatations of these trunks, so that some of the lateral
veins carry blood newly aerated by the lung-books directly to the
pericardium.
Page 350
The nervous system is not greatly concentrated except in the prosoma,
where there is a single ganglionic mass which innervates not only the whole
prosoma but the mesosoma as far as the first and sometimes the second pair
of lung-books. There are two mesosomatic ganglia, variously situated in
different genera, and each metasomatic segment has its ganglion.
The generative organs are more or less embedded in the gastric glands.
There are two testes, each composed of a pair of intercommunicating
tubules, and connected by a common vas deferens with the generative
aperture, which is furnished with a double protrusible intromittent organ. A
pair of vesiculae seminales and a pair of accessory glands are also present.
The female possesses a single ovary, consisting of a median and two lateral
tubules, all connected by cross branches.
In addition to the external sclerites a free internal skeletal plate, situated
in the prosoma between the alimentary canal and the nerve-cord, furnishes
convenient fulcra for muscular attachment. It is known as the
“endosternite.”
Brauer[246] has made the most complete study of the development of
Scorpio, and two of the most interesting of his conclusions may be
mentioned here. He has shown the lung-books to be derived from gills
borne on mesosomatic appendages. Moreover he found in the embryo five
pairs of segmental ducts—in segments 3–6 and 8—and demonstrated that
those of segment 5 persisted, though without external aperture, as coxal
glands, and those of segment 8 as the genital ducts.
Classification.
More than 350 species of scorpions have been described, but many of
these are “doubtful,” and probably the number of known forms may be put
at about 300. These are divided by Kraepelin[247] into six families and fifty-
six genera. The best indications of the family of a scorpion are to be found
in the shape of the sternum, the armature of the tarsi, and the number of the
lateral eyes, while assistance is also to be derived from the shape of the
stigmata and of the pectines, and from the absence or presence of a spine
beneath the aculeus.
The six families are: Buthidae, Scorpionidae, Chaerilidae, Chactidae,
Vejovidae, and Bothriuridae.
where there is a single ganglionic mass which innervates not only the whole
prosoma but the mesosoma as far as the first and sometimes the second pair
of lung-books. There are two mesosomatic ganglia, variously situated in
different genera, and each metasomatic segment has its ganglion.
The generative organs are more or less embedded in the gastric glands.
There are two testes, each composed of a pair of intercommunicating
tubules, and connected by a common vas deferens with the generative
aperture, which is furnished with a double protrusible intromittent organ. A
pair of vesiculae seminales and a pair of accessory glands are also present.
The female possesses a single ovary, consisting of a median and two lateral
tubules, all connected by cross branches.
In addition to the external sclerites a free internal skeletal plate, situated
in the prosoma between the alimentary canal and the nerve-cord, furnishes
convenient fulcra for muscular attachment. It is known as the
“endosternite.”
Brauer[246] has made the most complete study of the development of
Scorpio, and two of the most interesting of his conclusions may be
mentioned here. He has shown the lung-books to be derived from gills
borne on mesosomatic appendages. Moreover he found in the embryo five
pairs of segmental ducts—in segments 3–6 and 8—and demonstrated that
those of segment 5 persisted, though without external aperture, as coxal
glands, and those of segment 8 as the genital ducts.
Classification.
More than 350 species of scorpions have been described, but many of
these are “doubtful,” and probably the number of known forms may be put
at about 300. These are divided by Kraepelin[247] into six families and fifty-
six genera. The best indications of the family of a scorpion are to be found
in the shape of the sternum, the armature of the tarsi, and the number of the
lateral eyes, while assistance is also to be derived from the shape of the
stigmata and of the pectines, and from the absence or presence of a spine
beneath the aculeus.
The six families are: Buthidae, Scorpionidae, Chaerilidae, Chactidae,
Vejovidae, and Bothriuridae.
Page 351
Fam. 1. Buthidae.—Sternum small and generally triangular. Tibial
spurs in the third and fourth legs. Generally a spur beneath the aculeus.
Lateral eyes three to five in number.
There are two sub-families: Buthinae and Centrurinae.
The Buthinae, which possess a tibial spur, comprise fourteen genera,
most of them Old World forms. The principal genera are Buthus, which
contains about 25 species, and Archisometrus with 20 species. One genus
only, Ananteris, is South American, and it includes only a single species.
The genus Uroplectes, with 16 species, is almost entirely African.
The Centrurinae, without tibial spur, are New World scorpions, though
Isometrus europaeus (maculatus) is cosmopolitan. The principal genera are
Tityus with 30 species, Centrurus with 13, and Isometrus with 6.
Fam. 2. Scorpionidae.—Sternum broad and pentagonal, with sides
approximately parallel. No tibial spur, but a single pedal spur. Generally
three lateral eyes.
Nearly a hundred species of Scorpionidae have been described,
distributed among fifteen genera. The following sub-families are
recognised: Diplocentrinae, Urodacinae, Scorpioninae, Hemiscorpioninae,
and Ischnurinae.
The Diplocentrinae have a spur under the aculeus. They form a small
group of only eight species. The principal genus, Diplocentrus, is entirely
Neotropical, but Nebo has a single Old World representative in Syria.
The Urodacinae, with the single genus Urodacus, are Australian
scorpions. As in the next sub-family, there are rounded lobes on the tarsi,
but there is only a single keel on the “tail,” and the lateral eyes are two in
number. Six good and three doubtful species are recognised.
The Scorpioninae are Asiatic and African forms, and are recognised by
the tarsi having a large lobe on each side, by the convex upper surface of
the “hand,” by the presence of two median keels on the “tail,” and by the
possession of three lateral eyes. Palamnaeus (Heterometrus) has sixteen
species in the Indian region. There are about thirty species of
Opisthophthalmus, all natives of South Africa. Pandinus includes about ten
species, but there are only two species of the type genus Scorpio, S. maurus
and S. boehmei.
spurs in the third and fourth legs. Generally a spur beneath the aculeus.
Lateral eyes three to five in number.
There are two sub-families: Buthinae and Centrurinae.
The Buthinae, which possess a tibial spur, comprise fourteen genera,
most of them Old World forms. The principal genera are Buthus, which
contains about 25 species, and Archisometrus with 20 species. One genus
only, Ananteris, is South American, and it includes only a single species.
The genus Uroplectes, with 16 species, is almost entirely African.
The Centrurinae, without tibial spur, are New World scorpions, though
Isometrus europaeus (maculatus) is cosmopolitan. The principal genera are
Tityus with 30 species, Centrurus with 13, and Isometrus with 6.
Fam. 2. Scorpionidae.—Sternum broad and pentagonal, with sides
approximately parallel. No tibial spur, but a single pedal spur. Generally
three lateral eyes.
Nearly a hundred species of Scorpionidae have been described,
distributed among fifteen genera. The following sub-families are
recognised: Diplocentrinae, Urodacinae, Scorpioninae, Hemiscorpioninae,
and Ischnurinae.
The Diplocentrinae have a spur under the aculeus. They form a small
group of only eight species. The principal genus, Diplocentrus, is entirely
Neotropical, but Nebo has a single Old World representative in Syria.
The Urodacinae, with the single genus Urodacus, are Australian
scorpions. As in the next sub-family, there are rounded lobes on the tarsi,
but there is only a single keel on the “tail,” and the lateral eyes are two in
number. Six good and three doubtful species are recognised.
The Scorpioninae are Asiatic and African forms, and are recognised by
the tarsi having a large lobe on each side, by the convex upper surface of
the “hand,” by the presence of two median keels on the “tail,” and by the
possession of three lateral eyes. Palamnaeus (Heterometrus) has sixteen
species in the Indian region. There are about thirty species of
Opisthophthalmus, all natives of South Africa. Pandinus includes about ten
species, but there are only two species of the type genus Scorpio, S. maurus
and S. boehmei.
Page 352
The sub-family Hemiscorpioninae was formed for the reception of the
single Arabian species Hemiscorpion lepturus. Its most striking
characteristic is the cylindrical vesicle of the tail in the male.
The Ischnurinae differ from the Scorpioninae chiefly in the absence of
the tarsal lobes, the presence of a well-marked finger-keel, and the
generally more depressed form of the body and hand. In the opinion of
some authors they should be separated from the Scorpionidae as a distinct
family, the Ischnuridae. There are more than twenty species, divided among
six genera. The type genus Ischnurus has only the single species I.
ochropus. There are eight species of Opisthacanthus, which has
representatives in Africa and America.
Fam. 3. Chaerilidae.—Sternum pentagonal with median depression or
“sulcus” rounded posteriorly. Two pedal spurs. Stigmata circular. Two
lateral eyes with a yellow spot behind the second. Pectines very short.
This small family has the single genus Chaerilus with but seven species,
natives of the Oriental region.
Fam. 4. Chactidae.—Two pedal spurs. Two lateral eyes (or, rarely, no
eyes) but without yellow spot. Characteristic dentition on movable finger of
“hand.”
There are three sub-families, Megacorminae, Euscorpiinae, and
Chactinae.
The Megacorminae include but a single Mexican form, Megacormus
granosus. There is a single toothed keel under the “tail,” and all the under
surface is spiny. There is a row of long bristles under the tarsus.
In the Euscorpiinae the upper surface of the hand is divided into two
surfaces almost at right angles by a strong finger-keel. This is a small group
of about six species found in the Mediterranean region. The two genera are
Euscorpius and Belisarius.
The Chactinae are without any marked keel on the hand. The scorpions
of this sub-family are found in equatorial South America and the West
Indies, where there are more than twenty species divided about equally
between the four genera Chactas, Broteas, Broteochactas, and Teuthraustes.
Fam. 5. Vejovidae.—No tibial, but two pedal spurs. A single row of
hairs or papillae under the tarsus. Sternum generally broader than long.
Elongate stigmata, and three lateral eyes.
single Arabian species Hemiscorpion lepturus. Its most striking
characteristic is the cylindrical vesicle of the tail in the male.
The Ischnurinae differ from the Scorpioninae chiefly in the absence of
the tarsal lobes, the presence of a well-marked finger-keel, and the
generally more depressed form of the body and hand. In the opinion of
some authors they should be separated from the Scorpionidae as a distinct
family, the Ischnuridae. There are more than twenty species, divided among
six genera. The type genus Ischnurus has only the single species I.
ochropus. There are eight species of Opisthacanthus, which has
representatives in Africa and America.
Fam. 3. Chaerilidae.—Sternum pentagonal with median depression or
“sulcus” rounded posteriorly. Two pedal spurs. Stigmata circular. Two
lateral eyes with a yellow spot behind the second. Pectines very short.
This small family has the single genus Chaerilus with but seven species,
natives of the Oriental region.
Fam. 4. Chactidae.—Two pedal spurs. Two lateral eyes (or, rarely, no
eyes) but without yellow spot. Characteristic dentition on movable finger of
“hand.”
There are three sub-families, Megacorminae, Euscorpiinae, and
Chactinae.
The Megacorminae include but a single Mexican form, Megacormus
granosus. There is a single toothed keel under the “tail,” and all the under
surface is spiny. There is a row of long bristles under the tarsus.
In the Euscorpiinae the upper surface of the hand is divided into two
surfaces almost at right angles by a strong finger-keel. This is a small group
of about six species found in the Mediterranean region. The two genera are
Euscorpius and Belisarius.
The Chactinae are without any marked keel on the hand. The scorpions
of this sub-family are found in equatorial South America and the West
Indies, where there are more than twenty species divided about equally
between the four genera Chactas, Broteas, Broteochactas, and Teuthraustes.
Fam. 5. Vejovidae.—No tibial, but two pedal spurs. A single row of
hairs or papillae under the tarsus. Sternum generally broader than long.
Elongate stigmata, and three lateral eyes.
Page 353
Seven of the eight genera of this family include only American forms, the
principal genus being Vejovis, with about ten species. The genus Scorpiops,
however, belongs to the Indian region and numbers more than ten species.
[248]
Fam. 6. Bothriuridae.—Sternum much reduced and sometimes hardly
visible, consisting of two slight, nearly transverse bars.
Of the seven genera of this family one, Cercophonius, is Australian. The
other six genera include some dozen South American forms, Bothriurus
having four species.
Order II. Pedipalpi.
Arachnids with non-chelate, two-jointed chelicerae, powerful pedipalpi,
and four pairs of legs, of which only the last three are ambulatory, the first
being used as tactile organs. The cephalothorax is usually covered by an
undivided carapace, but the pedunculated abdomen is segmented.
Respiration is by lung-books.
The Pedipalpi are a little-known group of animals of nocturnal habits.
Though rarely seen they are widely distributed, being found in India,
Arabia, the greater part of Africa, and Central and South America. They are
of ancient origin, a fossil genus, Graeophonus, of the Tarantulidae
(Phrynidae, see p. 312), occurring in the Carboniferous strata in North
America. They live under stones and bark, and in caves, where, when
disturbed, they seek safety in crannies in the rock.
Little is known of their habits, but they are believed to feed chiefly upon
insects. The female Tarantula carries the developing eggs, somewhat after
the manner of the Chernetidea (see p. 434), in a bag beneath the abdomen,
the under surface of which becomes concave and dome-like during the
period of gestation.[249]
External Structure.—The external features which the members of this
Order have in common are the segmented pediculate abdomen (9 to 12
segments), the two-jointed non-chelate chelicerae, the antenniform first pair
of legs, and the presence of two pairs of lung-book stigmata beneath the
principal genus being Vejovis, with about ten species. The genus Scorpiops,
however, belongs to the Indian region and numbers more than ten species.
[248]
Fam. 6. Bothriuridae.—Sternum much reduced and sometimes hardly
visible, consisting of two slight, nearly transverse bars.
Of the seven genera of this family one, Cercophonius, is Australian. The
other six genera include some dozen South American forms, Bothriurus
having four species.
Order II. Pedipalpi.
Arachnids with non-chelate, two-jointed chelicerae, powerful pedipalpi,
and four pairs of legs, of which only the last three are ambulatory, the first
being used as tactile organs. The cephalothorax is usually covered by an
undivided carapace, but the pedunculated abdomen is segmented.
Respiration is by lung-books.
The Pedipalpi are a little-known group of animals of nocturnal habits.
Though rarely seen they are widely distributed, being found in India,
Arabia, the greater part of Africa, and Central and South America. They are
of ancient origin, a fossil genus, Graeophonus, of the Tarantulidae
(Phrynidae, see p. 312), occurring in the Carboniferous strata in North
America. They live under stones and bark, and in caves, where, when
disturbed, they seek safety in crannies in the rock.
Little is known of their habits, but they are believed to feed chiefly upon
insects. The female Tarantula carries the developing eggs, somewhat after
the manner of the Chernetidea (see p. 434), in a bag beneath the abdomen,
the under surface of which becomes concave and dome-like during the
period of gestation.[249]
External Structure.—The external features which the members of this
Order have in common are the segmented pediculate abdomen (9 to 12
segments), the two-jointed non-chelate chelicerae, the antenniform first pair
of legs, and the presence of two pairs of lung-book stigmata beneath the
Page 354
abdomen. The constituent families
differ so much in outward form that
they must be dealt with separately.
The Thelyphonidae or “Whip
Scorpions” (see p. 312) have a long-
oval carapace bearing well-
developed eyes, two in front, and a
group of three or five on either side
some distance behind. The pedipalpi
are chelate, and have their basal
joints fused beneath the mouth, being
thus incapable of any masticating
motion.
The first legs are six-jointed, and
have multi-articulate tarsi; the others
are seven-jointed, and their tarsi, in
some species at least, are tri-
articulate. The abdomen consists of
two portions, a wide nine-jointed pre-
abdomen and a short narrow three-
jointed post-abdomen, to which a
filiform tail is articulated. Beneath
the cephalothorax, between the coxae
of the legs, is a distinct sternal plate
in two portions (Fig. 171). The first
abdominal ventral plate is largely Fview;ig. 171.—Thelyphonus, diagrammatic ventral
about natural size. c, Coxal joint of
developed, and covers two segments. pedipalp; g, generative opening; p, pedipalp; sp,
Behind it are the median genital spiracles; st, sternal plates; 1, 2, 3, 4, ambulatory
opening and two pulmonary legs. (After Pickard-Cambridge.)
stigmata, while the other stigmata are
behind the second ventral plate, which corresponds to the third abdominal
segment. On the last abdominal segment there are often two or four light-
coloured spots called “ommatoids,” and considered by some authors to be
organs of sight. Laurie, however (vide infra), thinks it more probable that
they are olfactory in function.
differ so much in outward form that
they must be dealt with separately.
The Thelyphonidae or “Whip
Scorpions” (see p. 312) have a long-
oval carapace bearing well-
developed eyes, two in front, and a
group of three or five on either side
some distance behind. The pedipalpi
are chelate, and have their basal
joints fused beneath the mouth, being
thus incapable of any masticating
motion.
The first legs are six-jointed, and
have multi-articulate tarsi; the others
are seven-jointed, and their tarsi, in
some species at least, are tri-
articulate. The abdomen consists of
two portions, a wide nine-jointed pre-
abdomen and a short narrow three-
jointed post-abdomen, to which a
filiform tail is articulated. Beneath
the cephalothorax, between the coxae
of the legs, is a distinct sternal plate
in two portions (Fig. 171). The first
abdominal ventral plate is largely Fview;ig. 171.—Thelyphonus, diagrammatic ventral
about natural size. c, Coxal joint of
developed, and covers two segments. pedipalp; g, generative opening; p, pedipalp; sp,
Behind it are the median genital spiracles; st, sternal plates; 1, 2, 3, 4, ambulatory
opening and two pulmonary legs. (After Pickard-Cambridge.)
stigmata, while the other stigmata are
behind the second ventral plate, which corresponds to the third abdominal
segment. On the last abdominal segment there are often two or four light-
coloured spots called “ommatoids,” and considered by some authors to be
organs of sight. Laurie, however (vide infra), thinks it more probable that
they are olfactory in function.
Page 355
The Schizonotidae (see p. 312) have a two-jointed carapace, and do not
possess more than two eyes. There is a short unjointed tail-piece.
In the Tarantulidae (Phrynidae) the whole body is much flattened and
extended laterally, the undivided carapace being reniform, and broader than
long. The long non-chelate pedipalps have their basal joints free and
movable, and there are several sternal plates. There are nine abdominal
tergal plates, the last three diminishing rapidly in size, and the last plate
covering a button-like terminal portion of the abdomen. The first abdominal
ventral plate is largely developed, as in the Thelyphonidae, and the genital
orifice and pulmonary stigmata are in the same situation as in that group.
The Tarantulidae have glutinous glands in the first abdominal segment
which are capable of spinning a few irregular threads.
In the whole group paired circular depressions are conspicuous dorsally
on all the abdominal segments. These indicate the points of attachment of
the dorso-ventral muscles.
Internal Structure.—The anatomy of the Pedipalpi has been very
inadequately studied. Disconnected notes on various points of structure
have been published by various morphologists, but no complete
investigation has yet been made of the internal organs. This is largely due to
the difficulty of obtaining material, and the bad state of preservation of the
internal parts of such specimens as have been available for dissection.
The following points have been made out in the anatomy of Thelyphonus.
[250]
The alimentary canal commences after the mouth with a pharynx which,
though not dilated, is furnished with sucking muscles. It then narrows into
an oesophagus which passes through the nerve-mass, and afterwards dilates
to form the mid-gut, which immediately gives off two large lateral
diverticula which extend backwards, each having five lobes. There are also
two median diverticula which proceed from the ventral surface and pass
through the endosternite. The abdominal portion of the canal is entirely
concealed by the great “liver” mass which communicates with it by four
paired ducts in the anterior part of the abdomen. Behind the fourth
abdominal segment the gut is narrow till it expands in the seventh segment
into an hour-glass-shaped stercoral pocket which, according to Laurie, is a
portion of the mesenteron.
possess more than two eyes. There is a short unjointed tail-piece.
In the Tarantulidae (Phrynidae) the whole body is much flattened and
extended laterally, the undivided carapace being reniform, and broader than
long. The long non-chelate pedipalps have their basal joints free and
movable, and there are several sternal plates. There are nine abdominal
tergal plates, the last three diminishing rapidly in size, and the last plate
covering a button-like terminal portion of the abdomen. The first abdominal
ventral plate is largely developed, as in the Thelyphonidae, and the genital
orifice and pulmonary stigmata are in the same situation as in that group.
The Tarantulidae have glutinous glands in the first abdominal segment
which are capable of spinning a few irregular threads.
In the whole group paired circular depressions are conspicuous dorsally
on all the abdominal segments. These indicate the points of attachment of
the dorso-ventral muscles.
Internal Structure.—The anatomy of the Pedipalpi has been very
inadequately studied. Disconnected notes on various points of structure
have been published by various morphologists, but no complete
investigation has yet been made of the internal organs. This is largely due to
the difficulty of obtaining material, and the bad state of preservation of the
internal parts of such specimens as have been available for dissection.
The following points have been made out in the anatomy of Thelyphonus.
[250]
The alimentary canal commences after the mouth with a pharynx which,
though not dilated, is furnished with sucking muscles. It then narrows into
an oesophagus which passes through the nerve-mass, and afterwards dilates
to form the mid-gut, which immediately gives off two large lateral
diverticula which extend backwards, each having five lobes. There are also
two median diverticula which proceed from the ventral surface and pass
through the endosternite. The abdominal portion of the canal is entirely
concealed by the great “liver” mass which communicates with it by four
paired ducts in the anterior part of the abdomen. Behind the fourth
abdominal segment the gut is narrow till it expands in the seventh segment
into an hour-glass-shaped stercoral pocket which, according to Laurie, is a
portion of the mesenteron.
Page 356
The excretory organs are the Malpighian tubes and the coxal glands. The
former are generally described as entering the anterior portion of the
stercoral pocket, but according to Laurie they pass along its ventral surface,
attached to it by connective tissue, and really enter at the posterior end. The
coxal glands are well developed, and lie beneath the endosternite, opening
near the first coxae.
The nervous system is much concentrated and of the usual Arachnid type.
The median abdominal nerve has a ganglion towards its extremity,
supplying, according to Bernard,[251] the muscles which move the tail. The
heart is extremely long, and varies little in width. It has nine pairs of
ostia[252]—two in the thorax and seven in the abdomen. The generative
glands are paired, and in the male there are large seminal vesicles. In the
most ventral portion of the abdominal cavity lies a remarkable
asymmetrically-situated gland, the “stink-gland.” It consists of a number of
secretory tubules communicating with two elongated sacs, one of which lies
beneath the nerve-cord, and therefore medially, while the other lies far to
the left. Their ducts proceed to the anus or its vicinity.
The caudal organs, or white spots which, as already mentioned, are
usually found on the last of the three post-abdominal segments of
Thelyphonus, are of doubtful function. They have been variously explained
as the stink-gland orifices, and as organs sensitive to light (“ommatoids”).
Laurie[253] was unable to find any pore in this region, nor was there any of
the pigment so characteristic of organs of sight. The histological structure
indicated a sense-organ rather than a gland, but the use of these organs is
entirely conjectural.
Classification.—The order Pedipalpi is divided into three families—
Thelyphonidae, Schizonotidae and Tarantulidae. The first two are
considered by some authors to form a sub-order, Uropygi, or tailed
Pedipalpi, while the Tarantulidae constitute the remaining sub-order
Amblypygi, the members of which are tailless.
Fam. 1. Thelyphonidae.[254]—This family comprises nine or more
genera, differing chiefly in the position of the eyes, the structure of the
genital operculum, the armature of the pedipalps, and the presence or
absence of “ommatoids” in the anal segment.
The three following genera are among those most likely to be met with.
Two ommatoids are present in each.
former are generally described as entering the anterior portion of the
stercoral pocket, but according to Laurie they pass along its ventral surface,
attached to it by connective tissue, and really enter at the posterior end. The
coxal glands are well developed, and lie beneath the endosternite, opening
near the first coxae.
The nervous system is much concentrated and of the usual Arachnid type.
The median abdominal nerve has a ganglion towards its extremity,
supplying, according to Bernard,[251] the muscles which move the tail. The
heart is extremely long, and varies little in width. It has nine pairs of
ostia[252]—two in the thorax and seven in the abdomen. The generative
glands are paired, and in the male there are large seminal vesicles. In the
most ventral portion of the abdominal cavity lies a remarkable
asymmetrically-situated gland, the “stink-gland.” It consists of a number of
secretory tubules communicating with two elongated sacs, one of which lies
beneath the nerve-cord, and therefore medially, while the other lies far to
the left. Their ducts proceed to the anus or its vicinity.
The caudal organs, or white spots which, as already mentioned, are
usually found on the last of the three post-abdominal segments of
Thelyphonus, are of doubtful function. They have been variously explained
as the stink-gland orifices, and as organs sensitive to light (“ommatoids”).
Laurie[253] was unable to find any pore in this region, nor was there any of
the pigment so characteristic of organs of sight. The histological structure
indicated a sense-organ rather than a gland, but the use of these organs is
entirely conjectural.
Classification.—The order Pedipalpi is divided into three families—
Thelyphonidae, Schizonotidae and Tarantulidae. The first two are
considered by some authors to form a sub-order, Uropygi, or tailed
Pedipalpi, while the Tarantulidae constitute the remaining sub-order
Amblypygi, the members of which are tailless.
Fam. 1. Thelyphonidae.[254]—This family comprises nine or more
genera, differing chiefly in the position of the eyes, the structure of the
genital operculum, the armature of the pedipalps, and the presence or
absence of “ommatoids” in the anal segment.
The three following genera are among those most likely to be met with.
Two ommatoids are present in each.
Page 357
Thelyphonus has a spine on the second ventral plate, and a deep median
impression on the male genital operculum, which is, however, absent from
that of the female. There are about fifteen known species of this genus,
inhabiting Southern Asia and the East Indies.
Typopeltis has ridges running forward from the lateral eyes. The middle
third of the female operculum is raised and deeply impressed in the middle.
This genus is represented in China and Japan. Mastigoproctus has a short
and stout coxal apophysis of the pedipalp, without a tooth on its inner side.
It is found in Mexico, Brazil, and the West Indies. Other genera are
Thelyphonellus (Demerara), Labochirus (Ceylon), Hypoctonus (Burma),
Mimoscorpius (Philippines), Uroproctus (Assam), Abalius (New Guinea),
without ommatoids, and Tetrabalius (Borneo), with two pairs of
ommatoids.
Fam. 2. Schizonotidae (= Tartaridae).—This family contains only two
genera, Schizonotus (= Nyctalops, Pickard-Cambridge, nom. preocc. Aves)
and Trithyreus[255] (= Tripeltis, Thorell, nom. preocc. Reptilia). They are
very small, pale-coloured forms (about 5 mm. in length), found in Burma
and Ceylon.
Fam. 3. Tarantulidae, better known as Phrynidae. Pocock has shown
that Fabricius established the genus Tarantula from the species T.
reniformis in 1793, while there is no earlier record of Olivier’s Phrynus,
established for the same species, than Lamarck’s citation of it in 1801. The
family is divided into three sub-families, Tarantulinae, Phrynichinae, and
Charontinae.
(i.) The Tarantulinae are new-world forms, represented by three genera,
Tarantula, Acanthophrynus (Phrynopsis), and Admetus (Heterophrynus), in
Central and South America and the West Indies.
(ii.) The Phrynichinae belong to the Old World, being found in Africa,
India, and Ceylon. Phrynichus, Titanodamon and Nanodamon are genera of
this sub-family.
(iii.) The Charontinae are natives of South-East Asia and the Pacific
Islands. There are five genera and eight species.
impression on the male genital operculum, which is, however, absent from
that of the female. There are about fifteen known species of this genus,
inhabiting Southern Asia and the East Indies.
Typopeltis has ridges running forward from the lateral eyes. The middle
third of the female operculum is raised and deeply impressed in the middle.
This genus is represented in China and Japan. Mastigoproctus has a short
and stout coxal apophysis of the pedipalp, without a tooth on its inner side.
It is found in Mexico, Brazil, and the West Indies. Other genera are
Thelyphonellus (Demerara), Labochirus (Ceylon), Hypoctonus (Burma),
Mimoscorpius (Philippines), Uroproctus (Assam), Abalius (New Guinea),
without ommatoids, and Tetrabalius (Borneo), with two pairs of
ommatoids.
Fam. 2. Schizonotidae (= Tartaridae).—This family contains only two
genera, Schizonotus (= Nyctalops, Pickard-Cambridge, nom. preocc. Aves)
and Trithyreus[255] (= Tripeltis, Thorell, nom. preocc. Reptilia). They are
very small, pale-coloured forms (about 5 mm. in length), found in Burma
and Ceylon.
Fam. 3. Tarantulidae, better known as Phrynidae. Pocock has shown
that Fabricius established the genus Tarantula from the species T.
reniformis in 1793, while there is no earlier record of Olivier’s Phrynus,
established for the same species, than Lamarck’s citation of it in 1801. The
family is divided into three sub-families, Tarantulinae, Phrynichinae, and
Charontinae.
(i.) The Tarantulinae are new-world forms, represented by three genera,
Tarantula, Acanthophrynus (Phrynopsis), and Admetus (Heterophrynus), in
Central and South America and the West Indies.
(ii.) The Phrynichinae belong to the Old World, being found in Africa,
India, and Ceylon. Phrynichus, Titanodamon and Nanodamon are genera of
this sub-family.
(iii.) The Charontinae are natives of South-East Asia and the Pacific
Islands. There are five genera and eight species.
Page 358
CHAPTER XIII
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ARANEAE—EXTERNAL STRUCTURE—INTERNAL
STRUCTURE.
Order III. Araneae.
(ARANEIDA,[256] ARANEINA.)
Arachnida breathing by tracheae and “lung-books.” Cephalothorax and
pedicellate abdomen, the latter usually soft, and only very rarely showing
any traces of segmentation. Two-jointed non-chelate chelicerae, the distal
joint bearing the orifice of a poison-gland. The tarsal joint of the male
pedipalp develops a sexual organ. The abdomen is furnished with spinning
mammillae.
The true Spiders can readily be distinguished from allied Arachnid
groups, with which they are often popularly confounded, by the presence of
a narrow constriction or “waist” between the cephalothorax and abdomen,
and of a group of “spinnerets” or external spinning organs beneath the hind
portion of the body. Thus the so-called “Harvest-spider” or “Harvestman” is
clearly not a Spider, for there is no constriction of its body into two parts,
nor does it possess any spinnerets. It belongs to the Phalangidea. The same
considerations will exclude the “Red Spider” of popular nomenclature,
which must be referred to the Acarina or Mites.
The Araneae, even as at present known, form a very extensive and
widely-distributed order of animals. Compared with certain insect orders,
they have received little attention from the collector, and the number of
known forms is certain to be very largely increased. They form an
extremely compact and natural group, for though, within the order, there is
an infinite variety of detail, their uniformity in essential points of structure
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ARANEAE—EXTERNAL STRUCTURE—INTERNAL
STRUCTURE.
Order III. Araneae.
(ARANEIDA,[256] ARANEINA.)
Arachnida breathing by tracheae and “lung-books.” Cephalothorax and
pedicellate abdomen, the latter usually soft, and only very rarely showing
any traces of segmentation. Two-jointed non-chelate chelicerae, the distal
joint bearing the orifice of a poison-gland. The tarsal joint of the male
pedipalp develops a sexual organ. The abdomen is furnished with spinning
mammillae.
The true Spiders can readily be distinguished from allied Arachnid
groups, with which they are often popularly confounded, by the presence of
a narrow constriction or “waist” between the cephalothorax and abdomen,
and of a group of “spinnerets” or external spinning organs beneath the hind
portion of the body. Thus the so-called “Harvest-spider” or “Harvestman” is
clearly not a Spider, for there is no constriction of its body into two parts,
nor does it possess any spinnerets. It belongs to the Phalangidea. The same
considerations will exclude the “Red Spider” of popular nomenclature,
which must be referred to the Acarina or Mites.
The Araneae, even as at present known, form a very extensive and
widely-distributed order of animals. Compared with certain insect orders,
they have received little attention from the collector, and the number of
known forms is certain to be very largely increased. They form an
extremely compact and natural group, for though, within the order, there is
an infinite variety of detail, their uniformity in essential points of structure
Page 359
is remarkable, and they are sharply marked off from the neighbouring
groups of Arachnida.
It is perhaps unfortunate that the
obtrusiveness of particularly
unattractive specimens of the race
has always caused spiders to be
regarded with more or less aversion.
This prejudice can hardly fail to be
modified by a wider acquaintance
with these animals. There are
certainly few groups which present
points of greater interest in respect to
their adaptation to special modes of
life and the ingenuity displayed in the
construction of their nests and the
ensnaring of their prey.
Spiders are wingless, yet they may
often be observed travelling through
the air. They are air-breathing, yet
many are amphibious in their habits,
and one species at least spends the
greater part of its existence beneath
Fig. 172.—Epeira angulata. ♀. the surface of the water. On land they
may be found in all imaginable
localities which admit of the existence of that insect life on which they
depend for food.
External Structure.—The spider’s body consists of two portions, the
cephalothorax and the abdomen.
Cephalothorax.—Looked at dorsally (Fig. 173), the cephalothorax is
generally seen to have a depression near the middle, the “median fovea,”
and from this certain lines, the “radial striae,” radiate towards the sides.
These depressions indicate the attachment of internal muscles.
The head region or “caput” lies in front of the foremost of the radial
striae, and is often clearly marked off from the thorax, and different from it
in elevation. It bears the eyes, which, in the great majority of spiders, are
eight in number. Many, however, are six-eyed, while in rare cases the
groups of Arachnida.
It is perhaps unfortunate that the
obtrusiveness of particularly
unattractive specimens of the race
has always caused spiders to be
regarded with more or less aversion.
This prejudice can hardly fail to be
modified by a wider acquaintance
with these animals. There are
certainly few groups which present
points of greater interest in respect to
their adaptation to special modes of
life and the ingenuity displayed in the
construction of their nests and the
ensnaring of their prey.
Spiders are wingless, yet they may
often be observed travelling through
the air. They are air-breathing, yet
many are amphibious in their habits,
and one species at least spends the
greater part of its existence beneath
Fig. 172.—Epeira angulata. ♀. the surface of the water. On land they
may be found in all imaginable
localities which admit of the existence of that insect life on which they
depend for food.
External Structure.—The spider’s body consists of two portions, the
cephalothorax and the abdomen.
Cephalothorax.—Looked at dorsally (Fig. 173), the cephalothorax is
generally seen to have a depression near the middle, the “median fovea,”
and from this certain lines, the “radial striae,” radiate towards the sides.
These depressions indicate the attachment of internal muscles.
The head region or “caput” lies in front of the foremost of the radial
striae, and is often clearly marked off from the thorax, and different from it
in elevation. It bears the eyes, which, in the great majority of spiders, are
eight in number. Many, however, are six-eyed, while in rare cases the
Page 360
number is reduced to four (Tetrablemma, see p. 404), or even to two (Nops,
see p. 395). The number, relative size, and particular arrangement of these
eyes are of considerable systematic importance. Their disposition varies
very greatly, but it is generally possible to regard them as forming two
transverse rows, an anterior and a posterior, each possessing a pair of
median and a pair of lateral eyes.
In many spiders all the eyes have a
dorsal aspect, but in some groups
(Attidae, Lycosidae) the prevailing
arrangement is to have the anterior
eyes directed forwards and the
posterior upwards. In other spiders,
again, a dorsal view may only show
the eyes in profile, all having their
axes directed forwards or sideways,
or they may be mounted on turrets,
and thus command a wide range of
view. The rows are described as
straight, “procurved” (with the
convexity backwards), or “recurved”
(with the convexity forwards). Thus,
in Fig. 177, the anterior row is
slightly, and the posterior row
considerably “recurved.”
Sometimes there is a marked
difference in the colour of the eyes,
two or more being black, while the
remainder are pearly white. In other
cases they are homogeneous, either
of the black or the white type. Simon
considers the black eyes to be diurnal
and the white nocturnal, but the FSpider.ig. 173.—Diagrammatic dorsal view of a
ch, Chelicera; f, median fovea; n, normal
evidence for this is indirect and not marking; o, ocular area; p, pedipalp; st, stria.
altogether satisfactory. The portion of (The dotted line should reach the radial marking
on the cephalothorax.)
the caput occupied by the eyes is
often alluded to as the “ocular area.”
The space between the ocular area and the chelicerae, well shown in Fig.
see p. 395). The number, relative size, and particular arrangement of these
eyes are of considerable systematic importance. Their disposition varies
very greatly, but it is generally possible to regard them as forming two
transverse rows, an anterior and a posterior, each possessing a pair of
median and a pair of lateral eyes.
In many spiders all the eyes have a
dorsal aspect, but in some groups
(Attidae, Lycosidae) the prevailing
arrangement is to have the anterior
eyes directed forwards and the
posterior upwards. In other spiders,
again, a dorsal view may only show
the eyes in profile, all having their
axes directed forwards or sideways,
or they may be mounted on turrets,
and thus command a wide range of
view. The rows are described as
straight, “procurved” (with the
convexity backwards), or “recurved”
(with the convexity forwards). Thus,
in Fig. 177, the anterior row is
slightly, and the posterior row
considerably “recurved.”
Sometimes there is a marked
difference in the colour of the eyes,
two or more being black, while the
remainder are pearly white. In other
cases they are homogeneous, either
of the black or the white type. Simon
considers the black eyes to be diurnal
and the white nocturnal, but the FSpider.ig. 173.—Diagrammatic dorsal view of a
ch, Chelicera; f, median fovea; n, normal
evidence for this is indirect and not marking; o, ocular area; p, pedipalp; st, stria.
altogether satisfactory. The portion of (The dotted line should reach the radial marking
on the cephalothorax.)
the caput occupied by the eyes is
often alluded to as the “ocular area.”
The space between the ocular area and the chelicerae, well shown in Fig.
Page 361
177, is known as the “clypeus.” It is usually more or less vertical, but in the
Aviculariidae (see p. 386) it is horizontal and dorsal.
The under surface of the cephalothorax is protected by the “sternum” or
“plastron,” a large plate of variable shape, usually notched at either side for
the reception of the legs, and having in front a small plate, generally hinged,
but sometimes soldered to it, known as the “labium.” This has no homology
with the labium of insects, but is a true sternite, more correctly described as
“pars labialis sterni.”
The labium and the maxillary lobes of the palpi more or less conceal the
under surface of the caput. The shape of the sternum and of the labium, and
the contour and degree of inclination towards one another of the maxillae,
are important considerations in the taxonomy of Spiders.
The appendages of the cephalothorax, which are the chelicerae or jaws,
the pedipalpi or feelers, and the four pairs of ambulatory legs, will be
treated separately.
Pedicle.—The chitinous investment of the narrow stalk which unites the
thorax with the abdomen is for the most part thin and flexible, with only
slight indurations of various patterns on the dorsal surface, where it is in
most cases more or less protected by the forwardly-projecting abdomen.
Beneath, it is usually quite membranous, guarded only by a sort of collar
formed by the raised border of the anterior portion of the abdomen at the
point of insertion. In some Spiders, however (Dysderidae), there is a
posterior sternal plate, the “plagula,” closely corresponding with the labium
in front, which partly embraces the pedicle. In Hermippus (Zodariidae) the
plagula is detached from the sternum, and is succeeded posteriorly by two
smaller paired plates.
Abdomen.—The abdomen differs remarkably in shape in the different
groups of Spiders. In some families the prevailing shape is more or less
globular, and in others cylindrical, while it may be diversified to almost any
extent by prominences or spines. Ordinarily no sign of segmentation is
observable, but in Liphistius it is covered dorsally by seven well-marked
chitinous plates.
In most Spiders the integument of the abdomen is uniformly soft and
flexible all over, but it is not rare to find portions of it thickened and
hardened to form “scuta.” In the Gasteracanthinae and the Phoroncidinae
there is a great dorsal scutum armed with spines, while in several families
Aviculariidae (see p. 386) it is horizontal and dorsal.
The under surface of the cephalothorax is protected by the “sternum” or
“plastron,” a large plate of variable shape, usually notched at either side for
the reception of the legs, and having in front a small plate, generally hinged,
but sometimes soldered to it, known as the “labium.” This has no homology
with the labium of insects, but is a true sternite, more correctly described as
“pars labialis sterni.”
The labium and the maxillary lobes of the palpi more or less conceal the
under surface of the caput. The shape of the sternum and of the labium, and
the contour and degree of inclination towards one another of the maxillae,
are important considerations in the taxonomy of Spiders.
The appendages of the cephalothorax, which are the chelicerae or jaws,
the pedipalpi or feelers, and the four pairs of ambulatory legs, will be
treated separately.
Pedicle.—The chitinous investment of the narrow stalk which unites the
thorax with the abdomen is for the most part thin and flexible, with only
slight indurations of various patterns on the dorsal surface, where it is in
most cases more or less protected by the forwardly-projecting abdomen.
Beneath, it is usually quite membranous, guarded only by a sort of collar
formed by the raised border of the anterior portion of the abdomen at the
point of insertion. In some Spiders, however (Dysderidae), there is a
posterior sternal plate, the “plagula,” closely corresponding with the labium
in front, which partly embraces the pedicle. In Hermippus (Zodariidae) the
plagula is detached from the sternum, and is succeeded posteriorly by two
smaller paired plates.
Abdomen.—The abdomen differs remarkably in shape in the different
groups of Spiders. In some families the prevailing shape is more or less
globular, and in others cylindrical, while it may be diversified to almost any
extent by prominences or spines. Ordinarily no sign of segmentation is
observable, but in Liphistius it is covered dorsally by seven well-marked
chitinous plates.
In most Spiders the integument of the abdomen is uniformly soft and
flexible all over, but it is not rare to find portions of it thickened and
hardened to form “scuta.” In the Gasteracanthinae and the Phoroncidinae
there is a great dorsal scutum armed with spines, while in several families
Page 362
there are species characterised by the
possession of a smooth dorsal
scutum; and in some a ventral scutum
is present.
That these scuta are sometimes
indicative of an obsolete
segmentation would seem likely from
the study of the remarkable species,
Tetrablemma medioculatum (Fig.
176), described by Pickard-
Cambridge, from Ceylon. In addition
to large dorsal and ventral scuta, the
sides and posterior extremity are
guarded by smaller scuta, the
disposition of which is well seen in
the figure.
The normal smooth abdomen
presents dorsally no very striking
features. In species of variegated
coloration there is very generally
noticeable a median dentated band
(Fig. 173), the “normal marking” of
some writers, which would appear to
have some correlation with the
underlying dorsal vessel. Beneath the
abdomen are to be seen the orifices
of the breathing and genital organs,
Fig. 174.—Diagrammatic ventral view of a
Spider. Cephalothorax—l, Labium; m, maxilla; the spinnerets, and the anal aperture
p, paturon of chelicera; st, sternum; u, unguis of upon its tubercle.
chelicera. Abdomen—a.t, Anal tubercle; c,
colulus; ep, epigyne; s, stigma; sp, spinnerets; tr, The breathing organs are, as will
tracheal opening. be explained later, of two kinds,
lung-books and tracheae. The great
majority of Spiders possess only two lung-books, and their transverse, slit-
like openings (“stigmata” or “spiracles”) may be seen on either side of the
anterior part of the abdomen. Where, as in the Theraphosae, there are four
lung-books, the second pair open by similar slits a short distance behind the
possession of a smooth dorsal
scutum; and in some a ventral scutum
is present.
That these scuta are sometimes
indicative of an obsolete
segmentation would seem likely from
the study of the remarkable species,
Tetrablemma medioculatum (Fig.
176), described by Pickard-
Cambridge, from Ceylon. In addition
to large dorsal and ventral scuta, the
sides and posterior extremity are
guarded by smaller scuta, the
disposition of which is well seen in
the figure.
The normal smooth abdomen
presents dorsally no very striking
features. In species of variegated
coloration there is very generally
noticeable a median dentated band
(Fig. 173), the “normal marking” of
some writers, which would appear to
have some correlation with the
underlying dorsal vessel. Beneath the
abdomen are to be seen the orifices
of the breathing and genital organs,
Fig. 174.—Diagrammatic ventral view of a
Spider. Cephalothorax—l, Labium; m, maxilla; the spinnerets, and the anal aperture
p, paturon of chelicera; st, sternum; u, unguis of upon its tubercle.
chelicera. Abdomen—a.t, Anal tubercle; c,
colulus; ep, epigyne; s, stigma; sp, spinnerets; tr, The breathing organs are, as will
tracheal opening. be explained later, of two kinds,
lung-books and tracheae. The great
majority of Spiders possess only two lung-books, and their transverse, slit-
like openings (“stigmata” or “spiracles”) may be seen on either side of the
anterior part of the abdomen. Where, as in the Theraphosae, there are four
lung-books, the second pair open by similar slits a short distance behind the
Page 363
first. According to Bertkau,
pulmonary sacs are entirely lacking
in the genus Nops.
The tracheae generally debouch by
a single median stigma towards the
posterior end of the abdomen, just in
front of the spinnerets. This opening
clearly results from the fusion of two
stigmata, which in some species
retain their paired arrangement.
On a level with the openings of the
anterior lung-books or pulmonary
sacs there is usually observable a Fig. 175.—Spider profiles. 1, Poltys ideae; 2,
slight transverse ridge, the epigastric Phoroncidia 7–aculeata; 3, Ariamnes flagellum;
4, Stegosoma testudo; 5, Formicinoides
fold (Fig. 174), and in the centre of brasiliana.
this is the genital opening. This is
never visible until after the last
moult, and in the male is always a
simple inconspicuous aperture. This
is also the case with the females of
Fig. 176.—Tetrablemma medioculatum, much some groups (Theraphosae,
enlarged. A, Posterior view; B, profile, showing Filistatidae, Dysderidae, etc.), but in
the scuta. (After Cambridge.)
most cases there is a more or less
complicated armature, the “epigyne,”
the special design of which is of great specific value. In its simplest form it
is merely a plate, usually of dark colour, with one or two apertures (Fig.
174, ep), but in some families, notably the Epeiridae, it is more
complicated, and is furnished with a hooked median projection, the
“ovipositor” (“clavus” of Menge), which is often absurdly like a petrified
elephant’s trunk in miniature.
The abdomen also presents on its under surface, usually towards the
posterior end or apex, a group of finger-like mammillae or spinnerets. They
are normally six in number, two superior (or posterior), two median, and
two inferior (or anterior). The number is reduced, in most of the
Theraphosae, to four, while a few spiders possess only a single pair of
spinnerets. These organs are described more fully on p. 325.
pulmonary sacs are entirely lacking
in the genus Nops.
The tracheae generally debouch by
a single median stigma towards the
posterior end of the abdomen, just in
front of the spinnerets. This opening
clearly results from the fusion of two
stigmata, which in some species
retain their paired arrangement.
On a level with the openings of the
anterior lung-books or pulmonary
sacs there is usually observable a Fig. 175.—Spider profiles. 1, Poltys ideae; 2,
slight transverse ridge, the epigastric Phoroncidia 7–aculeata; 3, Ariamnes flagellum;
4, Stegosoma testudo; 5, Formicinoides
fold (Fig. 174), and in the centre of brasiliana.
this is the genital opening. This is
never visible until after the last
moult, and in the male is always a
simple inconspicuous aperture. This
is also the case with the females of
Fig. 176.—Tetrablemma medioculatum, much some groups (Theraphosae,
enlarged. A, Posterior view; B, profile, showing Filistatidae, Dysderidae, etc.), but in
the scuta. (After Cambridge.)
most cases there is a more or less
complicated armature, the “epigyne,”
the special design of which is of great specific value. In its simplest form it
is merely a plate, usually of dark colour, with one or two apertures (Fig.
174, ep), but in some families, notably the Epeiridae, it is more
complicated, and is furnished with a hooked median projection, the
“ovipositor” (“clavus” of Menge), which is often absurdly like a petrified
elephant’s trunk in miniature.
The abdomen also presents on its under surface, usually towards the
posterior end or apex, a group of finger-like mammillae or spinnerets. They
are normally six in number, two superior (or posterior), two median, and
two inferior (or anterior). The number is reduced, in most of the
Theraphosae, to four, while a few spiders possess only a single pair of
spinnerets. These organs are described more fully on p. 325.
Page 364
A small papilla, the “colulus” (Fig. 174, c), is often observable,
projecting between the anterior spinnerets. The “anal tubercle” (Fig. 174,
a.t), on which the vent is situated, terminates the abdomen, and is generally
in close juxtaposition with the posterior spinnerets.
Appendages.—The cephalothoracic appendages are the chelicerae, the
pedipalpi, and the four pairs of ambulatory legs. Those of the abdomen are
the mammillae or spinnerets.
Chelicerae.—These are two-jointed appendages, articulated immediately
below or in front of the clypeus. They are the “mandibles” of many authors,
but there is good reason for believing that they are not homologous with the
mandibles of Insects. There is little agreement, moreover, with regard to the
names given to the two joints of which they consist. The term “falx,” often
applied to the basal joint, is much more appropriate to the sickle-like distal
joint. Base and fang are tolerably satisfactory, or we may avoid ambiguity
by adopting the terms “paturon” and “unguis” suggested by Lyonnet.[257]
The paturon is a stout joint of more or less cylindrical or conical shape.
The unguis (the “crochet” of Simon) is hook-like, and can generally be
folded back upon the paturon, which often presents a groove for its
reception. The Theraphosid spiders are distinguished from all others by the
fact that the plane of action of the chelicerae is vertical and longitudinal.
The paturon projects forward in a line parallel with the axis of the body, and
its distal end can be raised or depressed, but not moved laterally; while the
unguis in action has the point directed downwards, and, at rest, is applied to
the under surface of the paturon.
In other spiders the patura hang more or less vertically, and while to
some extent mobile in all directions, their principal motion is lateral, and
the ungues have their points directed towards each other in action, and are
applied to the inner surfaces of the patura in repose. The plane of action in
this case is also more or less vertical, but transverse.
The paturon is always extremely hard and strong. In Theraphosae of
burrowing habits the distal end is furnished with a group of powerful teeth,
the “rastellus.” The groove for the reception of the unguis is often guarded
on one side or on both by rows of teeth, the arrangement of which is
frequently an important specific character. The inner anterior border is also
often furnished with a group of stiff hairs or bristles. This powerful joint is
projecting between the anterior spinnerets. The “anal tubercle” (Fig. 174,
a.t), on which the vent is situated, terminates the abdomen, and is generally
in close juxtaposition with the posterior spinnerets.
Appendages.—The cephalothoracic appendages are the chelicerae, the
pedipalpi, and the four pairs of ambulatory legs. Those of the abdomen are
the mammillae or spinnerets.
Chelicerae.—These are two-jointed appendages, articulated immediately
below or in front of the clypeus. They are the “mandibles” of many authors,
but there is good reason for believing that they are not homologous with the
mandibles of Insects. There is little agreement, moreover, with regard to the
names given to the two joints of which they consist. The term “falx,” often
applied to the basal joint, is much more appropriate to the sickle-like distal
joint. Base and fang are tolerably satisfactory, or we may avoid ambiguity
by adopting the terms “paturon” and “unguis” suggested by Lyonnet.[257]
The paturon is a stout joint of more or less cylindrical or conical shape.
The unguis (the “crochet” of Simon) is hook-like, and can generally be
folded back upon the paturon, which often presents a groove for its
reception. The Theraphosid spiders are distinguished from all others by the
fact that the plane of action of the chelicerae is vertical and longitudinal.
The paturon projects forward in a line parallel with the axis of the body, and
its distal end can be raised or depressed, but not moved laterally; while the
unguis in action has the point directed downwards, and, at rest, is applied to
the under surface of the paturon.
In other spiders the patura hang more or less vertically, and while to
some extent mobile in all directions, their principal motion is lateral, and
the ungues have their points directed towards each other in action, and are
applied to the inner surfaces of the patura in repose. The plane of action in
this case is also more or less vertical, but transverse.
The paturon is always extremely hard and strong. In Theraphosae of
burrowing habits the distal end is furnished with a group of powerful teeth,
the “rastellus.” The groove for the reception of the unguis is often guarded
on one side or on both by rows of teeth, the arrangement of which is
frequently an important specific character. The inner anterior border is also
often furnished with a group of stiff hairs or bristles. This powerful joint is
Page 365
of use in crushing and expressing the
fluids of insects pierced by the
ungues.
The crescent-shaped unguis is
tapering and smooth, except for the
presence, on the posterior surface, of
one or two feebly dentated ridges.
Near its free extremity there is a
small orifice leading to the poison
reservoir and gland.
In the genus Pholcus (see p. 401)
the chelicerae may almost be
regarded as chelate, the unguis being
met by a spiny projection from the
inner anterior border of the paturon.
Rostrum.—On examining a
spider, even under a dissecting
microscope, it will not be easy at first
to discover the mouth. Indeed,
Fig. 177.—Front view of Textrix denticulata. ×
Lyonnet had almost come to the
about 10. 1, Caput; 2, eyes; 3, paturon; and 4, conclusion that Spiders, like some
unguis of chelicera. Myrmelionid larvae, imbibed the
juices of their prey by way of the
mandibles, before he found the orifice and gave a remarkably accurate
description of the adjacent parts.
If a specimen be placed on its back, and the labium raised while the
chelicerae are pushed forward, no orifice is visible, but on careful
examination it will be found that what appears to be a thick and fleshy
labium is, in reality, two organs. The labium is thin and flat, and closely
opposed to its upper surface is a somewhat flattened cone. This is the
“rostrum,” and when it is separated from the labium the buccal orifice is
disclosed. In a few spiders (Archeidae) in which the chelicerae are far
removed from the mouth, the rostrum is tolerably conspicuous, but in most
it is so hidden as to have escaped the observation of the great majority of
observers. Schimkewitsch considers it homologous with the labrum of
insects, but Simon thinks that it represents all the insect mouth-parts
fluids of insects pierced by the
ungues.
The crescent-shaped unguis is
tapering and smooth, except for the
presence, on the posterior surface, of
one or two feebly dentated ridges.
Near its free extremity there is a
small orifice leading to the poison
reservoir and gland.
In the genus Pholcus (see p. 401)
the chelicerae may almost be
regarded as chelate, the unguis being
met by a spiny projection from the
inner anterior border of the paturon.
Rostrum.—On examining a
spider, even under a dissecting
microscope, it will not be easy at first
to discover the mouth. Indeed,
Fig. 177.—Front view of Textrix denticulata. ×
Lyonnet had almost come to the
about 10. 1, Caput; 2, eyes; 3, paturon; and 4, conclusion that Spiders, like some
unguis of chelicera. Myrmelionid larvae, imbibed the
juices of their prey by way of the
mandibles, before he found the orifice and gave a remarkably accurate
description of the adjacent parts.
If a specimen be placed on its back, and the labium raised while the
chelicerae are pushed forward, no orifice is visible, but on careful
examination it will be found that what appears to be a thick and fleshy
labium is, in reality, two organs. The labium is thin and flat, and closely
opposed to its upper surface is a somewhat flattened cone. This is the
“rostrum,” and when it is separated from the labium the buccal orifice is
disclosed. In a few spiders (Archeidae) in which the chelicerae are far
removed from the mouth, the rostrum is tolerably conspicuous, but in most
it is so hidden as to have escaped the observation of the great majority of
observers. Schimkewitsch considers it homologous with the labrum of
insects, but Simon thinks that it represents all the insect mouth-parts
Page 366
reduced to an exceedingly simple form. It is more probable that a beak
consisting of a simple labrum and labium was a primitive Arachnid
characteristic. If the rostrum be removed and its inner (or posterior) surface
examined, a lance-shaped chitinous plate, the “palate,” becomes visible. It
is furrowed down the middle by a narrow groove, which is converted into a
tube for the passage of fluids when the rostrum is opposed to the labium.
Pedipalpi.—The pedipalpi are
extremely leg-like feelers, and are
six-jointed, the metatarsal joint of the
ambulatory legs being absent. The
joints, therefore, are the coxa,
trochanter, femur, patella, tibia, and
tarsus (Fig. 178).[258]
In the Theraphosae the coxa
resembles that of the ambulatory leg,
but in other spiders it is furnished, on
the inner side, with a blade-like
projection, the “maxilla” (Fig. 178).
The shape of the maxillae and the F×ig5.. 1, 178.—Pedipalp of Tegenaria domestica ♂,
Coxa; 2, maxilla; 3, trochanter; 4, femur;
degree of their inclination towards 5, patella; 6, tibia; 7, tarsus; 8, palpal organ.
the labium are of considerable
taxonomic importance. The inner
border of the maxilla is furnished with a tuft of hairs, which assist in
retaining the juices expressed by the chelicerae, and its anterior border
presents a cutting edge with a finely dentated ridge called the “serrula.”
In the female, and in the immature male, the remaining joints differ little
from those of the legs, except that the tarsal joint is either clawless or has a
single claw, which is generally smooth, and is never much dentated.
At the last moult but one the male pedipalp appears tumid at the end, and
after the last moult the tarsus is seen to have developed a remarkable
copulatory apparatus, the “palpal organ,” comparatively simple in some
families, but in others presenting an extraordinary complexity of structure.
Palpal Organs.—Externally the essential parts of the palpal organ are
three, the “haematodocha,” the “bulb,” and the “style.” The spines and
projections, or “apophyses,” which often accompany the palpal organ
proper, are of secondary importance, and in many spiders are entirely
consisting of a simple labrum and labium was a primitive Arachnid
characteristic. If the rostrum be removed and its inner (or posterior) surface
examined, a lance-shaped chitinous plate, the “palate,” becomes visible. It
is furrowed down the middle by a narrow groove, which is converted into a
tube for the passage of fluids when the rostrum is opposed to the labium.
Pedipalpi.—The pedipalpi are
extremely leg-like feelers, and are
six-jointed, the metatarsal joint of the
ambulatory legs being absent. The
joints, therefore, are the coxa,
trochanter, femur, patella, tibia, and
tarsus (Fig. 178).[258]
In the Theraphosae the coxa
resembles that of the ambulatory leg,
but in other spiders it is furnished, on
the inner side, with a blade-like
projection, the “maxilla” (Fig. 178).
The shape of the maxillae and the F×ig5.. 1, 178.—Pedipalp of Tegenaria domestica ♂,
Coxa; 2, maxilla; 3, trochanter; 4, femur;
degree of their inclination towards 5, patella; 6, tibia; 7, tarsus; 8, palpal organ.
the labium are of considerable
taxonomic importance. The inner
border of the maxilla is furnished with a tuft of hairs, which assist in
retaining the juices expressed by the chelicerae, and its anterior border
presents a cutting edge with a finely dentated ridge called the “serrula.”
In the female, and in the immature male, the remaining joints differ little
from those of the legs, except that the tarsal joint is either clawless or has a
single claw, which is generally smooth, and is never much dentated.
At the last moult but one the male pedipalp appears tumid at the end, and
after the last moult the tarsus is seen to have developed a remarkable
copulatory apparatus, the “palpal organ,” comparatively simple in some
families, but in others presenting an extraordinary complexity of structure.
Palpal Organs.—Externally the essential parts of the palpal organ are
three, the “haematodocha,” the “bulb,” and the “style.” The spines and
projections, or “apophyses,” which often accompany the palpal organ
proper, are of secondary importance, and in many spiders are entirely
Page 367
absent; nor is their function when
present at all clear; but the infinite
variety of design which they exhibit,
and their singular uniformity in all
the males of a species, render them of
the utmost value as specific
characteristics.
The “haematodocha” is the portion
of the palpal organ attached to the
tarsus, and often received into an
excavation, the “alveolus,” on its
Fig. 179.—Diagram of palpal organ. 1, Tarsus; under surface. It is a fibro-elastic
2, bulb; 3, receptaculum seminis; 4, its aperture; bag, in its normal collapsed state
5, style; 6, haematodocha; 7, alveolus; 8, tibia.
usually somewhat spirally disposed
round the base of the following
portion, the “bulb.”
The bulb is generally the most conspicuous portion of the organ, and is a
sub-globular sac with firm, though often semi-transparent, integument. Its
base rests upon the haematodocha, and its apex is produced, often spirally,
to a point which bears the seminal orifice. This external opening leads into a
coiled tube within the bulb, ending in a blind sac, the “receptaculum
seminis,” which projects into the haematodocha; and it is the aperture by
which the sperm both enters and leaves the organ. How the sperm is
conveyed to the receptaculum was long a matter for speculation, after the
belief in a direct communication between the generative glands and the
pedipalpi had been abandoned. The process has been actually observed in
the case of a few spiders, which have been seen to deposit their sperm on a
small web woven for the purpose, and then, inserting the styles of their
palpal organs into the fluid, to suck it up into the receptacula seminis. This
is probably the usual method of procedure, though it may be true, as some
have asserted, that the palp is sometimes applied directly to the genital
orifice.
The receptaculum and its tube being thus charged with sperm, it is the
function of the haematodocha to eject it by exerting pressure on its base.
For this purpose the haematodocha is in communication with the cavity of
the tarsus, from which, in copulation, it receives a great flow of blood, and
present at all clear; but the infinite
variety of design which they exhibit,
and their singular uniformity in all
the males of a species, render them of
the utmost value as specific
characteristics.
The “haematodocha” is the portion
of the palpal organ attached to the
tarsus, and often received into an
excavation, the “alveolus,” on its
Fig. 179.—Diagram of palpal organ. 1, Tarsus; under surface. It is a fibro-elastic
2, bulb; 3, receptaculum seminis; 4, its aperture; bag, in its normal collapsed state
5, style; 6, haematodocha; 7, alveolus; 8, tibia.
usually somewhat spirally disposed
round the base of the following
portion, the “bulb.”
The bulb is generally the most conspicuous portion of the organ, and is a
sub-globular sac with firm, though often semi-transparent, integument. Its
base rests upon the haematodocha, and its apex is produced, often spirally,
to a point which bears the seminal orifice. This external opening leads into a
coiled tube within the bulb, ending in a blind sac, the “receptaculum
seminis,” which projects into the haematodocha; and it is the aperture by
which the sperm both enters and leaves the organ. How the sperm is
conveyed to the receptaculum was long a matter for speculation, after the
belief in a direct communication between the generative glands and the
pedipalpi had been abandoned. The process has been actually observed in
the case of a few spiders, which have been seen to deposit their sperm on a
small web woven for the purpose, and then, inserting the styles of their
palpal organs into the fluid, to suck it up into the receptacula seminis. This
is probably the usual method of procedure, though it may be true, as some
have asserted, that the palp is sometimes applied directly to the genital
orifice.
The receptaculum and its tube being thus charged with sperm, it is the
function of the haematodocha to eject it by exerting pressure on its base.
For this purpose the haematodocha is in communication with the cavity of
the tarsus, from which, in copulation, it receives a great flow of blood, and
Page 368
becomes greatly distended. Bertkau believes that he has detected very
minute pores (meatus sanguinis) communicating between the haematodocha
and the receptaculum, and allowing some of the blood-plasma from the
former to mingle with the semen, but this appears to be very doubtful.
The Legs are uniformly eight in number, and are seven-jointed, the
joints, counting from the body, being the coxa, trochanter, femur, patella,
tibia, metatarsus, and tarsus.[259] In a few cases, through the presence of
false articulations, i.e. rings of softer chitin, this number appears to be
exceeded. Some of the Palpimanidae (see p. 398) were at first thought to
have only six joints on their anterior legs, but the tarsus is present, though
very small.
In the case of most spiders, the legs take a general fore and aft direction,
the first pair being directed forwards, the second forwards or laterally, and
the third and fourth backwards. In the large group of “Crab-spiders”
(Thomisidae), and in many of the Sparassinae, all the legs have a more or
less lateral direction, and the spider moves with equal ease forwards,
backwards, or sideways. The legs are usually more or less thickly clothed
with hairs, but in some genera the clothing is so sparse that they appear
glossy, while in others they have a positively shaggy appearance. Stouter
hairs or “bristles” are often present, and some of the joints are also often
furnished with “spines,” which in many cases are erectile.
The tarsi of all spiders are furnished with terminal claws, usually three in
number, though in some families (Drassidae, Thomisidae, etc.) there are
only two. The two principal claws are paired and usually dentated, though
the number of their teeth may be unequal. The third claw, when present, is
always smaller, median, and inferior.
In many spiders of climbing habits the place of the third claw is taken by
a remarkable tuft of club-like hairs termed a “scopula” (Fig. 180, b), by
means of which they are able to cling to smooth surfaces where claws
would be able to obtain no hold. In some species there is a special false
articulation—the “onychium”—at the end of the tarsus to bear the claws.
In the Cribellatae the metatarsus is always furnished with a comb-like
organ, the “calamistrum,” correlated with an extra spinning apparatus, the
“cribellum,” but this will be dealt with when we reach the systematic
portion of the subject.
minute pores (meatus sanguinis) communicating between the haematodocha
and the receptaculum, and allowing some of the blood-plasma from the
former to mingle with the semen, but this appears to be very doubtful.
The Legs are uniformly eight in number, and are seven-jointed, the
joints, counting from the body, being the coxa, trochanter, femur, patella,
tibia, metatarsus, and tarsus.[259] In a few cases, through the presence of
false articulations, i.e. rings of softer chitin, this number appears to be
exceeded. Some of the Palpimanidae (see p. 398) were at first thought to
have only six joints on their anterior legs, but the tarsus is present, though
very small.
In the case of most spiders, the legs take a general fore and aft direction,
the first pair being directed forwards, the second forwards or laterally, and
the third and fourth backwards. In the large group of “Crab-spiders”
(Thomisidae), and in many of the Sparassinae, all the legs have a more or
less lateral direction, and the spider moves with equal ease forwards,
backwards, or sideways. The legs are usually more or less thickly clothed
with hairs, but in some genera the clothing is so sparse that they appear
glossy, while in others they have a positively shaggy appearance. Stouter
hairs or “bristles” are often present, and some of the joints are also often
furnished with “spines,” which in many cases are erectile.
The tarsi of all spiders are furnished with terminal claws, usually three in
number, though in some families (Drassidae, Thomisidae, etc.) there are
only two. The two principal claws are paired and usually dentated, though
the number of their teeth may be unequal. The third claw, when present, is
always smaller, median, and inferior.
In many spiders of climbing habits the place of the third claw is taken by
a remarkable tuft of club-like hairs termed a “scopula” (Fig. 180, b), by
means of which they are able to cling to smooth surfaces where claws
would be able to obtain no hold. In some species there is a special false
articulation—the “onychium”—at the end of the tarsus to bear the claws.
In the Cribellatae the metatarsus is always furnished with a comb-like
organ, the “calamistrum,” correlated with an extra spinning apparatus, the
“cribellum,” but this will be dealt with when we reach the systematic
portion of the subject.
Page 369
The general direction taken by the
legs, the comparative length of the
different joints, their armature of
hairs, bristles, and spines, and the
number and conformation of the
tarsal claws, are points of great
importance in the classification of
Spiders.
Under considerable magnification
the legs of all Spiders exhibit a
number of minute organs, arranged
with absolute uniformity throughout
the Araneae, and known as the
“lyriform organs.” They consist of
little parallel ridges of thickened
chitin, the slit between them being
covered by thinner chitin. They are
eleven on each leg, and are
distributed near the distal extremities Fig. 180.—Spider tarsi. 1, Tarsus of Epeira
of each of the first six joints. Their showing three claws and supplemental serrate
function is unknown, though some hairs (a); 2, tarsus of a Thomisid Spider, with
two claws; 3, 3a, lateral and dorsal view of
authors consider them to be organs of tarsus of an Attid Spider, showing scopula at b.
hearing.
The Spinnerets are normally six in number, and, except in rare instances,
are placed beneath the abdomen, near its apex and immediately in front of
the anal tubercle. Their arrangement varies greatly, but they can generally
be recognised as comprising three pairs, a posterior (or superior) pair, a
median pair, and an anterior (or inferior) pair.
In nearly all the Theraphosae the anterior pair are absent, while the
posterior spinnerets are largely developed. In the Palpimanidae only the
anterior spinnerets are present. When all six are found, the usual
arrangement is in the form of a rosette, the median spinnerets being hidden
by the others in repose, but this disposition is widely departed from. In
Hahnia (Agelenidae), for instance, they are ranged in a transverse row at
the end of the abdomen, the posterior spinnerets occupying the extremities
of the row, and the median ones the centre.
legs, the comparative length of the
different joints, their armature of
hairs, bristles, and spines, and the
number and conformation of the
tarsal claws, are points of great
importance in the classification of
Spiders.
Under considerable magnification
the legs of all Spiders exhibit a
number of minute organs, arranged
with absolute uniformity throughout
the Araneae, and known as the
“lyriform organs.” They consist of
little parallel ridges of thickened
chitin, the slit between them being
covered by thinner chitin. They are
eleven on each leg, and are
distributed near the distal extremities Fig. 180.—Spider tarsi. 1, Tarsus of Epeira
of each of the first six joints. Their showing three claws and supplemental serrate
function is unknown, though some hairs (a); 2, tarsus of a Thomisid Spider, with
two claws; 3, 3a, lateral and dorsal view of
authors consider them to be organs of tarsus of an Attid Spider, showing scopula at b.
hearing.
The Spinnerets are normally six in number, and, except in rare instances,
are placed beneath the abdomen, near its apex and immediately in front of
the anal tubercle. Their arrangement varies greatly, but they can generally
be recognised as comprising three pairs, a posterior (or superior) pair, a
median pair, and an anterior (or inferior) pair.
In nearly all the Theraphosae the anterior pair are absent, while the
posterior spinnerets are largely developed. In the Palpimanidae only the
anterior spinnerets are present. When all six are found, the usual
arrangement is in the form of a rosette, the median spinnerets being hidden
by the others in repose, but this disposition is widely departed from. In
Hahnia (Agelenidae), for instance, they are ranged in a transverse row at
the end of the abdomen, the posterior spinnerets occupying the extremities
of the row, and the median ones the centre.
Page 370
These spinnerets are highly mobile
appendages, and additional play is
given to their action by the presence
of articulations, much resembling the
“false” joints sometimes found on the
legs, on the posterior and anterior
pairs. They are always at least bi-
articulate, and sometimes present
three or four joints. They are
movable turrets on which are
mounted the “fusulae” or projections
where the tubes from the spinning
glands open. These are often very
numerous, especially in the orb-
weaving spiders, where the spinning
powers are most highly developed.
They consist of two portions, a
cylindrical or conical basal part,
succeeded by a very fine, generally
tapering tube.
In some spiders the fusulae are all
much alike, but usually a few very
much larger than the rest are
noticeable under the microscope, and
these are often alluded to as
“spigots.” The smaller ones are also
divisible into two kinds, a few short
conical fusulae being noticeable
amongst the much more numerous
cylindrical tubes. We shall treat of
the functions of the various fusulae
Fig. 181.—Spinnerets of Epeira diademata. A, later (see pp. 335 and 349).
Ventral view of Epeira; B, spinnerets magnified;
C, profile. Simon remarks that though the
battery of fusulae is most
complicated in those spiders which
possess the greatest spinning powers, it is by no means among them that
extremely long spinnerets are developed. The posterior spinnerets of some
appendages, and additional play is
given to their action by the presence
of articulations, much resembling the
“false” joints sometimes found on the
legs, on the posterior and anterior
pairs. They are always at least bi-
articulate, and sometimes present
three or four joints. They are
movable turrets on which are
mounted the “fusulae” or projections
where the tubes from the spinning
glands open. These are often very
numerous, especially in the orb-
weaving spiders, where the spinning
powers are most highly developed.
They consist of two portions, a
cylindrical or conical basal part,
succeeded by a very fine, generally
tapering tube.
In some spiders the fusulae are all
much alike, but usually a few very
much larger than the rest are
noticeable under the microscope, and
these are often alluded to as
“spigots.” The smaller ones are also
divisible into two kinds, a few short
conical fusulae being noticeable
amongst the much more numerous
cylindrical tubes. We shall treat of
the functions of the various fusulae
Fig. 181.—Spinnerets of Epeira diademata. A, later (see pp. 335 and 349).
Ventral view of Epeira; B, spinnerets magnified;
C, profile. Simon remarks that though the
battery of fusulae is most
complicated in those spiders which
possess the greatest spinning powers, it is by no means among them that
extremely long spinnerets are developed. The posterior spinnerets of some
Page 371
of the Hersiliidae are of great length, but these spiders spin very little
except in forming their egg-cocoons.
In addition to the six spinnerets,
and just in front of them, there is to
be found in some spiders an extra
spinning organ in the form of a
double sieve-like plate, the
“cribellum.” This is always
correlated with a comb of curved
bristles on the metatarsi of the fourth
pair of legs, the “calamistrum.” Such
importance is assigned to these
Fig. 182.—A, Spinnerets of Amaurobius similis
organs by Simon, that the Araneae ♀ . Much enlarged. a, Anus; cr, cribellum; i.s,
Veraeare divided by him according to inferior spinneret; m.s, median spinneret; s.s,
whether they are present or absent, superior spinneret. B, Part of the 4th leg of the
same Spider, showing the calamistrum (ca) on
into Cribellatae and Ecribellatae. the metatarsus.
This is probably an exaggerated view
of the importance of these organs,
and the spiders possessing them certainly do not seem to form a natural
group.
Stridulating Organs.—When Arthropod animals are capable of
producing a sound, the result is nearly always obtained by “stridulation,”
that is, by the friction of two rough surfaces against each other. The surfaces
which are modified for this purpose form what is called a “stridulating
organ.” Such organs have been found in three very distinct Spider families,
the Theridiidae, the Sicariidae, and the Aviculariidae. Hitherto they have
only been observed in three positions—either between the thorax and
abdomen, or between the chelicerae and the pedipalpi, or between the
pedipalpi and the first legs.
In the Sicariidae and the Aviculariidae, the sounds have been distinctly
heard and described. Those produced by the Theridiidae would appear to be
inaudible to human ears.
Westring[260] was the first to discover (1843) a stridulating organ in the
small Theridiid spider Asagena phalerata. The abdomen, where the pedicle
enters it, gives off a chitinous collar, which projects over the cephalothorax,
and has the inner surface of the dorsal part finely toothed. When the
except in forming their egg-cocoons.
In addition to the six spinnerets,
and just in front of them, there is to
be found in some spiders an extra
spinning organ in the form of a
double sieve-like plate, the
“cribellum.” This is always
correlated with a comb of curved
bristles on the metatarsi of the fourth
pair of legs, the “calamistrum.” Such
importance is assigned to these
Fig. 182.—A, Spinnerets of Amaurobius similis
organs by Simon, that the Araneae ♀ . Much enlarged. a, Anus; cr, cribellum; i.s,
Veraeare divided by him according to inferior spinneret; m.s, median spinneret; s.s,
whether they are present or absent, superior spinneret. B, Part of the 4th leg of the
same Spider, showing the calamistrum (ca) on
into Cribellatae and Ecribellatae. the metatarsus.
This is probably an exaggerated view
of the importance of these organs,
and the spiders possessing them certainly do not seem to form a natural
group.
Stridulating Organs.—When Arthropod animals are capable of
producing a sound, the result is nearly always obtained by “stridulation,”
that is, by the friction of two rough surfaces against each other. The surfaces
which are modified for this purpose form what is called a “stridulating
organ.” Such organs have been found in three very distinct Spider families,
the Theridiidae, the Sicariidae, and the Aviculariidae. Hitherto they have
only been observed in three positions—either between the thorax and
abdomen, or between the chelicerae and the pedipalpi, or between the
pedipalpi and the first legs.
In the Sicariidae and the Aviculariidae, the sounds have been distinctly
heard and described. Those produced by the Theridiidae would appear to be
inaudible to human ears.
Westring[260] was the first to discover (1843) a stridulating organ in the
small Theridiid spider Asagena phalerata. The abdomen, where the pedicle
enters it, gives off a chitinous collar, which projects over the cephalothorax,
and has the inner surface of the dorsal part finely toothed. When the
Page 372
abdomen is raised and depressed,
these teeth scrape against a number
of fine striae on the back of the
posterior part of the cephalothorax. A
similar organ has been since found in
various allied spiders, of which the
commonest English species is
Steatoda bipunctata. In this group it
is generally possessed by the male
alone, being merely rudimentary, if
Fig. 183.—Stridulating apparatus of Steatoda
present at all, in the female.
bipunctata, ♂ . Much enlarged. A, Ridged and In 1880 Campbell[261] observed that
toothed abdominal socket; B, striated area on in some of the Theridiid Spiders of
the cephalothorax; C, profile of the Spider, × 5.
the genus Lephthyphantes, the outer
surface of the chelicera and the inner
surface of the femur of the pedipalp were finely striated at the point, where
they were rubbed together when the palps were agitated, but though the
appropriate motion was frequently given, he could hear no sound.
Meanwhile the noise produced by
a large Theraphosid spider in Assam
(Chilobrachys stridulans) had
attracted attention, and its
stridulating apparatus was described
in 1875 by Wood-Mason.[262] The
sound resembled that obtained by
“drawing the back of a knife along
the edge of a strong comb.”
Subsequently certain Sicariid
spiders of a genus confined to the
southern hemisphere were heard to
produce a sound like the buzzing of a
bee by the agitation of their palps, Fig. 184.—Chilobrachys stridulans in
and both sexes were found to possess stridulating attitude. After Wood-Mason. Natural
a very perfect stridulating organ, size.
consisting of a row of short teeth on
these teeth scrape against a number
of fine striae on the back of the
posterior part of the cephalothorax. A
similar organ has been since found in
various allied spiders, of which the
commonest English species is
Steatoda bipunctata. In this group it
is generally possessed by the male
alone, being merely rudimentary, if
Fig. 183.—Stridulating apparatus of Steatoda
present at all, in the female.
bipunctata, ♂ . Much enlarged. A, Ridged and In 1880 Campbell[261] observed that
toothed abdominal socket; B, striated area on in some of the Theridiid Spiders of
the cephalothorax; C, profile of the Spider, × 5.
the genus Lephthyphantes, the outer
surface of the chelicera and the inner
surface of the femur of the pedipalp were finely striated at the point, where
they were rubbed together when the palps were agitated, but though the
appropriate motion was frequently given, he could hear no sound.
Meanwhile the noise produced by
a large Theraphosid spider in Assam
(Chilobrachys stridulans) had
attracted attention, and its
stridulating apparatus was described
in 1875 by Wood-Mason.[262] The
sound resembled that obtained by
“drawing the back of a knife along
the edge of a strong comb.”
Subsequently certain Sicariid
spiders of a genus confined to the
southern hemisphere were heard to
produce a sound like the buzzing of a
bee by the agitation of their palps, Fig. 184.—Chilobrachys stridulans in
and both sexes were found to possess stridulating attitude. After Wood-Mason. Natural
a very perfect stridulating organ, size.
consisting of a row of short teeth on
Page 373
the femur of the pedipalp, and a striated area on the paturon of the
chelicera.
Pocock has recently discovered that all the large kinds of Theraphosidae
in the countries between India and New Zealand are, like Chilobrachys,
provided with a stridulating organ. In these spiders also it is between the
palp and the chelicera, and consists of a row of teeth or spines constituting a
“pecten,” and a series of vibratile spines or “lyra,” but whereas in
Chilobrachys and its near relations the lyra is on the palp and the pecten on
the paturon, in other spiders the positions are reversed. The lyra is a very
remarkable organ, consisting of club-shaped, often feathery bristles or
spines, which lie parallel to the surface to which they are attached, and
which is slightly excavated for their reception.
Lastly, many African Theraphosids possess a similar organ, not between
the palp and the chelicera, but between the palp and the first leg.
Various suggestions have been hazarded as to the use of these organs, but
they partake largely of the nature of conjecture, especially in connexion
with the doubt as to the possession of a true auditory organ by the Araneae.
They may be summarised as follows. The Theridiid spiders are among those
which show most indication of auditory powers, and the stridulating organs,
being practically confined to the male, may have a sexual significance.
Chilobrachys stridulates when attacked, assuming at the same time a
“terrifying attitude,” and its stridulating organ may serve the purpose
attributed to the rattle of the rattlesnake, and warn its enemies that it is best
let alone. If this be the case, there is no need that it should itself hear the
sound, and, indeed, there is no evidence that the Aviculariidae possess the
power of hearing. In the inoffensive stridulating Sicariid spiders the sounds
could hardly serve this purpose, and the presence of the organ in both sexes,
and in immature examples, precludes the idea that its function is to utter a
sexual call. Instead of trying to escape when disturbed, the spider starts
stridulating, and Pocock suggests that the similarity of the sound produced
to the buzzing of a bee may be calculated to induce its enemies to leave it in
peace.
Internal Anatomy.
chelicera.
Pocock has recently discovered that all the large kinds of Theraphosidae
in the countries between India and New Zealand are, like Chilobrachys,
provided with a stridulating organ. In these spiders also it is between the
palp and the chelicera, and consists of a row of teeth or spines constituting a
“pecten,” and a series of vibratile spines or “lyra,” but whereas in
Chilobrachys and its near relations the lyra is on the palp and the pecten on
the paturon, in other spiders the positions are reversed. The lyra is a very
remarkable organ, consisting of club-shaped, often feathery bristles or
spines, which lie parallel to the surface to which they are attached, and
which is slightly excavated for their reception.
Lastly, many African Theraphosids possess a similar organ, not between
the palp and the chelicera, but between the palp and the first leg.
Various suggestions have been hazarded as to the use of these organs, but
they partake largely of the nature of conjecture, especially in connexion
with the doubt as to the possession of a true auditory organ by the Araneae.
They may be summarised as follows. The Theridiid spiders are among those
which show most indication of auditory powers, and the stridulating organs,
being practically confined to the male, may have a sexual significance.
Chilobrachys stridulates when attacked, assuming at the same time a
“terrifying attitude,” and its stridulating organ may serve the purpose
attributed to the rattle of the rattlesnake, and warn its enemies that it is best
let alone. If this be the case, there is no need that it should itself hear the
sound, and, indeed, there is no evidence that the Aviculariidae possess the
power of hearing. In the inoffensive stridulating Sicariid spiders the sounds
could hardly serve this purpose, and the presence of the organ in both sexes,
and in immature examples, precludes the idea that its function is to utter a
sexual call. Instead of trying to escape when disturbed, the spider starts
stridulating, and Pocock suggests that the similarity of the sound produced
to the buzzing of a bee may be calculated to induce its enemies to leave it in
peace.
Internal Anatomy.
Page 374
Alimentary System.—The alimentary canal of the Spider is divided into
three regions, the “stomodaeum,” the mid-gut or “mesenteron,” and the
hind-gut or “proctodaeum.”
The Stomodaeum consists of the pharynx, the oesophagus, and the
sucking stomach. As we have said, the mouth is to be found between the
rostrum and the labium. It opens into the pharynx, the anterior wall of
which is formed by a chitinous plate on the inner surface of the rostrum,
sometimes called the palate. As the inner surfaces of the rostrum and labium
are practically flat, the cavity of the pharynx would be obliterated when
they are pressed together, were it not for a groove running down the centre
of the palate, which the apposed labium converts into a tube, up which the
fluids of the prey are sucked. In the Theraphosidae there is a corresponding
groove on the inner surface of the labium.
At the top of the pharynx, which is nearly perpendicular, the canal
continues backwards and upwards as a narrow tube, the oesophagus,
passing right through the nerve-mass, which embraces it closely on all
sides, to the sucking stomach. At the commencement of the oesophagus is
the opening of a gland, probably salivary, which is situated in the rostrum.
We now reach the sucking stomach, which occupies the centre of the
cephalothorax. It is placed directly over a skeletal plate, the “endosternite”
(Fig. 185, e), to which its lower surface is connected by powerful muscles,
while its upper wall is protected by a hard plate or “buckler,” which is
similarly attached to the roof of the cephalothorax in the region of the
“fovea media.” The walls of the stomach are not themselves muscular, but
by the contraction of the muscles above mentioned its cavity is enlarged,
and fluids from the pharynx are pumped up into it.
The canal thus far is lined by chitin, like the exterior of the body, and
forms a sort of complicated mouth-apparatus.
The Mesenteron lies partly in the cephalothorax and partly in the
abdomen. The thoracic portion, shortly behind the sucking stomach, sends
forward on either side a large branch or “diverticulum,” from each of which
five secondary branches or “caeca” are given off (Fig. 185). Of these the
anterior pair sometimes join, thus forming a complete ring; but usually,
though adjacent, they remain distinct. The other four pairs of caeca curve
downwards, protruding into the coxae of the legs, where they often
terminate, but sometimes (Epeira) they continue their curve until they meet,
three regions, the “stomodaeum,” the mid-gut or “mesenteron,” and the
hind-gut or “proctodaeum.”
The Stomodaeum consists of the pharynx, the oesophagus, and the
sucking stomach. As we have said, the mouth is to be found between the
rostrum and the labium. It opens into the pharynx, the anterior wall of
which is formed by a chitinous plate on the inner surface of the rostrum,
sometimes called the palate. As the inner surfaces of the rostrum and labium
are practically flat, the cavity of the pharynx would be obliterated when
they are pressed together, were it not for a groove running down the centre
of the palate, which the apposed labium converts into a tube, up which the
fluids of the prey are sucked. In the Theraphosidae there is a corresponding
groove on the inner surface of the labium.
At the top of the pharynx, which is nearly perpendicular, the canal
continues backwards and upwards as a narrow tube, the oesophagus,
passing right through the nerve-mass, which embraces it closely on all
sides, to the sucking stomach. At the commencement of the oesophagus is
the opening of a gland, probably salivary, which is situated in the rostrum.
We now reach the sucking stomach, which occupies the centre of the
cephalothorax. It is placed directly over a skeletal plate, the “endosternite”
(Fig. 185, e), to which its lower surface is connected by powerful muscles,
while its upper wall is protected by a hard plate or “buckler,” which is
similarly attached to the roof of the cephalothorax in the region of the
“fovea media.” The walls of the stomach are not themselves muscular, but
by the contraction of the muscles above mentioned its cavity is enlarged,
and fluids from the pharynx are pumped up into it.
The canal thus far is lined by chitin, like the exterior of the body, and
forms a sort of complicated mouth-apparatus.
The Mesenteron lies partly in the cephalothorax and partly in the
abdomen. The thoracic portion, shortly behind the sucking stomach, sends
forward on either side a large branch or “diverticulum,” from each of which
five secondary branches or “caeca” are given off (Fig. 185). Of these the
anterior pair sometimes join, thus forming a complete ring; but usually,
though adjacent, they remain distinct. The other four pairs of caeca curve
downwards, protruding into the coxae of the legs, where they often
terminate, but sometimes (Epeira) they continue their curve until they meet,
Page 375
though they never fuse, under the
nerve-mass. Behind the origin of the
diverticula the mesenteron continues
as a widish tube, and shortly passes
through the pedicle and enters the
abdomen, where, curving slightly
upwards, it proceeds along the
middle line till it ends in the
proctodaeum.
In the abdomen it is surrounded by
a large gland, the so-called liver, and
is dilated at one spot (Fig. 186) to
receive the ducts from this gland. The
fluid elaborated by this large
abdominal gland has been shown to
have more affinity with pancreatic
Fig. 185.—Diagram showing the anatomy of the
cephalothorax of a Spider. The right alimentary juice than with bile.
diverticulum has been removed. a, Aorta; c, left The Proctodaeum consists of a
diverticulum with secondary caeca; e,
endosternite; oes, oesophagus, descending to the short rectum, from the dorsal side of
mouth; s, sucking stomach; sh, dorsal shield of which protrudes a large sac, the
sucking stomach.
“stercoral pocket.” At its origin, the
rectum receives the openings of two
lateral tubes which reach it after ramifying in the substance of the liver.
These have been called “Malpighian tubules,” but their function is
unknown. Loman[263] has shown that they open into the mid-gut and not into
the rectum, and there is reason to believe that true Malpighian tubules
homologous to those of Insecta are absent in Arachnida, where their place
seems to be taken by the coxal glands, which are considered to be the true
excretory organs. In most spiders they open near the third coxae. Like the
stomodaeum, the proctodaeum has a chitinous lining.
Vascular System.—The earlier investigations on the circulation of the
blood in Spiders were made by direct observations of the movements of the
blood corpuscles through the more or less transparent integuments of the
newly-hatched young. Claparède’s[264] results were arrived at by this
method. It is invaluable for demonstrating roughly the course taken by the
blood, but in these immature spiders the blood-system has not attained its
nerve-mass. Behind the origin of the
diverticula the mesenteron continues
as a widish tube, and shortly passes
through the pedicle and enters the
abdomen, where, curving slightly
upwards, it proceeds along the
middle line till it ends in the
proctodaeum.
In the abdomen it is surrounded by
a large gland, the so-called liver, and
is dilated at one spot (Fig. 186) to
receive the ducts from this gland. The
fluid elaborated by this large
abdominal gland has been shown to
have more affinity with pancreatic
Fig. 185.—Diagram showing the anatomy of the
cephalothorax of a Spider. The right alimentary juice than with bile.
diverticulum has been removed. a, Aorta; c, left The Proctodaeum consists of a
diverticulum with secondary caeca; e,
endosternite; oes, oesophagus, descending to the short rectum, from the dorsal side of
mouth; s, sucking stomach; sh, dorsal shield of which protrudes a large sac, the
sucking stomach.
“stercoral pocket.” At its origin, the
rectum receives the openings of two
lateral tubes which reach it after ramifying in the substance of the liver.
These have been called “Malpighian tubules,” but their function is
unknown. Loman[263] has shown that they open into the mid-gut and not into
the rectum, and there is reason to believe that true Malpighian tubules
homologous to those of Insecta are absent in Arachnida, where their place
seems to be taken by the coxal glands, which are considered to be the true
excretory organs. In most spiders they open near the third coxae. Like the
stomodaeum, the proctodaeum has a chitinous lining.
Vascular System.—The earlier investigations on the circulation of the
blood in Spiders were made by direct observations of the movements of the
blood corpuscles through the more or less transparent integuments of the
newly-hatched young. Claparède’s[264] results were arrived at by this
method. It is invaluable for demonstrating roughly the course taken by the
blood, but in these immature spiders the blood-system has not attained its
Page 376
full complexity, and other methods of research have shown the spider to
possess a much more elaborate vascular system than was at first suspected.
The tubular heart lies along the middle line in the anterior two-thirds of
the abdomen, sometimes close up against the dorsal wall, but occasionally
at some little distance from it, buried in the substance of the liver. It is a
muscular tube with three pairs of lateral openings or “ostia,” each furnished
with a simple valve which allows the entrance, but prevents the exit, of the
blood. It is contained in a bag, the “pericardium,” into which the ostia open.
Both heart and pericardium are kept in place by a complicated system of
connective tissue strands, by which they are anchored to the dorsal wall of
the abdomen. Eight arteries leave the heart, the principal one, or “aorta,”
plunging downward and passing through the pedicle to supply the
cephalothorax. Besides this, there is a caudal artery at the posterior end, and
three pairs of abdominal arteries, which proceed from the under surface of
the heart, and the ramifications of which supply, in a very complete manner,
the various organs of the abdomen. The heart is not divided up into
compartments. The anterior aorta passes through the pedicle, above the
intestine, and presently forks into two main branches, which run along
either side of the sucking stomach, near the front of which they bend
suddenly downwards and end in a “patte d’oie,” as Causard[265] expresses it
—a bundle of arteries which proceed to the limbs (Fig. 185). Where the
downward curve begins, a considerable artery, the mandibulo-cephalic, runs
forward to supply the chelicerae and the head region. We have omitted
certain minor branches from the main trunks which supply the thoracic
muscles. The nerve-mass receives fine vessels from the “patte d’oie.”
possess a much more elaborate vascular system than was at first suspected.
The tubular heart lies along the middle line in the anterior two-thirds of
the abdomen, sometimes close up against the dorsal wall, but occasionally
at some little distance from it, buried in the substance of the liver. It is a
muscular tube with three pairs of lateral openings or “ostia,” each furnished
with a simple valve which allows the entrance, but prevents the exit, of the
blood. It is contained in a bag, the “pericardium,” into which the ostia open.
Both heart and pericardium are kept in place by a complicated system of
connective tissue strands, by which they are anchored to the dorsal wall of
the abdomen. Eight arteries leave the heart, the principal one, or “aorta,”
plunging downward and passing through the pedicle to supply the
cephalothorax. Besides this, there is a caudal artery at the posterior end, and
three pairs of abdominal arteries, which proceed from the under surface of
the heart, and the ramifications of which supply, in a very complete manner,
the various organs of the abdomen. The heart is not divided up into
compartments. The anterior aorta passes through the pedicle, above the
intestine, and presently forks into two main branches, which run along
either side of the sucking stomach, near the front of which they bend
suddenly downwards and end in a “patte d’oie,” as Causard[265] expresses it
—a bundle of arteries which proceed to the limbs (Fig. 185). Where the
downward curve begins, a considerable artery, the mandibulo-cephalic, runs
forward to supply the chelicerae and the head region. We have omitted
certain minor branches from the main trunks which supply the thoracic
muscles. The nerve-mass receives fine vessels from the “patte d’oie.”
Page 377
Fig. 186.—Diagram of a Spider, Epeira diademata, showing the arrangement of
the internal organs, × about 8. 1, Mouth; 2, sucking stomach; 3, ducts of liver; 4,
so-called Malpighian tubules; 5, stercoral pocket; 6, anus; 7, dorsal muscle of
sucking stomach; 8, caecal prolongation of stomach; 9, cerebral ganglion giving
off nerves to eyes; 10, sub-oesophageal ganglionic mass; 11, heart with three
lateral openings or ostia; 12, lung-sac; 13, ovary; 14, acinate and pyriform silk-
glands; 15, tubuliform silk-gland; 16, ampulliform silk-gland; 17, aggregate or
dendriform silk-glands; 18, spinnerets or mammillae; 19, distal joint of chelicera;
20, poison-gland; 21, eye; 22, pericardium; 23, vessel bringing blood from lung-
sac to pericardium; 24, artery.
There are no capillaries, but the blood is delivered into the tissues and
finds its way, by irregular spaces or “lacunae,” into certain main venous
channels or “sinuses.” There are three such in the cephalothorax, one
median and the others lateral, considerably dilated in front, in the region of
the eyes, and connected by transverse passages. By these the blood is
brought back through the pedicle to the lung-books. In the abdomen also
there are three main sinuses, two parallel to one another near the lower
surface, and one beneath the pericardium. These likewise bring the blood to
the lung-books, whence it is conducted finally by pulmonary veins (Fig.
186) back to the pericardial chamber, and thus, by the ostia, to the heart.
The Spider’s blood is colourless, and the majority of the corpuscles are
“amoeboid,” or capable of changing their shape.
Generative System.—The internal generative organs present no great
complexity, consisting, in the male, of a pair of testes lying beneath the
liver, and connected by convoluted tubes, the “vasa deferentia,” with a
simple aperture under the abdomen, between the anterior stigmata.
The ovaries are hollow sacs with short oviducts which presently dilate to
form chambers called “spermathecae,” which open to the exterior by
the internal organs, × about 8. 1, Mouth; 2, sucking stomach; 3, ducts of liver; 4,
so-called Malpighian tubules; 5, stercoral pocket; 6, anus; 7, dorsal muscle of
sucking stomach; 8, caecal prolongation of stomach; 9, cerebral ganglion giving
off nerves to eyes; 10, sub-oesophageal ganglionic mass; 11, heart with three
lateral openings or ostia; 12, lung-sac; 13, ovary; 14, acinate and pyriform silk-
glands; 15, tubuliform silk-gland; 16, ampulliform silk-gland; 17, aggregate or
dendriform silk-glands; 18, spinnerets or mammillae; 19, distal joint of chelicera;
20, poison-gland; 21, eye; 22, pericardium; 23, vessel bringing blood from lung-
sac to pericardium; 24, artery.
There are no capillaries, but the blood is delivered into the tissues and
finds its way, by irregular spaces or “lacunae,” into certain main venous
channels or “sinuses.” There are three such in the cephalothorax, one
median and the others lateral, considerably dilated in front, in the region of
the eyes, and connected by transverse passages. By these the blood is
brought back through the pedicle to the lung-books. In the abdomen also
there are three main sinuses, two parallel to one another near the lower
surface, and one beneath the pericardium. These likewise bring the blood to
the lung-books, whence it is conducted finally by pulmonary veins (Fig.
186) back to the pericardial chamber, and thus, by the ostia, to the heart.
The Spider’s blood is colourless, and the majority of the corpuscles are
“amoeboid,” or capable of changing their shape.
Generative System.—The internal generative organs present no great
complexity, consisting, in the male, of a pair of testes lying beneath the
liver, and connected by convoluted tubes, the “vasa deferentia,” with a
simple aperture under the abdomen, between the anterior stigmata.
The ovaries are hollow sacs with short oviducts which presently dilate to
form chambers called “spermathecae,” which open to the exterior by
Page 378
distinct ducts, thus forming a double orifice, fortified by an external
structure already alluded to as the “epigyne.” The eggs project from the
outer surface of the ovary like beads, connected with the gland by narrow
stalks, and it was not at first clear how they found their way into the interior
cavity, but it has been ascertained that, when ripe, they pass through these
stalks, the empty capsules never presenting any external rupture.
The palpal organs have already been described. The spermatozoa, when
received by them, are not perfectly elaborated, but are contained in little
globular packets known as “spermatophores.”
Nervous System.—The Spider’s central nervous system is entirely
concentrated in the cephalothorax, near its floor, and presents the
appearance of a single mass, penetrated by the oesophagus. It may,
however, be divided into a pre-oesophageal portion or brain, and a post-
oesophageal or thoracic portion.
The brain supplies nerves to the eyes and chelicerae, while from the
thoracic mass nerves proceed to the other appendages, and through the
pedicle to the abdomen. The walls of the oesophagus are closely invested
on all sides by the nerve-sheath or neurilemma.
Sense-Organs.—Spiders possess the senses of sight, smell, and touch.
Whether or not they have a true auditory sense is still a matter of doubt.
Since sounds are conveyed by vibrations of the air, it is never very easy to
determine whether responses to sounds produced near the animal
experimented upon are proofs of the existence of an auditory organ, or
whether they are only perceived through the ordinary channels of touch. In
any case, the organs of hearing and of smell have not yet been located in the
Spider. M‘Cook considers various hairs scattered over the body of the
spider to be olfactory, but from Gaskell’s researches upon allied Arachnid
groups it would seem that the true smelling organ is to be sought for in the
rostrum.
Eyes.—Spiders possess from two to eight simple eyes, the external
appearance and arrangement of which have already been briefly explained.
They are sessile and immovable, though often so placed as to command a
view in several directions. In structure they are essentially like the ocelli of
Insects. Externally there is a lens, succeeded by a mass of transparent cells,
behind which is a layer of pigment. Then come the rods and cones of the
retina, to which the optic nerve is distributed. A comparison of this with the
structure already alluded to as the “epigyne.” The eggs project from the
outer surface of the ovary like beads, connected with the gland by narrow
stalks, and it was not at first clear how they found their way into the interior
cavity, but it has been ascertained that, when ripe, they pass through these
stalks, the empty capsules never presenting any external rupture.
The palpal organs have already been described. The spermatozoa, when
received by them, are not perfectly elaborated, but are contained in little
globular packets known as “spermatophores.”
Nervous System.—The Spider’s central nervous system is entirely
concentrated in the cephalothorax, near its floor, and presents the
appearance of a single mass, penetrated by the oesophagus. It may,
however, be divided into a pre-oesophageal portion or brain, and a post-
oesophageal or thoracic portion.
The brain supplies nerves to the eyes and chelicerae, while from the
thoracic mass nerves proceed to the other appendages, and through the
pedicle to the abdomen. The walls of the oesophagus are closely invested
on all sides by the nerve-sheath or neurilemma.
Sense-Organs.—Spiders possess the senses of sight, smell, and touch.
Whether or not they have a true auditory sense is still a matter of doubt.
Since sounds are conveyed by vibrations of the air, it is never very easy to
determine whether responses to sounds produced near the animal
experimented upon are proofs of the existence of an auditory organ, or
whether they are only perceived through the ordinary channels of touch. In
any case, the organs of hearing and of smell have not yet been located in the
Spider. M‘Cook considers various hairs scattered over the body of the
spider to be olfactory, but from Gaskell’s researches upon allied Arachnid
groups it would seem that the true smelling organ is to be sought for in the
rostrum.
Eyes.—Spiders possess from two to eight simple eyes, the external
appearance and arrangement of which have already been briefly explained.
They are sessile and immovable, though often so placed as to command a
view in several directions. In structure they are essentially like the ocelli of
Insects. Externally there is a lens, succeeded by a mass of transparent cells,
behind which is a layer of pigment. Then come the rods and cones of the
retina, to which the optic nerve is distributed. A comparison of this with the
Page 379
arrangement in the Vertebrate eye will show a reversal of the positions of
the retina and the pigment-layer. The lens is part of the outside covering of
the animal, and is cast at the time of moulting, when the spider is
temporarily blind. It is stated, however, that the eyes do not all moult
simultaneously. There is often a considerable difference between the
various eyes of the same spider, especially with regard to the convexity of
the lens and the number of rods and cones.
Though most spiders possess eight eyes, the number is sometimes
smaller, and in some groups of eight-eyed spiders two of the eyes are
sometimes so reduced and degenerate as to be practically rudimentary. As
might be expected, Cave-spiders (e.g. Anthrobia mammouthia) may be
entirely sightless.
Touch.—The sense of touch would appear to be extremely well
developed in some spiders, and there is reason for believing that the Orb-
weavers, at all events, depend far more upon it than upon that of sight.
Among the hairs which are distributed over the spider’s body and limbs,
several different forms may be distinguished, and some of them are
undoubtedly very delicate sense-organs of probably tactile function.
Spinning Glands.—Spiders vary greatly in their spinning powers. Some
only use their silk for spinning a cocoon to protect their eggs, while others
employ it to make snares and retreats, to bind up their prey, and to anchor
themselves to spots to which they may wish to return, and whence they
“drag at each remove a lengthening chain.”
All these functions are performed by the silk-glands of the Orb-weavers,
and hence it is with them that the organs have attained their greatest
perfection. We may conveniently take the case of the common large
Garden-spider, Epeira diademata. The glands occupy the entire floor of the
abdomen. They have been very thoroughly investigated by Apstein,[266] and
may be divided into five kinds.
On either side of the abdomen there are two large “ampullaceal” glands
debouching on “spigots,” one on the anterior, and one on the middle
spinneret; there are three large “aggregate” glands which all terminate on
spigots on the posterior spinneret; and three “tubuliform” glands, two of
which have their orifices on the posterior, and one on the middle spinneret.
Thus, in the entire abdomen there are sixteen large glands, terminating in
the large fusulae known as spigots. In addition to this there are about 200
the retina and the pigment-layer. The lens is part of the outside covering of
the animal, and is cast at the time of moulting, when the spider is
temporarily blind. It is stated, however, that the eyes do not all moult
simultaneously. There is often a considerable difference between the
various eyes of the same spider, especially with regard to the convexity of
the lens and the number of rods and cones.
Though most spiders possess eight eyes, the number is sometimes
smaller, and in some groups of eight-eyed spiders two of the eyes are
sometimes so reduced and degenerate as to be practically rudimentary. As
might be expected, Cave-spiders (e.g. Anthrobia mammouthia) may be
entirely sightless.
Touch.—The sense of touch would appear to be extremely well
developed in some spiders, and there is reason for believing that the Orb-
weavers, at all events, depend far more upon it than upon that of sight.
Among the hairs which are distributed over the spider’s body and limbs,
several different forms may be distinguished, and some of them are
undoubtedly very delicate sense-organs of probably tactile function.
Spinning Glands.—Spiders vary greatly in their spinning powers. Some
only use their silk for spinning a cocoon to protect their eggs, while others
employ it to make snares and retreats, to bind up their prey, and to anchor
themselves to spots to which they may wish to return, and whence they
“drag at each remove a lengthening chain.”
All these functions are performed by the silk-glands of the Orb-weavers,
and hence it is with them that the organs have attained their greatest
perfection. We may conveniently take the case of the common large
Garden-spider, Epeira diademata. The glands occupy the entire floor of the
abdomen. They have been very thoroughly investigated by Apstein,[266] and
may be divided into five kinds.
On either side of the abdomen there are two large “ampullaceal” glands
debouching on “spigots,” one on the anterior, and one on the middle
spinneret; there are three large “aggregate” glands which all terminate on
spigots on the posterior spinneret; and three “tubuliform” glands, two of
which have their orifices on the posterior, and one on the middle spinneret.
Thus, in the entire abdomen there are sixteen large glands, terminating in
the large fusulae known as spigots. In addition to this there are about 200
Page 380
“piriform” glands whose openings
are on the short conical fusulae of the
posterior and anterior spinnerets, and
about 400 “aciniform” glands which
debouch, by cylindrical fusulae, on
the middle and posterior spinnerets.
Thus there are, in all, about 600
glands with their separate fusulae in
the case of Epeira diademata.
The great number of orifices from
which silk may be emitted has given
rise to the widespread belief that, fine
as the Spider’s line is, it is woven of
hundreds of strands. This is an entire
misconception, as we shall have
occasion to show when we deal with
the various spinning operations.
A few families are, as has already
been stated, characterised by the Fig. 187.—Spinning glands. A, Aciniform; B,
possession of an extra spinning tubuliform; C, piriform gland.
organ, the cribellum, and the orifices
on this sieve-like plate lead to a large number of small glands, the
“cribellum glands.”
Respiratory Organs.—Spiders possess two kinds of breathing organs,
very different in form, though essentially much alike. They are called
respectively “lung-books” and “tracheae.” The Theraphosae (and
Hypochilus) have four lung-books, while all other spiders, except Nops,
have two. Tracheae appear to be present almost universally, but they have
not been found in the Pholcidae.
The pulmonary stigmata lead into chambers which extend forwards, and
which are practically filled with horizontal shelves, so to speak, attached at
the front and sides, but having their posterior edges free. These shelves are
the leaves of the lung-book. Each leaf is hollow, and its cavity is
continuous, anteriorly and laterally, with the blood-sinus into which the
blood from the various parts of the Spider’s body is poured.
are on the short conical fusulae of the
posterior and anterior spinnerets, and
about 400 “aciniform” glands which
debouch, by cylindrical fusulae, on
the middle and posterior spinnerets.
Thus there are, in all, about 600
glands with their separate fusulae in
the case of Epeira diademata.
The great number of orifices from
which silk may be emitted has given
rise to the widespread belief that, fine
as the Spider’s line is, it is woven of
hundreds of strands. This is an entire
misconception, as we shall have
occasion to show when we deal with
the various spinning operations.
A few families are, as has already
been stated, characterised by the Fig. 187.—Spinning glands. A, Aciniform; B,
possession of an extra spinning tubuliform; C, piriform gland.
organ, the cribellum, and the orifices
on this sieve-like plate lead to a large number of small glands, the
“cribellum glands.”
Respiratory Organs.—Spiders possess two kinds of breathing organs,
very different in form, though essentially much alike. They are called
respectively “lung-books” and “tracheae.” The Theraphosae (and
Hypochilus) have four lung-books, while all other spiders, except Nops,
have two. Tracheae appear to be present almost universally, but they have
not been found in the Pholcidae.
The pulmonary stigmata lead into chambers which extend forwards, and
which are practically filled with horizontal shelves, so to speak, attached at
the front and sides, but having their posterior edges free. These shelves are
the leaves of the lung-book. Each leaf is hollow, and its cavity is
continuous, anteriorly and laterally, with the blood-sinus into which the
blood from the various parts of the Spider’s body is poured.
Page 381
The minute structure of the leaf is curious. Its under surface is covered
with smooth chitin, but from its upper surface rise vast numbers of minute
chitinous points whose summits are connected to form a kind of trellis-
work. The roof and floor of the flattened chamber within are connected at
intervals by columns. The pulmonary chamber usually contains from fifteen
to twenty of these leaves, and the two chambers are always connected
internally between the stigmata.
The tracheae are either two or four (Dysderidae, Oonopidae, Filistatidae)
in number, and their stigmata may be separate or fused in the middle line.
Each consists of a large trunk, projecting forwards, and giving off tufts of
small tubes which lose themselves among the organs of the abdomen, but
do not ramify. In the tracheae of Argyroneta[267] a lateral tuft is given off
immediately after leaving the stigma, and another tuft proceeds from the
anterior end. Histologically the main trunk of the trachea is precisely like
the general chamber of the pulmonary sac, and differs greatly from the
trachea of an insect.
Cephalothoracic Glands.—In addition to the generative glands and the
so-called “liver” which occupy so large a portion of the abdomen, there are,
in Spiders, certain glandular organs situated in the cephalothorax which call
for some notice. These are the coxal glands and the poison-glands.
The COXAL GLANDS are two elongated brownish-yellow bodies, situated
beneath the lateral diverticula of the stomach, and between it and the
endosternite. They present four slight protuberances which project a short
distance into the coxae of the legs. The glands appear to be ductless, but
their function is thought to be excretory. They were first observed in the
Theraphosae.
All Spiders possess a pair of POISON-GLANDS, connected by a narrow duct
with a small opening near the extremity of the fang of the chelicerae. The
glands are sac-like bodies, usually situated in the cephalothorax, but
sometimes partially (Clubiona) or even entirely (Mygale) in the patura, or
basal joints of the chelicerae. Each sac has a thin outer layer of spirally-
arranged muscular and connective tissue fibres, and a deep inner epithelial
layer of glandular cells. The cavity of the gland acts as a reservoir for the
fluid it secretes. The virulence of the poison secreted by these glands has
been the subject of much discussion, and the most diverse opinions have
been held with regard to it. The matter is again referred to on p. 360.
with smooth chitin, but from its upper surface rise vast numbers of minute
chitinous points whose summits are connected to form a kind of trellis-
work. The roof and floor of the flattened chamber within are connected at
intervals by columns. The pulmonary chamber usually contains from fifteen
to twenty of these leaves, and the two chambers are always connected
internally between the stigmata.
The tracheae are either two or four (Dysderidae, Oonopidae, Filistatidae)
in number, and their stigmata may be separate or fused in the middle line.
Each consists of a large trunk, projecting forwards, and giving off tufts of
small tubes which lose themselves among the organs of the abdomen, but
do not ramify. In the tracheae of Argyroneta[267] a lateral tuft is given off
immediately after leaving the stigma, and another tuft proceeds from the
anterior end. Histologically the main trunk of the trachea is precisely like
the general chamber of the pulmonary sac, and differs greatly from the
trachea of an insect.
Cephalothoracic Glands.—In addition to the generative glands and the
so-called “liver” which occupy so large a portion of the abdomen, there are,
in Spiders, certain glandular organs situated in the cephalothorax which call
for some notice. These are the coxal glands and the poison-glands.
The COXAL GLANDS are two elongated brownish-yellow bodies, situated
beneath the lateral diverticula of the stomach, and between it and the
endosternite. They present four slight protuberances which project a short
distance into the coxae of the legs. The glands appear to be ductless, but
their function is thought to be excretory. They were first observed in the
Theraphosae.
All Spiders possess a pair of POISON-GLANDS, connected by a narrow duct
with a small opening near the extremity of the fang of the chelicerae. The
glands are sac-like bodies, usually situated in the cephalothorax, but
sometimes partially (Clubiona) or even entirely (Mygale) in the patura, or
basal joints of the chelicerae. Each sac has a thin outer layer of spirally-
arranged muscular and connective tissue fibres, and a deep inner epithelial
layer of glandular cells. The cavity of the gland acts as a reservoir for the
fluid it secretes. The virulence of the poison secreted by these glands has
been the subject of much discussion, and the most diverse opinions have
been held with regard to it. The matter is again referred to on p. 360.
Page 382
Page 383
CHAPTER XIV
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ARANEAE (CONTINUED)
HABITS—ECDYSIS—TREATMENT OF YOUNG—MIGRATION—
WEBS—NESTS—EGG-COCOONS—POISON—FERTILITY—
ENEMIES—PROTECTIVE COLORATION—MIMICRY—SENSES
—INTELLIGENCE—MATING HABITS—FOSSIL SPIDERS
EARLY LIFE OF SPIDERS.
Ecdysis or Moulting.—Spiders undergo no metamorphosis—that is to
say, no marked change of form takes place, as is so often the case among
Insects, in the period subsequent to the hatching of the egg. This fact, by the
by, is a great trouble to collectors, as it is generally extremely difficult, and
sometimes quite impossible, to identify immature specimens with certainty.
But although unmistakably a spider as soon as it leaves the egg, the
animal is, at first, in many respects incomplete, and it is only after a series
of moults, usually about nine in number, that it attains its full perfection of
form.
Until the occurrence of its first moult it is incapable of feeding or
spinning, mouth and spinning tubes being clogged by the membrane it then
throws off. It is at first pale-coloured and less thickly clothed with hairs and
spines than it eventually becomes, and the general proportions of the body
and the arrangement of the eyes are by no means those of the adult in
miniature, but will be greatly modified by unequal growth in various
directions. It speedily, however, attains its characteristic shape and
markings, and after one or two ecdyses little alteration is to be noticed,
except increase in size, until the final moult, when the spider at length
becomes sexually mature.
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ARANEAE (CONTINUED)
HABITS—ECDYSIS—TREATMENT OF YOUNG—MIGRATION—
WEBS—NESTS—EGG-COCOONS—POISON—FERTILITY—
ENEMIES—PROTECTIVE COLORATION—MIMICRY—SENSES
—INTELLIGENCE—MATING HABITS—FOSSIL SPIDERS
EARLY LIFE OF SPIDERS.
Ecdysis or Moulting.—Spiders undergo no metamorphosis—that is to
say, no marked change of form takes place, as is so often the case among
Insects, in the period subsequent to the hatching of the egg. This fact, by the
by, is a great trouble to collectors, as it is generally extremely difficult, and
sometimes quite impossible, to identify immature specimens with certainty.
But although unmistakably a spider as soon as it leaves the egg, the
animal is, at first, in many respects incomplete, and it is only after a series
of moults, usually about nine in number, that it attains its full perfection of
form.
Until the occurrence of its first moult it is incapable of feeding or
spinning, mouth and spinning tubes being clogged by the membrane it then
throws off. It is at first pale-coloured and less thickly clothed with hairs and
spines than it eventually becomes, and the general proportions of the body
and the arrangement of the eyes are by no means those of the adult in
miniature, but will be greatly modified by unequal growth in various
directions. It speedily, however, attains its characteristic shape and
markings, and after one or two ecdyses little alteration is to be noticed,
except increase in size, until the final moult, when the spider at length
becomes sexually mature.
Page 384
The first moult takes place while the newly-hatched spider is still with
the rest of the brood either in or close to the “cocoon” or egg-bag.
M‘Cook[268] thus describes the conclusion of the operation in the case of
Agelena naevia:—
“While it held on to the flossy nest with the two front and third pairs of
legs, the hind pair was drawn up and forward, and the feet grasped the
upper margin of the sac-like shell, which, when first seen, was about half-
way removed from the abdomen. The feet pushed downwards, and at the
same time the abdomen appeared to be pulled upward until the white pouch
was gradually worked off.”
The later moults are generally accomplished by the spider collecting all
its legs together and attaching them with silk to the web above, while the
body, also attached, hangs below. The old skin then splits along the sides of
the body, and the animal, by a series of violent efforts, wriggles itself free,
leaving a complete cast of itself, including the legs, suspended above it. For
a day or two before the operation the spider eats nothing, and immediately
upon its completion it hangs in a limp and helpless condition for a quarter
of an hour or so, until the new integument has had time to harden. It is not
unlikely that the reader has mistaken these casts for the shrivelled forms of
unlucky spiders, and has had his sympathies aroused, or has experienced a
grim satisfaction, in consequence—an expenditure of emotion which this
account may enable him to economise in future.
Limbs which the animal has accidentally lost are renewed at the time of
moulting, though their substitutes are at first smaller than those they
replace. On the other hand, the struggle to get rid of the old skin sometimes
results in the loss of a limb, and the spider is doomed to remain short-
handed until the next ecdysis.
Until the last moult the generative apertures, which are situated under the
anterior part of the abdomen, are completely sealed up. Their disclosure is
accompanied, in the case of the male, by a remarkable development of the
last joint of each pedipalp, which becomes swollen and often extremely
complicated with bulbs, spines, and bristles. A mature male spider may at
once be distinguished by the consequent knobbed appearance of its palps;
and the particular form they assume is highly characteristic of the species to
which the spider belongs.
the rest of the brood either in or close to the “cocoon” or egg-bag.
M‘Cook[268] thus describes the conclusion of the operation in the case of
Agelena naevia:—
“While it held on to the flossy nest with the two front and third pairs of
legs, the hind pair was drawn up and forward, and the feet grasped the
upper margin of the sac-like shell, which, when first seen, was about half-
way removed from the abdomen. The feet pushed downwards, and at the
same time the abdomen appeared to be pulled upward until the white pouch
was gradually worked off.”
The later moults are generally accomplished by the spider collecting all
its legs together and attaching them with silk to the web above, while the
body, also attached, hangs below. The old skin then splits along the sides of
the body, and the animal, by a series of violent efforts, wriggles itself free,
leaving a complete cast of itself, including the legs, suspended above it. For
a day or two before the operation the spider eats nothing, and immediately
upon its completion it hangs in a limp and helpless condition for a quarter
of an hour or so, until the new integument has had time to harden. It is not
unlikely that the reader has mistaken these casts for the shrivelled forms of
unlucky spiders, and has had his sympathies aroused, or has experienced a
grim satisfaction, in consequence—an expenditure of emotion which this
account may enable him to economise in future.
Limbs which the animal has accidentally lost are renewed at the time of
moulting, though their substitutes are at first smaller than those they
replace. On the other hand, the struggle to get rid of the old skin sometimes
results in the loss of a limb, and the spider is doomed to remain short-
handed until the next ecdysis.
Until the last moult the generative apertures, which are situated under the
anterior part of the abdomen, are completely sealed up. Their disclosure is
accompanied, in the case of the male, by a remarkable development of the
last joint of each pedipalp, which becomes swollen and often extremely
complicated with bulbs, spines, and bristles. A mature male spider may at
once be distinguished by the consequent knobbed appearance of its palps;
and the particular form they assume is highly characteristic of the species to
which the spider belongs.
Page 385
The number of moults, and the intervals at which they occur, no doubt
vary with different species. In the case of Argiope aurelia, Pollock[269] has
found that the female moults nine times after leaving the cocoon, the first
ecdysis occurring after an interval of from one to two months, according to
the abundance or scarcity of food. The subsequent intervals gradually
increase from about a fortnight to something over three weeks.
Behaviour of the Newly-hatched Spider.—The mode of life of a spider
just freed from the cocoon will of course vary greatly according to the
Family to which it belongs.
The Epeiridae are the builders of the familiar wheel or orb-web. Spiders
of this Family usually remain together on friendly terms for a week or more
after leaving the nest. Most of the time they are congregated in a ball-like
mass, perhaps for the sake of warmth, but upon being touched or shaken
they immediately disperse along the multitudinous fine lines which they
have spun in all directions, to reassemble as soon as the panic has subsided.
Such a ball of the yellow and black offspring of the large Garden-spider,
Epeira diademata, is no uncommon sight in the early autumn, and the
shower of “golden rain” that results from their disturbance is not likely to
be forgotten if it has ever been observed by the reader. This harmonious
family life only continues as long as the young spiders are unable to feed—
a period which, in some of the larger species, is said to extend to ten days or
a fortnight.
Individual life then commences, and each member of the dispersed group
sets up housekeeping on its own account, constructing at the first attempt a
snare in all respects similar, except in size, to those of its parent.
Of course the young Spiders have not migrated far, and a bush may
frequently be seen covered by the often contiguous nets of the members of a
single brood. This, as Dr. M‘Cook thinks, is the true explanation of some of
the cases of “gregarious spiders” which Darwin[270] and other naturalists
have occasionally described, though social spiders exist (see Uloborus, p.
411).
Very similar habits obtain among the Theridiidae, or line-weaving
spiders, a familiar example of which is the pretty little Theridion sisyphium,
whose highly-irregular snare may be found on any holly bush during the
summer months.
vary with different species. In the case of Argiope aurelia, Pollock[269] has
found that the female moults nine times after leaving the cocoon, the first
ecdysis occurring after an interval of from one to two months, according to
the abundance or scarcity of food. The subsequent intervals gradually
increase from about a fortnight to something over three weeks.
Behaviour of the Newly-hatched Spider.—The mode of life of a spider
just freed from the cocoon will of course vary greatly according to the
Family to which it belongs.
The Epeiridae are the builders of the familiar wheel or orb-web. Spiders
of this Family usually remain together on friendly terms for a week or more
after leaving the nest. Most of the time they are congregated in a ball-like
mass, perhaps for the sake of warmth, but upon being touched or shaken
they immediately disperse along the multitudinous fine lines which they
have spun in all directions, to reassemble as soon as the panic has subsided.
Such a ball of the yellow and black offspring of the large Garden-spider,
Epeira diademata, is no uncommon sight in the early autumn, and the
shower of “golden rain” that results from their disturbance is not likely to
be forgotten if it has ever been observed by the reader. This harmonious
family life only continues as long as the young spiders are unable to feed—
a period which, in some of the larger species, is said to extend to ten days or
a fortnight.
Individual life then commences, and each member of the dispersed group
sets up housekeeping on its own account, constructing at the first attempt a
snare in all respects similar, except in size, to those of its parent.
Of course the young Spiders have not migrated far, and a bush may
frequently be seen covered by the often contiguous nets of the members of a
single brood. This, as Dr. M‘Cook thinks, is the true explanation of some of
the cases of “gregarious spiders” which Darwin[270] and other naturalists
have occasionally described, though social spiders exist (see Uloborus, p.
411).
Very similar habits obtain among the Theridiidae, or line-weaving
spiders, a familiar example of which is the pretty little Theridion sisyphium,
whose highly-irregular snare may be found on any holly bush during the
summer months.
Page 386
The Lycosidae, or Wolf-spiders,
which chase their prey instead of
lying quietly in ambush to ensnare it,
are exceedingly interesting in their
treatment of their young. The cocoon,
or bag of eggs, is carried about on all
their expeditions, attached beneath
the abdomen, or held by the jaws,
and the young spiders, on escaping
from it, mount on the mother’s back,
and indulge vicariously in the
pleasures of the chase from this point
of vantage. The empty egg-bag is
soon discarded, but the brood
continues to ride on the mother’s
back for about a week, dismounting
only to follow her as she enters her
little silk-lined retreat in the ground.
Fig. 188.—A, Pardosa sp. ♀, with young on the
abdomen; B, young Pardosa detached; C, During this time they appear to
outline of the Spider with young removed. require no food, but they at length
(From the living specimen.) begin to disperse, the mother gently
but firmly removing such individuals
as are disposed to trespass upon her maternal solicitude longer than she
considers desirable.
Many young spiders of various Families proceed immediately to seek
new hunting-grounds by the aid of the wind, and become for the time being
diminutive aeronauts. This habit was observed by the earliest British
araneologist, Martin Lister,[271] as long ago as 1670, and has been alluded to
by many writers since his time.
The topmost bar of an iron railing in spring or early autumn will
generally be found peopled with minute spiders, and if the day be fair and
the wind light, the patient observer may be rewarded by a curious and
interesting sight.
The spider seeks the highest spot available, faces the wind, and
straightens its legs and body, standing, so to speak, upon its toes, its
abdomen with its spinning tubes being elevated as much as possible.
which chase their prey instead of
lying quietly in ambush to ensnare it,
are exceedingly interesting in their
treatment of their young. The cocoon,
or bag of eggs, is carried about on all
their expeditions, attached beneath
the abdomen, or held by the jaws,
and the young spiders, on escaping
from it, mount on the mother’s back,
and indulge vicariously in the
pleasures of the chase from this point
of vantage. The empty egg-bag is
soon discarded, but the brood
continues to ride on the mother’s
back for about a week, dismounting
only to follow her as she enters her
little silk-lined retreat in the ground.
Fig. 188.—A, Pardosa sp. ♀, with young on the
abdomen; B, young Pardosa detached; C, During this time they appear to
outline of the Spider with young removed. require no food, but they at length
(From the living specimen.) begin to disperse, the mother gently
but firmly removing such individuals
as are disposed to trespass upon her maternal solicitude longer than she
considers desirable.
Many young spiders of various Families proceed immediately to seek
new hunting-grounds by the aid of the wind, and become for the time being
diminutive aeronauts. This habit was observed by the earliest British
araneologist, Martin Lister,[271] as long ago as 1670, and has been alluded to
by many writers since his time.
The topmost bar of an iron railing in spring or early autumn will
generally be found peopled with minute spiders, and if the day be fair and
the wind light, the patient observer may be rewarded by a curious and
interesting sight.
The spider seeks the highest spot available, faces the wind, and
straightens its legs and body, standing, so to speak, upon its toes, its
abdomen with its spinning tubes being elevated as much as possible.
Page 387
Streamers of silk presently appear from the spinnerets and float gently to
leeward on the light current of air. The spider has no power to shoot out a
thread of silk to a distance, but it accomplishes the same result indirectly by
spinning a little sheet or flocculent mass which is borne away by the breeze.
When the streaming threads pull
with sufficient force the animal casts
off, seizes them with its legs, and
entrusts itself to the air, whose
currents determine the height to
which it is carried and the direction
of its journey. The duration, however,
is not quite beyond the spider’s
control, at all events in calm weather,
for it can furl its sail at will, hauling
in the threads “hand-over-hand,” and
rolling them up into a ball with jaws
and palps.
This curious ballooning habit of
young Spiders is independent of the
particular family to which they
belong, and it is remarkable that
newly-hatched Lycosidae and
Aviculariidae, whose adult existence
is spent entirely on or under the
ground, should manifest a disposition
to climb any elevated object which is
at hand.
The “Gossamer,” which so puzzled Fig. 189.—Young Spider preparing for an aerial
our forefathers, is probably no voyage. (After Emerton.)
mystery to the reader. It is, of course,
entirely the product of Spider industry, though not altogether attributable to
the habit of ballooning above described. Only a small proportion of
gossamer flakes are found to contain spiders, though minute insects are
constantly to be seen entangled in them. They are not formed in the air, as
was supposed long after their true origin was known, but the threads
emitted by multitudes of spiders in their various spinning operations have
leeward on the light current of air. The spider has no power to shoot out a
thread of silk to a distance, but it accomplishes the same result indirectly by
spinning a little sheet or flocculent mass which is borne away by the breeze.
When the streaming threads pull
with sufficient force the animal casts
off, seizes them with its legs, and
entrusts itself to the air, whose
currents determine the height to
which it is carried and the direction
of its journey. The duration, however,
is not quite beyond the spider’s
control, at all events in calm weather,
for it can furl its sail at will, hauling
in the threads “hand-over-hand,” and
rolling them up into a ball with jaws
and palps.
This curious ballooning habit of
young Spiders is independent of the
particular family to which they
belong, and it is remarkable that
newly-hatched Lycosidae and
Aviculariidae, whose adult existence
is spent entirely on or under the
ground, should manifest a disposition
to climb any elevated object which is
at hand.
The “Gossamer,” which so puzzled Fig. 189.—Young Spider preparing for an aerial
our forefathers, is probably no voyage. (After Emerton.)
mystery to the reader. It is, of course,
entirely the product of Spider industry, though not altogether attributable to
the habit of ballooning above described. Only a small proportion of
gossamer flakes are found to contain spiders, though minute insects are
constantly to be seen entangled in them. They are not formed in the air, as
was supposed long after their true origin was known, but the threads
emitted by multitudes of spiders in their various spinning operations have
Page 388
been intermingled and carried away by light currents of air, and on a still,
warm day in spring or autumn, when the newly-hatched spider-broods
swarm, the atmosphere is often full of them.
They rise to great heights, and may be carried to immense distances.
Martin Lister relates how he one day ascended to the highest accessible
point of York Minster, when the October air teemed with gossamer flakes,
and “could thence discern them yet exceeding high” above him. Gilbert
White describes a shower, at least eight miles in length, in which “on every
side, as the observer turned his eyes, he might behold a continual
succession of fresh flakes falling into his sight, and twinkling like stars as
they turned their sides toward the sun.” The ascent of a hill 300 feet in
height did not in the least enable him to escape the shower, which showed
no sign of diminution.
The mortality among very young spiders must be exceedingly great;
indeed, this is indicated by the large number of eggs laid by many species,
an unfailing sign of a small proportion of ultimate survivors. We shall have,
by and by, to speak of some of their natural enemies, but apart from these
their numbers are sadly reduced by the rigours of the weather, and
appreciably also by their tendency to cannibalism. A thunderstorm will
often destroy a whole brood, or they may perish from hunger in the absence
of an adequate supply of insects minute enough for their small snares and
feeble jaws. In the latter case they sometimes feed for a time on one
another, and it is even said that two or three of a brood may be reared on no
other food than their unfortunate companions.
The large and handsome Garden-spider, Epeira diademata, has been
known, when well fed, to construct six cocoons, each containing some
hundreds of eggs, and some species are even more fertile, while their adult
representatives remain stationary, or even diminish in number.
Spider-Webs.—Some account has already been given of the external and
internal spinning organs of Spiders. Within the body of the animal the silk is
in the form of a gummy fluid; and this, being emitted in exceedingly fine
streams, solidifies as it meets the air. It cannot be shot out to any distance,
but the animal usually draws it out by its hind legs, or attaches it to a spot,
and moves away by walking or allowing itself to drop. It has some power of
checking the output, and can stop at will at any point of its descent; but the
sphincter muscles of the apertures are but weak, and by steady winding the
warm day in spring or autumn, when the newly-hatched spider-broods
swarm, the atmosphere is often full of them.
They rise to great heights, and may be carried to immense distances.
Martin Lister relates how he one day ascended to the highest accessible
point of York Minster, when the October air teemed with gossamer flakes,
and “could thence discern them yet exceeding high” above him. Gilbert
White describes a shower, at least eight miles in length, in which “on every
side, as the observer turned his eyes, he might behold a continual
succession of fresh flakes falling into his sight, and twinkling like stars as
they turned their sides toward the sun.” The ascent of a hill 300 feet in
height did not in the least enable him to escape the shower, which showed
no sign of diminution.
The mortality among very young spiders must be exceedingly great;
indeed, this is indicated by the large number of eggs laid by many species,
an unfailing sign of a small proportion of ultimate survivors. We shall have,
by and by, to speak of some of their natural enemies, but apart from these
their numbers are sadly reduced by the rigours of the weather, and
appreciably also by their tendency to cannibalism. A thunderstorm will
often destroy a whole brood, or they may perish from hunger in the absence
of an adequate supply of insects minute enough for their small snares and
feeble jaws. In the latter case they sometimes feed for a time on one
another, and it is even said that two or three of a brood may be reared on no
other food than their unfortunate companions.
The large and handsome Garden-spider, Epeira diademata, has been
known, when well fed, to construct six cocoons, each containing some
hundreds of eggs, and some species are even more fertile, while their adult
representatives remain stationary, or even diminish in number.
Spider-Webs.—Some account has already been given of the external and
internal spinning organs of Spiders. Within the body of the animal the silk is
in the form of a gummy fluid; and this, being emitted in exceedingly fine
streams, solidifies as it meets the air. It cannot be shot out to any distance,
but the animal usually draws it out by its hind legs, or attaches it to a spot,
and moves away by walking or allowing itself to drop. It has some power of
checking the output, and can stop at will at any point of its descent; but the
sphincter muscles of the apertures are but weak, and by steady winding the
Page 389
writer has reeled out a hundred yards of the silk, the flow of which was only
then interrupted by the spider rubbing its spinnerets together and breaking
the thread.
There is, of course, no true spinning or interweaving of threads in the
process, but parallel silken lines are produced, varying in number according
to the special purpose for which they are designed, and sometimes adhering
more or less to one another on account of their viscidity and closeness.
The silk is utilised in many ways, serving for the construction of snares,
nests, and cocoons, as well as for enwrapping the captured prey, and for
anchoring the spider to a spot to which it may wish to return.
Spiders may be roughly distinguished as sedentary or vagabond, the
former constructing snares, and the latter chasing their prey in the open. We
will first consider the various forms of snare, beginning with that
characteristic of the Epeiridae.
The Circular Snare.—This familiar object, sometimes spoken of as the
orb-web or wheel-web, is always the work of some spider of the Family
Epeiridae.
The accuracy and regularity of form exhibited by these snares has caused
their architects to be sometimes called the geometric spiders. The ingenuity
displayed by them has always excited the admiration of the naturalist, and
this is increased on closer observation, for the snares are in reality even
more complex than they appear at first sight.
The first care of the spider is to lay down the foundation threads which
are to form the boundary lines of its net. If the animal can reach the
necessary points of attachment by walking along intervening surfaces the
matter is comparatively simple. The spinnerets are separated and rubbed
against one of the points selected, and the spider walks away, trailing
behind it a thread which it keeps free from neighbouring objects by the
action of one of its hind legs. On reaching another desirable point of
attachment the line is made taut and fixed by again rubbing the spinnerets
against it. By a repetition of this proceeding a framework is presently
constructed, within which the wheel or orb will ultimately be formed.
The process of fixing and drawing out a line can be conveniently
watched in the case of a Spider imprisoned in a glass vessel, and it will be
seen, by the aid of a lens, that a large number of very fine lines starting
from the point of attachment seem to merge into a single line as the Spider
then interrupted by the spider rubbing its spinnerets together and breaking
the thread.
There is, of course, no true spinning or interweaving of threads in the
process, but parallel silken lines are produced, varying in number according
to the special purpose for which they are designed, and sometimes adhering
more or less to one another on account of their viscidity and closeness.
The silk is utilised in many ways, serving for the construction of snares,
nests, and cocoons, as well as for enwrapping the captured prey, and for
anchoring the spider to a spot to which it may wish to return.
Spiders may be roughly distinguished as sedentary or vagabond, the
former constructing snares, and the latter chasing their prey in the open. We
will first consider the various forms of snare, beginning with that
characteristic of the Epeiridae.
The Circular Snare.—This familiar object, sometimes spoken of as the
orb-web or wheel-web, is always the work of some spider of the Family
Epeiridae.
The accuracy and regularity of form exhibited by these snares has caused
their architects to be sometimes called the geometric spiders. The ingenuity
displayed by them has always excited the admiration of the naturalist, and
this is increased on closer observation, for the snares are in reality even
more complex than they appear at first sight.
The first care of the spider is to lay down the foundation threads which
are to form the boundary lines of its net. If the animal can reach the
necessary points of attachment by walking along intervening surfaces the
matter is comparatively simple. The spinnerets are separated and rubbed
against one of the points selected, and the spider walks away, trailing
behind it a thread which it keeps free from neighbouring objects by the
action of one of its hind legs. On reaching another desirable point of
attachment the line is made taut and fixed by again rubbing the spinnerets
against it. By a repetition of this proceeding a framework is presently
constructed, within which the wheel or orb will ultimately be formed.
The process of fixing and drawing out a line can be conveniently
watched in the case of a Spider imprisoned in a glass vessel, and it will be
seen, by the aid of a lens, that a large number of very fine lines starting
from the point of attachment seem to merge into a single line as the Spider
Page 390
moves away. This has given rise to the prevalent and very natural idea that
the ordinary spider’s line is formed or “woven” of many strands. This,
however, is not the case,[272] for the fine attachment-lines are not continued
into the main thread, but only serve to anchor it to the starting-point.
As has been said, the spider can throw into play a varying number of
spinning tubes at will, and in point of fact those used in laying down these
foundation-lines are either two or four in number. The spider, however,
often finds it necessary to strengthen such a line by going over it afresh.
Every one must have noticed that orb-webs frequently bridge over gulfs
that are clearly quite impassable to the spider in the ordinary way. They
often span streams—and Epeirid spiders cannot swim—or they are
stretched between objects unattainable from each other on foot except by a
very long and roundabout journey. When this is the case, the animal has had
recourse to the aid of the wind. A spider of this family placed on a stick
standing upright in a vessel of water is helpless to escape if the experiment
be tried in a room free from draughts. With air-currents to aid it, silken
streamers will at length find their way across the water and become
accidentally entangled in some neighbouring object. When this has
happened, the spider hauls the new line taut, and tests its strength by gently
pulling at it, and if the result is satisfactory, it proceeds to walk across,
hand-over-hand, in an inverted position, carrying with it a second line to
strengthen the first. This is exactly what happens in nature when a snare is
constructed across chasms otherwise impassable, and it may be imagined
that the spider regards as very valuable landed property the foundation lines
of such a web, for, if destroyed, the direction or absence of the wind might
prevent their renewal for days. They are accordingly made strong by
repeated journeys, and are used as the framework of successive snares, till
accident at length destroys them.
A single line which finds anchorage in this way is sufficient for the
purposes of the spider. It has only to cross over to the new object, attach a
thread to some other point of it, and carry it back across the bridge to fix it
at a convenient spot on the surface which formed the base of its operations.
Between two such bridge-lines the circular snare is constructed in a manner
to be presently described. Sometimes the tentative threads emitted by the
spider travel far before finding attachment. In the case of the English Epeira
diademata the writer has measured bridge-lines of eleven feet in length; and
the ordinary spider’s line is formed or “woven” of many strands. This,
however, is not the case,[272] for the fine attachment-lines are not continued
into the main thread, but only serve to anchor it to the starting-point.
As has been said, the spider can throw into play a varying number of
spinning tubes at will, and in point of fact those used in laying down these
foundation-lines are either two or four in number. The spider, however,
often finds it necessary to strengthen such a line by going over it afresh.
Every one must have noticed that orb-webs frequently bridge over gulfs
that are clearly quite impassable to the spider in the ordinary way. They
often span streams—and Epeirid spiders cannot swim—or they are
stretched between objects unattainable from each other on foot except by a
very long and roundabout journey. When this is the case, the animal has had
recourse to the aid of the wind. A spider of this family placed on a stick
standing upright in a vessel of water is helpless to escape if the experiment
be tried in a room free from draughts. With air-currents to aid it, silken
streamers will at length find their way across the water and become
accidentally entangled in some neighbouring object. When this has
happened, the spider hauls the new line taut, and tests its strength by gently
pulling at it, and if the result is satisfactory, it proceeds to walk across,
hand-over-hand, in an inverted position, carrying with it a second line to
strengthen the first. This is exactly what happens in nature when a snare is
constructed across chasms otherwise impassable, and it may be imagined
that the spider regards as very valuable landed property the foundation lines
of such a web, for, if destroyed, the direction or absence of the wind might
prevent their renewal for days. They are accordingly made strong by
repeated journeys, and are used as the framework of successive snares, till
accident at length destroys them.
A single line which finds anchorage in this way is sufficient for the
purposes of the spider. It has only to cross over to the new object, attach a
thread to some other point of it, and carry it back across the bridge to fix it
at a convenient spot on the surface which formed the base of its operations.
Between two such bridge-lines the circular snare is constructed in a manner
to be presently described. Sometimes the tentative threads emitted by the
spider travel far before finding attachment. In the case of the English Epeira
diademata the writer has measured bridge-lines of eleven feet in length; and
Page 391
with the great Orb-weavers of tropical countries they frequently span
streams several yards in width.
Two stout bridge-lines thus constructed will form the upper and lower
boundaries of the net. The lateral limits are easily formed by cross lines
between them at a convenient distance apart. The spider chooses a point,
say, on the upper bridge-line, fixes its thread there, and carries it round to
the lower line, where it is hauled taut and firmly attached. Two such cross
lines give, with the bridge-lines, an irregular four-sided figure within which
to stretch the snare, and now the work is perfectly straightforward, and can
proceed without interruption.
Attention is first paid to the radii of the circular web. The first radii are
formed by drawing cross lines within the framework in the same manner as
before, but the spider carefully attaches these where they intersect by a
small flossy mass of silk, and this central point or hub becomes the basis of
its subsequent operations. It is a simple matter to add new radial lines by
walking from the centre along one of those already formed and fixing the
thread to some new point of the circumference. They are not laid down in
any invariable order, but with a kind of alternation which has the general
effect of keeping the strain on every side fairly equal. Almost every time the
spider reaches the centre it slowly revolves, uniting the radii afresh at their
point of junction, and increasing the strength and complexity of the hub. It
also occasionally digresses so far as to stretch the whole structure by
bracing the framework at additional points, so that it loses its four-sided
form and becomes polygonal. We have now a number of spokes connecting
a central hub with an irregular circumference.
The hub is next surrounded by what Dr. M‘Cook calls a “notched zone,”
consisting of a few turns of spiral thread which serve to bind more firmly
the spokes of the wheel. The most important part of the work is still to be
performed. The lines hitherto laid down are perfectly dry and free from
viscidity, so that an entangled insect would easily be able to free itself. A
viscid spiral line remains to be spun, and the snare will be complete. The
precise method of laying this down will vary somewhat according to the
species, but, to refer again to the large Garden-spider, the proceeding is as
follows:—Commencing at a point somewhat outside the notched zone, the
creature rapidly works in a spiral thread of ordinary silk with the successive
turns rather far apart. This forms a kind of scaffolding, by clinging to which
streams several yards in width.
Two stout bridge-lines thus constructed will form the upper and lower
boundaries of the net. The lateral limits are easily formed by cross lines
between them at a convenient distance apart. The spider chooses a point,
say, on the upper bridge-line, fixes its thread there, and carries it round to
the lower line, where it is hauled taut and firmly attached. Two such cross
lines give, with the bridge-lines, an irregular four-sided figure within which
to stretch the snare, and now the work is perfectly straightforward, and can
proceed without interruption.
Attention is first paid to the radii of the circular web. The first radii are
formed by drawing cross lines within the framework in the same manner as
before, but the spider carefully attaches these where they intersect by a
small flossy mass of silk, and this central point or hub becomes the basis of
its subsequent operations. It is a simple matter to add new radial lines by
walking from the centre along one of those already formed and fixing the
thread to some new point of the circumference. They are not laid down in
any invariable order, but with a kind of alternation which has the general
effect of keeping the strain on every side fairly equal. Almost every time the
spider reaches the centre it slowly revolves, uniting the radii afresh at their
point of junction, and increasing the strength and complexity of the hub. It
also occasionally digresses so far as to stretch the whole structure by
bracing the framework at additional points, so that it loses its four-sided
form and becomes polygonal. We have now a number of spokes connecting
a central hub with an irregular circumference.
The hub is next surrounded by what Dr. M‘Cook calls a “notched zone,”
consisting of a few turns of spiral thread which serve to bind more firmly
the spokes of the wheel. The most important part of the work is still to be
performed. The lines hitherto laid down are perfectly dry and free from
viscidity, so that an entangled insect would easily be able to free itself. A
viscid spiral line remains to be spun, and the snare will be complete. The
precise method of laying this down will vary somewhat according to the
species, but, to refer again to the large Garden-spider, the proceeding is as
follows:—Commencing at a point somewhat outside the notched zone, the
creature rapidly works in a spiral thread of ordinary silk with the successive
turns rather far apart. This forms a kind of scaffolding, by clinging to which
Page 392
the spider can put in the viscid spiral, which it commences at the
circumference.
Its action now becomes exceedingly careful and deliberate, though by no
means slow, and so great is its absorption in the work that it may be
observed quite closely with a hand-lens without fear of interrupting it. The
proceeding consists in drawing out from its spinnerets with one (or both) of
its hind legs successive lengths of a highly elastic line, which it stretches
just at the moment of fixing it to a radius, and then lets go with a snap.
There is no hesitation or pause for consideration, but there is a peculiar
deliberateness in drawing out each length of the thread which, together with
stretching and sudden release, require explanation. Now, it has already been
mentioned that the framework and radii of the snare are not at all moist or
adhesive. This, however, is not the case with the spiral, upon which the
spider chiefly relies in capturing its prey. A close examination of it—even
with the naked eye—will show it to be beaded over with little viscid
globules which, under a low magnifying power, are seen to be arranged
with remarkable regularity.
Fig. 190.—A, B, C, D, Stages in the formation of the viscid globules of the web.
A very convenient method of investigation is to carry off a newly-
constructed web—or, better still, one not quite finished—on a piece of plate
glass, to which it will adhere by reason of the viscid spiral, and on which it
may be examined at leisure. Immersion in a staining fluid will colour the
viscid spiral, and show its structure in a striking manner. It will appear to
consist of a thread strung with beads of two sizes, occurring with pretty
uniform alternation, though two of the larger beads are often separated by
two or more of the smaller.
circumference.
Its action now becomes exceedingly careful and deliberate, though by no
means slow, and so great is its absorption in the work that it may be
observed quite closely with a hand-lens without fear of interrupting it. The
proceeding consists in drawing out from its spinnerets with one (or both) of
its hind legs successive lengths of a highly elastic line, which it stretches
just at the moment of fixing it to a radius, and then lets go with a snap.
There is no hesitation or pause for consideration, but there is a peculiar
deliberateness in drawing out each length of the thread which, together with
stretching and sudden release, require explanation. Now, it has already been
mentioned that the framework and radii of the snare are not at all moist or
adhesive. This, however, is not the case with the spiral, upon which the
spider chiefly relies in capturing its prey. A close examination of it—even
with the naked eye—will show it to be beaded over with little viscid
globules which, under a low magnifying power, are seen to be arranged
with remarkable regularity.
Fig. 190.—A, B, C, D, Stages in the formation of the viscid globules of the web.
A very convenient method of investigation is to carry off a newly-
constructed web—or, better still, one not quite finished—on a piece of plate
glass, to which it will adhere by reason of the viscid spiral, and on which it
may be examined at leisure. Immersion in a staining fluid will colour the
viscid spiral, and show its structure in a striking manner. It will appear to
consist of a thread strung with beads of two sizes, occurring with pretty
uniform alternation, though two of the larger beads are often separated by
two or more of the smaller.
Page 393
Until recently it was supposed that the deposition of these beads upon the
spiral line was a subsequent operation, and, in view of their vast numbers
and regularity, the circumstance naturally excited great wonder and
admiration. Blackwall[273] estimated that, in a fourteen-inch net of Epeira
cornuta, there were at least 120,000 viscid globules, and yet he found that
its construction occupied only about forty minutes! The feat, from his point
of view, must be allowed to be rather startling.
As a matter of fact, the thread, on being slowly drawn out, is uniformly
coated with viscid matter which afterwards arranges itself into beads, the
change being assisted by the sudden liberation of the stretched line.
Boys[274] has shown their formation to be quite mechanical, and has
obtained an exact imitation of them by smearing with oil a fine thread
ingeniously drawn out from molten quartz. The oil arranged itself into
globules exactly resembling the viscid “beads” on the spider’s line. If the
web be carried bodily away on a sheet of glass, as above described, while
the spider is engaged upon the spiral line, the experimenter will have
permanent evidence of the manner in which the globules are formed. The
last part of the line will be quite free from them, but uniformly viscid.
Tracing it backwards, however, the beads are soon found, at first irregularly,
but soon with their usual uniformity. The thread which the spider has thus
“limed” for the capture of prey is really two-stranded—the strands not
being twisted, but lying side by side, and glued together by their viscid
envelope.
The snare is now practically complete, and the proprietor takes up her
position either in the centre thereof, or in some retreat close at hand, and
connected with the hub by special lines diverging somewhat from the plane
of the web. Notwithstanding the possession of eight eyes—which, in
sedentary spiders, are by no means sharp-sighted—it is mainly by the sense
of touch that the spider presently becomes aware that an insect is struggling
in the net. She immediately rushes to the spot, and suits her action to the
emergency.
If the intruder is small, it is at once seized, enveloped in a band of silken
threads drawn out from the spinnerets, and carried off to the retreat, to be
feasted on at leisure. If it seems formidable it is approached carefully—
especially if armed with a sting—and silk is deftly thrown over it from a
safe distance till it is thoroughly entangled, and can be seized in safety by
spiral line was a subsequent operation, and, in view of their vast numbers
and regularity, the circumstance naturally excited great wonder and
admiration. Blackwall[273] estimated that, in a fourteen-inch net of Epeira
cornuta, there were at least 120,000 viscid globules, and yet he found that
its construction occupied only about forty minutes! The feat, from his point
of view, must be allowed to be rather startling.
As a matter of fact, the thread, on being slowly drawn out, is uniformly
coated with viscid matter which afterwards arranges itself into beads, the
change being assisted by the sudden liberation of the stretched line.
Boys[274] has shown their formation to be quite mechanical, and has
obtained an exact imitation of them by smearing with oil a fine thread
ingeniously drawn out from molten quartz. The oil arranged itself into
globules exactly resembling the viscid “beads” on the spider’s line. If the
web be carried bodily away on a sheet of glass, as above described, while
the spider is engaged upon the spiral line, the experimenter will have
permanent evidence of the manner in which the globules are formed. The
last part of the line will be quite free from them, but uniformly viscid.
Tracing it backwards, however, the beads are soon found, at first irregularly,
but soon with their usual uniformity. The thread which the spider has thus
“limed” for the capture of prey is really two-stranded—the strands not
being twisted, but lying side by side, and glued together by their viscid
envelope.
The snare is now practically complete, and the proprietor takes up her
position either in the centre thereof, or in some retreat close at hand, and
connected with the hub by special lines diverging somewhat from the plane
of the web. Notwithstanding the possession of eight eyes—which, in
sedentary spiders, are by no means sharp-sighted—it is mainly by the sense
of touch that the spider presently becomes aware that an insect is struggling
in the net. She immediately rushes to the spot, and suits her action to the
emergency.
If the intruder is small, it is at once seized, enveloped in a band of silken
threads drawn out from the spinnerets, and carried off to the retreat, to be
feasted on at leisure. If it seems formidable it is approached carefully—
especially if armed with a sting—and silk is deftly thrown over it from a
safe distance till it is thoroughly entangled, and can be seized in safety by
Page 394
the venomous jaws of its captor. Sometimes the insect is so powerful, or the
spider so sated with food, that the latter hastens to set free the intruder by
biting away the threads which entangle it before much havoc has been
wrought with the net.
The viscid matter on the spiral line dries up after some hours, so that,
even if the web has not been destroyed by insects and stress of weather, this
portion of it must be frequently renewed. Commencing a new web is, as has
been seen, a troublesome matter, and it will readily be understood that the
spider prefers, where practicable, to patch up the old one. This is done by
biting away torn and ragged portions and inserting new lines in their place.
The part played by the various spinning glands in the construction of the
orb-web may be briefly stated.[275] The ampullaceal glands furnish the silk
for the foundation lines and radii. The spiral has a double ground-line
proceeding from the middle spinnerets, but it is not quite certain whether it
proceeds from the ampullaceal or the tubuliform glands. The chief function
of the latter, in the female, is to furnish silk for the egg-cocoon. The viscid
globules are the products of the aggregate glands. The aciniform and
piriform glands provide the multitudinous threads by which the spider
anchors its various lines and enwraps its prey.
Some Orb-weavers always decorate their snares with patches or tufts of
flossy silk. In the snare of the North American Argiope cophinaria the hub
is sheeted, and from it extends downwards a zigzag ribbon of silk stretched
between two consecutive radii. Vinson[276] discovered a remarkable use for
similar zigzag bands in the web of the Mauritian spider, Epeira mauritia. It
furnished a reserve supply of silk for enveloping partly entangled insects
whose struggles were too vigorous to succumb to the rather feeble threads
which the spider was able to emit at the moment of capture. The spider was
able to overcome a grasshopper much more powerful than itself by
dexterously throwing over it with one of its hind legs a portion of the ribbon
of silk which it had thus stored up for emergencies.
spider so sated with food, that the latter hastens to set free the intruder by
biting away the threads which entangle it before much havoc has been
wrought with the net.
The viscid matter on the spiral line dries up after some hours, so that,
even if the web has not been destroyed by insects and stress of weather, this
portion of it must be frequently renewed. Commencing a new web is, as has
been seen, a troublesome matter, and it will readily be understood that the
spider prefers, where practicable, to patch up the old one. This is done by
biting away torn and ragged portions and inserting new lines in their place.
The part played by the various spinning glands in the construction of the
orb-web may be briefly stated.[275] The ampullaceal glands furnish the silk
for the foundation lines and radii. The spiral has a double ground-line
proceeding from the middle spinnerets, but it is not quite certain whether it
proceeds from the ampullaceal or the tubuliform glands. The chief function
of the latter, in the female, is to furnish silk for the egg-cocoon. The viscid
globules are the products of the aggregate glands. The aciniform and
piriform glands provide the multitudinous threads by which the spider
anchors its various lines and enwraps its prey.
Some Orb-weavers always decorate their snares with patches or tufts of
flossy silk. In the snare of the North American Argiope cophinaria the hub
is sheeted, and from it extends downwards a zigzag ribbon of silk stretched
between two consecutive radii. Vinson[276] discovered a remarkable use for
similar zigzag bands in the web of the Mauritian spider, Epeira mauritia. It
furnished a reserve supply of silk for enveloping partly entangled insects
whose struggles were too vigorous to succumb to the rather feeble threads
which the spider was able to emit at the moment of capture. The spider was
able to overcome a grasshopper much more powerful than itself by
dexterously throwing over it with one of its hind legs a portion of the ribbon
of silk which it had thus stored up for emergencies.
Page 395
Many orb-webs are defective, a
sector of the circle being uniformly
omitted in the structure. The genus
Hyptiotes does not belong to the
Epeiridae but to the cribellate
Uloboridae, but its defective orb-web
is so curious that it deserves a special
mention. A single foundation-line is
laid down, and from it four radii are
drawn and are connected with cross
lines, the snare constituting about
one-sixth of a circle. From the centre
Fig. 191.—A, Snare of Hyptiotes cavatus; B,
enlarged view of the Spider, showing the of the incomplete circle a thread
“slack” of the hauled-in line. (After Emerton.) proceeds to some more or less distant
object, and on this the spider takes up
its position, inverted, and hauls in the line till the snare is taut. When the
trembling of the line shows the spider that an insect has struck the net, it
lets go with its fore-legs, and the web, springing back to its normal position,
entangles the intruder more thoroughly by its vibrations. When large insects
are in question the spider has been observed to “spring” the net several
times in succession. H. cavatus is common in the pine woods of
Pennsylvania, but the only English species, H. paradoxus, is extremely rare.
A remarkable spider has been discovered in Texas by M‘Cook, which,
after building a horizontal orb-web, converts it subsequently into a dome
(Fig. 192) of exceedingly perfect form. It is named Epeira basilica, and has
been the object of careful study by Dr. Marx, who observed the whole
process of web-construction. Threads are attached at various points on the
upper surface of the horizontal wheel, the central portion of which is
gradually pulled up until the height of the dome is nearly equal to the
diameter of its base. But the snare of this spider does not consist of the
dome alone. A sheet of irregular lines is stretched below, while above there
is a maze of threads in the form of a pyramid. Several other Orb-weavers,
as, for instance, E. labyrinthea and E. triaranea, supplement their typical
webs by an irregular structure of silk, and thus form connecting links, as
regards habit, between the group of which we have been speaking and the
Theridiidae or Line-weavers, which may now briefly be dealt with.
sector of the circle being uniformly
omitted in the structure. The genus
Hyptiotes does not belong to the
Epeiridae but to the cribellate
Uloboridae, but its defective orb-web
is so curious that it deserves a special
mention. A single foundation-line is
laid down, and from it four radii are
drawn and are connected with cross
lines, the snare constituting about
one-sixth of a circle. From the centre
Fig. 191.—A, Snare of Hyptiotes cavatus; B,
enlarged view of the Spider, showing the of the incomplete circle a thread
“slack” of the hauled-in line. (After Emerton.) proceeds to some more or less distant
object, and on this the spider takes up
its position, inverted, and hauls in the line till the snare is taut. When the
trembling of the line shows the spider that an insect has struck the net, it
lets go with its fore-legs, and the web, springing back to its normal position,
entangles the intruder more thoroughly by its vibrations. When large insects
are in question the spider has been observed to “spring” the net several
times in succession. H. cavatus is common in the pine woods of
Pennsylvania, but the only English species, H. paradoxus, is extremely rare.
A remarkable spider has been discovered in Texas by M‘Cook, which,
after building a horizontal orb-web, converts it subsequently into a dome
(Fig. 192) of exceedingly perfect form. It is named Epeira basilica, and has
been the object of careful study by Dr. Marx, who observed the whole
process of web-construction. Threads are attached at various points on the
upper surface of the horizontal wheel, the central portion of which is
gradually pulled up until the height of the dome is nearly equal to the
diameter of its base. But the snare of this spider does not consist of the
dome alone. A sheet of irregular lines is stretched below, while above there
is a maze of threads in the form of a pyramid. Several other Orb-weavers,
as, for instance, E. labyrinthea and E. triaranea, supplement their typical
webs by an irregular structure of silk, and thus form connecting links, as
regards habit, between the group of which we have been speaking and the
Theridiidae or Line-weavers, which may now briefly be dealt with.
Page 396
The Irregular Snare.—The great
majority of British Spiders belong to
the family of the Theridiidae, or
Line-weavers. Some of these are
among the handsomest of our native
species, and are in other respects
highly interesting, but their snares
lack the definiteness of structure
exhibited by the orb-web, and little
need be said about them.
For the most part they consist of
fine irregular lines running in all
directions between the twigs of
bushes or among the stems of grass
and herbage. One large and important
genus, Linyphia, always constructs a Fig. 192.—Snare of Epeira basilica. (After
horizontal sheet of irregular threads M‘Cook.)
with a maze of silk above it. Such
snares may be seen in myriads in the
wayside hedges during the summer, and they are especially notable objects
when heavily laden with dew. Insects impeded in their flight by the maze of
threads drop into the underlying sheet, and are soon completely entangled.
The spider usually runs beneath the sheet in an inverted position.
The sheet or hammock of silk is absent in the case of most of the other
genera of this family, their snares being innocent of any definite method in
their structure. They are frequently quite contiguous, and it is no uncommon
thing to find a holly bush completely covered with a continuous network of
threads, the work of a whole colony of the pretty little spider Theridion
sisyphium.
As might be imagined from the simplicity or absence of design in the
structure of the net, there appears to be very little complexity in the nature
of the silk used. It is interesting, however, to find that viscid globules, not
unlike those which stud the “spiral line” of the Epeiridae, are sometimes
present in the snares of the Line-weavers,[277] and in these, too, aggregate
glands are present. There is a large spider of this family, Theridion
tepidariorum, which may be found to a certainty in almost any hothouse in
majority of British Spiders belong to
the family of the Theridiidae, or
Line-weavers. Some of these are
among the handsomest of our native
species, and are in other respects
highly interesting, but their snares
lack the definiteness of structure
exhibited by the orb-web, and little
need be said about them.
For the most part they consist of
fine irregular lines running in all
directions between the twigs of
bushes or among the stems of grass
and herbage. One large and important
genus, Linyphia, always constructs a Fig. 192.—Snare of Epeira basilica. (After
horizontal sheet of irregular threads M‘Cook.)
with a maze of silk above it. Such
snares may be seen in myriads in the
wayside hedges during the summer, and they are especially notable objects
when heavily laden with dew. Insects impeded in their flight by the maze of
threads drop into the underlying sheet, and are soon completely entangled.
The spider usually runs beneath the sheet in an inverted position.
The sheet or hammock of silk is absent in the case of most of the other
genera of this family, their snares being innocent of any definite method in
their structure. They are frequently quite contiguous, and it is no uncommon
thing to find a holly bush completely covered with a continuous network of
threads, the work of a whole colony of the pretty little spider Theridion
sisyphium.
As might be imagined from the simplicity or absence of design in the
structure of the net, there appears to be very little complexity in the nature
of the silk used. It is interesting, however, to find that viscid globules, not
unlike those which stud the “spiral line” of the Epeiridae, are sometimes
present in the snares of the Line-weavers,[277] and in these, too, aggregate
glands are present. There is a large spider of this family, Theridion
tepidariorum, which may be found to a certainty in almost any hothouse in
Page 397
this country. In its snare, which is of the ordinary irregular type, F. Pickard-
Cambridge has observed little patches of flocculent silk, calculated to
render more certain the entanglement of prey, and he has further described a
curious comb-like structure on the hind leg of the animal which is probably
used in the production of this phenomenon. It is by no means unlikely that a
more careful study of these apparently simple snares will lead to the
discovery of further complexity of structure.
Uloborus, a cribellate genus which
has an Epeirid-like, orbicular snare,
decorates some of the lines with the
produce of the cribellate glands, but
viscid globules are absent.
Sheet-Webs.—The webs which
are such familiar—and, by
Fig. 193.—Snare of Uloborus sp., some of the
lines being thickened with threads from the
association, unpleasant—objects in
cribellum. (After M‘Cook.) unused rooms and outhouses are
usually the work of spiders belonging
to the Agelenidae and the Dictynidae.
To the first belongs the common House-spider, Tegenaria civilis, and its
larger congener, T. parietina. These spiders are not attractive in appearance,
and the last-named species especially, with the four-inch span of its
outstretched legs, is a formidable object, and a terror to domestic servants.
An obscure tradition connecting it with Cardinal Wolsey and Hampton
Court has caused it to be known as the Cardinal Spider. An out-door
example of the Agelenidae is the very abundant Agelena labyrinthica,
whose sheet-web, with its tubular retreat, is to be sought on the banks of
ditches, or in the hedges of our country lanes.
The snares of these spiders are exceedingly closely woven of very fine
silk, and take a long time to complete. The process of their construction
may be watched by keeping an Agelena labyrinthica confined in a box with
a glass front, and the web, kept free from dust, is a beautiful object, as its
fine texture gradually becomes visible as a delicate transparent film which
develops by imperceptible stages into an opaque white sheet. The excessive
fineness of the silk makes it difficult at first to see what is taking place. The
animal is seen to be busily moving about, but the result of its labours only
gradually becomes visible. A few delicate foundation-lines are first
Cambridge has observed little patches of flocculent silk, calculated to
render more certain the entanglement of prey, and he has further described a
curious comb-like structure on the hind leg of the animal which is probably
used in the production of this phenomenon. It is by no means unlikely that a
more careful study of these apparently simple snares will lead to the
discovery of further complexity of structure.
Uloborus, a cribellate genus which
has an Epeirid-like, orbicular snare,
decorates some of the lines with the
produce of the cribellate glands, but
viscid globules are absent.
Sheet-Webs.—The webs which
are such familiar—and, by
Fig. 193.—Snare of Uloborus sp., some of the
lines being thickened with threads from the
association, unpleasant—objects in
cribellum. (After M‘Cook.) unused rooms and outhouses are
usually the work of spiders belonging
to the Agelenidae and the Dictynidae.
To the first belongs the common House-spider, Tegenaria civilis, and its
larger congener, T. parietina. These spiders are not attractive in appearance,
and the last-named species especially, with the four-inch span of its
outstretched legs, is a formidable object, and a terror to domestic servants.
An obscure tradition connecting it with Cardinal Wolsey and Hampton
Court has caused it to be known as the Cardinal Spider. An out-door
example of the Agelenidae is the very abundant Agelena labyrinthica,
whose sheet-web, with its tubular retreat, is to be sought on the banks of
ditches, or in the hedges of our country lanes.
The snares of these spiders are exceedingly closely woven of very fine
silk, and take a long time to complete. The process of their construction
may be watched by keeping an Agelena labyrinthica confined in a box with
a glass front, and the web, kept free from dust, is a beautiful object, as its
fine texture gradually becomes visible as a delicate transparent film which
develops by imperceptible stages into an opaque white sheet. The excessive
fineness of the silk makes it difficult at first to see what is taking place. The
animal is seen to be busily moving about, but the result of its labours only
gradually becomes visible. A few delicate foundation-lines are first
Page 398
stretched across the compartment in which it is confined, and upon these the
spider walks to and fro incessantly with a serpentine motion, and by and by
a muslin-like floor of silk comes into view.
An examination of the spinnerets throws some light upon the operation.
The posterior pair are very long and mobile, and the hair-like spinning-
tubes are distributed on their under surface. The cephalothorax and
abdomen are far more rigidly connected in Agelena than in the Orb-
weavers, but its length of leg and the length and mobility of its posterior
spinnerets enable it to give a wide lateral sweep as it walks along, strewing
fine silken threads upon the foundation-lines already laid down. Some hours
elapse before even a moderately stout web is constructed, and for long
afterwards the spider devotes odd moments of leisure in going over the
ground again and strewing new silk upon the gradually thickening web. At
one corner a silken tube of similar structure is formed, and in this the spider
awaits the advent of any insect which may alight upon the sheet, when it
immediately rushes forth and seizes it.
The webs of the Dictynidae are very similar in general appearance to
those of the Agelenidae, consisting of a closely-woven sheet with a tubular
nest. They are to be found, moreover, in similar situations, stretching across
the angles of walls in cellars or outhouses, though some species prefer an
out-door existence. Crannies in rock form convenient sites for such snares,
but the family is not without its representatives in still more open situations.
The web, though so similar to that of Agelena, is, however, constructed in a
different manner. In the Dictynidae neither the legs nor the spinnerets are
unusually long, and they do not strew the foundation-lines by a swinging
motion of the body, but the operation is effected by a special apparatus.
These spiders are cribellate, and in front of the six ordinary spinnerets there
are a pair of perforated plates connected with a large number of additional
minute spinning glands (see Fig. 182, p. 326). In conjunction with this, the
female possesses on the last joint but one of each hind leg a curious comb-
like arrangement of spines, the “calamistrum.” The animal constructs a sort
of skeleton web by means of its ordinary spinnerets, and when this is
completed it combs out silk from the cribellum by means of the
calamistrum, using each hind leg alternately, and distributes it with a
curling motion upon the scaffolding prepared for it, a nearly opaque web
being the result. The silk from the cribellum is of an adhesive nature, and
renders escape from the web very difficult.
spider walks to and fro incessantly with a serpentine motion, and by and by
a muslin-like floor of silk comes into view.
An examination of the spinnerets throws some light upon the operation.
The posterior pair are very long and mobile, and the hair-like spinning-
tubes are distributed on their under surface. The cephalothorax and
abdomen are far more rigidly connected in Agelena than in the Orb-
weavers, but its length of leg and the length and mobility of its posterior
spinnerets enable it to give a wide lateral sweep as it walks along, strewing
fine silken threads upon the foundation-lines already laid down. Some hours
elapse before even a moderately stout web is constructed, and for long
afterwards the spider devotes odd moments of leisure in going over the
ground again and strewing new silk upon the gradually thickening web. At
one corner a silken tube of similar structure is formed, and in this the spider
awaits the advent of any insect which may alight upon the sheet, when it
immediately rushes forth and seizes it.
The webs of the Dictynidae are very similar in general appearance to
those of the Agelenidae, consisting of a closely-woven sheet with a tubular
nest. They are to be found, moreover, in similar situations, stretching across
the angles of walls in cellars or outhouses, though some species prefer an
out-door existence. Crannies in rock form convenient sites for such snares,
but the family is not without its representatives in still more open situations.
The web, though so similar to that of Agelena, is, however, constructed in a
different manner. In the Dictynidae neither the legs nor the spinnerets are
unusually long, and they do not strew the foundation-lines by a swinging
motion of the body, but the operation is effected by a special apparatus.
These spiders are cribellate, and in front of the six ordinary spinnerets there
are a pair of perforated plates connected with a large number of additional
minute spinning glands (see Fig. 182, p. 326). In conjunction with this, the
female possesses on the last joint but one of each hind leg a curious comb-
like arrangement of spines, the “calamistrum.” The animal constructs a sort
of skeleton web by means of its ordinary spinnerets, and when this is
completed it combs out silk from the cribellum by means of the
calamistrum, using each hind leg alternately, and distributes it with a
curling motion upon the scaffolding prepared for it, a nearly opaque web
being the result. The silk from the cribellum is of an adhesive nature, and
renders escape from the web very difficult.
Page 399
Spiders’ Nests and Retreats.—All Spiders construct some description
of nest, and often display great ingenuity in building them. Perhaps none
are more curious than those of the burrowing Aviculariidae, a family which
includes the interesting “Trap-door Spiders.” They are nocturnal in their
habits, about which, consequently, little is known, but their nests have been
carefully studied, especially by Moggridge, who found them in considerable
abundance in various districts of the Riviera.
The jaws of these spiders are especially adapted for digging, and with
them a hole is excavated in the ground to the depth of several inches, and
wide enough to allow the animal to turn. This is carefully lined with silk
which the spider throws against the sides from its long and upturned
posterior spinnerets. But the chef d’œuvre of the whole structure is a lid or
door which protects the entrance to the tube. There are two types of door
which find favour with different species—the wafer and the cork type, as
Moggridge has named them. The former consists of a thin circular or oval
sheet of silk which flaps down loosely over the tube-entrance, with which it
is connected by a hinge-like attachment. A trap-door of the cork type is a
more complicated structure, being of considerable thickness and having a
bevelled edge, so that it fits into the tube like a plug. Like the wafer door, it
possesses a silken hinge.
To form the wafer door, the spider covers the entrance to the tube with a
closely-woven layer of silk, which it afterwards bites away at the edge,
except at the point where the hinge is to be. Doors of the cork type consist
of alternate layers of silk and earth. After weaving a covering of silk, the
creature brings earth in its jaws and lays it on the top, binding it down with
a second layer of silk, and the process is repeated until the requisite
thickness is attained.
The nests are exceedingly difficult to detect, as the spiders take the
precaution of attaching leaves, moss, or small twigs to the outer surface of
the doors. This does not appear to be the result of intelligence, but a mere
instinctive habit; for if a door be removed and the surrounding earth
denuded of moss, the spider will render the new door conspicuous by
bringing moss from a distance, and thus making a green spot in the bare
patch of earth.[278]
The cork doors fit with great exactness, and there is always to be found
on their under surface a notch by which they are held down by the fore-legs
of nest, and often display great ingenuity in building them. Perhaps none
are more curious than those of the burrowing Aviculariidae, a family which
includes the interesting “Trap-door Spiders.” They are nocturnal in their
habits, about which, consequently, little is known, but their nests have been
carefully studied, especially by Moggridge, who found them in considerable
abundance in various districts of the Riviera.
The jaws of these spiders are especially adapted for digging, and with
them a hole is excavated in the ground to the depth of several inches, and
wide enough to allow the animal to turn. This is carefully lined with silk
which the spider throws against the sides from its long and upturned
posterior spinnerets. But the chef d’œuvre of the whole structure is a lid or
door which protects the entrance to the tube. There are two types of door
which find favour with different species—the wafer and the cork type, as
Moggridge has named them. The former consists of a thin circular or oval
sheet of silk which flaps down loosely over the tube-entrance, with which it
is connected by a hinge-like attachment. A trap-door of the cork type is a
more complicated structure, being of considerable thickness and having a
bevelled edge, so that it fits into the tube like a plug. Like the wafer door, it
possesses a silken hinge.
To form the wafer door, the spider covers the entrance to the tube with a
closely-woven layer of silk, which it afterwards bites away at the edge,
except at the point where the hinge is to be. Doors of the cork type consist
of alternate layers of silk and earth. After weaving a covering of silk, the
creature brings earth in its jaws and lays it on the top, binding it down with
a second layer of silk, and the process is repeated until the requisite
thickness is attained.
The nests are exceedingly difficult to detect, as the spiders take the
precaution of attaching leaves, moss, or small twigs to the outer surface of
the doors. This does not appear to be the result of intelligence, but a mere
instinctive habit; for if a door be removed and the surrounding earth
denuded of moss, the spider will render the new door conspicuous by
bringing moss from a distance, and thus making a green spot in the bare
patch of earth.[278]
The cork doors fit with great exactness, and there is always to be found
on their under surface a notch by which they are held down by the fore-legs
Page 400
of the spider against any attempt to open them from without.
Many nests with trap-doors of the wafer type are found to have a second
and more solid door within the tube. This serves to shut off the lower part of
the nest as a still more secure retreat. This second door opens downwards,
and the Spider, getting beneath it, is effectually shielded from an enemy
which may have mastered the secret of the outer barrier. The nests of some
species present still further complications in the way of lateral branches
from the main tube. In one case (Nemesia congener) the burrow becomes
Y-shaped, and the second door hangs at the fork of the Y in such a manner
as to connect the bottom chamber either with the entrance or with the
branch, which does not reach the surface, but ends blindly.
Trap-door Spiders are greatly attached to their tubes, which they enlarge
and repair at need. They begin burrowing very early in life, and their tiny
tubes resemble in all respects those of their parents. Their habits are
nocturnal, and little is known of them; an observation, however, on a
species inhabiting the island of Tinos in the Grecian Archipelago (Cteniza
ariana), by Erber,[279] must not be omitted. This spider leaves its tube at
night and spins a web near at hand and close to the ground. It carries
captured insects into its tube, and in the morning clears away the net,
adding the material of it, M. Erber believes, to the trap-door.
No true trap-door Spider has as yet been found in this country, but the
allied Atypidae are represented by at least one species, Atypus affinis, which
has been discovered in colonies in some localities in the south of England,
notably near Ventnor in the Isle of Wight, and on Bloxworth Heath in
Dorsetshire. This spider, like its continental cousins, excavates a hole in the
earth, generally near the edge of a heathery bank, and lines it with a tube of
silk of such firm texture that it may be removed intact from the earth in
which it is embedded. The silken tube projects some two inches above the
ground, either erect among the roots of the heather, or lying loosely upon
the surface. Its extremity is always found to be closed, whether from its
own elasticity or by the deliberate act of the proprietor is uncertain, and it
seems probable that the animal spends almost the whole of its existence in
the tube. Simon believes that it feeds almost entirely upon earth-worms
which burrow into its vicinity, and which it, therefore, need not leave its
nest to catch; but the remains of beetles and earwigs have been found in the
tubes at Ventnor.
Many nests with trap-doors of the wafer type are found to have a second
and more solid door within the tube. This serves to shut off the lower part of
the nest as a still more secure retreat. This second door opens downwards,
and the Spider, getting beneath it, is effectually shielded from an enemy
which may have mastered the secret of the outer barrier. The nests of some
species present still further complications in the way of lateral branches
from the main tube. In one case (Nemesia congener) the burrow becomes
Y-shaped, and the second door hangs at the fork of the Y in such a manner
as to connect the bottom chamber either with the entrance or with the
branch, which does not reach the surface, but ends blindly.
Trap-door Spiders are greatly attached to their tubes, which they enlarge
and repair at need. They begin burrowing very early in life, and their tiny
tubes resemble in all respects those of their parents. Their habits are
nocturnal, and little is known of them; an observation, however, on a
species inhabiting the island of Tinos in the Grecian Archipelago (Cteniza
ariana), by Erber,[279] must not be omitted. This spider leaves its tube at
night and spins a web near at hand and close to the ground. It carries
captured insects into its tube, and in the morning clears away the net,
adding the material of it, M. Erber believes, to the trap-door.
No true trap-door Spider has as yet been found in this country, but the
allied Atypidae are represented by at least one species, Atypus affinis, which
has been discovered in colonies in some localities in the south of England,
notably near Ventnor in the Isle of Wight, and on Bloxworth Heath in
Dorsetshire. This spider, like its continental cousins, excavates a hole in the
earth, generally near the edge of a heathery bank, and lines it with a tube of
silk of such firm texture that it may be removed intact from the earth in
which it is embedded. The silken tube projects some two inches above the
ground, either erect among the roots of the heather, or lying loosely upon
the surface. Its extremity is always found to be closed, whether from its
own elasticity or by the deliberate act of the proprietor is uncertain, and it
seems probable that the animal spends almost the whole of its existence in
the tube. Simon believes that it feeds almost entirely upon earth-worms
which burrow into its vicinity, and which it, therefore, need not leave its
nest to catch; but the remains of beetles and earwigs have been found in the
tubes at Ventnor.
Page 401
This description of nest seems
common to all species of the genus
Atypus. The American “Purse-web
Spider,” A. abboti, burrows at the
foot of a tree, against the trunk of
which it rears the projecting portion
of its silken tube. At the bottom of
the nest the cavity is enlarged, and
blind processes project in different
directions.
Another burrowing spider,
Cyrtauchenius elongatus, surmounts
its silk-lined burrow by a funnel-
shaped structure of pure white silk,
about three inches in height and two
or three inches in width. There is no
attempt at concealment, and the
white funnels are conspicuous among
the thin grass, presenting the
appearance of fungi. Fig. 194.—Funnel of Cyrtauchenius elongatus.
(After M‘Cook.)
The burrowing habit is also
common to the Wolf-spiders or
Lycosidae, but beyond a very slight lining of silk there is usually little
spinning work about their nests. Occasionally there is a certain amount of
superstructure in the shape of a silken funnel (Lycosa tigrina, M‘Cook), or
of an agglomeration of twigs and pebbles, as in the case of the “Turret-
spider” (Lycosa arenicola, Scudder).
A colony of our handsome species, Lycosa picta, is an interesting sight to
watch. Their favourite habitat is a sandy soil, variegated with many-
coloured patches of moss and lichen, among which their own markings are
calculated to render them inconspicuous. The observer, by lying perfectly
still, may see them silently stealing forth from their burrows in the bright
sunshine, and hunting diligently in the neighbourhood, ready to dart back
on the faintest alarm, or if the sun should be temporarily obscured by a
passing cloud. So closely do they resemble their surroundings, that it is only
when in motion that they can readily be detected. It is very curious to see
common to all species of the genus
Atypus. The American “Purse-web
Spider,” A. abboti, burrows at the
foot of a tree, against the trunk of
which it rears the projecting portion
of its silken tube. At the bottom of
the nest the cavity is enlarged, and
blind processes project in different
directions.
Another burrowing spider,
Cyrtauchenius elongatus, surmounts
its silk-lined burrow by a funnel-
shaped structure of pure white silk,
about three inches in height and two
or three inches in width. There is no
attempt at concealment, and the
white funnels are conspicuous among
the thin grass, presenting the
appearance of fungi. Fig. 194.—Funnel of Cyrtauchenius elongatus.
(After M‘Cook.)
The burrowing habit is also
common to the Wolf-spiders or
Lycosidae, but beyond a very slight lining of silk there is usually little
spinning work about their nests. Occasionally there is a certain amount of
superstructure in the shape of a silken funnel (Lycosa tigrina, M‘Cook), or
of an agglomeration of twigs and pebbles, as in the case of the “Turret-
spider” (Lycosa arenicola, Scudder).
A colony of our handsome species, Lycosa picta, is an interesting sight to
watch. Their favourite habitat is a sandy soil, variegated with many-
coloured patches of moss and lichen, among which their own markings are
calculated to render them inconspicuous. The observer, by lying perfectly
still, may see them silently stealing forth from their burrows in the bright
sunshine, and hunting diligently in the neighbourhood, ready to dart back
on the faintest alarm, or if the sun should be temporarily obscured by a
passing cloud. So closely do they resemble their surroundings, that it is only
when in motion that they can readily be detected. It is very curious to see
Page 402
them popping out their heads to
ascertain that the coast is clear before
venturing forth, and the utter silence
of their operations adds to the
eeriness of the effect. The tubes of
these spiders, though without a trap-
door, and only slightly lined with
silk, are Y-shaped like those of
Fig. 195.—Turret of Lycosa carolinensis. (After
Nemesia congener, the main tunnel
M‘Cook.) giving off a blind branch about half-
way down.
The nest of the Water-spider, Argyroneta aquatica, must not be passed
over without mention. This spider, though strictly an air-breathing animal,
spends almost the whole of its existence beneath the water. That it can live
in such a medium is due to the fact that the long hairs which clothe its
abdomen retain a bubble of air as it swims beneath the water, so that it
carries with it its own atmosphere. The air-bubble which invests its body
gives it a strong resemblance to a globule of quicksilver, and renders it a
pretty object in an aquarium as it swims about in search of food or in
prosecution of its spinning operations.
Of these the most interesting is the building of its nest. Working upon a
water plant some distance below the surface, it forms a silken dome of
closely-woven threads, which it next proceeds to fill with air. To do this the
spider rises in the water, raises its abdomen above the surface, and jerks it
down again quickly, so as to carry with it a bubble of air which it helps to
retain with its hind legs. With this it swims back to its tent, into which it
allows the imprisoned air-globules to escape. By degrees the dome or bell is
filled, and the creature has a dry and snug retreat beneath the water. In this
it passes the winter in a torpid condition. The young of this species appear
to be fond of utilising the empty shells of water-snails, which they float by
filling them with air, and thus save themselves the trouble of nest-
construction.
Cocoon.—The last important spinning operation which remains to be
described is the building of the so-called cocoon. This must be
distinguished from the cocoon of insects, which is a protective covering of
silk within which the larva assumes the pupa form. In the case of the Spider,
ascertain that the coast is clear before
venturing forth, and the utter silence
of their operations adds to the
eeriness of the effect. The tubes of
these spiders, though without a trap-
door, and only slightly lined with
silk, are Y-shaped like those of
Fig. 195.—Turret of Lycosa carolinensis. (After
Nemesia congener, the main tunnel
M‘Cook.) giving off a blind branch about half-
way down.
The nest of the Water-spider, Argyroneta aquatica, must not be passed
over without mention. This spider, though strictly an air-breathing animal,
spends almost the whole of its existence beneath the water. That it can live
in such a medium is due to the fact that the long hairs which clothe its
abdomen retain a bubble of air as it swims beneath the water, so that it
carries with it its own atmosphere. The air-bubble which invests its body
gives it a strong resemblance to a globule of quicksilver, and renders it a
pretty object in an aquarium as it swims about in search of food or in
prosecution of its spinning operations.
Of these the most interesting is the building of its nest. Working upon a
water plant some distance below the surface, it forms a silken dome of
closely-woven threads, which it next proceeds to fill with air. To do this the
spider rises in the water, raises its abdomen above the surface, and jerks it
down again quickly, so as to carry with it a bubble of air which it helps to
retain with its hind legs. With this it swims back to its tent, into which it
allows the imprisoned air-globules to escape. By degrees the dome or bell is
filled, and the creature has a dry and snug retreat beneath the water. In this
it passes the winter in a torpid condition. The young of this species appear
to be fond of utilising the empty shells of water-snails, which they float by
filling them with air, and thus save themselves the trouble of nest-
construction.
Cocoon.—The last important spinning operation which remains to be
described is the building of the so-called cocoon. This must be
distinguished from the cocoon of insects, which is a protective covering of
silk within which the larva assumes the pupa form. In the case of the Spider,
Page 403
the term is applied to the structure
which serves to protect and conceal
the eggs. It is often of considerable
complexity, and is highly
characteristic of the particular species
which constructs it.
All egg-bags are commenced in
very much the same way. A small
sheet of silk is woven, and against
this, sometimes upon the upper and
sometimes on the under surface, the
eggs are deposited, and then covered
in with a second silken layer. The
compact silk-covered ball of eggs is
then, in many cases, enclosed in a Fig. 196.—Egg-cocoons. A, Epeira diademata,
small compartment which the spider nat. size. B, Theridion pallens × 4, attached to a
leaf. C, Agroeca brunnea, nat. size, attached to a
builds with infinite care and unfailing weed, and not yet coated with mud. D, Ero
uniformity, after the pattern peculiar furcata × 4, attached to a log.
to its kind. A considerable number of
the Orb-weavers are content with a simple silken case closely investing the
eggs, and by its thickness and the non-conducting quality of the material,
sufficient protection is afforded against inclement weather.
The egg-bag of the large Garden-spider (E. diademata) may be
recognised by its great size and its yellow colour, which is deepened by the
still more yellow tint of the eggs within. Those of Zilla x-notata and of
many other English Epeirids are of similar structure, but of white silk. The
mother generally avails herself of some natural shelter, hiding her cocoon
beneath loose bark, in the crannies of masonry, or under the copings of
walls.
Many species, on the contrary, boldly expose their cocoons in their
snares, sometimes as many as fourteen being constructed in succession and
strung in a chain. The American species Epeira caudata and E. bifurca are
good examples of this habit, stringing a chain of characteristic cocoons
upon the line connecting the retreat with the web.
The sedentary Theridiid spiders usually suspend their cocoons in the
neighbourhood of their irregular snares. The green cocoon of Theridion
which serves to protect and conceal
the eggs. It is often of considerable
complexity, and is highly
characteristic of the particular species
which constructs it.
All egg-bags are commenced in
very much the same way. A small
sheet of silk is woven, and against
this, sometimes upon the upper and
sometimes on the under surface, the
eggs are deposited, and then covered
in with a second silken layer. The
compact silk-covered ball of eggs is
then, in many cases, enclosed in a Fig. 196.—Egg-cocoons. A, Epeira diademata,
small compartment which the spider nat. size. B, Theridion pallens × 4, attached to a
leaf. C, Agroeca brunnea, nat. size, attached to a
builds with infinite care and unfailing weed, and not yet coated with mud. D, Ero
uniformity, after the pattern peculiar furcata × 4, attached to a log.
to its kind. A considerable number of
the Orb-weavers are content with a simple silken case closely investing the
eggs, and by its thickness and the non-conducting quality of the material,
sufficient protection is afforded against inclement weather.
The egg-bag of the large Garden-spider (E. diademata) may be
recognised by its great size and its yellow colour, which is deepened by the
still more yellow tint of the eggs within. Those of Zilla x-notata and of
many other English Epeirids are of similar structure, but of white silk. The
mother generally avails herself of some natural shelter, hiding her cocoon
beneath loose bark, in the crannies of masonry, or under the copings of
walls.
Many species, on the contrary, boldly expose their cocoons in their
snares, sometimes as many as fourteen being constructed in succession and
strung in a chain. The American species Epeira caudata and E. bifurca are
good examples of this habit, stringing a chain of characteristic cocoons
upon the line connecting the retreat with the web.
The sedentary Theridiid spiders usually suspend their cocoons in the
neighbourhood of their irregular snares. The green cocoon of Theridion
Page 404
sisyphium is generally more or less concealed by an accumulation of débris.
The minute species T. pallens constructs a cocoon of peculiar shape on the
under surface of a leaf (Fig. 196, B). It is a conical structure of white silk,
considerably larger than the spider itself, attached at its broad end,[280] and
having several curious lateral projections near the middle.
Among the Lycosidae or “Wolf-spiders” the prevailing habit of the
mother is to carry the egg-bag attached beneath her abdomen upon all her
hunting excursions. It is spheroidal in shape, made up of an upper and a
lower half, with a seam-like junction at the equator, so to speak. The lower
half is first woven, and the eggs are deposited within it. The upper
hemisphere is then spun, and the edges gathered in and finished off, the
seam or suture being always discernible. The bag is now attached by silken
threads to the spinnerets, and bumps merrily over the ground as the animal
hurries along in search of prey. If deprived of it she evinces the greatest
distress, and frequently will not try to escape without it.
Attempts to utilise Spider Silk.—It is long since the web of the House-
spider, taken internally, was considered a specific for the ague, though its
value as a styptic has been recognised in quite recent times. It is, however,
with other uses of Spider silk that we are here concerned.
Spider silk has been extensively used in the micrometer eyepieces of
telescopes where very fine intersecting lines are required. For this purpose
the radial or scaffolding lines of the circular snare were selected, the spiral
being unsuited on account of its row of viscid beads. Professor C. V. Boys
has, however, discovered in his quartz fibres a material better adapted for
this purpose.
Several attempts have been made to weave the silk of Spiders as a
substitute for that of the silk-worm. Web silk is, of course, far too fine to
furnish a durable material, but the cocoons are usually formed of coarser
silk, and it is with them that the experiment has been tried. About the
beginning of the eighteenth century certain stockings and mittens made of
Spider silk from the cocoons of Epeira diademata, by M. Bon of
Languedoc, attracted so much attention that the Academy desired M.
Réaumur to investigate the matter. His report was unfavourable to the
commercial utility of Spider silk. The cocoon threads, though eighteen
times stronger than those of the web, were but one-fifth of the strength of
those obtained from the silk-worm, and the lustre was inferior. A still more
The minute species T. pallens constructs a cocoon of peculiar shape on the
under surface of a leaf (Fig. 196, B). It is a conical structure of white silk,
considerably larger than the spider itself, attached at its broad end,[280] and
having several curious lateral projections near the middle.
Among the Lycosidae or “Wolf-spiders” the prevailing habit of the
mother is to carry the egg-bag attached beneath her abdomen upon all her
hunting excursions. It is spheroidal in shape, made up of an upper and a
lower half, with a seam-like junction at the equator, so to speak. The lower
half is first woven, and the eggs are deposited within it. The upper
hemisphere is then spun, and the edges gathered in and finished off, the
seam or suture being always discernible. The bag is now attached by silken
threads to the spinnerets, and bumps merrily over the ground as the animal
hurries along in search of prey. If deprived of it she evinces the greatest
distress, and frequently will not try to escape without it.
Attempts to utilise Spider Silk.—It is long since the web of the House-
spider, taken internally, was considered a specific for the ague, though its
value as a styptic has been recognised in quite recent times. It is, however,
with other uses of Spider silk that we are here concerned.
Spider silk has been extensively used in the micrometer eyepieces of
telescopes where very fine intersecting lines are required. For this purpose
the radial or scaffolding lines of the circular snare were selected, the spiral
being unsuited on account of its row of viscid beads. Professor C. V. Boys
has, however, discovered in his quartz fibres a material better adapted for
this purpose.
Several attempts have been made to weave the silk of Spiders as a
substitute for that of the silk-worm. Web silk is, of course, far too fine to
furnish a durable material, but the cocoons are usually formed of coarser
silk, and it is with them that the experiment has been tried. About the
beginning of the eighteenth century certain stockings and mittens made of
Spider silk from the cocoons of Epeira diademata, by M. Bon of
Languedoc, attracted so much attention that the Academy desired M.
Réaumur to investigate the matter. His report was unfavourable to the
commercial utility of Spider silk. The cocoon threads, though eighteen
times stronger than those of the web, were but one-fifth of the strength of
those obtained from the silk-worm, and the lustre was inferior. A still more
Page 405
fatal objection, however, was founded upon the cannibalistic habits of the
spider, and the difficulty of furnishing it with acceptable food.
M. Vinson has recorded that some of the spiders of Madagascar,
especially Epeira madagascarensis, are far better adapted than any of our
English species to a commercial use. They furnish silk of a beautiful clear
yellow colour; they are accustomed to live harmoniously together in
families; and the range of climate in which they can thrive is very
considerable. The Creole ladies of this island, under the administration of
General Decaen, wove a magnificent pair of gloves from spider silk, with
their own hands, for presentation to the French Empress.
Poison of Spiders.—All spiders possess poison-glands, which have their
openings on the fangs of the chelicerae. The action of the chelicera in
striking does not express the venom, but the poison-bag itself is covered
with a muscular coat by which the contained fluid is expelled. It is highly
probable, therefore, that the venom is under the control of the animal’s will,
and is economised when the simple wound is sufficient for the purpose—a
supposition which may partially explain the very divergent opinions held
with regard to the effect of the spider’s bite. The reputation of the
“Tarantula” Spider is well known, but what particular species, if any, was
intended by the name is quite uncertain. The name is derived from the town
Tarentum, and was certainly applied to a Lycosid spider. Probably the
common south European species, Lycosa narbonensis, has as good a claim
to the honour as any. The confusion has been increased by extending the
name to spiders of quite a different family. Eurypelma hentzii, one of the
Aviculariidae, is commonly known as the Tarantula in America.
The superstition of the tarantula dance is well known. The bite of the
spider was supposed to induce a species of madness which found its
expression—and its cure—in frantic and extravagant contortions of the
body. If the dance was not sufficiently frenzied, death ensued. In the case of
survivors, the symptoms were said to recur on the anniversary of the bite.
Particular descriptions of music were supposed to incite the patient to the
excessive exertion necessary for his relief; hence the “Tarantella.”
In the Middle Ages epidemics of “tarantism” were of frequent
occurrence, and spread with alarming rapidity. They were seizures of an
hysterical character, analogous to the ancient Bacchic dances, and quite
unconnected with the venom of the spider from which they took their name.
spider, and the difficulty of furnishing it with acceptable food.
M. Vinson has recorded that some of the spiders of Madagascar,
especially Epeira madagascarensis, are far better adapted than any of our
English species to a commercial use. They furnish silk of a beautiful clear
yellow colour; they are accustomed to live harmoniously together in
families; and the range of climate in which they can thrive is very
considerable. The Creole ladies of this island, under the administration of
General Decaen, wove a magnificent pair of gloves from spider silk, with
their own hands, for presentation to the French Empress.
Poison of Spiders.—All spiders possess poison-glands, which have their
openings on the fangs of the chelicerae. The action of the chelicera in
striking does not express the venom, but the poison-bag itself is covered
with a muscular coat by which the contained fluid is expelled. It is highly
probable, therefore, that the venom is under the control of the animal’s will,
and is economised when the simple wound is sufficient for the purpose—a
supposition which may partially explain the very divergent opinions held
with regard to the effect of the spider’s bite. The reputation of the
“Tarantula” Spider is well known, but what particular species, if any, was
intended by the name is quite uncertain. The name is derived from the town
Tarentum, and was certainly applied to a Lycosid spider. Probably the
common south European species, Lycosa narbonensis, has as good a claim
to the honour as any. The confusion has been increased by extending the
name to spiders of quite a different family. Eurypelma hentzii, one of the
Aviculariidae, is commonly known as the Tarantula in America.
The superstition of the tarantula dance is well known. The bite of the
spider was supposed to induce a species of madness which found its
expression—and its cure—in frantic and extravagant contortions of the
body. If the dance was not sufficiently frenzied, death ensued. In the case of
survivors, the symptoms were said to recur on the anniversary of the bite.
Particular descriptions of music were supposed to incite the patient to the
excessive exertion necessary for his relief; hence the “Tarantella.”
In the Middle Ages epidemics of “tarantism” were of frequent
occurrence, and spread with alarming rapidity. They were seizures of an
hysterical character, analogous to the ancient Bacchic dances, and quite
unconnected with the venom of the spider from which they took their name.
Page 406
The condition of exaltation and frenzy was contagious, and would run
through whole districts, with its subsequent relapse to a state of utter
prostration and exhaustion. The evil reputation of the Tarantula appears to
have exceedingly little basis in fact.
Baglivi relates how the country people capture the Tarantula by imitating
the buzzing of an insect at the mouth of its hole. “Quo audito, ferox exit
Tarentula ut muscas, quorum murmur esse putat, captet; captatur tamen a
rustico insidiatore.”
Fabre[281] acted the part of the “insidious rustic” with slight success; but
by other stratagems he enticed the creatures from their holes, and made
some interesting observations upon the effects of their bite. He found that
bees and wasps were instantaneously killed by them. This immediately fatal
effect he found to be due to the fact that the spider invariably struck the
insect in a particular spot, at the junction of the head with the thorax. Bees
must often wander into Tarantula’s holes, and a prolonged contest, though it
might end in the death of the insect, would be certain also to result fatally
for the spider. It has, therefore, acquired the habit of striking its foe in the
one spot which causes instant death. When Fabre presented a bee to a
Tarantula in such a manner that it was bitten in some other region, the insect
survived several hours.
A young sparrow, just ready to leave the nest, was bitten in the leg. The
wound became inflamed, and the limb appeared to be paralysed, but the
victim did not at first suffer in general health, and fed heartily; death
resulted, however, on the third day. A mole died in thirty-six hours after the
bite.
From these experiments, Fabre came to the conclusion that the venom of
the Tarantula was at all events too powerful to be entirely negligible by
man.
Trifling causes may have a fatal effect upon a man in ill health, and it is
quite possible that death has sometimes resulted from the Tarantula’s bite.
Its effect upon a healthy subject, however, is certainly not serious.
Goldsmith, in his Animated Nature, entirely discredits the current stories
about this animal, saying that the Italian peasants impose upon credulous
travellers by allowing themselves, for money, to be bitten by the Tarantula,
and then feigning all the symptoms which are traditionally supposed to
ensue.
through whole districts, with its subsequent relapse to a state of utter
prostration and exhaustion. The evil reputation of the Tarantula appears to
have exceedingly little basis in fact.
Baglivi relates how the country people capture the Tarantula by imitating
the buzzing of an insect at the mouth of its hole. “Quo audito, ferox exit
Tarentula ut muscas, quorum murmur esse putat, captet; captatur tamen a
rustico insidiatore.”
Fabre[281] acted the part of the “insidious rustic” with slight success; but
by other stratagems he enticed the creatures from their holes, and made
some interesting observations upon the effects of their bite. He found that
bees and wasps were instantaneously killed by them. This immediately fatal
effect he found to be due to the fact that the spider invariably struck the
insect in a particular spot, at the junction of the head with the thorax. Bees
must often wander into Tarantula’s holes, and a prolonged contest, though it
might end in the death of the insect, would be certain also to result fatally
for the spider. It has, therefore, acquired the habit of striking its foe in the
one spot which causes instant death. When Fabre presented a bee to a
Tarantula in such a manner that it was bitten in some other region, the insect
survived several hours.
A young sparrow, just ready to leave the nest, was bitten in the leg. The
wound became inflamed, and the limb appeared to be paralysed, but the
victim did not at first suffer in general health, and fed heartily; death
resulted, however, on the third day. A mole died in thirty-six hours after the
bite.
From these experiments, Fabre came to the conclusion that the venom of
the Tarantula was at all events too powerful to be entirely negligible by
man.
Trifling causes may have a fatal effect upon a man in ill health, and it is
quite possible that death has sometimes resulted from the Tarantula’s bite.
Its effect upon a healthy subject, however, is certainly not serious.
Goldsmith, in his Animated Nature, entirely discredits the current stories
about this animal, saying that the Italian peasants impose upon credulous
travellers by allowing themselves, for money, to be bitten by the Tarantula,
and then feigning all the symptoms which are traditionally supposed to
ensue.
Page 407
There is a genus of the
Theridiidae, by name Latrodectus,
whose poisonous reputation almost
rivals that of the Tarantula. It is
remarkable, moreover, that it is
regarded as particularly dangerous in
such widely separated portions of the
world as Madagascar, New Zealand,
Algeria, the West Indies, and North
America. These spiders, strangely
enough, are by no means particularly
large or formidable in appearance.
There are two species in
Madagascar, known to the natives by
the names of Mena-vodi and
Vancoho. Vinson[282] describes the
terror which is locally inspired by the
first-named species, whose bite is
believed to be fatal unless measures
are promptly taken to counteract the
poison. They sometimes cauterise the
wound, but the usual treatment
consists in inducing profuse
perspiration—a method of cure
which recalls the Tarantula dance of
Southern Europe. Flacourt[283]
Fig. 197.—Latrodectus mactans, ♂, natural size.
mentions the Vancoho as the most
dangerous animal of Madagascar,
and more formidable than the
scorpion. He relates cases among his own negroes where the bite was
followed by a condition of syncope which lasted two days.
A New Zealand species is known by the natives as the Katipo. It is of
about the size of a pea, and almost black in colour. Mr. Meek of Waiwera
gives a most circumstantial account of the effect of its bite upon his son.[284]
During the four days which followed the bite he suffered excruciating pain,
which spread from his leg to the spine, arms, and chest, and he lost twelve
Theridiidae, by name Latrodectus,
whose poisonous reputation almost
rivals that of the Tarantula. It is
remarkable, moreover, that it is
regarded as particularly dangerous in
such widely separated portions of the
world as Madagascar, New Zealand,
Algeria, the West Indies, and North
America. These spiders, strangely
enough, are by no means particularly
large or formidable in appearance.
There are two species in
Madagascar, known to the natives by
the names of Mena-vodi and
Vancoho. Vinson[282] describes the
terror which is locally inspired by the
first-named species, whose bite is
believed to be fatal unless measures
are promptly taken to counteract the
poison. They sometimes cauterise the
wound, but the usual treatment
consists in inducing profuse
perspiration—a method of cure
which recalls the Tarantula dance of
Southern Europe. Flacourt[283]
Fig. 197.—Latrodectus mactans, ♂, natural size.
mentions the Vancoho as the most
dangerous animal of Madagascar,
and more formidable than the
scorpion. He relates cases among his own negroes where the bite was
followed by a condition of syncope which lasted two days.
A New Zealand species is known by the natives as the Katipo. It is of
about the size of a pea, and almost black in colour. Mr. Meek of Waiwera
gives a most circumstantial account of the effect of its bite upon his son.[284]
During the four days which followed the bite he suffered excruciating pain,
which spread from his leg to the spine, arms, and chest, and he lost twelve
Page 408
pounds in weight. Relief was obtained by frequent doses of brandy and the
use of a liniment.
The natives of New Zealand have a great horror of this spider, but hold
the curious belief that its death will ensure the cure of any one it may have
bitten. If unable to find it, they will burn the house down rather than allow it
to escape. Their dread, however, is confined to a variety which lives among
the sedge of the sea-beach, and they carefully avoid sleeping in such places.
Two of the best authenticated cases of serious results ensuing from the
bite of a spider of this genus come from North Carolina.[285]
A farm labourer in the employ of Mr. John Dick of Greensborough was
bitten by Latrodectus mactans about half-past eight in the morning, and
died between ten and eleven o’clock at night. Small pimples were raised in
the neighbourhood of the bite, but no puncture was discernible. Intermittent
pains and spasms ended in a comatose condition from which he did not
rally. The man appeared previously to be in perfect health.
Another man on Mr. Dick’s farm was bitten by the same species of
spider. He resumed work, but a spasm of pain caused him to mount his
horse and endeavour to ride home, but he fell off, and lay in a state of
unconsciousness. He was found in this condition by a fellow-workman, and
taken home. Large quantities of whisky were administered without any
intoxicating effect, and this afforded some relief from the constantly-
recurring spasms. The paroxysms continued for three weeks, and two
months elapsed before he was able to resume work. On the ankle where he
was bitten pimples appeared as in the previous case, and these broke out
again, long after the occurrence, whenever he became overheated in his
work.
These accounts are sufficiently circumstantial and well authenticated, but
the fact of the actual bite depends upon the statement of the victims alone,
and they may possibly have mistaken the cause of their trouble.
Southern Europe possesses a congener of this spider in Latrodectus 13–
guttatus, the well-known “Malmignatte,” which is also considered
extremely poisonous. The Royal Academy of Medicine and Surgery at
Barcelona appointed Dr. Graells, in 1833, to inquire into the effects of the
bite of this spider, cases of which had become exceedingly frequent. He
found a curious correspondence between the frequency of these cases and
the advent of migratory locusts, which the spider successfully attacked. In
use of a liniment.
The natives of New Zealand have a great horror of this spider, but hold
the curious belief that its death will ensure the cure of any one it may have
bitten. If unable to find it, they will burn the house down rather than allow it
to escape. Their dread, however, is confined to a variety which lives among
the sedge of the sea-beach, and they carefully avoid sleeping in such places.
Two of the best authenticated cases of serious results ensuing from the
bite of a spider of this genus come from North Carolina.[285]
A farm labourer in the employ of Mr. John Dick of Greensborough was
bitten by Latrodectus mactans about half-past eight in the morning, and
died between ten and eleven o’clock at night. Small pimples were raised in
the neighbourhood of the bite, but no puncture was discernible. Intermittent
pains and spasms ended in a comatose condition from which he did not
rally. The man appeared previously to be in perfect health.
Another man on Mr. Dick’s farm was bitten by the same species of
spider. He resumed work, but a spasm of pain caused him to mount his
horse and endeavour to ride home, but he fell off, and lay in a state of
unconsciousness. He was found in this condition by a fellow-workman, and
taken home. Large quantities of whisky were administered without any
intoxicating effect, and this afforded some relief from the constantly-
recurring spasms. The paroxysms continued for three weeks, and two
months elapsed before he was able to resume work. On the ankle where he
was bitten pimples appeared as in the previous case, and these broke out
again, long after the occurrence, whenever he became overheated in his
work.
These accounts are sufficiently circumstantial and well authenticated, but
the fact of the actual bite depends upon the statement of the victims alone,
and they may possibly have mistaken the cause of their trouble.
Southern Europe possesses a congener of this spider in Latrodectus 13–
guttatus, the well-known “Malmignatte,” which is also considered
extremely poisonous. The Royal Academy of Medicine and Surgery at
Barcelona appointed Dr. Graells, in 1833, to inquire into the effects of the
bite of this spider, cases of which had become exceedingly frequent. He
found a curious correspondence between the frequency of these cases and
the advent of migratory locusts, which the spider successfully attacked. In
Page 409
his report[286] he details the symptoms in certain unquestionably authentic
cases. There was a double puncture, surrounded by red circles, the region of
the wound afterwards swelling greatly. The pain and swelling extended over
the whole limb, and often to the body, and convulsions occurred, followed
by great prostration and collapse. All the patients eventually recovered,
their cure being heralded by profuse perspiration.
It must be mentioned, however, that the eminent Arachnologist M. Lucas
states that he has several times allowed himself to be bitten by this identical
spider without any ill effects.
The testimony is thus conflicting in this case also. It is impossible,
however, to believe that there is no basis in fact for the poisonous reputation
of a comparatively insignificant-looking spider in so many widely separated
parts of the world, supported as it is by certain well-substantiated cases. The
variable effects of its bite may find a partial explanation in a variation in the
strength of its venom at different seasons, and it has already been
mentioned that the injection of poison into its victim is a voluntary act, and
does not necessarily accompany its bite. Among the species regarded as
especially venomous must be mentioned Phidippus morsitans, one of the
larger of the Attidae.
It is exceedingly likely that the bite of the large tropical Aviculariidae is
really formidable. They appear, however, more anxious to escape than to
show fight, and we possess little reliable information with regard to them.
Doleschall shut up small birds with two West Indian species, and death
followed their bite almost immediately. Ten days’ starvation appeared to
weaken the venom, for a bird bitten by a spider fasting for that period
recovered after an indisposition of six hours.
Most Arachnologists have recorded experiments with regard to the
venom of the commoner European species, with equally conflicting results.
Blackwall came to the conclusion that loss of blood, and not poison, caused
the death of spider-bitten insects. He could not himself distinguish a spider
bite from the prick of a needle inflicted upon his hand at the same time.
Bees, wasps, and grasshoppers survived the bite about as long as other
insects of the same species outlived a needle-prick in the same part of the
body. Walckenaer’s experience was of the same nature. Bertkau, however,
when bitten in the hand, felt clear indications of an irritant poison in the
wound. The hairs of some of the large hairy species of the Aviculariidae
cases. There was a double puncture, surrounded by red circles, the region of
the wound afterwards swelling greatly. The pain and swelling extended over
the whole limb, and often to the body, and convulsions occurred, followed
by great prostration and collapse. All the patients eventually recovered,
their cure being heralded by profuse perspiration.
It must be mentioned, however, that the eminent Arachnologist M. Lucas
states that he has several times allowed himself to be bitten by this identical
spider without any ill effects.
The testimony is thus conflicting in this case also. It is impossible,
however, to believe that there is no basis in fact for the poisonous reputation
of a comparatively insignificant-looking spider in so many widely separated
parts of the world, supported as it is by certain well-substantiated cases. The
variable effects of its bite may find a partial explanation in a variation in the
strength of its venom at different seasons, and it has already been
mentioned that the injection of poison into its victim is a voluntary act, and
does not necessarily accompany its bite. Among the species regarded as
especially venomous must be mentioned Phidippus morsitans, one of the
larger of the Attidae.
It is exceedingly likely that the bite of the large tropical Aviculariidae is
really formidable. They appear, however, more anxious to escape than to
show fight, and we possess little reliable information with regard to them.
Doleschall shut up small birds with two West Indian species, and death
followed their bite almost immediately. Ten days’ starvation appeared to
weaken the venom, for a bird bitten by a spider fasting for that period
recovered after an indisposition of six hours.
Most Arachnologists have recorded experiments with regard to the
venom of the commoner European species, with equally conflicting results.
Blackwall came to the conclusion that loss of blood, and not poison, caused
the death of spider-bitten insects. He could not himself distinguish a spider
bite from the prick of a needle inflicted upon his hand at the same time.
Bees, wasps, and grasshoppers survived the bite about as long as other
insects of the same species outlived a needle-prick in the same part of the
body. Walckenaer’s experience was of the same nature. Bertkau, however,
when bitten in the hand, felt clear indications of an irritant poison in the
wound. The hairs of some of the large hairy species of the Aviculariidae
Page 410
possess poisonous properties. They are readily parted with, and when the
animal is touched by the hand considerable irritation is set up.
Fertility of Spiders.—Spiders vary greatly in the average number of
eggs laid by different species, and within the limits of each species there is
a very considerable variation in fertility. As a rule it appears that the large
and vigorous spiders are more prolific than the smaller and weaker
members of the order. Were all the facts before us, however, we should no
doubt find that the number of eggs laid bore a direct proportion, not to the
size of the species, but to the dangers to which the young of that species are
exposed. Where the total numerical strength of a species is fairly stationary,
such a proportion must of course exist. Some species, no doubt, are tending
to become extinct, while others are increasing in numerical importance. As
a general rule, however, it is safe to infer that, if a species is especially
prolific, special dangers attend the rearing of the young. The largest of
North American Epeirids, Argiope cophinaria,[287] constructs a cocoon
containing, on an average, 1150 eggs. As many as 2200 have been counted
in exceptional cases. Even this number is exceeded in the case of some of
the great Aviculariidae. Theraphosa leblondi deposits as many as 3000
eggs. The large European Epeirids, E. quadrata and E. diademata, lay about
600 eggs, those of Lycosa narbonensis reaching about the same number.
Those American spiders which have been described as stringing up a series
of cocoons in their webs usually attain about the same aggregate, the eggs
being less numerous in each cocoon.
These are examples of fairly large and fertile spiders. In the case of other
species the number of eggs laid is exceedingly small. Ero furcata makes a
single cocoon containing six eggs. Synageles picata, an ant-like Attid, lays
only three. Oonops pulcher constructs several cocoons, but each contains
only two eggs. The eggs of Cave-spiders, and such as live in dark and damp
places, are generally few in number. Anthrobia mammouthia, for example,
an inhabitant of the great American caves, deposits only from two to five
eggs.
Our knowledge of the special perils which beset particular species is so
incomplete that we are often at a loss for the reason of this great inequality
in fertility. For instance, how does Synageles picata maintain its numerical
strength by laying only three eggs, when, as M‘Cook points out, its
resemblance to the ant, though advantageous to the adult spider, affords no
animal is touched by the hand considerable irritation is set up.
Fertility of Spiders.—Spiders vary greatly in the average number of
eggs laid by different species, and within the limits of each species there is
a very considerable variation in fertility. As a rule it appears that the large
and vigorous spiders are more prolific than the smaller and weaker
members of the order. Were all the facts before us, however, we should no
doubt find that the number of eggs laid bore a direct proportion, not to the
size of the species, but to the dangers to which the young of that species are
exposed. Where the total numerical strength of a species is fairly stationary,
such a proportion must of course exist. Some species, no doubt, are tending
to become extinct, while others are increasing in numerical importance. As
a general rule, however, it is safe to infer that, if a species is especially
prolific, special dangers attend the rearing of the young. The largest of
North American Epeirids, Argiope cophinaria,[287] constructs a cocoon
containing, on an average, 1150 eggs. As many as 2200 have been counted
in exceptional cases. Even this number is exceeded in the case of some of
the great Aviculariidae. Theraphosa leblondi deposits as many as 3000
eggs. The large European Epeirids, E. quadrata and E. diademata, lay about
600 eggs, those of Lycosa narbonensis reaching about the same number.
Those American spiders which have been described as stringing up a series
of cocoons in their webs usually attain about the same aggregate, the eggs
being less numerous in each cocoon.
These are examples of fairly large and fertile spiders. In the case of other
species the number of eggs laid is exceedingly small. Ero furcata makes a
single cocoon containing six eggs. Synageles picata, an ant-like Attid, lays
only three. Oonops pulcher constructs several cocoons, but each contains
only two eggs. The eggs of Cave-spiders, and such as live in dark and damp
places, are generally few in number. Anthrobia mammouthia, for example,
an inhabitant of the great American caves, deposits only from two to five
eggs.
Our knowledge of the special perils which beset particular species is so
incomplete that we are often at a loss for the reason of this great inequality
in fertility. For instance, how does Synageles picata maintain its numerical
strength by laying only three eggs, when, as M‘Cook points out, its
resemblance to the ant, though advantageous to the adult spider, affords no
Page 411
protection to the egg? Our knowledge must be greatly extended before we
are able to account for particular cases. Many influences hostile to spiders
as a group are, however, well known, and we may here enumerate them.
Natural Enemies.—The precautions taken by the mother in constructing
the cocoon render the inclemency of the weather very much less destructive
to the eggs than to the newly-hatched young. Nevertheless, among spiders
inhabiting swampy regions great havoc is wrought by the occasional
wholesale swamping of the cocoons by floods. Professor Wilder considers
the great fertility of Nephila plumipes necessary to counterbalance the
immense destruction worked by the heavy rains upon their cocoons, which
are washed in great numbers from the trees, to the leaves of which they are
attached. But such exposed situations are avoided by many species, and
their eggs, enclosed in their silken envelope, are well protected against the
severities of the weather.
A more universal enemy to the egg is found in Ichneumon flies. On
examining the cocoons of almost any species of spider, a large proportion
are almost certain to be found to contain Ichneumon larvae. Mr. F. Smith, in
the Transactions of the Entomological Society for 1860, describes two
species, Hemeteles fasciatus and H. formosus, which are parasitic on the
eggs of Agelena brunnea. They are figured in Mr. Blackwall’s book on
British Spiders. Pezomachus gracilis attacks the cocoons of many kinds of
American spiders, appearing to have no special preference for any
particular species, while Acoloides saitidis seems to pay special attention to
the eggs of certain of the Jumping-spiders, and particularly of Saitis pulex.
The Ichneumons which thus regard the Spider’s eggs as convenient food
for their own larvae are probably very numerous. Nor are they themselves
always free from parasites. Occasionally the larvae of minute
Hymenopterous insects are found to be parasitic upon the eggs of an
Ichneumon which have been laid in a Spider’s cocoon.
It sometimes happens that the development of the young spiders has so
far advanced at the time of the Ichneumon’s intrusion that the latter’s
intention is frustrated, and its offspring, instead of devouring, are
themselves devoured. Again, some few of the eggs in an infested cocoon
occasionally escape the general destruction and reach the adult condition,
but there can be no doubt that Ichneumons are largely instrumental in
keeping down the numbers of most species of spiders. The perils which
are able to account for particular cases. Many influences hostile to spiders
as a group are, however, well known, and we may here enumerate them.
Natural Enemies.—The precautions taken by the mother in constructing
the cocoon render the inclemency of the weather very much less destructive
to the eggs than to the newly-hatched young. Nevertheless, among spiders
inhabiting swampy regions great havoc is wrought by the occasional
wholesale swamping of the cocoons by floods. Professor Wilder considers
the great fertility of Nephila plumipes necessary to counterbalance the
immense destruction worked by the heavy rains upon their cocoons, which
are washed in great numbers from the trees, to the leaves of which they are
attached. But such exposed situations are avoided by many species, and
their eggs, enclosed in their silken envelope, are well protected against the
severities of the weather.
A more universal enemy to the egg is found in Ichneumon flies. On
examining the cocoons of almost any species of spider, a large proportion
are almost certain to be found to contain Ichneumon larvae. Mr. F. Smith, in
the Transactions of the Entomological Society for 1860, describes two
species, Hemeteles fasciatus and H. formosus, which are parasitic on the
eggs of Agelena brunnea. They are figured in Mr. Blackwall’s book on
British Spiders. Pezomachus gracilis attacks the cocoons of many kinds of
American spiders, appearing to have no special preference for any
particular species, while Acoloides saitidis seems to pay special attention to
the eggs of certain of the Jumping-spiders, and particularly of Saitis pulex.
The Ichneumons which thus regard the Spider’s eggs as convenient food
for their own larvae are probably very numerous. Nor are they themselves
always free from parasites. Occasionally the larvae of minute
Hymenopterous insects are found to be parasitic upon the eggs of an
Ichneumon which have been laid in a Spider’s cocoon.
It sometimes happens that the development of the young spiders has so
far advanced at the time of the Ichneumon’s intrusion that the latter’s
intention is frustrated, and its offspring, instead of devouring, are
themselves devoured. Again, some few of the eggs in an infested cocoon
occasionally escape the general destruction and reach the adult condition,
but there can be no doubt that Ichneumons are largely instrumental in
keeping down the numbers of most species of spiders. The perils which
Page 412
attend the Spider after leaving the cocoon are no less formidable, and much
more numerous. The whole newly-hatched brood may be destroyed by a
heavy rain-storm. If there is not a sufficient supply of food suitable to their
feeble digestive powers they perish of inanition, or eat one another. This
cannibalistic propensity is a considerable factor in the mortality among
young spiders, and the adult animals frequently prey upon one another.
Argyrodes piraticum, in California, invades the webs of larger spiders of
the family Epeiridae, which it seizes and devours. A. trigonum, common in
the eastern states of North America, has the same habit.[288] Hentz found in
Alabama a spider, which he named Mimetus interfector, of still more
ferocious and piratical habits. Its special quarry is Theridion tepidariorum.
Sometimes the Theridion overcomes the invader, and one case was
observed in which a second Mimetus was devouring a Theridion beside the
dead body of its predecessor, who had come off the worse in the combat.
The eggs of Theridion tepidariorum are also sometimes devoured by this
spider, and a similar propensity has been observed in some English species,
for Staveley[289] states that it is common to see certain spiders of the genus
Clubiona feeding upon the eggs which have been laid by their neighbours.
The larvae of some Hymenopterous insects are parasitic upon Spiders
themselves, and not upon their eggs. Blackwall found this to be the case
with the larvae of Polysphincta carbonaria, an Ichneumon which selects
spiders of the genera Epeira and Linyphia on which to deposit its eggs.[290]
The spider thus infested does not moult, and is soon destroyed by the
parasite which it is unable to dislodge from its back. Menge, in his
Preussische Spinnen, enumerates several cases of parasitism in which the
larva, as soon as it has developed from the egg, enters the spider’s body,
there to continue its growth. Spiders are also subject to the attack of a
parasitic worm, Gordius (cf. vol. ii. p. 173).
Some of the most deadly foes of Spiders are the Solitary Wasps. There
are many species of Pompilus (vol. vi. p. 101), which, having excavated
holes in clay banks, store them with spiders or other creatures which they
have paralysed by their sting. They then deposit an egg in the hole, and
immediately seal up the orifice. This habit is found to characterise the
solitary wasps of all parts of the world. Belt[291] relates the capture of a large
Australian spider by a wasp. While dragging its victim along, it was much
annoyed by the persistent presence of two minute flies, which it repeatedly
more numerous. The whole newly-hatched brood may be destroyed by a
heavy rain-storm. If there is not a sufficient supply of food suitable to their
feeble digestive powers they perish of inanition, or eat one another. This
cannibalistic propensity is a considerable factor in the mortality among
young spiders, and the adult animals frequently prey upon one another.
Argyrodes piraticum, in California, invades the webs of larger spiders of
the family Epeiridae, which it seizes and devours. A. trigonum, common in
the eastern states of North America, has the same habit.[288] Hentz found in
Alabama a spider, which he named Mimetus interfector, of still more
ferocious and piratical habits. Its special quarry is Theridion tepidariorum.
Sometimes the Theridion overcomes the invader, and one case was
observed in which a second Mimetus was devouring a Theridion beside the
dead body of its predecessor, who had come off the worse in the combat.
The eggs of Theridion tepidariorum are also sometimes devoured by this
spider, and a similar propensity has been observed in some English species,
for Staveley[289] states that it is common to see certain spiders of the genus
Clubiona feeding upon the eggs which have been laid by their neighbours.
The larvae of some Hymenopterous insects are parasitic upon Spiders
themselves, and not upon their eggs. Blackwall found this to be the case
with the larvae of Polysphincta carbonaria, an Ichneumon which selects
spiders of the genera Epeira and Linyphia on which to deposit its eggs.[290]
The spider thus infested does not moult, and is soon destroyed by the
parasite which it is unable to dislodge from its back. Menge, in his
Preussische Spinnen, enumerates several cases of parasitism in which the
larva, as soon as it has developed from the egg, enters the spider’s body,
there to continue its growth. Spiders are also subject to the attack of a
parasitic worm, Gordius (cf. vol. ii. p. 173).
Some of the most deadly foes of Spiders are the Solitary Wasps. There
are many species of Pompilus (vol. vi. p. 101), which, having excavated
holes in clay banks, store them with spiders or other creatures which they
have paralysed by their sting. They then deposit an egg in the hole, and
immediately seal up the orifice. This habit is found to characterise the
solitary wasps of all parts of the world. Belt[291] relates the capture of a large
Australian spider by a wasp. While dragging its victim along, it was much
annoyed by the persistent presence of two minute flies, which it repeatedly
Page 413
left its prey to attempt to drive away. When the burrow was reached and the
spider dragged into it, the two flies took up a position on either side of the
entrance, doubtless with the intention of descending and laying their own
eggs as soon as the wasp went away in search of a new victim. Fabre[292]
gives an interesting account of one of the largest European Pompilidae,
Calicurgus annulatus, which he observed dragging a “Tarentula” to a hole
in a wall. Having with great difficulty introduced its burden into the cavity,
the wasp deposited an egg, sealed up the orifice, and flew away. Fabre
opened the cell and removed the spider, which, though completely
paralysed, lived for seven weeks.
The same indefatigable observer describes the method adopted by the
comparatively small Pompilus apicalis in attacking the formidable Wall-
spider, Segestria perfida. The combatants are well matched, and the issue of
the battle would be doubtful if the wasp did not have recourse to stratagem.
Its whole energies are directed towards forcing the spider away from its
web. At home, it is confident and dangerous; when once dislodged, it
appears bewildered and demoralised. The wasp darts suddenly towards the
spider and seizes it by a leg, with a rapid effort to jerk it forth, releasing its
hold before the enemy has had time to retaliate. The spider, however, as
well as being anchored by a thread from its spinnerets, is clinging to its web
with its hind legs, and if the jerk is not sufficiently energetic, it hastily
scrambles back and resumes its defensive position. Before renewing the
attack the wasp gives the spider time to recover from the excitement of the
first onset, seeking, meanwhile, the retreats of other victims. Returning, it
succeeds, by a more skilful effort, in drawing the spider from its retreat and
hurling it to the ground, where, terrified and helpless, it falls an easy prey.
Should the insect bungle in its first attack and become entangled in the web,
it would itself become the victim. Certain wasps thus appear to seek out
particular species of spiders as food for their larvae. Others are less
discriminate in their tastes. Again, some, as in the cases cited above, store
their egg-nest with a single spider, while others collect many for the
purpose.
The American “blue digger wasp” (Chlorion caeruleum) excavates its
nest in the ground, and inserts a single large spider of any species.[293]
Another wasp, of the genus Elis, selects the Wolf-spiders, and especially
Lycosa tigrina, for the use of its larvae, while Priocnemus pomilius shows a
preference for the Crab-spiders, or Thomisidae.
spider dragged into it, the two flies took up a position on either side of the
entrance, doubtless with the intention of descending and laying their own
eggs as soon as the wasp went away in search of a new victim. Fabre[292]
gives an interesting account of one of the largest European Pompilidae,
Calicurgus annulatus, which he observed dragging a “Tarentula” to a hole
in a wall. Having with great difficulty introduced its burden into the cavity,
the wasp deposited an egg, sealed up the orifice, and flew away. Fabre
opened the cell and removed the spider, which, though completely
paralysed, lived for seven weeks.
The same indefatigable observer describes the method adopted by the
comparatively small Pompilus apicalis in attacking the formidable Wall-
spider, Segestria perfida. The combatants are well matched, and the issue of
the battle would be doubtful if the wasp did not have recourse to stratagem.
Its whole energies are directed towards forcing the spider away from its
web. At home, it is confident and dangerous; when once dislodged, it
appears bewildered and demoralised. The wasp darts suddenly towards the
spider and seizes it by a leg, with a rapid effort to jerk it forth, releasing its
hold before the enemy has had time to retaliate. The spider, however, as
well as being anchored by a thread from its spinnerets, is clinging to its web
with its hind legs, and if the jerk is not sufficiently energetic, it hastily
scrambles back and resumes its defensive position. Before renewing the
attack the wasp gives the spider time to recover from the excitement of the
first onset, seeking, meanwhile, the retreats of other victims. Returning, it
succeeds, by a more skilful effort, in drawing the spider from its retreat and
hurling it to the ground, where, terrified and helpless, it falls an easy prey.
Should the insect bungle in its first attack and become entangled in the web,
it would itself become the victim. Certain wasps thus appear to seek out
particular species of spiders as food for their larvae. Others are less
discriminate in their tastes. Again, some, as in the cases cited above, store
their egg-nest with a single spider, while others collect many for the
purpose.
The American “blue digger wasp” (Chlorion caeruleum) excavates its
nest in the ground, and inserts a single large spider of any species.[293]
Another wasp, of the genus Elis, selects the Wolf-spiders, and especially
Lycosa tigrina, for the use of its larvae, while Priocnemus pomilius shows a
preference for the Crab-spiders, or Thomisidae.
Page 414
One of the most remarkable instances is that of Pepsis formosa, which
preys upon the gigantic spider Eurypelma hentzii, wrongly styled in
America the “tarantula,” but really belonging to an entirely different family,
the Aviculariidae.
Fabre’s most interesting researches have established the fact that the
instinct of the wasp leads it to sting the spider in a particular spot, so as to
pierce the nerve-ganglion in the thorax. The precision with which this is
effected is absolutely necessary for the purpose of the insect. If stung
elsewhere, the spider is either incompletely paralysed, or it is killed
outright, and thus rendered useless as food for the future larvae of the wasp.
On the one hand, therefore, the Tarantula has acquired the habit of striking
the wasp in the only point where its blow is instantaneously fatal, while on
the other the wasp, with a different object in view, has been led to select the
precise spot where its sting will disable without immediately destroying the
spider. The latter case is, if anything, the more extraordinary, as the insect
can hardly have any recollection of its larval tastes, and yet it stores up for
progeny, which it will never see, food which is entirely abhorrent to itself in
its imago state.
Spiders taken from the egg-nests of wasps by M‘Cook survived, on the
average, about a fortnight, during which period they remained entirely
motionless, and would retain any attitude in which they were placed.
There are many animals which either habitually or occasionally feed
upon spiders. They are the staple food of some hummingbirds, and many
other birds appear to find in them a pleasing variation on their customary
insect diet. These creatures, moreover, are destructive to spiders in another
way, by stealing the material of their webs, and especially the more closely
textured silk of their egg-cocoons, to aid in the construction of their nests.
M‘Cook has observed this habit in the case of Vireo noveborocensis, and he
states, on the authority of others, that the “Plover” and the “Wren” are
addicted to it. The smaller species of monkeys are extremely fond of
spiders, and devour large numbers of them. They are said, moreover, to take
a mischievous delight in pulling them in pieces. Armadillos, ant-eaters,
snakes, lizards, and indeed all animals of insectivorous habit, draw no
distinction between Insecta and Arachnida, but feed upon both
indiscriminately. The army ants, so destructive to insect life in tropical
countries, include spiders among their victims. These formidable insects
preys upon the gigantic spider Eurypelma hentzii, wrongly styled in
America the “tarantula,” but really belonging to an entirely different family,
the Aviculariidae.
Fabre’s most interesting researches have established the fact that the
instinct of the wasp leads it to sting the spider in a particular spot, so as to
pierce the nerve-ganglion in the thorax. The precision with which this is
effected is absolutely necessary for the purpose of the insect. If stung
elsewhere, the spider is either incompletely paralysed, or it is killed
outright, and thus rendered useless as food for the future larvae of the wasp.
On the one hand, therefore, the Tarantula has acquired the habit of striking
the wasp in the only point where its blow is instantaneously fatal, while on
the other the wasp, with a different object in view, has been led to select the
precise spot where its sting will disable without immediately destroying the
spider. The latter case is, if anything, the more extraordinary, as the insect
can hardly have any recollection of its larval tastes, and yet it stores up for
progeny, which it will never see, food which is entirely abhorrent to itself in
its imago state.
Spiders taken from the egg-nests of wasps by M‘Cook survived, on the
average, about a fortnight, during which period they remained entirely
motionless, and would retain any attitude in which they were placed.
There are many animals which either habitually or occasionally feed
upon spiders. They are the staple food of some hummingbirds, and many
other birds appear to find in them a pleasing variation on their customary
insect diet. These creatures, moreover, are destructive to spiders in another
way, by stealing the material of their webs, and especially the more closely
textured silk of their egg-cocoons, to aid in the construction of their nests.
M‘Cook has observed this habit in the case of Vireo noveborocensis, and he
states, on the authority of others, that the “Plover” and the “Wren” are
addicted to it. The smaller species of monkeys are extremely fond of
spiders, and devour large numbers of them. They are said, moreover, to take
a mischievous delight in pulling them in pieces. Armadillos, ant-eaters,
snakes, lizards, and indeed all animals of insectivorous habit, draw no
distinction between Insecta and Arachnida, but feed upon both
indiscriminately. The army ants, so destructive to insect life in tropical
countries, include spiders among their victims. These formidable insects
Page 415
march along in vast hordes, swarming over and tearing in pieces any small
animal which lies in their path. They climb over intervening obstacles,
searching every cranny, and stripping them bare of animal life. Insects
which attempt to save themselves by flight are preyed upon by the birds,
which are always to be seen hovering above the advancing army. The
spider’s only resource is to hang from its thread in mid-air beneath the
branch over which the ants are swarming, for the spider line is
impracticable to the ant. Belt[294] has observed a spider escape the general
destruction by this means.
Protective Coloration.—Examples are numerous in which the spider
relies upon the inconspicuousness not of its nest, but of itself, to escape its
natural foes. Its general hues and markings are either such as to render it not
readily distinguishable among its ordinary surroundings, or the principle
has been carried still further, and a special object has been “mimicked” with
more or less fidelity.
This country is not rich in the more striking mimetic forms, but the
observer cannot fail to notice a very general correspondence in hue between
the spiders of various habits of life and their environment. Those which run
on the ground are usually dull-coloured; tree-living species affect grey and
green tints, and those which hunt their food amongst sand and stones are
frequently so mottled with yellow, red, and grey, that they can scarcely be
recognised except when in motion.
A few of our indigenous species may be mentioned as especially
protected by their colour and conformation. Tibellus oblongus is a straw-
coloured spider with an elongated body, which lives among dry grass and
rushes. When alarmed it clings closely to a dry stem, remains motionless,
and escapes observation by its peculiarity of colour and shape. Misumena
vatia, another of the Thomisidae or Crab-spiders, approximates in colour to
the flowers in which it is accustomed to lurk on the watch for prey. It is of a
variable hue, generally yellow or pink, and some observers believe that they
have seen it gently waving its anterior legs in a way which made them
easily mistaken for the stamens of the flower stirred by the breeze. Its
purpose appears to be to deceive, not its enemies, but its victims. It seems to
be partial to the blooms of the great mullein (Verbascum thapsus), and
Pickard-Cambridge has more than once seen it seize and overcome a bee
animal which lies in their path. They climb over intervening obstacles,
searching every cranny, and stripping them bare of animal life. Insects
which attempt to save themselves by flight are preyed upon by the birds,
which are always to be seen hovering above the advancing army. The
spider’s only resource is to hang from its thread in mid-air beneath the
branch over which the ants are swarming, for the spider line is
impracticable to the ant. Belt[294] has observed a spider escape the general
destruction by this means.
Protective Coloration.—Examples are numerous in which the spider
relies upon the inconspicuousness not of its nest, but of itself, to escape its
natural foes. Its general hues and markings are either such as to render it not
readily distinguishable among its ordinary surroundings, or the principle
has been carried still further, and a special object has been “mimicked” with
more or less fidelity.
This country is not rich in the more striking mimetic forms, but the
observer cannot fail to notice a very general correspondence in hue between
the spiders of various habits of life and their environment. Those which run
on the ground are usually dull-coloured; tree-living species affect grey and
green tints, and those which hunt their food amongst sand and stones are
frequently so mottled with yellow, red, and grey, that they can scarcely be
recognised except when in motion.
A few of our indigenous species may be mentioned as especially
protected by their colour and conformation. Tibellus oblongus is a straw-
coloured spider with an elongated body, which lives among dry grass and
rushes. When alarmed it clings closely to a dry stem, remains motionless,
and escapes observation by its peculiarity of colour and shape. Misumena
vatia, another of the Thomisidae or Crab-spiders, approximates in colour to
the flowers in which it is accustomed to lurk on the watch for prey. It is of a
variable hue, generally yellow or pink, and some observers believe that they
have seen it gently waving its anterior legs in a way which made them
easily mistaken for the stamens of the flower stirred by the breeze. Its
purpose appears to be to deceive, not its enemies, but its victims. It seems to
be partial to the blooms of the great mullein (Verbascum thapsus), and
Pickard-Cambridge has more than once seen it seize and overcome a bee
Page 416
which had visited the flower in search of honey. He has also observed it in
the blossoms of rose and furze bushes.[295]
An Epeirid (Tetragnatha extensa) resembles Tibellus in its method of
concealing itself when alarmed. It also possesses an elongated abdomen, of
a grey-green tint, which it closely applies to one of the twigs among which
it has stretched its net, at the same time extending its four long anterior legs
straight before it, and in this position it lies perdu, and is very easily
overlooked. Another Orb-weaver, Epeira cucurbitina, is of an apple-green
colour, which is admirably calculated to conceal it among the leaves which
surround its snare.
Most of our English Attidae, or Jumping-spiders, imitate closely the
prevailing tone of the surfaces on which they are accustomed to hunt. This
will be recognised in the familiar striped Wall-spider, Salticus scenicus, and
we may also mention the grey Attus pubescens, which affects stone walls,
and the speckled Attus saltator, which is hardly distinguishable from the
sand which it searches for food.
Examples may also be found among the Lycosidae or Wolf-spiders. Of
the prettily variegated Lycosa picta, Pickard-Cambridge says: “Much
variation exists in the extent of the different portions of the pattern and in
their depth of colouring, these often taking their prevailing tint from the
colour of the soil in which the spider is found. The best marked, richest
coloured, and largest examples are found on sandy and gravelly heaths,
where there is considerable depth and variety of colouring.... But on the
uniformly tinted greyish-yellow sandhills between Poole and Christchurch I
have found a dwarf, pale yellow-brown variety, with scarcely any dark
markings on it at all, the legs being of a uniform hue, and wholly destitute
of dark annuli.”[296]
Mimicry.—In the island of Portland, a locality remarkable for the
number of species peculiar to itself, there is found a spider, Micaria
scintillans, very closely resembling a large blackish ant which frequents the
same neighbourhood. Its movements, moreover, are exceedingly ant-like, as
it hurries along in a zigzag course, frequently running up and down grass
stems after the manner of those insects. It is a great lover of sunshine, and
disappears as soon as the sun is obscured by a passing cloud.
Such resemblances, obvious enough in nature, and heightened by the
behaviour of the mimetic form, are often by no means striking in the
the blossoms of rose and furze bushes.[295]
An Epeirid (Tetragnatha extensa) resembles Tibellus in its method of
concealing itself when alarmed. It also possesses an elongated abdomen, of
a grey-green tint, which it closely applies to one of the twigs among which
it has stretched its net, at the same time extending its four long anterior legs
straight before it, and in this position it lies perdu, and is very easily
overlooked. Another Orb-weaver, Epeira cucurbitina, is of an apple-green
colour, which is admirably calculated to conceal it among the leaves which
surround its snare.
Most of our English Attidae, or Jumping-spiders, imitate closely the
prevailing tone of the surfaces on which they are accustomed to hunt. This
will be recognised in the familiar striped Wall-spider, Salticus scenicus, and
we may also mention the grey Attus pubescens, which affects stone walls,
and the speckled Attus saltator, which is hardly distinguishable from the
sand which it searches for food.
Examples may also be found among the Lycosidae or Wolf-spiders. Of
the prettily variegated Lycosa picta, Pickard-Cambridge says: “Much
variation exists in the extent of the different portions of the pattern and in
their depth of colouring, these often taking their prevailing tint from the
colour of the soil in which the spider is found. The best marked, richest
coloured, and largest examples are found on sandy and gravelly heaths,
where there is considerable depth and variety of colouring.... But on the
uniformly tinted greyish-yellow sandhills between Poole and Christchurch I
have found a dwarf, pale yellow-brown variety, with scarcely any dark
markings on it at all, the legs being of a uniform hue, and wholly destitute
of dark annuli.”[296]
Mimicry.—In the island of Portland, a locality remarkable for the
number of species peculiar to itself, there is found a spider, Micaria
scintillans, very closely resembling a large blackish ant which frequents the
same neighbourhood. Its movements, moreover, are exceedingly ant-like, as
it hurries along in a zigzag course, frequently running up and down grass
stems after the manner of those insects. It is a great lover of sunshine, and
disappears as soon as the sun is obscured by a passing cloud.
Such resemblances, obvious enough in nature, and heightened by the
behaviour of the mimetic form, are often by no means striking in the
Page 417
cabinet. In some American species of spiders, however, imitation of the ant
has passed beyond the stage of a general resemblance as regards size and
colour and method of progression. The head of the ant is well marked off
from the body, and the thorax is frequently divided into distinct regions.
These peculiarities are imitated by constrictions in the cephalothorax of
mimetic spiders. The resemblance, moreover, is much increased by their
habit of using but six legs for locomotion, and carrying the second pair as
ants do their antennae. The best known examples of these spiders are
Synageles picata and Synemosyna formica (see Fig. 215, C, p. 420), and
even more striking resemblances have been observed among some
undescribed South American species.
The object of such mimicry seems to vary in different cases. Sometimes
the spider preys upon the ant which it resembles. Sometimes, again, by its
disguise, it escapes the notice of the ant which would otherwise feed upon
it. More often spider and ant are neutral as regards each other, but, under
cover of its resemblance, the Arachnid is enabled to approach an
unsuspecting victim to which the ant is not a terror. Again, the unpleasantly
acid taste of ants is unpalatable to most birds, though not to all, and the
increased danger from specially ant-eating birds may be more than
counterbalanced by the immunity they acquire from other birds.
There is quite a large class of Spiders of nocturnal habits, whose only
precaution by day is to sit perfectly still and be mistaken for something else.
We have referred to the adaptation in colour of our English species,
Misumena vatia, to the flowers in which it lies in wait for prey. Bates[297]
mentions exotic examples of the same family which mimic flower-buds in
the axils of leaves. Herbert Smith says of a spider which sits upon a leaf
waiting for prey: “The pink three-lobed body appears just like a withered
flower that might have fallen from the tree above; to the flies, no doubt, the
deception is increased by the strong sweet odour, like jasmine.”
Trimen[298] describes a Cape Town species which is of the exact rose-red
of the flower of the oleander. “To more effectually conceal it, the palpi, top
of the cephalothorax, and four lateral stripes on the abdomen are white,
according remarkably with the irregular white markings so frequent on the
petals of Nerium.”
The same observer, approaching a bush of the yellow-flowered Senecio
pubigera, noticed that two of the numerous butterflies settled upon it did
has passed beyond the stage of a general resemblance as regards size and
colour and method of progression. The head of the ant is well marked off
from the body, and the thorax is frequently divided into distinct regions.
These peculiarities are imitated by constrictions in the cephalothorax of
mimetic spiders. The resemblance, moreover, is much increased by their
habit of using but six legs for locomotion, and carrying the second pair as
ants do their antennae. The best known examples of these spiders are
Synageles picata and Synemosyna formica (see Fig. 215, C, p. 420), and
even more striking resemblances have been observed among some
undescribed South American species.
The object of such mimicry seems to vary in different cases. Sometimes
the spider preys upon the ant which it resembles. Sometimes, again, by its
disguise, it escapes the notice of the ant which would otherwise feed upon
it. More often spider and ant are neutral as regards each other, but, under
cover of its resemblance, the Arachnid is enabled to approach an
unsuspecting victim to which the ant is not a terror. Again, the unpleasantly
acid taste of ants is unpalatable to most birds, though not to all, and the
increased danger from specially ant-eating birds may be more than
counterbalanced by the immunity they acquire from other birds.
There is quite a large class of Spiders of nocturnal habits, whose only
precaution by day is to sit perfectly still and be mistaken for something else.
We have referred to the adaptation in colour of our English species,
Misumena vatia, to the flowers in which it lies in wait for prey. Bates[297]
mentions exotic examples of the same family which mimic flower-buds in
the axils of leaves. Herbert Smith says of a spider which sits upon a leaf
waiting for prey: “The pink three-lobed body appears just like a withered
flower that might have fallen from the tree above; to the flies, no doubt, the
deception is increased by the strong sweet odour, like jasmine.”
Trimen[298] describes a Cape Town species which is of the exact rose-red
of the flower of the oleander. “To more effectually conceal it, the palpi, top
of the cephalothorax, and four lateral stripes on the abdomen are white,
according remarkably with the irregular white markings so frequent on the
petals of Nerium.”
The same observer, approaching a bush of the yellow-flowered Senecio
pubigera, noticed that two of the numerous butterflies settled upon it did
Page 418
not fly away with their companions. Each of these he found to be in the
clutches of a spider, whose remarkable resemblance to the flower lay not
only in its colour, but in the attitude it assumed. “Holding on to the flower-
stalk by the two hinder pairs of legs, it extended the two long front pairs
upward and laterally. In this position it was scarcely possible to believe that
it was not a flower seen in profile, the rounded abdomen representing the
central mass of florets, and the extended legs the ray florets; while, to
complete the illusion, the femora of the front pair of legs, adpressed to the
thorax, have each a longitudinal red stripe which represents the ferruginous
stripe on the sepals of the flower.”
Cambridge found in Palestine some species of Thomisidae which, when
at rest, were indistinguishable from bits of coarse fleecy wool, or the rough
seeds of some plant.
There is perhaps no more curious case of mimicry than that of a spider,
Phrynarachne (= Ornithoscatoides) decipiens, which Forbes discovered in
Java while butterfly-hunting. It appears that butterflies of the Family
Hesperidae have a custom of settling, for reasons best known to themselves,
upon the excreta of birds, dropped upon a leaf. Forbes noticed one in this
position. Creeping up, he seized the butterfly, but found it mysteriously
glued by the feet. On further investigation the “excreta” proved to be a
spider. So accurate was the mimicry that he was again completely deceived
by the same species in Sumatra. Its habit is to weave upon a leaf a small
white patch of web, of a shape which greatly assists the deception, and in
the midst of this it lies on its back, holding on by the spines with which its
legs are furnished. It then folds its legs over its thorax, and waits for some
insect to settle upon it.
In rare cases spiders have come to resemble their enemies the Ichneumon
flies. A frequent habit of these insects is to deposit their eggs in the newly-
formed cocoon of the spider. The Ichneumon eggs are the first to hatch, and
the larvae have a convenient food-supply at hand. Sometimes, however,
they adopt another method, and insert their eggs into the body of the spider
itself. It is probably in order to avoid this unpleasant contingency that the
spider has evinced towards the Ichneumon the sincerest form of flattery.
The Senses of Spiders.
clutches of a spider, whose remarkable resemblance to the flower lay not
only in its colour, but in the attitude it assumed. “Holding on to the flower-
stalk by the two hinder pairs of legs, it extended the two long front pairs
upward and laterally. In this position it was scarcely possible to believe that
it was not a flower seen in profile, the rounded abdomen representing the
central mass of florets, and the extended legs the ray florets; while, to
complete the illusion, the femora of the front pair of legs, adpressed to the
thorax, have each a longitudinal red stripe which represents the ferruginous
stripe on the sepals of the flower.”
Cambridge found in Palestine some species of Thomisidae which, when
at rest, were indistinguishable from bits of coarse fleecy wool, or the rough
seeds of some plant.
There is perhaps no more curious case of mimicry than that of a spider,
Phrynarachne (= Ornithoscatoides) decipiens, which Forbes discovered in
Java while butterfly-hunting. It appears that butterflies of the Family
Hesperidae have a custom of settling, for reasons best known to themselves,
upon the excreta of birds, dropped upon a leaf. Forbes noticed one in this
position. Creeping up, he seized the butterfly, but found it mysteriously
glued by the feet. On further investigation the “excreta” proved to be a
spider. So accurate was the mimicry that he was again completely deceived
by the same species in Sumatra. Its habit is to weave upon a leaf a small
white patch of web, of a shape which greatly assists the deception, and in
the midst of this it lies on its back, holding on by the spines with which its
legs are furnished. It then folds its legs over its thorax, and waits for some
insect to settle upon it.
In rare cases spiders have come to resemble their enemies the Ichneumon
flies. A frequent habit of these insects is to deposit their eggs in the newly-
formed cocoon of the spider. The Ichneumon eggs are the first to hatch, and
the larvae have a convenient food-supply at hand. Sometimes, however,
they adopt another method, and insert their eggs into the body of the spider
itself. It is probably in order to avoid this unpleasant contingency that the
spider has evinced towards the Ichneumon the sincerest form of flattery.
The Senses of Spiders.
Page 419
Sight.—Though, as has been shown, spiders are well provided with eyes,
their power of vision, in most cases, is by no means remarkable. As might
be expected, it is less developed in those of sedentary than in those of
nomadic habit.
It is noticeable that, in most spiders, some of the eyes are of a pearly grey
colour, and others of a much darker hue. Simon designates the former
nocturnal and the latter diurnal eyes, according to the special use which he
believes them to subserve.
This view of the matter cannot be regarded as at all established, and has
not found general acceptation. Moreover, Pillai[299] has shown that certain
Attid spiders can change the colour of their eyes by a movement of the
internal mechanism. The Epeiridae, spinners of the round web, are certainly,
as a rule, very dim-sighted creatures. A fly may be held within an inch of
them, but, unless it buzz, it will excite no notice whatever. A careful
observation of the performances of the large Garden-spider in securing her
prey will soon convince the onlooker that she is guided almost entirely by
appeals to her sense of touch communicated along the tremulous lines of
her snare. Interpreting these too hastily, she will sometimes rush straight
past the entangled fly, and wait for it to renew its struggles before making
sure of its whereabouts. Keen sight would be of little utility to such spiders,
as they are concerned with nothing beyond the limits of their snare, and
within its range they are furnished with the equivalent of complete
telegraphic communication.
That most of the vagabond spiders can see well within the range of
several inches there is no doubt, though some observers have been misled
by the result of certain experiments on the Lycosidae, or “Wolf-spiders.” It
will be remembered that the female Lycosid carries her egg-bag about with
her, attached usually to her spinnerets. If it be removed and placed close at
hand, the spider experiences the greatest difficulty in finding it again.
Lubbock attributed this to defective sight, whereas it merely arises from
unfamiliarity with the appearance of the egg-bag, which, since its
construction, has been so situated as to be out of the view of the spider.
Peckham found that spiders of the genus Theridion, accustomed to the sight
of their cocoons, readily recognised them by that sense when removed to a
distance.
their power of vision, in most cases, is by no means remarkable. As might
be expected, it is less developed in those of sedentary than in those of
nomadic habit.
It is noticeable that, in most spiders, some of the eyes are of a pearly grey
colour, and others of a much darker hue. Simon designates the former
nocturnal and the latter diurnal eyes, according to the special use which he
believes them to subserve.
This view of the matter cannot be regarded as at all established, and has
not found general acceptation. Moreover, Pillai[299] has shown that certain
Attid spiders can change the colour of their eyes by a movement of the
internal mechanism. The Epeiridae, spinners of the round web, are certainly,
as a rule, very dim-sighted creatures. A fly may be held within an inch of
them, but, unless it buzz, it will excite no notice whatever. A careful
observation of the performances of the large Garden-spider in securing her
prey will soon convince the onlooker that she is guided almost entirely by
appeals to her sense of touch communicated along the tremulous lines of
her snare. Interpreting these too hastily, she will sometimes rush straight
past the entangled fly, and wait for it to renew its struggles before making
sure of its whereabouts. Keen sight would be of little utility to such spiders,
as they are concerned with nothing beyond the limits of their snare, and
within its range they are furnished with the equivalent of complete
telegraphic communication.
That most of the vagabond spiders can see well within the range of
several inches there is no doubt, though some observers have been misled
by the result of certain experiments on the Lycosidae, or “Wolf-spiders.” It
will be remembered that the female Lycosid carries her egg-bag about with
her, attached usually to her spinnerets. If it be removed and placed close at
hand, the spider experiences the greatest difficulty in finding it again.
Lubbock attributed this to defective sight, whereas it merely arises from
unfamiliarity with the appearance of the egg-bag, which, since its
construction, has been so situated as to be out of the view of the spider.
Peckham found that spiders of the genus Theridion, accustomed to the sight
of their cocoons, readily recognised them by that sense when removed to a
distance.
Page 420
The most keen-sighted of the spider tribe are undoubtedly the Attidae, or
Leaping-spiders. The little black and white striped Wall-spider, Salticus
scenicus, is probably a familiar object to most of our readers, and a very
little observation of its movements, like those of a cat stalking a bird, will
convince the observer that its visual powers are wonderfully keen and
accurate. Its attitude of “attention” on sighting its prey, its stealthy
manœuvring to approach it unobserved, and the unerring certainty of its
final leap, are very interesting to witness.
It is somewhat noticeable that both in the Epeiridae and in the Attidae the
two portions of the body, cephalothorax and abdomen, have more than the
usual freedom of independent motion. In the Orb-weavers this gives play to
the spinnerets in binding up a captured insect, but in the Leaping-spiders it
allows of the rapid directing of the large anterior eyes towards the quarry, as
it continually alters its position.
Professor and Mrs. Peckham of Wisconsin[300] performed some interesting
experiments to ascertain the sensitiveness of the spider’s eye to colour.
Freely communicating compartments of differently coloured glass were
constructed, and spiders were confined in them, when it was found that red
was the most and blue the least attractive hue. This agrees well with what
Lubbock found to be the case with ants, but those insects displayed a
greater antipathy for blue and not so marked a preference for red.
Hearing.—Most of our knowledge about the auditory sense of spiders is
due to experiments performed by C. V. Boys,[301] and repeated by Professor
and Mrs. Peckham.
The spider usually responds to the stimulus in one of two ways; it either
raises its front legs, extending them in the direction of the sound, or it
allows itself to drop suddenly, as though in alarm. It was only in the case of
the Epeiridae that any results were obtained, and these spiders were more
sensitive to low than to high notes. Now, as M‘Cook points out, it is
exceedingly strange that the nomadic and hunting spiders, to which the
sense of hearing might be expected to be extremely useful, should be
deficient in this faculty, while the sedentary spiders, to which it would
appear comparatively unimportant, should possess it in a tolerably
developed form. That writer may possibly be correct in supposing that the
sense, as possessed by spiders, is hardly differentiated from that of ordinary
touch, and that the web-making species are only aware of sounds by the
Leaping-spiders. The little black and white striped Wall-spider, Salticus
scenicus, is probably a familiar object to most of our readers, and a very
little observation of its movements, like those of a cat stalking a bird, will
convince the observer that its visual powers are wonderfully keen and
accurate. Its attitude of “attention” on sighting its prey, its stealthy
manœuvring to approach it unobserved, and the unerring certainty of its
final leap, are very interesting to witness.
It is somewhat noticeable that both in the Epeiridae and in the Attidae the
two portions of the body, cephalothorax and abdomen, have more than the
usual freedom of independent motion. In the Orb-weavers this gives play to
the spinnerets in binding up a captured insect, but in the Leaping-spiders it
allows of the rapid directing of the large anterior eyes towards the quarry, as
it continually alters its position.
Professor and Mrs. Peckham of Wisconsin[300] performed some interesting
experiments to ascertain the sensitiveness of the spider’s eye to colour.
Freely communicating compartments of differently coloured glass were
constructed, and spiders were confined in them, when it was found that red
was the most and blue the least attractive hue. This agrees well with what
Lubbock found to be the case with ants, but those insects displayed a
greater antipathy for blue and not so marked a preference for red.
Hearing.—Most of our knowledge about the auditory sense of spiders is
due to experiments performed by C. V. Boys,[301] and repeated by Professor
and Mrs. Peckham.
The spider usually responds to the stimulus in one of two ways; it either
raises its front legs, extending them in the direction of the sound, or it
allows itself to drop suddenly, as though in alarm. It was only in the case of
the Epeiridae that any results were obtained, and these spiders were more
sensitive to low than to high notes. Now, as M‘Cook points out, it is
exceedingly strange that the nomadic and hunting spiders, to which the
sense of hearing might be expected to be extremely useful, should be
deficient in this faculty, while the sedentary spiders, to which it would
appear comparatively unimportant, should possess it in a tolerably
developed form. That writer may possibly be correct in supposing that the
sense, as possessed by spiders, is hardly differentiated from that of ordinary
touch, and that the web-making species are only aware of sounds by the
Page 421
vibrations communicated to their feet by the medium of the web. However
this may be, we must reluctantly but sternly reject the numerous and
seemingly authentic stories, often connected with historic personages,
which credit the spider with a cultivated taste for music.
We have seen that among the spiders which possess a stridulating
apparatus it is confined, in certain groups, to the male, or if present in the
female it exists only in a rudimentary form. If in these cases stridulation has
been rightly interpreted as a sexual call, the power of hearing, at least in the
female, is of course connoted. The spiders in question are members of the
Theridiidae, a family closely allied to the Epeiridae, and therefore more
likely than most groups to possess the power of hearing.
Theraphosid spiders show no response to the stimulus of sound, and
among them stridulation is not confined to one sex. If, as is generally
believed, the organ is used to warn off enemies, it is not necessary that the
sound produced should be audible to the spider itself. If there be any true
hearing organ in spiders its location is quite uncertain. Some have supposed
the so-called lyriform organs in the legs to have an auditory function, while
others have supposed the power of hearing to reside in certain hairs, of
which there are several different types distributed over the body and limbs
of the animal.
Spider Intelligence.—The experiments performed by the Peckhams
clearly proved that spiders have short memories—a sure indication of a low
state of intelligence. Members of the Lycosid or “Wolf-spider” group, when
deprived of their cocoons, recognised them again after a few hours, but in
most instances they refused to resume them after a lapse of twenty-four
hours, and in every case an absence of two days sufficed to prevent any sign
of recognition on their restoration. Moreover, when, after a shorter interval,
the cocoons of other spiders, even of different genera, were offered to them,
they appeared equally satisfied, and attached them in the orthodox manner,
beneath the abdomen. The same treatment was even accorded to pith balls,
which, if of the right size, seemed to be a perfectly satisfactory substitute.
The contents of one cocoon were replaced by a shot three or four times their
weight, but the spider accepted it with alacrity, spending half an hour in
refixing it, when its weight caused it to fall from its attachment.
The habit of “feigning death,” which seems to be especially characteristic
of the Epeiridae or orb-weaving spiders, probably arises from no desire to
this may be, we must reluctantly but sternly reject the numerous and
seemingly authentic stories, often connected with historic personages,
which credit the spider with a cultivated taste for music.
We have seen that among the spiders which possess a stridulating
apparatus it is confined, in certain groups, to the male, or if present in the
female it exists only in a rudimentary form. If in these cases stridulation has
been rightly interpreted as a sexual call, the power of hearing, at least in the
female, is of course connoted. The spiders in question are members of the
Theridiidae, a family closely allied to the Epeiridae, and therefore more
likely than most groups to possess the power of hearing.
Theraphosid spiders show no response to the stimulus of sound, and
among them stridulation is not confined to one sex. If, as is generally
believed, the organ is used to warn off enemies, it is not necessary that the
sound produced should be audible to the spider itself. If there be any true
hearing organ in spiders its location is quite uncertain. Some have supposed
the so-called lyriform organs in the legs to have an auditory function, while
others have supposed the power of hearing to reside in certain hairs, of
which there are several different types distributed over the body and limbs
of the animal.
Spider Intelligence.—The experiments performed by the Peckhams
clearly proved that spiders have short memories—a sure indication of a low
state of intelligence. Members of the Lycosid or “Wolf-spider” group, when
deprived of their cocoons, recognised them again after a few hours, but in
most instances they refused to resume them after a lapse of twenty-four
hours, and in every case an absence of two days sufficed to prevent any sign
of recognition on their restoration. Moreover, when, after a shorter interval,
the cocoons of other spiders, even of different genera, were offered to them,
they appeared equally satisfied, and attached them in the orthodox manner,
beneath the abdomen. The same treatment was even accorded to pith balls,
which, if of the right size, seemed to be a perfectly satisfactory substitute.
The contents of one cocoon were replaced by a shot three or four times their
weight, but the spider accepted it with alacrity, spending half an hour in
refixing it, when its weight caused it to fall from its attachment.
The habit of “feigning death,” which seems to be especially characteristic
of the Epeiridae or orb-weaving spiders, probably arises from no desire to
Page 422
deceive its adversary as to its condition, but from an instinct to remain
motionless, and therefore inconspicuous. Where a nomadic spider seeks
safety in flight, a sedentary species finds a greater chance of escape in
dropping a certain distance, and, while still attached by its silken line,
giving as little evidence of its whereabouts as possible—trusting, in many
cases, to its protective colouring. This method, moreover, has the advantage
of facilitating its return to the web when the danger is past—a feat of which
it would be quite incapable were it once to relinquish its clue.
All the remarkable and apparently intelligent actions of these creatures
seem to be done in obedience to a blind instinct, which is obeyed even
when there is no longer any object to be served. We have seen how the
Trap-door spiders decorate the lids of their nests with moss even when the
surrounding ground is bare, and Agelena labyrinthica has been observed to
go through the whole lengthy and laborious operation of constructing its
egg-cocoon though all its eggs were removed immediately on being laid.[302]
Mating Habits.—The sex of a mature spider can readily be recognised
by the palpus which, as we have seen, is furnished in the male with a
“palpal organ.” After the last moult but one the palp appears tumid, but it is
only at the last moult that the organ is fully formed, and that the genital
orifice is visible under the anterior part of the abdomen.
No alteration takes place in the female palp at maturity, but it is only after
the last moult that the “epigyne” is distinguishable.
That the palpal organs are used in the fertilisation of the female has long
been established. How they came to contain the sperm matured in the
abdomen was a problem which has only been solved comparatively
recently. No direct connection could be found by way of the palpus with the
abdominal organs, which, indeed, were seen to have an orifice between the
lung-sacs. It is now known that some spiders at all events spin a slight web
upon which they deposit a drop of spermatic fluid, which they afterwards
absorb into their palpal organs for transference to the female. Secondary
sexual differences are often very marked, the male being almost invariably
the smaller in body, though its legs are frequently longer and more powerful
than those of the female.
Among some of the sedentary spiders the disparity in size is excessive.
The most striking examples are furnished by the Epeirid genera Argiope
and Nephila, the male in some instances not attaining more than the
motionless, and therefore inconspicuous. Where a nomadic spider seeks
safety in flight, a sedentary species finds a greater chance of escape in
dropping a certain distance, and, while still attached by its silken line,
giving as little evidence of its whereabouts as possible—trusting, in many
cases, to its protective colouring. This method, moreover, has the advantage
of facilitating its return to the web when the danger is past—a feat of which
it would be quite incapable were it once to relinquish its clue.
All the remarkable and apparently intelligent actions of these creatures
seem to be done in obedience to a blind instinct, which is obeyed even
when there is no longer any object to be served. We have seen how the
Trap-door spiders decorate the lids of their nests with moss even when the
surrounding ground is bare, and Agelena labyrinthica has been observed to
go through the whole lengthy and laborious operation of constructing its
egg-cocoon though all its eggs were removed immediately on being laid.[302]
Mating Habits.—The sex of a mature spider can readily be recognised
by the palpus which, as we have seen, is furnished in the male with a
“palpal organ.” After the last moult but one the palp appears tumid, but it is
only at the last moult that the organ is fully formed, and that the genital
orifice is visible under the anterior part of the abdomen.
No alteration takes place in the female palp at maturity, but it is only after
the last moult that the “epigyne” is distinguishable.
That the palpal organs are used in the fertilisation of the female has long
been established. How they came to contain the sperm matured in the
abdomen was a problem which has only been solved comparatively
recently. No direct connection could be found by way of the palpus with the
abdominal organs, which, indeed, were seen to have an orifice between the
lung-sacs. It is now known that some spiders at all events spin a slight web
upon which they deposit a drop of spermatic fluid, which they afterwards
absorb into their palpal organs for transference to the female. Secondary
sexual differences are often very marked, the male being almost invariably
the smaller in body, though its legs are frequently longer and more powerful
than those of the female.
Among some of the sedentary spiders the disparity in size is excessive.
The most striking examples are furnished by the Epeirid genera Argiope
and Nephila, the male in some instances not attaining more than the
Page 423
thousandth part of the mass of the
female. The coloration of the sexes is
frequently quite dissimilar, the male
being usually the darker, though in
the Attidae he is in many cases the
more strikingly ornamented.
In the minute Theridiid spiders of
the group Erigoninae (see p. 404), the
male cephalothorax often presents
remarkable and characteristic
excrescences not observable in the
female. Some curious examples of
this phenomenon may be seen in Fig.
209.
To the ordinary observer male
spiders will appear to be
comparatively rare, and to be greatly
outnumbered by the females. This is
probably to some degree true, but the
unsettled habits of the males and the
shorter duration of their life are Fig. 198.—Argiope aurelia, ♂ and ♀ , natural
calculated to give an exaggerated size.
impression of their rarity. They only
appear in considerable numbers at the mating season, shortly after which
the males, in the case of many species, may be sought for in vain, as, after
performing their functions, they quickly die. The snares they spin are often
rudimentary, their capabilities in this direction appearing to deteriorate after
the adult form is attained. Young spiders of indistinguishable sex make
perfect snares on a small scale, while such as eventually develop male
organs will often thereafter be content with a few straggling lines made with
very slight regard to symmetry. They become nomadic in their habits,
wandering off in search of the females, and pitching a hasty tent by the way.
The relations between the sexes in the Spider tribe present points of
extreme interest, but in this connexion the various groups must be
separately treated on account of their very different habits of life.
female. The coloration of the sexes is
frequently quite dissimilar, the male
being usually the darker, though in
the Attidae he is in many cases the
more strikingly ornamented.
In the minute Theridiid spiders of
the group Erigoninae (see p. 404), the
male cephalothorax often presents
remarkable and characteristic
excrescences not observable in the
female. Some curious examples of
this phenomenon may be seen in Fig.
209.
To the ordinary observer male
spiders will appear to be
comparatively rare, and to be greatly
outnumbered by the females. This is
probably to some degree true, but the
unsettled habits of the males and the
shorter duration of their life are Fig. 198.—Argiope aurelia, ♂ and ♀ , natural
calculated to give an exaggerated size.
impression of their rarity. They only
appear in considerable numbers at the mating season, shortly after which
the males, in the case of many species, may be sought for in vain, as, after
performing their functions, they quickly die. The snares they spin are often
rudimentary, their capabilities in this direction appearing to deteriorate after
the adult form is attained. Young spiders of indistinguishable sex make
perfect snares on a small scale, while such as eventually develop male
organs will often thereafter be content with a few straggling lines made with
very slight regard to symmetry. They become nomadic in their habits,
wandering off in search of the females, and pitching a hasty tent by the way.
The relations between the sexes in the Spider tribe present points of
extreme interest, but in this connexion the various groups must be
separately treated on account of their very different habits of life.
Page 424
In no group are these relations more curious than in the Epeiridae, the
constructors of the familiar wheel-like web. Love-making is no trifling
matter here. If the female is not in the mood for the advances of the male
she will probably regard him as a desirable addition to her larder. Even if
his wooing is accepted, he has to beat a precipitate retreat after effecting his
purpose, or he may fall a victim to his partner’s hunger.
This strange peril braved by the male in courting the female, which has,
as far as is known, no parallel in any other department of the animal
kingdom, is frequently mentioned as universal among spiders. It
unquestionably exists, and may be verified by any patient observer in the
case of the large Garden-spider Epeira diademata, but it has only been
observed among certain species of the Epeiridae and Attidae. It will be
remembered that in the Epeiridae the males are sometimes absurdly small in
comparison with the females, and this diminution of size is thought to have
a direct connection with the danger undergone at the mating season. Small
active males stand a better chance of escape from ferocious females, so that
natural selection has acted in the direction of reducing their size as far as is
compatible with the performance of their functions.
Pickard-Cambridge[303] cites an extreme case. He says: “The female of
Nephila chrysogaster, Walck. (an almost universally distributed tropical
Epeirid), measures 2 inches in the length of its body, while that of the male
scarcely exceeds ⅒ th of an inch, and is less than ¹⁄₁₃₀₀th part of her
weight.”
During the mating season the males may be looked for on the borders of
the snares of the females. Their action is hesitating and irresolute, as it well
may be, and for hours they will linger on the confines of the web, feeling it
cautiously with their legs, and apparently trying to ascertain the nature of
the welcome likely to be extended to them. If accepted, they accomplish
their purpose by applying their palps alternately to the epigyne of their
mate. If repulsed, they do their best to make their escape, and wait for a
more auspicious moment. Emerton[304] says: “In these encounters the males
are often injured; they frequently lose some of their legs; and I have seen
one, that had only four out of his eight left, still standing up to his work.”
Among the other groups of sedentary spiders the relations between the
sexes seem to be more pacific, and there is even some approach to
domesticity. Males and females of Linyphia may be found during the
constructors of the familiar wheel-like web. Love-making is no trifling
matter here. If the female is not in the mood for the advances of the male
she will probably regard him as a desirable addition to her larder. Even if
his wooing is accepted, he has to beat a precipitate retreat after effecting his
purpose, or he may fall a victim to his partner’s hunger.
This strange peril braved by the male in courting the female, which has,
as far as is known, no parallel in any other department of the animal
kingdom, is frequently mentioned as universal among spiders. It
unquestionably exists, and may be verified by any patient observer in the
case of the large Garden-spider Epeira diademata, but it has only been
observed among certain species of the Epeiridae and Attidae. It will be
remembered that in the Epeiridae the males are sometimes absurdly small in
comparison with the females, and this diminution of size is thought to have
a direct connection with the danger undergone at the mating season. Small
active males stand a better chance of escape from ferocious females, so that
natural selection has acted in the direction of reducing their size as far as is
compatible with the performance of their functions.
Pickard-Cambridge[303] cites an extreme case. He says: “The female of
Nephila chrysogaster, Walck. (an almost universally distributed tropical
Epeirid), measures 2 inches in the length of its body, while that of the male
scarcely exceeds ⅒ th of an inch, and is less than ¹⁄₁₃₀₀th part of her
weight.”
During the mating season the males may be looked for on the borders of
the snares of the females. Their action is hesitating and irresolute, as it well
may be, and for hours they will linger on the confines of the web, feeling it
cautiously with their legs, and apparently trying to ascertain the nature of
the welcome likely to be extended to them. If accepted, they accomplish
their purpose by applying their palps alternately to the epigyne of their
mate. If repulsed, they do their best to make their escape, and wait for a
more auspicious moment. Emerton[304] says: “In these encounters the males
are often injured; they frequently lose some of their legs; and I have seen
one, that had only four out of his eight left, still standing up to his work.”
Among the other groups of sedentary spiders the relations between the
sexes seem to be more pacific, and there is even some approach to
domesticity. Males and females of Linyphia may be found during the
Page 425
mating season living happily together in their irregular snares. The same
harmony seems to exist among the Tube-weavers, and Agelena labyrinthica
lingers for days unmolested about the web of the female, though it is
perhaps hardly correct to say that they have their home in common.
Among the wandering spiders the male usually seeks out the female and
leaps on her back, from which position his sperm-laden palps can reach
their destination. This is the habit of the Thomisidae or Crab-spiders, and of
the quick-running Wolf-spiders, or Lycosidae.
The sexual relations of the
Leaping-spiders, or Attidae, are so
remarkable as to deserve a longer
notice. This Family includes the most
beautiful and highly ornamented
examples of spider life. Their
headquarters are the tropics, and their
brilliant colouring led Wallace to
speak of those he saw in the Malay
Archipelago as “perfect gems of
beauty.”
Now among these spiders the male
is almost always more highly
decorated than the female, and
Fig. 199.—Male Astia vittata dancing before the Peckham’s observations would lead
female. (After Peckham.) to the conclusion that the female is
influenced by the display of these
decorations in the selection of her mate.
The so-called “love-dances” of certain tropical birds are known to all
readers of natural history, but it was hardly to be expected that their
counterpart would exist among spiders. Yet the antics by which male
Attidae endeavour to attract the attention of the females afford an almost
exact parallel.
The following extract from the account of Professor and Mrs.
Peckham[305] of their observations on Saitis pulex will make this abundantly
clear: “When some four inches from her he stood still, and then began the
most remarkable performances that an amorous male could offer to an
admiring female. She eyed him eagerly, changing her position from time to
harmony seems to exist among the Tube-weavers, and Agelena labyrinthica
lingers for days unmolested about the web of the female, though it is
perhaps hardly correct to say that they have their home in common.
Among the wandering spiders the male usually seeks out the female and
leaps on her back, from which position his sperm-laden palps can reach
their destination. This is the habit of the Thomisidae or Crab-spiders, and of
the quick-running Wolf-spiders, or Lycosidae.
The sexual relations of the
Leaping-spiders, or Attidae, are so
remarkable as to deserve a longer
notice. This Family includes the most
beautiful and highly ornamented
examples of spider life. Their
headquarters are the tropics, and their
brilliant colouring led Wallace to
speak of those he saw in the Malay
Archipelago as “perfect gems of
beauty.”
Now among these spiders the male
is almost always more highly
decorated than the female, and
Fig. 199.—Male Astia vittata dancing before the Peckham’s observations would lead
female. (After Peckham.) to the conclusion that the female is
influenced by the display of these
decorations in the selection of her mate.
The so-called “love-dances” of certain tropical birds are known to all
readers of natural history, but it was hardly to be expected that their
counterpart would exist among spiders. Yet the antics by which male
Attidae endeavour to attract the attention of the females afford an almost
exact parallel.
The following extract from the account of Professor and Mrs.
Peckham[305] of their observations on Saitis pulex will make this abundantly
clear: “When some four inches from her he stood still, and then began the
most remarkable performances that an amorous male could offer to an
admiring female. She eyed him eagerly, changing her position from time to
Page 426
time, so that he might be always in view. He, raising his whole body on one
side by straightening out the legs, and lowering it on the other by folding
the first two pairs of legs up and under, leaned so far over as to be in danger
of losing his balance, which he only maintained by sidling rapidly towards
the lowered side.... Again and again he circles from side to side, she gazing
towards him in a softer mood, evidently admiring the grace of his antics.
This is repeated until we have counted a hundred and eleven circles made
by the ardent little male. Now he approaches nearer and nearer, and when
almost within reach whirls madly around and around her, she joining with
him in a giddy maze. Again he falls back and resumes his semicircular
motions, with his body tilted over; she, all excitement, lowers her head and
raises her body so that it is almost vertical; both draw nearer; she moves
slowly under him, he crawling over her head, and the mating is
accomplished.”
A similar but not exactly identical
performance was gone through by
the male of several different species,
but it was noteworthy that the
particular attitudes he adopted were
always such as to display to the best
advantage his special beauties,
whether they consisted in crested Fig. 200.—Dancing attitude of male Icius
head, fringed palpi and fore-legs, or mitratus. (After Peckham.)
iridescent abdomen. Sometimes even
such exertions failed to captivate the female, and she would savagely attack
the male, occasionally with fatal effect.
In the case of some species, when the male had won the consent of his
mate, he would weave a small nuptial tent or web, into which he would
partly lead and partly drive the female, who no longer offered serious
resistance.
Fossil Spiders.
About 250 species of fossil spiders have been discovered. Of these about
180 are embedded in amber, a fossil resinous substance which exuded from
side by straightening out the legs, and lowering it on the other by folding
the first two pairs of legs up and under, leaned so far over as to be in danger
of losing his balance, which he only maintained by sidling rapidly towards
the lowered side.... Again and again he circles from side to side, she gazing
towards him in a softer mood, evidently admiring the grace of his antics.
This is repeated until we have counted a hundred and eleven circles made
by the ardent little male. Now he approaches nearer and nearer, and when
almost within reach whirls madly around and around her, she joining with
him in a giddy maze. Again he falls back and resumes his semicircular
motions, with his body tilted over; she, all excitement, lowers her head and
raises her body so that it is almost vertical; both draw nearer; she moves
slowly under him, he crawling over her head, and the mating is
accomplished.”
A similar but not exactly identical
performance was gone through by
the male of several different species,
but it was noteworthy that the
particular attitudes he adopted were
always such as to display to the best
advantage his special beauties,
whether they consisted in crested Fig. 200.—Dancing attitude of male Icius
head, fringed palpi and fore-legs, or mitratus. (After Peckham.)
iridescent abdomen. Sometimes even
such exertions failed to captivate the female, and she would savagely attack
the male, occasionally with fatal effect.
In the case of some species, when the male had won the consent of his
mate, he would weave a small nuptial tent or web, into which he would
partly lead and partly drive the female, who no longer offered serious
resistance.
Fossil Spiders.
About 250 species of fossil spiders have been discovered. Of these about
180 are embedded in amber, a fossil resinous substance which exuded from
Page 427
ancient coniferous trees, and quantities of which are annually washed up
from the Baltic upon the shores of northern Prussia.
The most ancient fossil spider known was obtained from the argillaceous
slate of Kattowitz in Silesia, and belongs, therefore, to the Carboniferous
strata of the Palaeozoic epoch. It has been named Protolycosa
anthrocophila. There is some doubt as to the affinities of this spider.
Roemer, who described it, placed it among the Citigradae, while others
have thought it to belong rather to the Territelariae. Thorell, on account of
its agreement in certain important points with the very curious recent Malay
spider Liphistius, has placed them both in a separate sub-family,
Liphistioidae. To the same epoch belongs the American fossil spider
Arthrolycosa antiqua, which was found in the Coal measures of Illinois.
The other localities from which fossil spiders have been obtained are the
Swiss Miocene at Oeningen, the Oligocene deposits at Aix, the Oligocene
of Florissant, Colorado, Green River, Wyoming, and Quesnel, British
Columbia.
Many of the spiders from the rocks are so fragmentary that it is
impossible to decide with certainty on their systematic position, but a
considerable number of them—more than half—have been assigned to
recent genera.
The amber spiders are mostly well preserved, and can be classified with
more certainty. Many of them are surprisingly like existing forms, though
others, like Archaea paradoxa, differ greatly from most spiders now extant,
though they show some affinities with one or two remarkable and aberrant
forms.
from the Baltic upon the shores of northern Prussia.
The most ancient fossil spider known was obtained from the argillaceous
slate of Kattowitz in Silesia, and belongs, therefore, to the Carboniferous
strata of the Palaeozoic epoch. It has been named Protolycosa
anthrocophila. There is some doubt as to the affinities of this spider.
Roemer, who described it, placed it among the Citigradae, while others
have thought it to belong rather to the Territelariae. Thorell, on account of
its agreement in certain important points with the very curious recent Malay
spider Liphistius, has placed them both in a separate sub-family,
Liphistioidae. To the same epoch belongs the American fossil spider
Arthrolycosa antiqua, which was found in the Coal measures of Illinois.
The other localities from which fossil spiders have been obtained are the
Swiss Miocene at Oeningen, the Oligocene deposits at Aix, the Oligocene
of Florissant, Colorado, Green River, Wyoming, and Quesnel, British
Columbia.
Many of the spiders from the rocks are so fragmentary that it is
impossible to decide with certainty on their systematic position, but a
considerable number of them—more than half—have been assigned to
recent genera.
The amber spiders are mostly well preserved, and can be classified with
more certainty. Many of them are surprisingly like existing forms, though
others, like Archaea paradoxa, differ greatly from most spiders now extant,
though they show some affinities with one or two remarkable and aberrant
forms.
Page 428
CHAPTER XV
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ARANEAE (CONTINUED)—CLASSIFICATION
The systematic study of Spiders has hitherto presented very great
difficulties. There is an extensive literature on the subject, but the more
important works are costly, not commonly to be found in libraries, and
written in diverse languages. Moreover, the nomenclature is only now
emerging from a condition of chaos. Able and diligent Arachnologists have
done admirable work in studying and describing the Spider fauna of their
various countries, and occasional tentative suggestions have been put forth
with a view to reducing to some sort of order the vast mass of
heterogeneous material thus collected. Most schemes of classification,
based chiefly upon a knowledge of European forms, have proved quite
inadequate for the reception of the vast numbers of strange exotic species
with which recent years have made us acquainted. The number of described
species is very large, and is rapidly increasing; but though we are very far
indeed from anything like an exhaustive knowledge of existing forms, it
may now be said that almost every considerable area of the earth’s surface
is at least partially represented in the cabinets of collectors, and it is
possible to take a comprehensive view of the whole Spider fauna, and to
suggest a scheme of classification very much less likely than heretofore to
be fundamentally deranged by new discoveries.
The first to apply the Linnaean nomenclature to Spiders was Clerck, in
his Araneae Suecicae (1757), which gives an account of seventy spiders,
some of which are varieties of the same species. A few new species were
added by Linnaeus, De Geer, Scopoli, Fabricius, etc., but the next work of
real importance was that of Westring (1861), who, under the same title,
described 308 species, divided among six families. Blackwall’s beautiful
work, the Spiders of Great Britain and Ireland, was published by the Ray
Society in 1864. He divides spiders into three tribes, Octonoculina,
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ARANEAE (CONTINUED)—CLASSIFICATION
The systematic study of Spiders has hitherto presented very great
difficulties. There is an extensive literature on the subject, but the more
important works are costly, not commonly to be found in libraries, and
written in diverse languages. Moreover, the nomenclature is only now
emerging from a condition of chaos. Able and diligent Arachnologists have
done admirable work in studying and describing the Spider fauna of their
various countries, and occasional tentative suggestions have been put forth
with a view to reducing to some sort of order the vast mass of
heterogeneous material thus collected. Most schemes of classification,
based chiefly upon a knowledge of European forms, have proved quite
inadequate for the reception of the vast numbers of strange exotic species
with which recent years have made us acquainted. The number of described
species is very large, and is rapidly increasing; but though we are very far
indeed from anything like an exhaustive knowledge of existing forms, it
may now be said that almost every considerable area of the earth’s surface
is at least partially represented in the cabinets of collectors, and it is
possible to take a comprehensive view of the whole Spider fauna, and to
suggest a scheme of classification very much less likely than heretofore to
be fundamentally deranged by new discoveries.
The first to apply the Linnaean nomenclature to Spiders was Clerck, in
his Araneae Suecicae (1757), which gives an account of seventy spiders,
some of which are varieties of the same species. A few new species were
added by Linnaeus, De Geer, Scopoli, Fabricius, etc., but the next work of
real importance was that of Westring (1861), who, under the same title,
described 308 species, divided among six families. Blackwall’s beautiful
work, the Spiders of Great Britain and Ireland, was published by the Ray
Society in 1864. He divides spiders into three tribes, Octonoculina,
Page 429
Senoculina, and Binoculina, according to the number of the eyes, and
describes 304 British species, distributed among eleven families.
His successor in this country has been Pickard-Cambridge, whose work,
under the modest title of The Spiders of Dorset (1879–81), is indispensable
to British collectors.
Blackwall’s division of the order into tribes was evidently artificial, and
has not been followed by later Arachnologists. Dufour (1820) founded two
sub-orders, Dipneumones and Tetrapneumones, based on the presence of
two or four pulmonary sacs. Latreille (1825) established, and many
Arachnologists adopted, a division into tribes based upon habits,
Orbitelariae, Retitelariae, Citigradae, Latigradae, etc., and this method of
classification was followed in the important work of Menge, entitled
Preussische Spinnen, which was published between 1866 and 1874.
Since 1870 determined efforts have been made to grapple with the
difficult subject of Spider classification, notably by Thorell and Simon. The
latter, undoubtedly the foremost living Arachnologist, writes with especial
authority, and it is inevitable that he should be largely followed by students
of Arachnology, who cannot pretend to anything like the same width of
outlook.
It is indicative of the transition stage through which the subject is passing
that Simon in his two most important works,[306] propounds somewhat
different schemes of classification, while in the Histoire naturelle, where
his latest views are to be found, he introduces in the course of the work
quite considerable modifications of the scheme set forth in the first volume.
In that work the order is divided into two sub-orders, Araneae
theraphosae and Araneae verae, the first sub-order containing Liphistius
and the Mygalidae or Theraphosidae of other authors, while all other
spiders fall under the second sub-order. The Araneae verae are subdivided
into Cribellatae and Ecribellatae, according to the presence or absence of
“cribellum” and “calamistrum” (see p. 326) in the female. Important as
these organs doubtless are, the Cribellatae do not appear to form a natural
group, some of the families having apparently much closer affinities with
certain of the Ecribellatae than with one another. This is especially evident
in the case of the cribellate Oecobiidae and the ecribellate Urocteidae (see
p. 392), which most authors unite in a single family.
describes 304 British species, distributed among eleven families.
His successor in this country has been Pickard-Cambridge, whose work,
under the modest title of The Spiders of Dorset (1879–81), is indispensable
to British collectors.
Blackwall’s division of the order into tribes was evidently artificial, and
has not been followed by later Arachnologists. Dufour (1820) founded two
sub-orders, Dipneumones and Tetrapneumones, based on the presence of
two or four pulmonary sacs. Latreille (1825) established, and many
Arachnologists adopted, a division into tribes based upon habits,
Orbitelariae, Retitelariae, Citigradae, Latigradae, etc., and this method of
classification was followed in the important work of Menge, entitled
Preussische Spinnen, which was published between 1866 and 1874.
Since 1870 determined efforts have been made to grapple with the
difficult subject of Spider classification, notably by Thorell and Simon. The
latter, undoubtedly the foremost living Arachnologist, writes with especial
authority, and it is inevitable that he should be largely followed by students
of Arachnology, who cannot pretend to anything like the same width of
outlook.
It is indicative of the transition stage through which the subject is passing
that Simon in his two most important works,[306] propounds somewhat
different schemes of classification, while in the Histoire naturelle, where
his latest views are to be found, he introduces in the course of the work
quite considerable modifications of the scheme set forth in the first volume.
In that work the order is divided into two sub-orders, Araneae
theraphosae and Araneae verae, the first sub-order containing Liphistius
and the Mygalidae or Theraphosidae of other authors, while all other
spiders fall under the second sub-order. The Araneae verae are subdivided
into Cribellatae and Ecribellatae, according to the presence or absence of
“cribellum” and “calamistrum” (see p. 326) in the female. Important as
these organs doubtless are, the Cribellatae do not appear to form a natural
group, some of the families having apparently much closer affinities with
certain of the Ecribellatae than with one another. This is especially evident
in the case of the cribellate Oecobiidae and the ecribellate Urocteidae (see
p. 392), which most authors unite in a single family.
Page 430
After all, the larger divisions of the order are not of great importance, and
in the present chapter Simon’s linear arrangement of families will in the
main be followed, except for the distribution of the eight families which
constitute his Cribellatae[307] to the positions which a more general view of
their structure would seem to indicate.
Fam. 1. Liphistiidae.—Spiders with segmented abdomen, as shown by
the presence of a series of tergal plates. Eight spinnerets in the middle of
the ventral surface of the abdomen, far removed from the anal tubercle.
Sternum long and narrow. Eight compact eyes on a small eminence. Four
pulmonary stigmata.
This Family includes a single
genus and two species of large
spiders (about two inches in length),
one from Penang and one from
Sumatra. Very few examples have
been found, and these are more or
Fig. 201.—Profile (nat. size) and ocular area less defective and in bad condition.
(enlarged) of Liphistius desultor.
In some respects, especially the
distinct segmentation of the
abdomen, this genus much more nearly approaches the Pedipalpi than do
any others of the order. No other spider possesses more than six spinning
mammillae, but it is possible that eight was the more primitive number, and
that the “cribellum” (see p. 326) of the so-called Cribellate spiders is
derived from the pair now possessed by Liphistius alone.
Some Arachnologists consider the genus Liphistius so different from all
other spiders as to constitute in itself a sub-order, for which, on account of
the position of its spinnerets, the name MESOTHELAE has been suggested,
all other forms falling into the sub-order OPISTHOTHELAE.
Fam. 2. Aviculariidae. (Mygalidae).[308]—Spiders with independent
chelicerae, the paturon directed forward and the unguis or fang articulating
in a vertical plane. The eyes are eight (except Masteria, six), usually
compact, and situated on an eminence. Pedipalpi very leg-like, and palpal
organs of male simple. No maxillae. Four pulmonary stigmata. Spinnerets
normally four. No colulus.
The Aviculariidae inhabit the warmer portions of the world, and are
entirely unrepresented in this country. The monster spiders which excite
in the present chapter Simon’s linear arrangement of families will in the
main be followed, except for the distribution of the eight families which
constitute his Cribellatae[307] to the positions which a more general view of
their structure would seem to indicate.
Fam. 1. Liphistiidae.—Spiders with segmented abdomen, as shown by
the presence of a series of tergal plates. Eight spinnerets in the middle of
the ventral surface of the abdomen, far removed from the anal tubercle.
Sternum long and narrow. Eight compact eyes on a small eminence. Four
pulmonary stigmata.
This Family includes a single
genus and two species of large
spiders (about two inches in length),
one from Penang and one from
Sumatra. Very few examples have
been found, and these are more or
Fig. 201.—Profile (nat. size) and ocular area less defective and in bad condition.
(enlarged) of Liphistius desultor.
In some respects, especially the
distinct segmentation of the
abdomen, this genus much more nearly approaches the Pedipalpi than do
any others of the order. No other spider possesses more than six spinning
mammillae, but it is possible that eight was the more primitive number, and
that the “cribellum” (see p. 326) of the so-called Cribellate spiders is
derived from the pair now possessed by Liphistius alone.
Some Arachnologists consider the genus Liphistius so different from all
other spiders as to constitute in itself a sub-order, for which, on account of
the position of its spinnerets, the name MESOTHELAE has been suggested,
all other forms falling into the sub-order OPISTHOTHELAE.
Fam. 2. Aviculariidae. (Mygalidae).[308]—Spiders with independent
chelicerae, the paturon directed forward and the unguis or fang articulating
in a vertical plane. The eyes are eight (except Masteria, six), usually
compact, and situated on an eminence. Pedipalpi very leg-like, and palpal
organs of male simple. No maxillae. Four pulmonary stigmata. Spinnerets
normally four. No colulus.
The Aviculariidae inhabit the warmer portions of the world, and are
entirely unrepresented in this country. The monster spiders which excite
Page 431
wonder in zoological collections belong to this group, as do the moderate-
sized “Trap-door” Spiders which are found abundantly in the Mediterranean
region.
The Family has been divided into about a hundred and fifty genera,
nearly half of which, however, contain only a single species.
They have been grouped by Simon[309] into seven sub-families,
Paratropidinae, Actinopodinae, Miginae, Ctenizinae, Barychelinae,
Aviculariinae, and Diplurinae, of which the first three may be dealt with
very briefly.
(i.) The Paratropidinae include only two American species, Paratropis
scrupea from the Amazon, and Anisaspis bacillifera from St. Vincent. They
have thick, rugose integuments, and the internal angle of the coxa of the
pedipalp is produced. The labium is fused with the sternum, which is very
broad. Nothing is known of their habits, but as they do not possess a
“rastellus” (see p. 320) they are probably not burrowing spiders.
(ii.) The Actinopodinae comprise three genera, Stasinopus represented by
a single South African species, S. caffrus; Eriodon, of which about ten
species inhabit Australia; and Actinopus, of which about ten species are
found in Central and South America. They have the coxae of the pedipalps
very short and broad, and somewhat produced at the internal angle. The
eyes are not in the usual compact group, but are somewhat extended across
the caput. Actinopus burrows a deep cylindrical hole lined with silk, and
furnished with a round, bevelled trap-door.
(iii.) The sub-family Miginae is established for the reception of three
genera, Moggridgea (South Africa), Migas (Australia and South-West
Africa), and Myrtale, whose single species, M. perroti, inhabits
Madagascar. They are chiefly characterised by their very short and
downwardly-directed chelicerae. They are not terricolous, but inhabit trees,
either boring holes in the bark, or constructing a sort of silken retreat
fortified by particles of wood.
(iv.) The Ctenizinae form a large group, including some forty genera. All
the “Trap-door” Spiders of the Continent fall under this sub-family, which,
moreover, has representatives in all the tropical and sub-tropical regions of
the world. A rastellus is always present, and the eyes form a compact group
on an eminence. The coxae of the pedipalps are longer than in the groups
sized “Trap-door” Spiders which are found abundantly in the Mediterranean
region.
The Family has been divided into about a hundred and fifty genera,
nearly half of which, however, contain only a single species.
They have been grouped by Simon[309] into seven sub-families,
Paratropidinae, Actinopodinae, Miginae, Ctenizinae, Barychelinae,
Aviculariinae, and Diplurinae, of which the first three may be dealt with
very briefly.
(i.) The Paratropidinae include only two American species, Paratropis
scrupea from the Amazon, and Anisaspis bacillifera from St. Vincent. They
have thick, rugose integuments, and the internal angle of the coxa of the
pedipalp is produced. The labium is fused with the sternum, which is very
broad. Nothing is known of their habits, but as they do not possess a
“rastellus” (see p. 320) they are probably not burrowing spiders.
(ii.) The Actinopodinae comprise three genera, Stasinopus represented by
a single South African species, S. caffrus; Eriodon, of which about ten
species inhabit Australia; and Actinopus, of which about ten species are
found in Central and South America. They have the coxae of the pedipalps
very short and broad, and somewhat produced at the internal angle. The
eyes are not in the usual compact group, but are somewhat extended across
the caput. Actinopus burrows a deep cylindrical hole lined with silk, and
furnished with a round, bevelled trap-door.
(iii.) The sub-family Miginae is established for the reception of three
genera, Moggridgea (South Africa), Migas (Australia and South-West
Africa), and Myrtale, whose single species, M. perroti, inhabits
Madagascar. They are chiefly characterised by their very short and
downwardly-directed chelicerae. They are not terricolous, but inhabit trees,
either boring holes in the bark, or constructing a sort of silken retreat
fortified by particles of wood.
(iv.) The Ctenizinae form a large group, including some forty genera. All
the “Trap-door” Spiders of the Continent fall under this sub-family, which,
moreover, has representatives in all the tropical and sub-tropical regions of
the world. A rastellus is always present, and the eyes form a compact group
on an eminence. The coxae of the pedipalps are longer than in the groups
Page 432
previously mentioned, and there is no production of the internal angle. The
labium is generally free.
The commonest European genus is Nemesia, of which about thirty
species inhabit the Mediterranean region. The cephalothorax is rather flat,
and the central fovea is recurved (◠). The burrow is sometimes simple and
sometimes branched, and the trap-door may be either thin, or thick with
bevelled edges.
Allied genera are Hermacha and Rachias in South America, Spiroctenus
in South Africa, Genysa in Madagascar, Scalidognathus in Ceylon, and
Arbanitis in New Zealand. The genus Cteniza (fovea procurved ◡)
possesses only a single species (C. sauvagei), found in South-East France
and Italy.
Pachylomerus is a widely-distributed genus, being represented in North
and South America, Japan, and North Africa. The tibiae of the third pair of
legs are marked above by a deep impression near the base. A closely allied
genus, Conothele. inhabits Southern Asia and New Guinea.
The widely-distributed genus Acanthodon, which has representatives in
all the sub-tropical countries of the world, together with the South
American genera Idiops and Pseudidiops, and the Indian genus
Heligmonerus, present a peculiar arrangement of the eyes, one pair being
situated close together in the middle of the front of the caput, while the
remaining six form a more or less compact group some distance behind
them.
Among the many other genera of the Ctenizinae may be mentioned
Cyrtauchenius, of which many species inhabit North-West Africa, and its
close ally Amblyocarenum, represented on both shores of the
Mediterranean, and in North and South America. They differ from Cteniza
chiefly in the possession of strong scopulae on the tarsi and metatarsi of the
first pair of legs, and in the double row of teeth with which the tarsal claws
are furnished. Their burrows are often surmounted by a sort of turret raised
above the level of the ground.
(v.) The Barychelinae are burrowing forms which resemble Nemesia, but
have only two tarsal claws. Leptopelma is the only European genus, and has
close affinities with certain South American genera (Psalistops,
Euthycoelus, etc.). Pisenor inhabits tropical Africa, and Diplothele, unique
in possessing only two spinning mammillae, is an inhabitant of India.
labium is generally free.
The commonest European genus is Nemesia, of which about thirty
species inhabit the Mediterranean region. The cephalothorax is rather flat,
and the central fovea is recurved (◠). The burrow is sometimes simple and
sometimes branched, and the trap-door may be either thin, or thick with
bevelled edges.
Allied genera are Hermacha and Rachias in South America, Spiroctenus
in South Africa, Genysa in Madagascar, Scalidognathus in Ceylon, and
Arbanitis in New Zealand. The genus Cteniza (fovea procurved ◡)
possesses only a single species (C. sauvagei), found in South-East France
and Italy.
Pachylomerus is a widely-distributed genus, being represented in North
and South America, Japan, and North Africa. The tibiae of the third pair of
legs are marked above by a deep impression near the base. A closely allied
genus, Conothele. inhabits Southern Asia and New Guinea.
The widely-distributed genus Acanthodon, which has representatives in
all the sub-tropical countries of the world, together with the South
American genera Idiops and Pseudidiops, and the Indian genus
Heligmonerus, present a peculiar arrangement of the eyes, one pair being
situated close together in the middle of the front of the caput, while the
remaining six form a more or less compact group some distance behind
them.
Among the many other genera of the Ctenizinae may be mentioned
Cyrtauchenius, of which many species inhabit North-West Africa, and its
close ally Amblyocarenum, represented on both shores of the
Mediterranean, and in North and South America. They differ from Cteniza
chiefly in the possession of strong scopulae on the tarsi and metatarsi of the
first pair of legs, and in the double row of teeth with which the tarsal claws
are furnished. Their burrows are often surmounted by a sort of turret raised
above the level of the ground.
(v.) The Barychelinae are burrowing forms which resemble Nemesia, but
have only two tarsal claws. Leptopelma is the only European genus, and has
close affinities with certain South American genera (Psalistops,
Euthycoelus, etc.). Pisenor inhabits tropical Africa, and Diplothele, unique
in possessing only two spinning mammillae, is an inhabitant of India.
Page 433
(vi.) The Aviculariinae include all the large hairy spiders which are
commonly called Mygale. The genus Phlogius, which inhabits Southern
Asia, forms a lidless burrow, though it has no rastellus, but practically all
the other members of the group are non-terricolous, living under stones or
in holes in trees, where they weave a slight web. They are nocturnal in their
habits. They all possess two tarsal claws, and the labium is free and spined
at the tip. Of the four spinnerets the posterior pair are long and three-
jointed, while the anterior are short and not very close together.
The particular form of the tarsi and the nature of the scopulae,[310] “claw-
tufts,” and spines upon them are of great importance in distinguishing the
members of this group.
The Aviculariinae comprise about sixty genera from all the tropical and
sub-tropical regions of the world.
The genus Ischnocolus extends into the Mediterranean region, having
representatives besides in Southern Asia and in Central and South America.
All the tarsi have their scopulae divided longitudinally by a band of hairs.
Chaetopelma inhabits Egypt, Syria, and Arabia, and Cyclosternum is found
in West Africa as well as in Central and South America. In these genera the
scopulae of the last two pairs of legs are alone divided. The largest known
spider is Theraphosa leblondi, which is a native of Guiana. It measures 9
cm. (about three and a half inches) in length.
Eurypelma is a genus of large spiders entirely confined to the New
World, where it possesses many species. The genus Avicularia is also
American, and includes a number of large long-haired spiders with short
and very strong legs, on which the scopulae and claw-tufts are well
developed. Its nearest allies in the Old World are the Indian genus
Poecilotheria, and the West African genus Scodra. The stridulating spider
figured on p. 328 belongs to this group, Chilobrachys being a genus from
Ceylon.
(vii.) The Diplurinae are a very aberrant group, including some twenty
genera of Aviculariidae, usually of medium size, and possessed, as a rule, of
very long posterior spinnerets. They do not burrow or live in holes or under
stones, but weave webs of close texture, much resembling those
characteristic of the Agelenidae (see p. 415). The tarsal claws are three in
number, and there are never any claw-tufts. The rastellus, of course, is
absent.
commonly called Mygale. The genus Phlogius, which inhabits Southern
Asia, forms a lidless burrow, though it has no rastellus, but practically all
the other members of the group are non-terricolous, living under stones or
in holes in trees, where they weave a slight web. They are nocturnal in their
habits. They all possess two tarsal claws, and the labium is free and spined
at the tip. Of the four spinnerets the posterior pair are long and three-
jointed, while the anterior are short and not very close together.
The particular form of the tarsi and the nature of the scopulae,[310] “claw-
tufts,” and spines upon them are of great importance in distinguishing the
members of this group.
The Aviculariinae comprise about sixty genera from all the tropical and
sub-tropical regions of the world.
The genus Ischnocolus extends into the Mediterranean region, having
representatives besides in Southern Asia and in Central and South America.
All the tarsi have their scopulae divided longitudinally by a band of hairs.
Chaetopelma inhabits Egypt, Syria, and Arabia, and Cyclosternum is found
in West Africa as well as in Central and South America. In these genera the
scopulae of the last two pairs of legs are alone divided. The largest known
spider is Theraphosa leblondi, which is a native of Guiana. It measures 9
cm. (about three and a half inches) in length.
Eurypelma is a genus of large spiders entirely confined to the New
World, where it possesses many species. The genus Avicularia is also
American, and includes a number of large long-haired spiders with short
and very strong legs, on which the scopulae and claw-tufts are well
developed. Its nearest allies in the Old World are the Indian genus
Poecilotheria, and the West African genus Scodra. The stridulating spider
figured on p. 328 belongs to this group, Chilobrachys being a genus from
Ceylon.
(vii.) The Diplurinae are a very aberrant group, including some twenty
genera of Aviculariidae, usually of medium size, and possessed, as a rule, of
very long posterior spinnerets. They do not burrow or live in holes or under
stones, but weave webs of close texture, much resembling those
characteristic of the Agelenidae (see p. 415). The tarsal claws are three in
number, and there are never any claw-tufts. The rastellus, of course, is
absent.
Page 434
Two genera have representatives in
Europe, Brachythele inhabiting the
East Mediterranean region (as well as
many other parts of the world), while
Macrothele is found in Spain as well
as in the Malay Peninsula and New
Zealand. Ischnothele dumicola is a
native of Western India. Diplura is a
South American genus. Trechona
venosa, a large species remarkable
for the orange bands which decorate
its abdomen, is also a native of South
America. The New Zealand genus
Hexathele, and the genus Scotinoecus
from Chili, possess six spinnerets.
Masteria (Ovalan Island) and Accola Fig. 202.—Ischnothele dumicola, ♀ × 2. (After
(Philippines and South America) Pocock.)
differ from the rest of the family in
having only six eyes.
Fam. 3. Atypidae.—Spiders with anteriorly projecting and vertically
articulating chelicerae, but with no trough on the paturon for the reception
of the unguis, which is guarded when closed by a single row of teeth. The
spinnerets are normally six, and the anal tubercle is above, and well
removed from the posterior spinnerets.
The Atypidae are a small family of six genera, rather closely related to
the Aviculariidae, and by some Arachnologists incorporated with them.
They may be regarded as the representatives of that family in sub-tropical
and temperate regions. In form they are strongly built, with smooth
integuments, and their legs are short and powerful. Of the twenty-four
species hitherto described almost all belong to the northern hemisphere.
Five are natives of Europe, and two are included in the English fauna. The
best known is Atypus affinis, which has been found in several localities in
the south of England, and which has occurred on the Devil’s Dyke, near
Cambridge. The female measures about half an inch in length, the male
being smaller. It burrows a deep cylindrical hole at the edge of a grassy or
heathery bank and lines it with a loose tube of silk, which extends
considerably beyond the orifice of the burrow, either lying flat on the
Europe, Brachythele inhabiting the
East Mediterranean region (as well as
many other parts of the world), while
Macrothele is found in Spain as well
as in the Malay Peninsula and New
Zealand. Ischnothele dumicola is a
native of Western India. Diplura is a
South American genus. Trechona
venosa, a large species remarkable
for the orange bands which decorate
its abdomen, is also a native of South
America. The New Zealand genus
Hexathele, and the genus Scotinoecus
from Chili, possess six spinnerets.
Masteria (Ovalan Island) and Accola Fig. 202.—Ischnothele dumicola, ♀ × 2. (After
(Philippines and South America) Pocock.)
differ from the rest of the family in
having only six eyes.
Fam. 3. Atypidae.—Spiders with anteriorly projecting and vertically
articulating chelicerae, but with no trough on the paturon for the reception
of the unguis, which is guarded when closed by a single row of teeth. The
spinnerets are normally six, and the anal tubercle is above, and well
removed from the posterior spinnerets.
The Atypidae are a small family of six genera, rather closely related to
the Aviculariidae, and by some Arachnologists incorporated with them.
They may be regarded as the representatives of that family in sub-tropical
and temperate regions. In form they are strongly built, with smooth
integuments, and their legs are short and powerful. Of the twenty-four
species hitherto described almost all belong to the northern hemisphere.
Five are natives of Europe, and two are included in the English fauna. The
best known is Atypus affinis, which has been found in several localities in
the south of England, and which has occurred on the Devil’s Dyke, near
Cambridge. The female measures about half an inch in length, the male
being smaller. It burrows a deep cylindrical hole at the edge of a grassy or
heathery bank and lines it with a loose tube of silk, which extends
considerably beyond the orifice of the burrow, either lying flat on the
Page 435
ground, or raised up and attached to
the neighbouring herbage. There is
no lid, but the upper end of the tube
is always found closed, whether by
its elasticity or by the deliberate
operation of the spider is not known.
The animal is nocturnal in its habits.
Another species, A. beckii, occurs
very rarely in the south of England.
The genus Atypus has
representatives in Central and South
Europe, North Africa, Japan, Java,
and North America. Of the other
genera, Calommata inhabits Central
and South-East Asia and Japan,
Brachybothrium, Atypoides, and
Hexura are peculiar to North
Fig. 203.—Atypus affinis, ♀. America, while Mecicobothrium
comprises a single species (M.
thorelli) native to the Argentine.[311]
Fam. 4. Filistatidae.—Cribellate Spiders of moderate size, usually
brown or yellow in colour, with smooth integuments and somewhat long
tapering legs. The eight eyes are compactly arranged, and the palpal
organs of the male are of simple structure. The six spinnerets are short, the
anterior pair being thick and separated. Two pulmonary sacs, with two
minute tracheal stigmata close behind them and widely separate.
There is but one genus, Filistata, in this family. About fifteen species
have been described, five of which inhabit the Mediterranean region. Three
are found in America, and others inhabit Central Asia, the Philippines, and
Australia. The genus is not represented in this country, but one species, F.
testacea, has an extremely wide distribution in the Old World, while F.
capitata extends throughout the American continent.
The calamistrum of the female is short, only occupying a portion of the
metatarsus of the fourth leg. The cribellum is divided. These spiders weave
a web of close texture, of an irregular tubular form.
the neighbouring herbage. There is
no lid, but the upper end of the tube
is always found closed, whether by
its elasticity or by the deliberate
operation of the spider is not known.
The animal is nocturnal in its habits.
Another species, A. beckii, occurs
very rarely in the south of England.
The genus Atypus has
representatives in Central and South
Europe, North Africa, Japan, Java,
and North America. Of the other
genera, Calommata inhabits Central
and South-East Asia and Japan,
Brachybothrium, Atypoides, and
Hexura are peculiar to North
Fig. 203.—Atypus affinis, ♀. America, while Mecicobothrium
comprises a single species (M.
thorelli) native to the Argentine.[311]
Fam. 4. Filistatidae.—Cribellate Spiders of moderate size, usually
brown or yellow in colour, with smooth integuments and somewhat long
tapering legs. The eight eyes are compactly arranged, and the palpal
organs of the male are of simple structure. The six spinnerets are short, the
anterior pair being thick and separated. Two pulmonary sacs, with two
minute tracheal stigmata close behind them and widely separate.
There is but one genus, Filistata, in this family. About fifteen species
have been described, five of which inhabit the Mediterranean region. Three
are found in America, and others inhabit Central Asia, the Philippines, and
Australia. The genus is not represented in this country, but one species, F.
testacea, has an extremely wide distribution in the Old World, while F.
capitata extends throughout the American continent.
The calamistrum of the female is short, only occupying a portion of the
metatarsus of the fourth leg. The cribellum is divided. These spiders weave
a web of close texture, of an irregular tubular form.
Page 436
Fam. 5. Oecobiidae (Urocteidae).—Two very remarkable genera
constitute this family, Oecobius and Uroctea.
The species of Oecobius, about fifteen in number, are small spiders,
inhabiting sub-tropical countries—and especially desert regions—and
spinning a slight web under stones, or in holes in walls. The female
possesses a small transverse cribellum, the two halves of which are widely
separated. The calamistrum is but feebly developed. No example has
occurred in this country, but nine species have been described in the
Mediterranean region.
Fig. 204.—A, Oecobius maculatus, much enlarged; B, Uroctea durandi, slightly
enlarged. (After Simon.)
The three species of Uroctea are rather large spiders, two being native to
Africa, while the third inhabits China and Japan. They are ecribellate. These
two genera very closely resemble each other, not only superficially, but in
certain structural details—notably the remarkably developed and two-
jointed anal tubercle—and their close affinity supplies the strongest
argument against separating the spiders which possess cribellum and
calamistrum into a group by themselves. In both genera the cephalothorax
is very broad and rounded at the sides. The eight eyes are compactly
arranged. The sternum is broad and heart-shaped. The legs are nearly of
equal length, and the posterior spinnerets have very long terminal joints.
constitute this family, Oecobius and Uroctea.
The species of Oecobius, about fifteen in number, are small spiders,
inhabiting sub-tropical countries—and especially desert regions—and
spinning a slight web under stones, or in holes in walls. The female
possesses a small transverse cribellum, the two halves of which are widely
separated. The calamistrum is but feebly developed. No example has
occurred in this country, but nine species have been described in the
Mediterranean region.
Fig. 204.—A, Oecobius maculatus, much enlarged; B, Uroctea durandi, slightly
enlarged. (After Simon.)
The three species of Uroctea are rather large spiders, two being native to
Africa, while the third inhabits China and Japan. They are ecribellate. These
two genera very closely resemble each other, not only superficially, but in
certain structural details—notably the remarkably developed and two-
jointed anal tubercle—and their close affinity supplies the strongest
argument against separating the spiders which possess cribellum and
calamistrum into a group by themselves. In both genera the cephalothorax
is very broad and rounded at the sides. The eight eyes are compactly
arranged. The sternum is broad and heart-shaped. The legs are nearly of
equal length, and the posterior spinnerets have very long terminal joints.
Page 437
Fam. 6. Sicariidae (Scytodidae).—The Sicariidae are a small group of
six-eyed spiders, usually with weak legs and slow halting movements; they
live under stones or in outhouses. The cephalothorax is generally smooth
and devoid of the median fovea, and the palpal organs of the male are
extremely simple. The best known genus is Scytodes, one species of which
(S. thoracica) has on rare occasions been found in outhouses in the south of
England, in Dorsetshire, and Kent. This is a remarkable spider, about one-
third of an inch long, with a pale yellow ground-colour, marked with black
spots and patches. The cephalothorax is smooth and dome-shaped, and
highest near the posterior end.
All the other members of the family are exotic. Loxosceles is found in the
Mediterranean region and all over America, as well as in Japan. The median
fovea is present in this genus. Sicarius is a native of America and South
Africa. It is of stouter build than Scytodes, and the legs are stronger.
Drymusa belongs to South Africa. The peculiar New Zealand species
Periegops hirsutus is placed by Simon in this family, as is also the North
American genus Plectreurys, notwithstanding its possession of eight eyes.
Fam. 7. Hypochilidae.—Two species only are included in this family,
Hypochilus thorelli of North America, and Ectatosticta davidi, a native of
China. They have four pulmonary sacs, though they possess little else in
common with the “Theraphosae.” The pedipalpus of the male is very
remarkable, the tarsus being almost unmodified, and the very small palpal
organ being inserted at its extremity. These spiders are cribellate.
Fam. 8. Leptonetidae.—The Leptonetidae are small spiders with smooth
and usually dull-coloured integuments. Most of them are cave-living, but
some are found amidst vegetable débris in damp spots in forests. The eyes
are six in number, and the legs are generally long and thin. There are five
genera. Leptoneta has about ten species living in caves in the Pyrenees. The
single species of Telema (T. tenella) has the same habitat. Ochyrocera has
representatives in tropical Asia and America, and is somewhat more ornate
than most members of the group. Usofila has a single species, inhabiting
North America, while Theotina is found in caves in the Philippines and in
Venezuela.
Fam. 9. Oonopidae.—The Oonopidae are very small spiders, seldom
exceeding 2 mm. in length (the largest 4 mm.), living among vegetable
débris. Oonops pulcher, the only English representative of the family, is not
six-eyed spiders, usually with weak legs and slow halting movements; they
live under stones or in outhouses. The cephalothorax is generally smooth
and devoid of the median fovea, and the palpal organs of the male are
extremely simple. The best known genus is Scytodes, one species of which
(S. thoracica) has on rare occasions been found in outhouses in the south of
England, in Dorsetshire, and Kent. This is a remarkable spider, about one-
third of an inch long, with a pale yellow ground-colour, marked with black
spots and patches. The cephalothorax is smooth and dome-shaped, and
highest near the posterior end.
All the other members of the family are exotic. Loxosceles is found in the
Mediterranean region and all over America, as well as in Japan. The median
fovea is present in this genus. Sicarius is a native of America and South
Africa. It is of stouter build than Scytodes, and the legs are stronger.
Drymusa belongs to South Africa. The peculiar New Zealand species
Periegops hirsutus is placed by Simon in this family, as is also the North
American genus Plectreurys, notwithstanding its possession of eight eyes.
Fam. 7. Hypochilidae.—Two species only are included in this family,
Hypochilus thorelli of North America, and Ectatosticta davidi, a native of
China. They have four pulmonary sacs, though they possess little else in
common with the “Theraphosae.” The pedipalpus of the male is very
remarkable, the tarsus being almost unmodified, and the very small palpal
organ being inserted at its extremity. These spiders are cribellate.
Fam. 8. Leptonetidae.—The Leptonetidae are small spiders with smooth
and usually dull-coloured integuments. Most of them are cave-living, but
some are found amidst vegetable débris in damp spots in forests. The eyes
are six in number, and the legs are generally long and thin. There are five
genera. Leptoneta has about ten species living in caves in the Pyrenees. The
single species of Telema (T. tenella) has the same habitat. Ochyrocera has
representatives in tropical Asia and America, and is somewhat more ornate
than most members of the group. Usofila has a single species, inhabiting
North America, while Theotina is found in caves in the Philippines and in
Venezuela.
Fam. 9. Oonopidae.—The Oonopidae are very small spiders, seldom
exceeding 2 mm. in length (the largest 4 mm.), living among vegetable
débris. Oonops pulcher, the only English representative of the family, is not
Page 438
rare under stones or in the débris at the bottom of hedges. It is a small brick-
red spider, easily recognised by its six comparatively large oval eyes, which
are pale-coloured, and occupy the whole of the caput.
The minute spiders of this family were until recently overlooked by
collectors in foreign countries, but now more than a hundred species have
been described, belonging to some eighteen genera. Thirteen species inhabit
the Mediterranean region, occurring especially on the African side. In
several genera there is a “scutum” or hard plate on the abdomen. This is the
case with Dysderina, which has a wide distribution, as have also
Ischnyothyreus and Opopaea, and the non-scutate genus Orchestina.
Fam. 10. Hadrotarsidae.—This family contains only two species,
Hadrotarsus babirusa from New Guinea, and Gmogala scarabeus from
Sydney. In general appearance they resemble the scutate Oonopidae, but
they have eight eyes, curiously arranged, two large, somewhat triangular
eyes being situated near the middle of the cephalothorax, and two groups of
three small eyes on either side of the front part of the caput. These spiders
are very minute.
Fam. 11. Dysderidae.—Six-eyed spiders, with long free labium, and
long maxillae provided with a well-developed scopula. The cephalothorax
is rather flat, and the abdomen is oval or cylindrical, the integument being
smooth and usually rather soft. The palpal organ of the male is of simple
structure.
The Dysderidae are divided into two sub-families, Dysderinae and
Segestriinae, for the most part confined to temperate regions.
(i.) The Dysderinae are easily recognised by a peculiarity of the sternum.
Instead of being merely excavated along its border for the reception of the
legs, its edge is folded round the coxae to meet the carapace, and thus forms
a series of collars or sockets in which the limbs are articulated in perfect
isolation from each other. These spiders vary considerably in size, and are
generally of a somewhat uniform coloration, never marked with vivid
patterns. There are eight genera of this sub-family, two of which are
represented in England.
Dysdera cambridgii is not a rare spider under stones in rocky localities,
such as the Isle of Portland, and occurs, though less commonly, all over the
country in similar situations, and under the loose bark of trees. It is half an
inch in length, with a chestnut-coloured cephalothorax and legs, and dull
red spider, easily recognised by its six comparatively large oval eyes, which
are pale-coloured, and occupy the whole of the caput.
The minute spiders of this family were until recently overlooked by
collectors in foreign countries, but now more than a hundred species have
been described, belonging to some eighteen genera. Thirteen species inhabit
the Mediterranean region, occurring especially on the African side. In
several genera there is a “scutum” or hard plate on the abdomen. This is the
case with Dysderina, which has a wide distribution, as have also
Ischnyothyreus and Opopaea, and the non-scutate genus Orchestina.
Fam. 10. Hadrotarsidae.—This family contains only two species,
Hadrotarsus babirusa from New Guinea, and Gmogala scarabeus from
Sydney. In general appearance they resemble the scutate Oonopidae, but
they have eight eyes, curiously arranged, two large, somewhat triangular
eyes being situated near the middle of the cephalothorax, and two groups of
three small eyes on either side of the front part of the caput. These spiders
are very minute.
Fam. 11. Dysderidae.—Six-eyed spiders, with long free labium, and
long maxillae provided with a well-developed scopula. The cephalothorax
is rather flat, and the abdomen is oval or cylindrical, the integument being
smooth and usually rather soft. The palpal organ of the male is of simple
structure.
The Dysderidae are divided into two sub-families, Dysderinae and
Segestriinae, for the most part confined to temperate regions.
(i.) The Dysderinae are easily recognised by a peculiarity of the sternum.
Instead of being merely excavated along its border for the reception of the
legs, its edge is folded round the coxae to meet the carapace, and thus forms
a series of collars or sockets in which the limbs are articulated in perfect
isolation from each other. These spiders vary considerably in size, and are
generally of a somewhat uniform coloration, never marked with vivid
patterns. There are eight genera of this sub-family, two of which are
represented in England.
Dysdera cambridgii is not a rare spider under stones in rocky localities,
such as the Isle of Portland, and occurs, though less commonly, all over the
country in similar situations, and under the loose bark of trees. It is half an
inch in length, with a chestnut-coloured cephalothorax and legs, and dull
Page 439
yellow abdomen. A closely allied species, D. crocota, also occurs more
rarely.
Harpactes hombergii is common in vegetable débris and under decaying
bark. It is about a quarter of an inch in length, of slender form, with black-
brown cephalothorax and clay-coloured abdomen. The legs are yellowish
and annulated. More than forty exotic species of Dysdera and twenty-four
of Harpactes have been described. Another genus of the Dysderinae is
Stalita, which comprises three species, inhabiting the caves of Dalmatia and
Carniola.
(ii.) The Segestriinae include two genera, Segestria and Ariadna.
Segestria senoculata occurs in England in similar localities to those
where Dysdera cambridgii is found. It is not much smaller than that spider,
and has a dark brown cephalothorax and legs and a dull yellow abdomen,
with a series of adder-like diamond-shaped black markings along the
middle. Two other species have occurred on rare occasions in England, and
twelve more are recorded from the various temperate regions of the world.
Ariadna is the only Dysderid genus which invades the tropical regions. It
includes about twenty species.
Fam. 12. Caponiidae.—This is a small family of three genera and about
twelve species, remarkable in having no pulmonary sacs but five tracheal
stigmata,[312] and in the peculiar arrangement of their six spinnerets, those
which are ordinarily median being in the same transverse line with the
anterior ones.
The single species of Caponia (C. natalensis) inhabits South Africa,
while Caponina has two species in South America. These spiders are eight-
eyed, but the two median posterior eyes are much the largest, and these
alone are present in the remarkable genus Nops, of which several species
inhabit South America and adjacent islands.
Fam. 13. Prodidomidae.—This small family includes about twenty
species of minute spiders from sub-tropical regions. They are eight-eyed,
with short smooth legs, terminated by two claws not dentated. The
spinnerets are especially characteristic.
Prodidomus (Miltia) includes fifteen species from the Mediterranean
region, Africa, and America. Zimris is an Asiatic genus. The single species
of Eleleis (E. crinita) is from the Cape.
rarely.
Harpactes hombergii is common in vegetable débris and under decaying
bark. It is about a quarter of an inch in length, of slender form, with black-
brown cephalothorax and clay-coloured abdomen. The legs are yellowish
and annulated. More than forty exotic species of Dysdera and twenty-four
of Harpactes have been described. Another genus of the Dysderinae is
Stalita, which comprises three species, inhabiting the caves of Dalmatia and
Carniola.
(ii.) The Segestriinae include two genera, Segestria and Ariadna.
Segestria senoculata occurs in England in similar localities to those
where Dysdera cambridgii is found. It is not much smaller than that spider,
and has a dark brown cephalothorax and legs and a dull yellow abdomen,
with a series of adder-like diamond-shaped black markings along the
middle. Two other species have occurred on rare occasions in England, and
twelve more are recorded from the various temperate regions of the world.
Ariadna is the only Dysderid genus which invades the tropical regions. It
includes about twenty species.
Fam. 12. Caponiidae.—This is a small family of three genera and about
twelve species, remarkable in having no pulmonary sacs but five tracheal
stigmata,[312] and in the peculiar arrangement of their six spinnerets, those
which are ordinarily median being in the same transverse line with the
anterior ones.
The single species of Caponia (C. natalensis) inhabits South Africa,
while Caponina has two species in South America. These spiders are eight-
eyed, but the two median posterior eyes are much the largest, and these
alone are present in the remarkable genus Nops, of which several species
inhabit South America and adjacent islands.
Fam. 13. Prodidomidae.—This small family includes about twenty
species of minute spiders from sub-tropical regions. They are eight-eyed,
with short smooth legs, terminated by two claws not dentated. The
spinnerets are especially characteristic.
Prodidomus (Miltia) includes fifteen species from the Mediterranean
region, Africa, and America. Zimris is an Asiatic genus. The single species
of Eleleis (E. crinita) is from the Cape.
Page 440
Fam. 14. Drassidae.—Elongate
spiders with low cephalothorax. Legs
usually rather long, strong, and
tapering, terminated by two pectinate
claws, armed with spines, and
scopulate. The body is smooth or
short haired and frequently
unicolorous and sombre-coloured,
seldom ornate. The eyes, normally
eight, are in two transverse rows. The
mouth-parts (labium and maxillae)
are long. Spinnerets as a rule
terminal, and visible from above.
This important family includes a
large number of species from all
parts of the world, fifty-six being
natives of the British Isles. There are
familiar examples in the brown or
mouse-coloured spiders which scurry
away when stones are raised, or
when loose bark is pulled off a tree.
Fig. 205.—Drassid Spiders. 1. Drassus The family may be divided into
lapidosus. 2. Clubiona corticalis. 3. Zora
spinimana. 4. Micaria pulicaria.
seven sub-families, of which four,
Drassinae, Clubioninae,
Liocraninae, and Micariinae, are
represented in this country.
(i.) The Drassinae include more than twenty genera, some of which
possess numerous species and have a wide distribution. The following may
be mentioned:—
Drassus contains twelve British species. The commonest is D. lapidosus,
a large dull brown spider, more than half an inch in length, which lives
beneath stones in all parts of the country. At least a hundred species of this
genus have been described.
Melanophora (= Prosthesima)[313] includes a large number of species.
They are dark-coloured active spiders, many of them jet black and glossy.
Seven are recorded from the British Isles, the average size being about a
spiders with low cephalothorax. Legs
usually rather long, strong, and
tapering, terminated by two pectinate
claws, armed with spines, and
scopulate. The body is smooth or
short haired and frequently
unicolorous and sombre-coloured,
seldom ornate. The eyes, normally
eight, are in two transverse rows. The
mouth-parts (labium and maxillae)
are long. Spinnerets as a rule
terminal, and visible from above.
This important family includes a
large number of species from all
parts of the world, fifty-six being
natives of the British Isles. There are
familiar examples in the brown or
mouse-coloured spiders which scurry
away when stones are raised, or
when loose bark is pulled off a tree.
Fig. 205.—Drassid Spiders. 1. Drassus The family may be divided into
lapidosus. 2. Clubiona corticalis. 3. Zora
spinimana. 4. Micaria pulicaria.
seven sub-families, of which four,
Drassinae, Clubioninae,
Liocraninae, and Micariinae, are
represented in this country.
(i.) The Drassinae include more than twenty genera, some of which
possess numerous species and have a wide distribution. The following may
be mentioned:—
Drassus contains twelve British species. The commonest is D. lapidosus,
a large dull brown spider, more than half an inch in length, which lives
beneath stones in all parts of the country. At least a hundred species of this
genus have been described.
Melanophora (= Prosthesima)[313] includes a large number of species.
They are dark-coloured active spiders, many of them jet black and glossy.
Seven are recorded from the British Isles, the average size being about a
Page 441
quarter of an inch. They are found under stones. A closely allied genus is
Phaeocedus, whose single species (P. braccatus) has occurred, though very
rarely, in the south of England. Gnaphosa has fifty-five species, of which
twenty-eight are European, and four are British.
(ii.) The Clubioninae have the anterior spinnerets closer together, and the
eyes more extended across the caput than in the foregoing sub-family.
Nearly thirty genera have been established, of which three claim special
attention. Clubiona includes more than 100 species, chiefly inhabiting
temperate regions. Fifteen are included in the British list. They are mostly
unicolorous, and yellow or brown in colour, but a few (C. corticalis, C.
compta, etc.) have a distinct pattern on the abdomen. Cheiracanthium is a
large and widely spread genus, counting three English species. There are
more than a hundred species of the genus Anyphaena, of which one only (A.
accentuata) occurs in this country, where it is common upon bushes and
trees in the south.
(iii.) The Liocraninae include about twenty-four genera, of which Zora,
Liocranum, Agroeca, and Micariosoma are sparingly represented in this
country.
(iv.) The Micariinae are a remarkable group of Spiders containing
numerous ant-like mimetic forms. Two species of Micaria alone are
English, but that genus is abundantly represented on the Continent, where
the species mount up to forty. They are mostly small, dark, shining spiders,
which, though not particularly ant-like in form, recall those insects both by
their appearance and movements. Some of the exotic genera, and
particularly the South American genus Myrmecium, possess remarkable
instances of mimetic resemblance to ants. Micaria pulicaria is a very pretty
little spider, about a sixth of an inch in length, black, with iridescent hairs,
and some white marks on the abdomen. It runs about in a very active ant-
like fashion and does not object to the sunshine. It is fairly abundant in
England.
Fam. 15. Palpimanidae.—This family includes a few genera of exotic
spiders. They are especially characterised by the great development of their
anterior legs, which are not much used for locomotion, but are frequently
raised as the spider moves along, generally somewhat slowly, by means of
the other three pairs. The best known genera are Metronax and Stenochilus
Phaeocedus, whose single species (P. braccatus) has occurred, though very
rarely, in the south of England. Gnaphosa has fifty-five species, of which
twenty-eight are European, and four are British.
(ii.) The Clubioninae have the anterior spinnerets closer together, and the
eyes more extended across the caput than in the foregoing sub-family.
Nearly thirty genera have been established, of which three claim special
attention. Clubiona includes more than 100 species, chiefly inhabiting
temperate regions. Fifteen are included in the British list. They are mostly
unicolorous, and yellow or brown in colour, but a few (C. corticalis, C.
compta, etc.) have a distinct pattern on the abdomen. Cheiracanthium is a
large and widely spread genus, counting three English species. There are
more than a hundred species of the genus Anyphaena, of which one only (A.
accentuata) occurs in this country, where it is common upon bushes and
trees in the south.
(iii.) The Liocraninae include about twenty-four genera, of which Zora,
Liocranum, Agroeca, and Micariosoma are sparingly represented in this
country.
(iv.) The Micariinae are a remarkable group of Spiders containing
numerous ant-like mimetic forms. Two species of Micaria alone are
English, but that genus is abundantly represented on the Continent, where
the species mount up to forty. They are mostly small, dark, shining spiders,
which, though not particularly ant-like in form, recall those insects both by
their appearance and movements. Some of the exotic genera, and
particularly the South American genus Myrmecium, possess remarkable
instances of mimetic resemblance to ants. Micaria pulicaria is a very pretty
little spider, about a sixth of an inch in length, black, with iridescent hairs,
and some white marks on the abdomen. It runs about in a very active ant-
like fashion and does not object to the sunshine. It is fairly abundant in
England.
Fam. 15. Palpimanidae.—This family includes a few genera of exotic
spiders. They are especially characterised by the great development of their
anterior legs, which are not much used for locomotion, but are frequently
raised as the spider moves along, generally somewhat slowly, by means of
the other three pairs. The best known genera are Metronax and Stenochilus
Page 442
from India, Huttonia from New Zealand, and Palpimanus from the
Mediterranean region, Africa, and South Asia.
Fam. 16. Eresidae.—The Eresidae are a small family of cribellate
spiders whose systematic position has been the subject of much discussion.
In general appearance they resemble the Attidae (vide infra), but this
resemblance is quite superficial. On the whole they seem more nearly allied
to the following family than to any other. They are stoutly built, with thick,
strong legs, and live either in the ground or on bushes, where they weave a
close-textured web. One species, Eresus cinnaberinus, has occurred on rare
occasions in the south of England, and the male, which is a third of an inch
in length, is perhaps the most striking member of our Spider fauna, the
abdomen being scarlet, with four (or sometimes six) black spots edged with
white hairs. The cephalothorax is black, with red on the postero-lateral
borders. The abdomen of the female is black.
Fam. 17. Dictynidae.—Cribellate spiders, with oval cephalothorax and
broad convex caput, with the eyes, normally eight, ranged across it in two
straight or slightly curved transverse rows. Basal joints of chelicerae long
and strong, often bowed. Legs rather strong. Tarsi three-clawed and devoid
of scopula.
The Dictynidae are sedentary spiders which weave a web of irregular
strands, covered by the close weft which is the product of the cribellum.
Some live under stones or in holes in walls, while others spin their webs in
bushes or herbage. There are about sixteen genera, of which Dictyna and
Amaurobius are the most important.
Nearly a hundred species of Dictyna have been described. They are small
spiders, usually living in grass and herbage. Thirty species inhabit Europe
and the neighbouring coast of Africa, and eight of these are natives of
Britain. D. arundinacea is very abundant, especially in heather. It is about
an eighth of an inch in length. D. uncinata is also often met with.
Amaurobius, of which about eighty species are known, includes some
species of much larger size. Three species are native to this country, A.
ferox, A. similis, and A. fenestralis. A. ferox is a large and rather formidable-
looking spider, more than half an inch in length, with powerful chelicerae. It
is found under stones and bark, and in cellars and outhouses. A. similis is
the commonest species in England, though A. fenestralis somewhat replaces
Mediterranean region, Africa, and South Asia.
Fam. 16. Eresidae.—The Eresidae are a small family of cribellate
spiders whose systematic position has been the subject of much discussion.
In general appearance they resemble the Attidae (vide infra), but this
resemblance is quite superficial. On the whole they seem more nearly allied
to the following family than to any other. They are stoutly built, with thick,
strong legs, and live either in the ground or on bushes, where they weave a
close-textured web. One species, Eresus cinnaberinus, has occurred on rare
occasions in the south of England, and the male, which is a third of an inch
in length, is perhaps the most striking member of our Spider fauna, the
abdomen being scarlet, with four (or sometimes six) black spots edged with
white hairs. The cephalothorax is black, with red on the postero-lateral
borders. The abdomen of the female is black.
Fam. 17. Dictynidae.—Cribellate spiders, with oval cephalothorax and
broad convex caput, with the eyes, normally eight, ranged across it in two
straight or slightly curved transverse rows. Basal joints of chelicerae long
and strong, often bowed. Legs rather strong. Tarsi three-clawed and devoid
of scopula.
The Dictynidae are sedentary spiders which weave a web of irregular
strands, covered by the close weft which is the product of the cribellum.
Some live under stones or in holes in walls, while others spin their webs in
bushes or herbage. There are about sixteen genera, of which Dictyna and
Amaurobius are the most important.
Nearly a hundred species of Dictyna have been described. They are small
spiders, usually living in grass and herbage. Thirty species inhabit Europe
and the neighbouring coast of Africa, and eight of these are natives of
Britain. D. arundinacea is very abundant, especially in heather. It is about
an eighth of an inch in length. D. uncinata is also often met with.
Amaurobius, of which about eighty species are known, includes some
species of much larger size. Three species are native to this country, A.
ferox, A. similis, and A. fenestralis. A. ferox is a large and rather formidable-
looking spider, more than half an inch in length, with powerful chelicerae. It
is found under stones and bark, and in cellars and outhouses. A. similis is
the commonest species in England, though A. fenestralis somewhat replaces
Page 443
it in the north. They are smaller than A. ferox, but are found in similar
situations.
Fam. 18. Psechridae.—This is a small family of cribellate spiders,
consisting only of two genera, Psechrus and Fecenia, and some eight
species, all natives of Southern Asia and the adjacent islands. The two
species of Psechrus are large spiders. They make large domed webs, which
they stretch between trees or rocks, and beneath which they hang in an
inverted position.
The calamistrum of these spiders is short, about half the length of the
fourth metatarsus.
Fam. 19. Zodariidae (Enyoidae).—In this family are included a number
of remarkable exotic spiders, most of them somewhat Drassid-like in
appearance, but generally with three-clawed tarsi. The group appears to be a
somewhat heterogeneous one, the twenty genera of which it consists
presenting rather a wide range of characteristics.
Cydrela is an African genus of moderate sized spiders, containing five
species of very curious habits. They scramble about and burrow in the sand,
in which, according to Simon,[314] they appear to swim, and their chief
burrowing implements are their pedipalpi, which are specially modified, the
tarsi in the female bristling with spines, and being armed with one or more
terminal claws.
Laches (Lachesis) includes some larger pale-coloured spiders found in
Egypt and Syria, under stones in very hot and dry localities.
Storena has representatives in all the tropical and sub-tropical parts of the
world, and numbers about fifty species. They are of moderate size, with
integuments smooth and glossy or finely shagreened, usually dark-coloured,
with white or yellow spots on the abdomen. Hermippus (Fig. 206) is also
African. Zodarion (Enyo) includes about thirty-five species of rather small,
generally unicolorous spiders, very active and fond of the sunshine. They
spin no web, but have a retreat under a stone. Their chief prey appear to be
ants. Most of the species are native to the Mediterranean region, the others
belonging to Central and Southern Asia.
Simon includes in this family the remarkable genus Cryptothele, found in
Ceylon, Malacca, New Guinea, and various Oceanic islands. They are
moderate sized brownish spiders, with hard integuments rugged with
tubercles and projections. Their most curious characteristic is their power of
situations.
Fam. 18. Psechridae.—This is a small family of cribellate spiders,
consisting only of two genera, Psechrus and Fecenia, and some eight
species, all natives of Southern Asia and the adjacent islands. The two
species of Psechrus are large spiders. They make large domed webs, which
they stretch between trees or rocks, and beneath which they hang in an
inverted position.
The calamistrum of these spiders is short, about half the length of the
fourth metatarsus.
Fam. 19. Zodariidae (Enyoidae).—In this family are included a number
of remarkable exotic spiders, most of them somewhat Drassid-like in
appearance, but generally with three-clawed tarsi. The group appears to be a
somewhat heterogeneous one, the twenty genera of which it consists
presenting rather a wide range of characteristics.
Cydrela is an African genus of moderate sized spiders, containing five
species of very curious habits. They scramble about and burrow in the sand,
in which, according to Simon,[314] they appear to swim, and their chief
burrowing implements are their pedipalpi, which are specially modified, the
tarsi in the female bristling with spines, and being armed with one or more
terminal claws.
Laches (Lachesis) includes some larger pale-coloured spiders found in
Egypt and Syria, under stones in very hot and dry localities.
Storena has representatives in all the tropical and sub-tropical parts of the
world, and numbers about fifty species. They are of moderate size, with
integuments smooth and glossy or finely shagreened, usually dark-coloured,
with white or yellow spots on the abdomen. Hermippus (Fig. 206) is also
African. Zodarion (Enyo) includes about thirty-five species of rather small,
generally unicolorous spiders, very active and fond of the sunshine. They
spin no web, but have a retreat under a stone. Their chief prey appear to be
ants. Most of the species are native to the Mediterranean region, the others
belonging to Central and Southern Asia.
Simon includes in this family the remarkable genus Cryptothele, found in
Ceylon, Malacca, New Guinea, and various Oceanic islands. They are
moderate sized brownish spiders, with hard integuments rugged with
tubercles and projections. Their most curious characteristic is their power of
Page 444
retracting their spinnerets within a
sort of sheath, so that they become
entirely invisible.
Fam. 20. Hersiliidae.—This is a
very distinct family of spiders, with
broad cephalothorax, with well-
marked fovea and striae, and small,
well defined caput. The eyes, usually
eight, are black except the median
anterior pair. The legs are long and
thin, and the tarsi three-clawed. The
abdomen is oval or sub-globular,
short haired, and generally of greyish
coloration. The spinnerets supply the
chief characteristic, the posterior pair
being long—often excessively long
—and two-jointed, the terminal joint
tapering and flexible. The colulus is
Fig. 206.—Hermippus loricatus, ♂ × 2½. (After
large. They are very active spiders, Simon.)
living on tree trunks or walls, or
under stones, but spreading no snare.
Some of them are of considerable
size.
Hersilia includes nine species
native to Africa and Asia. Tama is the
only genus represented in the New
World, two of its species being found
in South America, while others
inhabit Africa, Asia, and Australia.
Another genus, Hersiliola, is
Fig. 207.—Hersilia caudata, ♀. (After Pickard- principally African, but extends into
Cambridge.)
Spain.
Fam. 21. Pholcidae.—This is
another very well-marked family. The most striking peculiarity of its
members is the possession of extremely long and thin legs, the metatarsi
sort of sheath, so that they become
entirely invisible.
Fam. 20. Hersiliidae.—This is a
very distinct family of spiders, with
broad cephalothorax, with well-
marked fovea and striae, and small,
well defined caput. The eyes, usually
eight, are black except the median
anterior pair. The legs are long and
thin, and the tarsi three-clawed. The
abdomen is oval or sub-globular,
short haired, and generally of greyish
coloration. The spinnerets supply the
chief characteristic, the posterior pair
being long—often excessively long
—and two-jointed, the terminal joint
tapering and flexible. The colulus is
Fig. 206.—Hermippus loricatus, ♂ × 2½. (After
large. They are very active spiders, Simon.)
living on tree trunks or walls, or
under stones, but spreading no snare.
Some of them are of considerable
size.
Hersilia includes nine species
native to Africa and Asia. Tama is the
only genus represented in the New
World, two of its species being found
in South America, while others
inhabit Africa, Asia, and Australia.
Another genus, Hersiliola, is
Fig. 207.—Hersilia caudata, ♀. (After Pickard- principally African, but extends into
Cambridge.)
Spain.
Fam. 21. Pholcidae.—This is
another very well-marked family. The most striking peculiarity of its
members is the possession of extremely long and thin legs, the metatarsi
Page 445
being especially elongated, and the tarsi furnished with several false
articulations.
The eyes are also very characteristic. They are usually eight in number,
the two anterior median eyes being black, while the other six are white, and
arranged in lateral groups of three, sometimes on prominences or stalks.
The abdomen is sometimes nearly globular, but more often long and
cylindrical. Most of the genera, which, including several new genera lately
established by Simon, number more than twenty, are poor in species, but
enjoy a very wide distribution. This is explained by the fact that many of
them live in cellars and outhouses. This is the case with the genus Pholcus,
of which the sole English species Ph. phalangioides is a perfect nuisance in
buildings in the most southern parts of the country, “spinning large sheets of
irregular webs in the corners and angles, and adding to them year by
year.”[315] Other genera are Artema (Africa, South Asia, Polynesia,
America), which includes the largest examples, and Spermophora, a six-
eyed genus whose few species are widely distributed.
Fam. 22. Theridiidae.—Sedentary spiders, usually with feeble
chelicerae and relatively large abdomen. Snare irregular.
The Theridiidae, as here understood, are a very extensive family, and
more than half the British spiders (about 270 species) are included within it.
This family and the next present unusual difficulties of treatment, and there
is great divergence of opinion as to the most satisfactory way of dealing
with them. This is chiefly due to the fact that, notwithstanding an infinite
variation of facies, important points of structure are wonderfully uniform
throughout both the two groups, while any differences that do occur are
bridged over by intermediate forms which merge into each other.
Simon[316] has become so impressed with the difficulty of drawing any
clear line between certain groups which he previously classed under the
Theridiidae and the spiders commonly known as Epeiridae, that he has
recently removed them from the Theridiidae and united them with the orb-
weaving spiders to form the Family Argiopidae, the family name Epeiridae
being discarded. The groups which, in his view, belong to the Argiopidae
will be indicated below. This view has not met with universal acceptance,
and notwithstanding the undoubted difficulty of clearly distinguishing
between the two families, it is more convenient in the present work to
maintain as a separate family a group of spiders nearly all of whose
articulations.
The eyes are also very characteristic. They are usually eight in number,
the two anterior median eyes being black, while the other six are white, and
arranged in lateral groups of three, sometimes on prominences or stalks.
The abdomen is sometimes nearly globular, but more often long and
cylindrical. Most of the genera, which, including several new genera lately
established by Simon, number more than twenty, are poor in species, but
enjoy a very wide distribution. This is explained by the fact that many of
them live in cellars and outhouses. This is the case with the genus Pholcus,
of which the sole English species Ph. phalangioides is a perfect nuisance in
buildings in the most southern parts of the country, “spinning large sheets of
irregular webs in the corners and angles, and adding to them year by
year.”[315] Other genera are Artema (Africa, South Asia, Polynesia,
America), which includes the largest examples, and Spermophora, a six-
eyed genus whose few species are widely distributed.
Fam. 22. Theridiidae.—Sedentary spiders, usually with feeble
chelicerae and relatively large abdomen. Snare irregular.
The Theridiidae, as here understood, are a very extensive family, and
more than half the British spiders (about 270 species) are included within it.
This family and the next present unusual difficulties of treatment, and there
is great divergence of opinion as to the most satisfactory way of dealing
with them. This is chiefly due to the fact that, notwithstanding an infinite
variation of facies, important points of structure are wonderfully uniform
throughout both the two groups, while any differences that do occur are
bridged over by intermediate forms which merge into each other.
Simon[316] has become so impressed with the difficulty of drawing any
clear line between certain groups which he previously classed under the
Theridiidae and the spiders commonly known as Epeiridae, that he has
recently removed them from the Theridiidae and united them with the orb-
weaving spiders to form the Family Argiopidae, the family name Epeiridae
being discarded. The groups which, in his view, belong to the Argiopidae
will be indicated below. This view has not met with universal acceptance,
and notwithstanding the undoubted difficulty of clearly distinguishing
between the two families, it is more convenient in the present work to
maintain as a separate family a group of spiders nearly all of whose
Page 446
members possess the easily recognised characteristic of spinning a circular
snare.
The Theridiidae and the Epeiridae form the great bulk of the sedentary
spiders. They do not wander in search of prey, but sit in snares of various
structure and wait for their victims to entangle themselves. The spinnerets,
organs whose peculiarities are often strongly marked in other families, are
here wonderfully constant in their arrangement and general appearance,
forming a compact rosette-like group beneath the abdomen. Their eyes,
normally eight in number, present an infinite variety of arrangement. Their
chelicerae and mouth-parts vary considerably, but no abruptness of
variation is distinguishable. This is unsatisfactory from a systematic point
of view, and the necessary result is that certain groups might with equal
propriety be classed with the Theridiidae or the Epeiridae. The latter family
will here be taken as including all the orb-weaving spiders and a few groups
which appear inseparable from them.
We shall consider the Theridiidae as comprising the seven sub-families,
Argyrodinae, Episininae, Theridioninae, Phoroncidiinae, Erigoninae,
Formicinae, and Linyphiinae, and shall briefly deal with them in this order.
(i.) The Argyrodinae are very curious spiders with very long and often
flexible abdomen. They are commonly parasitic on the circular snares of
Epeirid spiders, between the rays of which they spin their own irregular
webs. There are three genera, Argyrodes, Ariamnes, and Rhomphaea, which
are distributed in the tropical and sub-tropical regions all over the world.
(ii.) The Episininae hardly conform to the character of sedentary spiders,
being frequently found outside their webs. In most species the abdomen is
narrow in front and broader behind, where it is abruptly truncated or bluntly
pointed. The genus Episinus is widely distributed, and one species, E.
truncatus, is one of our most peculiar English spiders. It occurs
occasionally under ledges of grassy or heathery banks. The genus Tomoxena
is an inhabitant of tropical Asia. Janulus is found in the same regions, and
in tropical America.
(iii.) The Theridioninae are a large group of spiders, often very ornate,
and spinning snares of irregular threads running in all directions. The
abdomen is usually more or less globular. The chelicerae are small and
weak, and the paturon is transversely (not obliquely) truncated for the
snare.
The Theridiidae and the Epeiridae form the great bulk of the sedentary
spiders. They do not wander in search of prey, but sit in snares of various
structure and wait for their victims to entangle themselves. The spinnerets,
organs whose peculiarities are often strongly marked in other families, are
here wonderfully constant in their arrangement and general appearance,
forming a compact rosette-like group beneath the abdomen. Their eyes,
normally eight in number, present an infinite variety of arrangement. Their
chelicerae and mouth-parts vary considerably, but no abruptness of
variation is distinguishable. This is unsatisfactory from a systematic point
of view, and the necessary result is that certain groups might with equal
propriety be classed with the Theridiidae or the Epeiridae. The latter family
will here be taken as including all the orb-weaving spiders and a few groups
which appear inseparable from them.
We shall consider the Theridiidae as comprising the seven sub-families,
Argyrodinae, Episininae, Theridioninae, Phoroncidiinae, Erigoninae,
Formicinae, and Linyphiinae, and shall briefly deal with them in this order.
(i.) The Argyrodinae are very curious spiders with very long and often
flexible abdomen. They are commonly parasitic on the circular snares of
Epeirid spiders, between the rays of which they spin their own irregular
webs. There are three genera, Argyrodes, Ariamnes, and Rhomphaea, which
are distributed in the tropical and sub-tropical regions all over the world.
(ii.) The Episininae hardly conform to the character of sedentary spiders,
being frequently found outside their webs. In most species the abdomen is
narrow in front and broader behind, where it is abruptly truncated or bluntly
pointed. The genus Episinus is widely distributed, and one species, E.
truncatus, is one of our most peculiar English spiders. It occurs
occasionally under ledges of grassy or heathery banks. The genus Tomoxena
is an inhabitant of tropical Asia. Janulus is found in the same regions, and
in tropical America.
(iii.) The Theridioninae are a large group of spiders, often very ornate,
and spinning snares of irregular threads running in all directions. The
abdomen is usually more or less globular. The chelicerae are small and
weak, and the paturon is transversely (not obliquely) truncated for the
Page 447
reception of the small unguis or fang. The somewhat long thin legs are
almost or entirely destitute of spines.
We may consider certain genera as typical of the various groups into
which this sub-family naturally falls. Theridion is the richest genus of the
entire order, numbering some 320 species, of which seventeen inhabit the
British Isles. During the summer months nearly every bush is studded with
the irregular webs of these little spiders, generally prettily coloured, and
with globular abdomen. The commonest is T. sisyphium, which swarms on
hollies and other bushes all over the country. One of the handsomest is T.
formosum, a rather local species, about a sixth of an inch in length, with the
abdomen beautifully marked with oblique lines of white, yellow, red, and
black. T. tepidariorum, common in conservatories, is like a large and
plainer edition of T. formosum. T. riparium is remarkable for the curious
earth-encrusted tube which it forms for the reception of its egg-cocoon. T.
bimaculatum may often be seen among coarse herbage, holding on to its
ridiculously large egg-cocoon; it is a small spider, and the sexes are more
than usually unlike.
Latrodectus and Dipoena are associated exotic genera, including some of
the largest species of the group. Latrodectus is peculiarly interesting on
account of the great reputation for especially poisonous properties which
some of its species have acquired. The New Zealand “Katipo” is L. scelio,
while L. 13–guttatus enjoys an almost equally evil reputation as the
“malmignatte” in Corsica. The American species L. mactans (Fig. 197, p.
362) is also considered highly venomous. These spiders form their irregular
webs on low bushes, and it is curious that they are usually marked with red
or yellow spots on the abdomen. They have been referred to in the section
on the venom of spiders (see p. 362).
The genus Steatoda possesses one English species (S. bipunctata) which
is extremely common in buildings and in the angles of walls, and is a rather
striking spider, with dark cephalothorax, and livid brown abdomen with a
broken white stripe down the middle. Several closely allied genera are also
sparingly represented in this country, among which may be mentioned
Crustulina (two species), Asagena (one species), Teutana (two species),
Lithyphantes (one species), Laseola (five species), and Euryopis (two
species). In some of these the male is provided with a stridulating organ
between the thorax and abdomen (Fig. 183, p. 327). The remarkable genus
almost or entirely destitute of spines.
We may consider certain genera as typical of the various groups into
which this sub-family naturally falls. Theridion is the richest genus of the
entire order, numbering some 320 species, of which seventeen inhabit the
British Isles. During the summer months nearly every bush is studded with
the irregular webs of these little spiders, generally prettily coloured, and
with globular abdomen. The commonest is T. sisyphium, which swarms on
hollies and other bushes all over the country. One of the handsomest is T.
formosum, a rather local species, about a sixth of an inch in length, with the
abdomen beautifully marked with oblique lines of white, yellow, red, and
black. T. tepidariorum, common in conservatories, is like a large and
plainer edition of T. formosum. T. riparium is remarkable for the curious
earth-encrusted tube which it forms for the reception of its egg-cocoon. T.
bimaculatum may often be seen among coarse herbage, holding on to its
ridiculously large egg-cocoon; it is a small spider, and the sexes are more
than usually unlike.
Latrodectus and Dipoena are associated exotic genera, including some of
the largest species of the group. Latrodectus is peculiarly interesting on
account of the great reputation for especially poisonous properties which
some of its species have acquired. The New Zealand “Katipo” is L. scelio,
while L. 13–guttatus enjoys an almost equally evil reputation as the
“malmignatte” in Corsica. The American species L. mactans (Fig. 197, p.
362) is also considered highly venomous. These spiders form their irregular
webs on low bushes, and it is curious that they are usually marked with red
or yellow spots on the abdomen. They have been referred to in the section
on the venom of spiders (see p. 362).
The genus Steatoda possesses one English species (S. bipunctata) which
is extremely common in buildings and in the angles of walls, and is a rather
striking spider, with dark cephalothorax, and livid brown abdomen with a
broken white stripe down the middle. Several closely allied genera are also
sparingly represented in this country, among which may be mentioned
Crustulina (two species), Asagena (one species), Teutana (two species),
Lithyphantes (one species), Laseola (five species), and Euryopis (two
species). In some of these the male is provided with a stridulating organ
between the thorax and abdomen (Fig. 183, p. 327). The remarkable genus
Page 448
Tetrablemma (see p. 318) is considered by Simon to have affinities with this
group, though Pickard-Cambridge, who first described it, is inclined to rank
it among the Dysderidae.
group, though Pickard-Cambridge, who first described it, is inclined to rank
it among the Dysderidae.
Page 449
(iv.) The Phoroncidiinae are a
remarkable group of spiny Theridiids
whose superficial resemblance to the
Gasteracanthinae of the Epeiridae
(see p. 409) has often deceived
Arachnologists as to their true
affinities. There are eight genera, all
exotic, inhabiting hot countries, and
spinning a Theridion-like web on
bushes. Phoroncidia has twelve
species in South Asia and
Madagascar. Trithena (Fig. 208) is its
American representative, five species
being found in South America.
Ulesanis has about twenty species,
and extends from South America to
Australia.
(v.) The Erigoninae are an
immense group of minute, sober- Fig. 208.—Trithena tricuspidata ♀ . × 3½.
coloured spiders, which include the (After Simon.)
“Money-spinners” of popular
nomenclature, and are largely responsible for the gossamer which fills the
air and covers every tuft of grass in the autumn. The number of species
described is very large and constantly increasing, and more than a hundred
are recognised as British.
Desperate efforts have been made of late years to grapple with this
almost unmanageable group, but the multitude of genera which have been
proposed can hardly as yet be considered to be finally established. The
small size of these spiders, which renders the aid of a microscope necessary
to make out their structural peculiarities, robs them of their attractiveness to
any but the ardent Arachnologist, but they number among them some of our
most remarkable English forms, and many of them well repay examination.
The smallest English species, Panamomops diceros, measures about 1 mm.
(about ¹⁄₂₅ inch) in length. Many of the groups are jet black, some with dull
and others with shiny integuments. They are never greatly variegated in
remarkable group of spiny Theridiids
whose superficial resemblance to the
Gasteracanthinae of the Epeiridae
(see p. 409) has often deceived
Arachnologists as to their true
affinities. There are eight genera, all
exotic, inhabiting hot countries, and
spinning a Theridion-like web on
bushes. Phoroncidia has twelve
species in South Asia and
Madagascar. Trithena (Fig. 208) is its
American representative, five species
being found in South America.
Ulesanis has about twenty species,
and extends from South America to
Australia.
(v.) The Erigoninae are an
immense group of minute, sober- Fig. 208.—Trithena tricuspidata ♀ . × 3½.
coloured spiders, which include the (After Simon.)
“Money-spinners” of popular
nomenclature, and are largely responsible for the gossamer which fills the
air and covers every tuft of grass in the autumn. The number of species
described is very large and constantly increasing, and more than a hundred
are recognised as British.
Desperate efforts have been made of late years to grapple with this
almost unmanageable group, but the multitude of genera which have been
proposed can hardly as yet be considered to be finally established. The
small size of these spiders, which renders the aid of a microscope necessary
to make out their structural peculiarities, robs them of their attractiveness to
any but the ardent Arachnologist, but they number among them some of our
most remarkable English forms, and many of them well repay examination.
The smallest English species, Panamomops diceros, measures about 1 mm.
(about ¹⁄₂₅ inch) in length. Many of the groups are jet black, some with dull
and others with shiny integuments. They are never greatly variegated in
Page 450
hue, but the glossy black of the cephalothorax, combined with red-brown or
yellow legs, gives to some species a rather rich coloration.
It is impossible here to deal with
this sub-family in detail. Some of its
members must be familiar enough to
everybody, and the reader is
recommended to spend an hour of a
warm autumn day in watching them
depart on the ballooning excursions,
of which a description has been given
(see p. 341), from the knobs which
surmount iron railings in a sunny
spot. Among them he is pretty sure to
find the genus Erigone—containing
some of the largest members of the
group—strongly represented.
In some species the male presents
a remarkable difference from the
Fig. 209.—Profile of cephalothorax of 1, female in the structure of its
Lophocarenum insanum; 2, Dactylopisthes cephalothorax, which has the head
digiticeps; 3, Walckenaera acuminata (+
abdomen); 4, Diplocephalus bicephalus; 5, region produced into eminences
Metopobractus rayi. sometimes of the oddest
conformation. An extreme example is
seen in Walckenaera acuminata, a fine species in which the male caput is
produced into a sort of spire, bearing the eyes, and nearly as high as the
cephalothorax is long (Fig. 209, 3).
(vi.) The Formicinae include only two genera, Formicina (South Europe)
and Solenysa (Japan). They are somewhat ant-like in appearance.
(vii.) The Linyphiinae are closely allied to the Erigoninae, but the legs are
usually armed with spines, and very commonly the female has a dentated
claw at the end of the pedipalp.
We include here about thirty genera of spiders of moderate or small size,
living for the most part on bushes or herbage. The characteristic Linyphian
web is a horizontal sheet of irregular strands, anchored to neighbouring
twigs or leaves by cross threads in all directions, and the spider generally
lurks beneath the web in an inverted position. Some of the larger species are
yellow legs, gives to some species a rather rich coloration.
It is impossible here to deal with
this sub-family in detail. Some of its
members must be familiar enough to
everybody, and the reader is
recommended to spend an hour of a
warm autumn day in watching them
depart on the ballooning excursions,
of which a description has been given
(see p. 341), from the knobs which
surmount iron railings in a sunny
spot. Among them he is pretty sure to
find the genus Erigone—containing
some of the largest members of the
group—strongly represented.
In some species the male presents
a remarkable difference from the
Fig. 209.—Profile of cephalothorax of 1, female in the structure of its
Lophocarenum insanum; 2, Dactylopisthes cephalothorax, which has the head
digiticeps; 3, Walckenaera acuminata (+
abdomen); 4, Diplocephalus bicephalus; 5, region produced into eminences
Metopobractus rayi. sometimes of the oddest
conformation. An extreme example is
seen in Walckenaera acuminata, a fine species in which the male caput is
produced into a sort of spire, bearing the eyes, and nearly as high as the
cephalothorax is long (Fig. 209, 3).
(vi.) The Formicinae include only two genera, Formicina (South Europe)
and Solenysa (Japan). They are somewhat ant-like in appearance.
(vii.) The Linyphiinae are closely allied to the Erigoninae, but the legs are
usually armed with spines, and very commonly the female has a dentated
claw at the end of the pedipalp.
We include here about thirty genera of spiders of moderate or small size,
living for the most part on bushes or herbage. The characteristic Linyphian
web is a horizontal sheet of irregular strands, anchored to neighbouring
twigs or leaves by cross threads in all directions, and the spider generally
lurks beneath the web in an inverted position. Some of the larger species are
Page 451
very familiar objects, Linyphia triangularis being one of the most abundant
English spiders, filling furze and other bushes with its extensive spinning
work.
The sub-family may be roughly divided into three groups, of which the
first is small, consisting of only three exotic genera of one species each.
Donachochara may be taken as the type genus. They are moderate-sized
spiders with rather short legs, found in France and Holland.
The second group consists of a number of genera of small spiders, sober-
coloured, and generally more or less unicolorous in brown, yellow, or black,
living in herbage. The sexes are much alike, the males never exhibiting the
excrescences on the caput so often met with in the Erigoninae. The genus
Tmeticus may be considered the type. It includes about forty species, of
which about half are British. They are mostly dull yellow or brown spiders,
averaging perhaps the eighth of an inch in length. Allied genera which are
represented in England are Porhomma (twelve species), Microneta (twelve
species), Sintula (twelve species). The American cave-genus Anthrobia
comes here.
The third and last group is that including Linyphia and allied genera.
They are moderate-sized or small spiders with long spiny legs and
particularly long tarsi. The abdomen is generally decorated. The caput is
frequently rather prominent and crowned with hairs.
Of the large number of spiders which have been described under the
generic name of Linyphia, Simon[317] only admits about fifty species. Ten
are included in the British list. L. triangularis has already been mentioned,
but there are other common species, as L. montana, L. marginata, and L.
clathrata. The members of most of the associated genera are rather small in
size. We may briefly mention Bolyphantes, Bathyphantes, Lephthyphantes,
and Labulla, all of which include English species.[318]
Fam. 23. Epeiridae.—This family includes all the spiders which spin
circular or wheel-like snares, the highest form of spider industry, together
with a few forms so closely allied in structure to orb-weaving species as to
be systematically inseparable from them. It is practically co-extensive with
the Argiopinae, Tetragnathinae, and Nephilinae of Simon’s Argiopidae in
the Histoire naturelle des araignées.[319]
No one is unfamiliar with the orbicular snares, the structure of which has
already been described with some minuteness (see p. 344), and some of the
English spiders, filling furze and other bushes with its extensive spinning
work.
The sub-family may be roughly divided into three groups, of which the
first is small, consisting of only three exotic genera of one species each.
Donachochara may be taken as the type genus. They are moderate-sized
spiders with rather short legs, found in France and Holland.
The second group consists of a number of genera of small spiders, sober-
coloured, and generally more or less unicolorous in brown, yellow, or black,
living in herbage. The sexes are much alike, the males never exhibiting the
excrescences on the caput so often met with in the Erigoninae. The genus
Tmeticus may be considered the type. It includes about forty species, of
which about half are British. They are mostly dull yellow or brown spiders,
averaging perhaps the eighth of an inch in length. Allied genera which are
represented in England are Porhomma (twelve species), Microneta (twelve
species), Sintula (twelve species). The American cave-genus Anthrobia
comes here.
The third and last group is that including Linyphia and allied genera.
They are moderate-sized or small spiders with long spiny legs and
particularly long tarsi. The abdomen is generally decorated. The caput is
frequently rather prominent and crowned with hairs.
Of the large number of spiders which have been described under the
generic name of Linyphia, Simon[317] only admits about fifty species. Ten
are included in the British list. L. triangularis has already been mentioned,
but there are other common species, as L. montana, L. marginata, and L.
clathrata. The members of most of the associated genera are rather small in
size. We may briefly mention Bolyphantes, Bathyphantes, Lephthyphantes,
and Labulla, all of which include English species.[318]
Fam. 23. Epeiridae.—This family includes all the spiders which spin
circular or wheel-like snares, the highest form of spider industry, together
with a few forms so closely allied in structure to orb-weaving species as to
be systematically inseparable from them. It is practically co-extensive with
the Argiopinae, Tetragnathinae, and Nephilinae of Simon’s Argiopidae in
the Histoire naturelle des araignées.[319]
No one is unfamiliar with the orbicular snares, the structure of which has
already been described with some minuteness (see p. 344), and some of the
Page 452
spiders which construct them are among the best known members of the
order.
It is impossible here to deal with the multitudinous forms embraced by
this family. We must mention those genera richest in species, and some
others of special interest. It will be convenient to indicate eight sub-families
or groups, which include most of the forms likely to be met with. These are
the Theridiosomatinae, Tetragnathinae, Argiopinae, Nephilinae, Epeirinae,
Gasteracanthinae, Poltyinae, and Arcyinae.
(i.) The Theridiosomatinae are a small group which might with equal
propriety be classed with the Theridiidae or the Epeiridae. Theridiosoma
argenteolum is a rare spider in Dorsetshire. It is a minute spider, one-twelfth
of an inch in length, with silvery white globular abdomen variegated with
reddish brown, and yellow cephalothorax with darker caput. Some allied
spiders spin a roughly circular snare.
(ii.) The Tetragnathinae consist chiefly of two genera, Pachygnatha and
Tetragnatha. The first consists of spiders which are not orb-weavers, but
live in herbage, especially in swampy places. Two species, Pachygnatha
clerckii and P. degeerii, are common in England, and a third, P. listeri, is
sometimes met with. They are rather striking, prettily marked spiders, with
strongly developed chelicerae.
The species of Tetragnatha are true orb-weavers, and may easily be
recognised by their cylindrical bodies, elongated chelicerae, and long legs,
stretched fore and aft along the rays of their webs. Five species have been
recorded from England, and the genus contains at least a hundred species in
all; almost every country in the world, regardless of its latitude, supplying
examples.
Simon associates with these spiders the genus Meta, which includes
perhaps our commonest Epeirid, Meta segmentata, a smallish and not very
striking Orb-weaver, with a rather elongated or subcylindrical abdomen.
Every garden is pretty sure to abound in it.
(iii.) The Argiopinae include many large and very striking members of
the Epeiridae. There are about a hundred species of Argiope (Fig. 198, p.
379) spread over the tropical and sub-tropical countries of the world. They
rarely invade the temperate regions, but A. bruennichi is found in South
Europe, and A. trifasciata in Canada. The large spiders with transverse bars
of yellow or orange on their abdomen, and often with a silvery sheen,
order.
It is impossible here to deal with the multitudinous forms embraced by
this family. We must mention those genera richest in species, and some
others of special interest. It will be convenient to indicate eight sub-families
or groups, which include most of the forms likely to be met with. These are
the Theridiosomatinae, Tetragnathinae, Argiopinae, Nephilinae, Epeirinae,
Gasteracanthinae, Poltyinae, and Arcyinae.
(i.) The Theridiosomatinae are a small group which might with equal
propriety be classed with the Theridiidae or the Epeiridae. Theridiosoma
argenteolum is a rare spider in Dorsetshire. It is a minute spider, one-twelfth
of an inch in length, with silvery white globular abdomen variegated with
reddish brown, and yellow cephalothorax with darker caput. Some allied
spiders spin a roughly circular snare.
(ii.) The Tetragnathinae consist chiefly of two genera, Pachygnatha and
Tetragnatha. The first consists of spiders which are not orb-weavers, but
live in herbage, especially in swampy places. Two species, Pachygnatha
clerckii and P. degeerii, are common in England, and a third, P. listeri, is
sometimes met with. They are rather striking, prettily marked spiders, with
strongly developed chelicerae.
The species of Tetragnatha are true orb-weavers, and may easily be
recognised by their cylindrical bodies, elongated chelicerae, and long legs,
stretched fore and aft along the rays of their webs. Five species have been
recorded from England, and the genus contains at least a hundred species in
all; almost every country in the world, regardless of its latitude, supplying
examples.
Simon associates with these spiders the genus Meta, which includes
perhaps our commonest Epeirid, Meta segmentata, a smallish and not very
striking Orb-weaver, with a rather elongated or subcylindrical abdomen.
Every garden is pretty sure to abound in it.
(iii.) The Argiopinae include many large and very striking members of
the Epeiridae. There are about a hundred species of Argiope (Fig. 198, p.
379) spread over the tropical and sub-tropical countries of the world. They
rarely invade the temperate regions, but A. bruennichi is found in South
Europe, and A. trifasciata in Canada. The large spiders with transverse bars
of yellow or orange on their abdomen, and often with a silvery sheen,
Page 453
belong to this genus. The species of the allied genus Gea are generally
much smaller, and their abdomen more elongated. Both genera are found in
tropical and sub-tropical regions all over the world. Argiope always sits in
the middle of its circular web. There are invariably some flossy zigzag
bands of silk stretched between two of the rays, and the web is generally
accompanied by an irregular net on its border, where the much smaller male
may be found.
(iv.) Among the Nephilinae are to be found the largest Epeirids. Indeed,
the largest yield in size only to the Aviculariidae. Nephila is a tropical
genus, numbering about sixty species. The abdomen is generally elongated
and somewhat cylindrical, and is strikingly variegated. It is in this group
that the disparity in size between the sexes is most marked (see p. 379).
(v.) The Epeirinae[320] include the bulk of the Orb-weavers, and form a
very extensive group. Five genera and twenty-eight species are in the
British list.
No spider is more familiar than Epeira diademata (Fig. 181, p. 325), the
Garden-spider, par excellence, which attains its greatest size and spreads its
largest snares in the autumn. The smaller and much less conspicuous Zilla
x-notata is sure to be found abundantly in the same locality. Several other
Epeirids are to be found in this country, especially in the south, by sweeping
heather or bushes with a net, or shaking the boughs of trees over an
umbrella or other receptacle. The little apple-green species is Epeira
cucurbitina. E. cornuta is extremely common in marshy places all over the
country. In furze bushes, and often among sedge in swampy places, will
frequently be found E. quadrata, one of the largest and handsomest species
we possess. The ground-colour may vary from orange-red to green, and
there are four conspicuous white spots on the abdomen. The tent-like retreat
which this spider makes near its snare often catches the eye.
E. umbratica is a dark flat, somewhat toad-like Epeirid of retiring habits,
which stretches its snare usually on wooden palings, between the timbers of
which it squeezes its flat body, and waits for insects to entangle themselves.
Two of our finest Epeiras, E. pyramidata and E. angulata (Fig. 210), are
seldom met with, and only in the south.
Our only Cyclosa (C. conica) is easily recognised by the peculiar form of
its abdomen, which is greatly prolonged beyond the spinnerets. It is a small,
rather dark species, which constructs a particularly perfect snare.
much smaller, and their abdomen more elongated. Both genera are found in
tropical and sub-tropical regions all over the world. Argiope always sits in
the middle of its circular web. There are invariably some flossy zigzag
bands of silk stretched between two of the rays, and the web is generally
accompanied by an irregular net on its border, where the much smaller male
may be found.
(iv.) Among the Nephilinae are to be found the largest Epeirids. Indeed,
the largest yield in size only to the Aviculariidae. Nephila is a tropical
genus, numbering about sixty species. The abdomen is generally elongated
and somewhat cylindrical, and is strikingly variegated. It is in this group
that the disparity in size between the sexes is most marked (see p. 379).
(v.) The Epeirinae[320] include the bulk of the Orb-weavers, and form a
very extensive group. Five genera and twenty-eight species are in the
British list.
No spider is more familiar than Epeira diademata (Fig. 181, p. 325), the
Garden-spider, par excellence, which attains its greatest size and spreads its
largest snares in the autumn. The smaller and much less conspicuous Zilla
x-notata is sure to be found abundantly in the same locality. Several other
Epeirids are to be found in this country, especially in the south, by sweeping
heather or bushes with a net, or shaking the boughs of trees over an
umbrella or other receptacle. The little apple-green species is Epeira
cucurbitina. E. cornuta is extremely common in marshy places all over the
country. In furze bushes, and often among sedge in swampy places, will
frequently be found E. quadrata, one of the largest and handsomest species
we possess. The ground-colour may vary from orange-red to green, and
there are four conspicuous white spots on the abdomen. The tent-like retreat
which this spider makes near its snare often catches the eye.
E. umbratica is a dark flat, somewhat toad-like Epeirid of retiring habits,
which stretches its snare usually on wooden palings, between the timbers of
which it squeezes its flat body, and waits for insects to entangle themselves.
Two of our finest Epeiras, E. pyramidata and E. angulata (Fig. 210), are
seldom met with, and only in the south.
Our only Cyclosa (C. conica) is easily recognised by the peculiar form of
its abdomen, which is greatly prolonged beyond the spinnerets. It is a small,
rather dark species, which constructs a particularly perfect snare.
Page 454
Five British Epeirids belong to the
genus Singa. They are small
creatures, not exceeding a sixth of an
inch in length. They live in heathery
and marshy localities.
(vi.) The Gasteracanthinae are a
remarkable group of Epeirids,
characterised by the hard and
coriaceous integument covering the
abdomen, which is usually furnished
with a number of more or less
formidable thorn-like spines,
calculated to render these spiders by
no means pleasant eating for
insectivorous birds. An even more
constant characteristic is the presence
on the back of the abdomen of a
number of “sigilla,” or somewhat
seal-like impressions arranged
symmetrically, four forming a Fig. 210.—Epeira angulata, ♀.
trapezium in the middle, while the
others are distributed round the
border.
There are about 200 species of Gasteracantha, all natives of tropical
countries.
The spiders of the genus Micrathena (Acrosoma) have a more elongate
cephalothorax, and sometimes the spines are exceedingly long, far
exceeding the length of the body proper. Among the less spiny members of
this group are some remarkable mimetic ant-like forms.
(vii.) The Poltyinae include some remarkable spiders, found in Africa
and South Asia for the most part, though sparingly represented in America
and Oceania. They are generally largish spiders, often with a very odd
conformation of the abdomen, which is generally much raised. The type
genus is Poltys.
(viii.) The Arcyinae, which are more characteristic of Australia and the
neighbouring islands, are a small group of spiders, usually yellow with
genus Singa. They are small
creatures, not exceeding a sixth of an
inch in length. They live in heathery
and marshy localities.
(vi.) The Gasteracanthinae are a
remarkable group of Epeirids,
characterised by the hard and
coriaceous integument covering the
abdomen, which is usually furnished
with a number of more or less
formidable thorn-like spines,
calculated to render these spiders by
no means pleasant eating for
insectivorous birds. An even more
constant characteristic is the presence
on the back of the abdomen of a
number of “sigilla,” or somewhat
seal-like impressions arranged
symmetrically, four forming a Fig. 210.—Epeira angulata, ♀.
trapezium in the middle, while the
others are distributed round the
border.
There are about 200 species of Gasteracantha, all natives of tropical
countries.
The spiders of the genus Micrathena (Acrosoma) have a more elongate
cephalothorax, and sometimes the spines are exceedingly long, far
exceeding the length of the body proper. Among the less spiny members of
this group are some remarkable mimetic ant-like forms.
(vii.) The Poltyinae include some remarkable spiders, found in Africa
and South Asia for the most part, though sparingly represented in America
and Oceania. They are generally largish spiders, often with a very odd
conformation of the abdomen, which is generally much raised. The type
genus is Poltys.
(viii.) The Arcyinae, which are more characteristic of Australia and the
neighbouring islands, are a small group of spiders, usually yellow with
Page 455
black markings, and with the
somewhat square-shaped
cephalothorax usually prominent at
the angles. The type genus is Arcys.
Fam. 24. Uloboridae.—The
Uloboridae are cribellate spiders,
with rather elongate cephalothorax,
devoid of median fovea. The
cribellum is transverse and generally
undivided. The first pair of legs are
usually much the longest. The
metatarsi of the fourth legs, in
addition to the calamistrum, bear a
number of generally regularly
arranged spines. The eyes are often
situated on tubercles. Three sub-
families are recognised, Dinopinae,
Fig. 211.—Gasteracantha minax, ♀. Uloborinae, and Miagrammopinae.
(i.) The Dinopinae are a small
group comprising only two genera, Dinopis and Menneus. The calamistrum
is short, occupying not more than half of the metatarsus. Twenty species of
Dinopis and six of Menneus are scattered over the tropical regions of the
world.
(ii.) The Uloborinae include a number of spiders which have been
described under several generic names, but are now considered to fall into
two genera, Sybota and Uloborus. Sybota has only two species, one in the
Mediterranean region and one in Chili. There are about sixty species of
Uloborus, some of which have a wide distribution, while many (e.g. U.
republicanus, of Venezuela) are social. The type species, U. walckenaerius,
is a very rare spider in England.
(iii.) The Miagrammopinae include two genera containing some very
interesting forms. The genus Miagrammopes, of which twenty species have
been described, though the number is probably far greater, is characterised
by a very long cylindrical abdomen, and by the apparent possession of only
four eyes, in a transverse row. These are really the posterior eyes; and the
somewhat square-shaped
cephalothorax usually prominent at
the angles. The type genus is Arcys.
Fam. 24. Uloboridae.—The
Uloboridae are cribellate spiders,
with rather elongate cephalothorax,
devoid of median fovea. The
cribellum is transverse and generally
undivided. The first pair of legs are
usually much the longest. The
metatarsi of the fourth legs, in
addition to the calamistrum, bear a
number of generally regularly
arranged spines. The eyes are often
situated on tubercles. Three sub-
families are recognised, Dinopinae,
Fig. 211.—Gasteracantha minax, ♀. Uloborinae, and Miagrammopinae.
(i.) The Dinopinae are a small
group comprising only two genera, Dinopis and Menneus. The calamistrum
is short, occupying not more than half of the metatarsus. Twenty species of
Dinopis and six of Menneus are scattered over the tropical regions of the
world.
(ii.) The Uloborinae include a number of spiders which have been
described under several generic names, but are now considered to fall into
two genera, Sybota and Uloborus. Sybota has only two species, one in the
Mediterranean region and one in Chili. There are about sixty species of
Uloborus, some of which have a wide distribution, while many (e.g. U.
republicanus, of Venezuela) are social. The type species, U. walckenaerius,
is a very rare spider in England.
(iii.) The Miagrammopinae include two genera containing some very
interesting forms. The genus Miagrammopes, of which twenty species have
been described, though the number is probably far greater, is characterised
by a very long cylindrical abdomen, and by the apparent possession of only
four eyes, in a transverse row. These are really the posterior eyes; and the
Page 456
anterior eyes, or some of them, are present in a very reduced condition.
Little is known of the habits of these spiders.
The other genus, Hyptiotes, though
only boasting three species,
possesses a special interest on
account of the remarkable snare
constructed by the spiders which
belong to it. This has already been
described in the section upon
defective orb-webs (see p. 349).
The type species, H. paradoxus, is
very rare in England, and though
small and inconspicuous, it is
certainly one of the most curious
members of our Spider fauna.
Fam. 25. Archeidae.—This small
family includes certain remarkable
fossil spiders from Baltic amber, and
two rare recent forms, Archea
(Eriauchenus) workmani from
Madagascar, and Mecysmauchenius
segmentatus from America. The
chelicerae, which are extraordinarily
long, are articulated far away from
the mouth-parts. The caput is clearly
marked off from the thorax, and is Fig. 212.—Hyptiotes paradoxus, ♀.
much raised. In several other respects
these spiders are very distinct from
all other members of the order.
Fam. 26. Mimetidae.—The Mimetidae form a small group in general
appearance recalling the Theridiidae, with which family they were for a
long time incorporated. The chief genera are Ero, Mimetus, and Gelanor.
Ero furcata (= thoracica) is a pretty little spider, not rare among grass in
England. The upper side of its very convex abdomen is marked with red,
yellow, and black, and bears two little protuberances or humps near the
middle. It is only about an eighth of an inch long. Its interesting egg-cocoon
Little is known of the habits of these spiders.
The other genus, Hyptiotes, though
only boasting three species,
possesses a special interest on
account of the remarkable snare
constructed by the spiders which
belong to it. This has already been
described in the section upon
defective orb-webs (see p. 349).
The type species, H. paradoxus, is
very rare in England, and though
small and inconspicuous, it is
certainly one of the most curious
members of our Spider fauna.
Fam. 25. Archeidae.—This small
family includes certain remarkable
fossil spiders from Baltic amber, and
two rare recent forms, Archea
(Eriauchenus) workmani from
Madagascar, and Mecysmauchenius
segmentatus from America. The
chelicerae, which are extraordinarily
long, are articulated far away from
the mouth-parts. The caput is clearly
marked off from the thorax, and is Fig. 212.—Hyptiotes paradoxus, ♀.
much raised. In several other respects
these spiders are very distinct from
all other members of the order.
Fam. 26. Mimetidae.—The Mimetidae form a small group in general
appearance recalling the Theridiidae, with which family they were for a
long time incorporated. The chief genera are Ero, Mimetus, and Gelanor.
Ero furcata (= thoracica) is a pretty little spider, not rare among grass in
England. The upper side of its very convex abdomen is marked with red,
yellow, and black, and bears two little protuberances or humps near the
middle. It is only about an eighth of an inch long. Its interesting egg-cocoon
Page 457
has already been alluded to (see p. 358). E. tuberculata has been found on
rare occasions in this country. There are about ten other species of Ero, all
small spiders, and living in temperate regions. The genus Mimetus (in
which is merged Blackwall’s Ctenophora) includes a number of larger,
more strongly-built spiders, living for the most part in tropical countries.
The genus Gelanor (Galena) is the American representative of the group,
its three species being rather large spiders, inhabiting Central and South
America. The males of this genus have remarkably long and slender
pedipalpi, much longer than the whole body.
Fam. 27. Thomisidae.—The Thomisidae are the Latigrade spiders of
Latreille, and the “Crab-spiders” of popular nomenclature. Their legs are
extended more or less laterally instead of in the normal fore and aft
directions, and their progression is frequently strikingly crab-like. They
form a very large group of more than 140 genera, including spiders of every
size, and they are to be found in every quarter of the world. Forty-three
species are British. Many strange forms are included in this group, and
several of the sub-families into which it has been divided contain only one
or two genera. The bulk of its members fall into the sub-families
Thomisinae, Philodrominae, and Sparassinae.
(i.) The Thomisinae (Misumeninae of Simon’s Hist. Nat.) include what
may be called the more normal members of the family, distributed among
more than sixty genera. Six of these genera are represented in the British
Isles. Our commonest Crab-spider is probably Xysticus cristatus, abundant
everywhere in grass and herbage. Young specimens may often be seen upon
iron railings in the autumn. Twelve other species of that genus are on the
British list. They are of small or moderate size, rarely exceeding a quarter
of an inch in length. A closely allied genus is Oxyptila, of which we have
seven species. The more striking members of this sub-family to be found in
England are our single representatives of the genera Misumena, Diaea, and
Thomisus. Misumena vatia is a handsome species, the female measuring
sometimes more than a third of an inch, and having its large yellow or green
abdomen marked, in many specimens, with a pair of bright red bands,
which, however, are not always present. The males are much smaller and
darker. It is common in some parts of England, especially in the south,
where it is to be sought for in bushes and trees.
rare occasions in this country. There are about ten other species of Ero, all
small spiders, and living in temperate regions. The genus Mimetus (in
which is merged Blackwall’s Ctenophora) includes a number of larger,
more strongly-built spiders, living for the most part in tropical countries.
The genus Gelanor (Galena) is the American representative of the group,
its three species being rather large spiders, inhabiting Central and South
America. The males of this genus have remarkably long and slender
pedipalpi, much longer than the whole body.
Fam. 27. Thomisidae.—The Thomisidae are the Latigrade spiders of
Latreille, and the “Crab-spiders” of popular nomenclature. Their legs are
extended more or less laterally instead of in the normal fore and aft
directions, and their progression is frequently strikingly crab-like. They
form a very large group of more than 140 genera, including spiders of every
size, and they are to be found in every quarter of the world. Forty-three
species are British. Many strange forms are included in this group, and
several of the sub-families into which it has been divided contain only one
or two genera. The bulk of its members fall into the sub-families
Thomisinae, Philodrominae, and Sparassinae.
(i.) The Thomisinae (Misumeninae of Simon’s Hist. Nat.) include what
may be called the more normal members of the family, distributed among
more than sixty genera. Six of these genera are represented in the British
Isles. Our commonest Crab-spider is probably Xysticus cristatus, abundant
everywhere in grass and herbage. Young specimens may often be seen upon
iron railings in the autumn. Twelve other species of that genus are on the
British list. They are of small or moderate size, rarely exceeding a quarter
of an inch in length. A closely allied genus is Oxyptila, of which we have
seven species. The more striking members of this sub-family to be found in
England are our single representatives of the genera Misumena, Diaea, and
Thomisus. Misumena vatia is a handsome species, the female measuring
sometimes more than a third of an inch, and having its large yellow or green
abdomen marked, in many specimens, with a pair of bright red bands,
which, however, are not always present. The males are much smaller and
darker. It is common in some parts of England, especially in the south,
where it is to be sought for in bushes and trees.
Page 458
Diaea dorsata is one of our
prettiest British species, with light
green legs and cephalothorax, and a
yellow abdomen with a red-brown
central marking. It is common in the
New Forest and other southern
localities. The female attains a
quarter of an inch in length.
Thomisus onustus, a rare spider
among heather, is recognisable by the
shape of its abdomen, which is
broadest behind and abruptly
truncated. When adult the abdomen
is a pale yellow, but the young are
suffused with a pink hue closely
corresponding with that of the
heather blossom in which they are
frequently found sitting.
(ii.) The Philodrominae have the
cephalothorax more rounded in front,
and the legs, especially the second
pair, usually longer than in the
Fig. 213.—Thomisid spiders. A, Micrommata Thomisinae. There are ten genera, of
virescens, ♀ ; B, Xysticus pini, ♀ ; C,
Philodromus margaritatus, ♂ ; D, Tibellus which the most important is
oblongus, ♀. Philodromus, which numbers about a
hundred species. They are active
spiders, living upon bushes and trees, and most of them are inhabitants of
temperate regions. We have about twelve species in the British Isles. The
commonest is Ph. aureolus, which is abundant on bushes in most parts of
the country. Some species are very prettily marked, and one, Ph.
margaritatus (Fig. 213, C) presents a very good example of protective
coloration, being almost indistinguishable on the blue-grey lichen on tree
trunks, where it lies in wait for insects.
Another important genus, including some fifty species, is Thanatus,
extending from tropical to arctic regions, but very sparingly represented in
England. Th. striatus (= hirsutus) occurs occasionally, and one example of
prettiest British species, with light
green legs and cephalothorax, and a
yellow abdomen with a red-brown
central marking. It is common in the
New Forest and other southern
localities. The female attains a
quarter of an inch in length.
Thomisus onustus, a rare spider
among heather, is recognisable by the
shape of its abdomen, which is
broadest behind and abruptly
truncated. When adult the abdomen
is a pale yellow, but the young are
suffused with a pink hue closely
corresponding with that of the
heather blossom in which they are
frequently found sitting.
(ii.) The Philodrominae have the
cephalothorax more rounded in front,
and the legs, especially the second
pair, usually longer than in the
Fig. 213.—Thomisid spiders. A, Micrommata Thomisinae. There are ten genera, of
virescens, ♀ ; B, Xysticus pini, ♀ ; C,
Philodromus margaritatus, ♂ ; D, Tibellus which the most important is
oblongus, ♀. Philodromus, which numbers about a
hundred species. They are active
spiders, living upon bushes and trees, and most of them are inhabitants of
temperate regions. We have about twelve species in the British Isles. The
commonest is Ph. aureolus, which is abundant on bushes in most parts of
the country. Some species are very prettily marked, and one, Ph.
margaritatus (Fig. 213, C) presents a very good example of protective
coloration, being almost indistinguishable on the blue-grey lichen on tree
trunks, where it lies in wait for insects.
Another important genus, including some fifty species, is Thanatus,
extending from tropical to arctic regions, but very sparingly represented in
England. Th. striatus (= hirsutus) occurs occasionally, and one example of
Page 459
the fine species Th. formicinus has been taken in the New Forest. The
members of this genus as a rule affect dry and sandy habitats.
The genus Tibellus includes few species, but has a wide distribution. The
type species T. oblongus (Fig. 213, D) is found in the temperate regions all
over the world, and is common in England. It is a pale straw-coloured
spider with a much elongated abdomen. It closely resembles the stems of
dry grass in hue, and when alarmed it remains perfectly still with its legs
embracing the stem and its abdomen closely applied to it.
(iii.) The Sparassinae[321] include most of the large Latigrade forms, and
number about forty genera.
Heteropoda venatoria is a cosmopolitan species, and though proper to
warm countries, is often introduced here on hothouse plants, and has been
known to establish itself in the open air in botanical gardens. Our only
indigenous member of this sub-family is Micrommata virescens (Fig. 213,
A). This striking spider is found, though rarely, in the south of England. The
female is half an inch in length and of a vivid green hue, while the more
cylindrical abdomen of the male is yellow with three longitudinal scarlet
lines. Other genera are Sparassus, Torania, and Delena.
(iv.) The Aphantochilinae include two curious genera which are
exclusively American. The labium is much reduced and the sternum is
shortened, terminating between the third pair of legs. The species of
Aphantochilus are largish, glossy-black spiders, sometimes spotted with
white. Some of them mimic ants of the genus Cryptocerus. The other genus
is Bucranium.
(v.) The Stephanopsinae include about sixteen genera, of which the best
known are Stephanopsis and Regillus. There are about fifty species of
Stephanopsis, most of them Australian, while the eight species of Regillus
belong to Africa and South Asia.
The mimetic form Phrynarachne decipiens has already been alluded to
(see p. 374).
(vi.) The Selenopinae consist of a single genus, Selenops, of which ten or
twelve species are known, some of which are very widely distributed,
though confined to hot regions. These spiders, which are all large, are easily
recognised by their extremely flat bodies and the peculiar arrangement of
their eyes, all eight of them being placed more or less in a single transverse
line.
members of this genus as a rule affect dry and sandy habitats.
The genus Tibellus includes few species, but has a wide distribution. The
type species T. oblongus (Fig. 213, D) is found in the temperate regions all
over the world, and is common in England. It is a pale straw-coloured
spider with a much elongated abdomen. It closely resembles the stems of
dry grass in hue, and when alarmed it remains perfectly still with its legs
embracing the stem and its abdomen closely applied to it.
(iii.) The Sparassinae[321] include most of the large Latigrade forms, and
number about forty genera.
Heteropoda venatoria is a cosmopolitan species, and though proper to
warm countries, is often introduced here on hothouse plants, and has been
known to establish itself in the open air in botanical gardens. Our only
indigenous member of this sub-family is Micrommata virescens (Fig. 213,
A). This striking spider is found, though rarely, in the south of England. The
female is half an inch in length and of a vivid green hue, while the more
cylindrical abdomen of the male is yellow with three longitudinal scarlet
lines. Other genera are Sparassus, Torania, and Delena.
(iv.) The Aphantochilinae include two curious genera which are
exclusively American. The labium is much reduced and the sternum is
shortened, terminating between the third pair of legs. The species of
Aphantochilus are largish, glossy-black spiders, sometimes spotted with
white. Some of them mimic ants of the genus Cryptocerus. The other genus
is Bucranium.
(v.) The Stephanopsinae include about sixteen genera, of which the best
known are Stephanopsis and Regillus. There are about fifty species of
Stephanopsis, most of them Australian, while the eight species of Regillus
belong to Africa and South Asia.
The mimetic form Phrynarachne decipiens has already been alluded to
(see p. 374).
(vi.) The Selenopinae consist of a single genus, Selenops, of which ten or
twelve species are known, some of which are very widely distributed,
though confined to hot regions. These spiders, which are all large, are easily
recognised by their extremely flat bodies and the peculiar arrangement of
their eyes, all eight of them being placed more or less in a single transverse
line.
Page 460
Fam. 28. Zoropsidae.—The Zoropsidae are cribellate spiders of large
size, with well-developed scopulae on tarsi and metatarsi. The cribellum is
divided, and the calamistrum, which is very short, is not well developed.
Most are inhabitants of hot regions, where they live under stones or bark.
Zoropsis has six species, chiefly inhabitants of North Africa, though
representatives occur on the European side of the Mediterranean.
Acanthoctenus has two species in South and Central America.
Fam. 29. Platoridae.—The Platoridae are Thomisid-like, medium-sized
spiders, generally with a uniform yellow or brown coloration. The
spinnerets are their most characteristic features. The median pair present a
large flat surface studded with two parallel rows of large fusulae, while the
anterior pair are situated outside them, and are thus widely separated. There
are only three genera, and very few species of this family. Plator insolens is
a Chinese species. Doliomalus and Vectius belong to South America.
Fam. 30. Agelenidae.—Sedentary spiders with slight sexual
dimorphism; with three tarsal claws and devoid of scopulae.
The Agelenidae spin a more or less extensive web of fine texture, usually
accompanied by a tubular retreat. Our commonest cellar spiders belong to
this group, which may be divided into three sub-families, Cybaeinae,
Ageleninae, and Hahniinae.
(i.) The Cybaeinae include some sixteen genera, of which two deserve
special mention on account of the peculiar habits of the spiders belonging to
them.
Desis is a genus of marine spiders, said to live on coral reefs below high-
water mark, and to remain in holes in the rock during high tide, enclosed in
cocoons impermeable to the sea-water. At low tide it is stated that they
come forth and prey upon small crustaceans. Argyroneta has only one
species, A. aquatica, spread throughout Europe and North and Central Asia.
It is the well-known “Water-spider,” which is so often an object of interest
in aquaria.
(ii.) The Ageleninae also contain sixteen genera, but it is a much larger
group, some of the genera being rich in species. They are mostly moderate
or large-sized hairy spiders, living in temperate or cold climates. There are
about fifty species of Tegenaria, seven of which have been recorded as
British.
size, with well-developed scopulae on tarsi and metatarsi. The cribellum is
divided, and the calamistrum, which is very short, is not well developed.
Most are inhabitants of hot regions, where they live under stones or bark.
Zoropsis has six species, chiefly inhabitants of North Africa, though
representatives occur on the European side of the Mediterranean.
Acanthoctenus has two species in South and Central America.
Fam. 29. Platoridae.—The Platoridae are Thomisid-like, medium-sized
spiders, generally with a uniform yellow or brown coloration. The
spinnerets are their most characteristic features. The median pair present a
large flat surface studded with two parallel rows of large fusulae, while the
anterior pair are situated outside them, and are thus widely separated. There
are only three genera, and very few species of this family. Plator insolens is
a Chinese species. Doliomalus and Vectius belong to South America.
Fam. 30. Agelenidae.—Sedentary spiders with slight sexual
dimorphism; with three tarsal claws and devoid of scopulae.
The Agelenidae spin a more or less extensive web of fine texture, usually
accompanied by a tubular retreat. Our commonest cellar spiders belong to
this group, which may be divided into three sub-families, Cybaeinae,
Ageleninae, and Hahniinae.
(i.) The Cybaeinae include some sixteen genera, of which two deserve
special mention on account of the peculiar habits of the spiders belonging to
them.
Desis is a genus of marine spiders, said to live on coral reefs below high-
water mark, and to remain in holes in the rock during high tide, enclosed in
cocoons impermeable to the sea-water. At low tide it is stated that they
come forth and prey upon small crustaceans. Argyroneta has only one
species, A. aquatica, spread throughout Europe and North and Central Asia.
It is the well-known “Water-spider,” which is so often an object of interest
in aquaria.
(ii.) The Ageleninae also contain sixteen genera, but it is a much larger
group, some of the genera being rich in species. They are mostly moderate
or large-sized hairy spiders, living in temperate or cold climates. There are
about fifty species of Tegenaria, seven of which have been recorded as
British.
Page 461
Our commonest Cellar-spider is T. derhamii, but the very large long-
legged species found in houses in the southern counties of England is T.
parietina (= guyonii = domestica). There are not many species of Agelena,
but one, A. labyrinthica, is a common object in this country, with its large,
close-textured web and accompanying tube spread on grassy banks by the
wayside. Coelotes atropos is a formidable-looking spider, found
occasionally under stones in England and Wales. Another genus,
Cryphoeca, has three British representatives.
(iii.) The Hahniinae are recognised at once by their spinnerets, which are
arranged in a single transverse line, the posterior pair being on the outside,
and generally much the longest. Hahnia contains several species of very
small spiders, of which four or five are British, usually occurring among
moss or herbage. The aberrant form Nicodamus (Centropelma), usually
placed among the Theridiidae, is removed by Simon to the Agelenidae,
forming by itself the sub-family (iv.) Nicodaminae.
Fam. 31. Pisauridae.—The Pisauridae are hairy, long-legged spiders,
intermediate, both in structure and in habits, between the Agelenidae and
the Lycosidae. Many new genera have recently been added to the group, but
many of them only include one or two species.
Pisaura is spread throughout the temperate regions of the Old World, and
P. (Ocyale) mirabilis is common in England, being found abundantly in
woods and on commons. It is a striking spider, more than half an inch in
length, and its elongate abdomen is marked on either side with a sinuous
longitudinal white band.
There are some thirty species of Dolomedes scattered over the temperate
regions of the world. D. fimbriatus is a rare species in marshy spots in the
south of England, and is one of the largest British spiders. The ground-
colour is deep brown, with two longitudinal yellowish stripes both on
cephalothorax and abdomen.
The genus Dolomedes is replaced by Thaumasia in South America.
Fam. 32. Lycosidae.—These are what are popularly known as “Wolf-
spiders.” They are vagabond hunting spiders, spinning no snare, but chasing
their prey along the ground, and in the breeding season carrying their egg-
bags with them, attached beneath the abdomen. Some of them burrow in the
loose earth or sand, but others seem to have nothing in the way of a
habitation.
legged species found in houses in the southern counties of England is T.
parietina (= guyonii = domestica). There are not many species of Agelena,
but one, A. labyrinthica, is a common object in this country, with its large,
close-textured web and accompanying tube spread on grassy banks by the
wayside. Coelotes atropos is a formidable-looking spider, found
occasionally under stones in England and Wales. Another genus,
Cryphoeca, has three British representatives.
(iii.) The Hahniinae are recognised at once by their spinnerets, which are
arranged in a single transverse line, the posterior pair being on the outside,
and generally much the longest. Hahnia contains several species of very
small spiders, of which four or five are British, usually occurring among
moss or herbage. The aberrant form Nicodamus (Centropelma), usually
placed among the Theridiidae, is removed by Simon to the Agelenidae,
forming by itself the sub-family (iv.) Nicodaminae.
Fam. 31. Pisauridae.—The Pisauridae are hairy, long-legged spiders,
intermediate, both in structure and in habits, between the Agelenidae and
the Lycosidae. Many new genera have recently been added to the group, but
many of them only include one or two species.
Pisaura is spread throughout the temperate regions of the Old World, and
P. (Ocyale) mirabilis is common in England, being found abundantly in
woods and on commons. It is a striking spider, more than half an inch in
length, and its elongate abdomen is marked on either side with a sinuous
longitudinal white band.
There are some thirty species of Dolomedes scattered over the temperate
regions of the world. D. fimbriatus is a rare species in marshy spots in the
south of England, and is one of the largest British spiders. The ground-
colour is deep brown, with two longitudinal yellowish stripes both on
cephalothorax and abdomen.
The genus Dolomedes is replaced by Thaumasia in South America.
Fam. 32. Lycosidae.—These are what are popularly known as “Wolf-
spiders.” They are vagabond hunting spiders, spinning no snare, but chasing
their prey along the ground, and in the breeding season carrying their egg-
bags with them, attached beneath the abdomen. Some of them burrow in the
loose earth or sand, but others seem to have nothing in the way of a
habitation.
Page 462
The arrangement of the eyes is
very characteristic. They are in three
rows. The front row consists of four
small eyes above the insertion of the
chelicerae, and directed forwards.
Two comparatively very large eyes
form the next row, and occupy the
upper angles of the facies, being also
directed forwards. The third row
consists of two medium-sized eyes
placed dorso-laterally on the caput,
some distance behind the rest, and
looking upwards. The tarsi are three-
clawed. The so-called “Tarantula”
spiders belong to this group, though
the name has been so abused in Fig. 214.—Lycosid Spiders. 1, Lycosa fabrilis,
popular usage, and has passed ♀; 2, Lycosa picta, ♀; 3, Pardosa amentata, ♀.
through so many vicissitudes in
scientific nomenclature, that it is difficult to tell what creature is intended
by it. In America the Aviculariidae are commonly called Tarantulas.
The two chief genera of this extensive family are Lycosa and Pardosa.
The genus Lycosa includes about 400 species. It has been broken up from
time to time into various genera (Trochosa, Pirata, Tarentula, etc.), but
these glide into each other by imperceptible degrees, and are now discarded.
They are large or moderate-sized spiders, found in every part of the world.
About twenty species are British, some of them being fine and handsomely
marked. One of the prettiest is Lycosa picta, common on the sandhills in
some localities.
Some exotic species are very large, Lycosa ingens, from Madeira,
measuring sometimes more than an inch and a half in length.
Pardosa (Fig. 188, p. 341) is not so rich in species, but the individuals of
some species are wonderfully numerous. Hundreds of P. lugubris, for
example, may be seen scampering over the dead leaves of a wood in the
autumn. These spiders are generally sombrely coloured and well covered
with hair. Perhaps the commonest and most widely spread species in this
country is P. amentata.
very characteristic. They are in three
rows. The front row consists of four
small eyes above the insertion of the
chelicerae, and directed forwards.
Two comparatively very large eyes
form the next row, and occupy the
upper angles of the facies, being also
directed forwards. The third row
consists of two medium-sized eyes
placed dorso-laterally on the caput,
some distance behind the rest, and
looking upwards. The tarsi are three-
clawed. The so-called “Tarantula”
spiders belong to this group, though
the name has been so abused in Fig. 214.—Lycosid Spiders. 1, Lycosa fabrilis,
popular usage, and has passed ♀; 2, Lycosa picta, ♀; 3, Pardosa amentata, ♀.
through so many vicissitudes in
scientific nomenclature, that it is difficult to tell what creature is intended
by it. In America the Aviculariidae are commonly called Tarantulas.
The two chief genera of this extensive family are Lycosa and Pardosa.
The genus Lycosa includes about 400 species. It has been broken up from
time to time into various genera (Trochosa, Pirata, Tarentula, etc.), but
these glide into each other by imperceptible degrees, and are now discarded.
They are large or moderate-sized spiders, found in every part of the world.
About twenty species are British, some of them being fine and handsomely
marked. One of the prettiest is Lycosa picta, common on the sandhills in
some localities.
Some exotic species are very large, Lycosa ingens, from Madeira,
measuring sometimes more than an inch and a half in length.
Pardosa (Fig. 188, p. 341) is not so rich in species, but the individuals of
some species are wonderfully numerous. Hundreds of P. lugubris, for
example, may be seen scampering over the dead leaves of a wood in the
autumn. These spiders are generally sombrely coloured and well covered
with hair. Perhaps the commonest and most widely spread species in this
country is P. amentata.
Page 463
Fam. 33. Ctenidae.—The Ctenidae are Lycosa-like spiders, having in
certain points of structure close affinities with the Pisauridae and the
Sparassinae of the Thomisidae. The limits of the family are not well
defined, and many arachnologists place in it some of the genera allotted
above to the Pisauridae, while others do not consider the group sufficiently
marked off to constitute a separate family at all. As here understood they are
equivalent to the Cteninae of the Clubionidae in Simon’s Histoire naturelle.
The eyes are arranged in the Lycosa fashion, but the tarsi have only two
terminal claws and well-developed “claw-tufts,” frequently accompanied by
a scopula. There are strong, regularly-arranged spines under the tibiae and
tarsi.
There are about fifteen genera. Uliodon numbers six species of large
hairy spiders in Australia. Ctenus is rich in species, having about sixty,
found in all hot countries, but especially in America and Africa. They are
also of large size and usually of yellowish coloration, often diversified by a
pattern on the abdomen. The fifteen species of Leptoctenus are proper to
tropical Asia. Acantheis from South Asia and Enoplectenus from Brazil are
more slender, elongate forms, recalling Tetragnatha. Caloctenus includes a
number of Pardosa-like spiders found at a high elevation in South America.
The Ctenidae have the habits of the Lycosidae, and are wandering
spiders, some forming a burrow in the ground.
Fam. 34. Senoculidae.—The South American genus Senoculus
(Labdacus) alone constitutes this family. The species are probably
numerous, but ten only have been described. They are moderate-sized
spiders, spinning no web, but running with astonishing speed over the
leaves and stems of plants. The generic name is really inapplicable, as there
are eight eyes, but the anterior laterals are much reduced. The abdomen is
long, and the legs are long and unequal, the first pair much the longest and
the third much the shortest.
Fam. 35. Oxyopidae.—The Oxyopidae form a well-marked group, with
oval cephalothorax somewhat narrowed in front, and lanceolate abdomen.
The eight black eyes have a characteristic arrangement, and the anterior
medians are always very small. The legs are long and tapering, and not very
unequal, and are furnished with particularly long spines, which give these
spiders a very characteristic appearance. There are eight genera, of which
the most important are Pucetia and Oxyopes.
certain points of structure close affinities with the Pisauridae and the
Sparassinae of the Thomisidae. The limits of the family are not well
defined, and many arachnologists place in it some of the genera allotted
above to the Pisauridae, while others do not consider the group sufficiently
marked off to constitute a separate family at all. As here understood they are
equivalent to the Cteninae of the Clubionidae in Simon’s Histoire naturelle.
The eyes are arranged in the Lycosa fashion, but the tarsi have only two
terminal claws and well-developed “claw-tufts,” frequently accompanied by
a scopula. There are strong, regularly-arranged spines under the tibiae and
tarsi.
There are about fifteen genera. Uliodon numbers six species of large
hairy spiders in Australia. Ctenus is rich in species, having about sixty,
found in all hot countries, but especially in America and Africa. They are
also of large size and usually of yellowish coloration, often diversified by a
pattern on the abdomen. The fifteen species of Leptoctenus are proper to
tropical Asia. Acantheis from South Asia and Enoplectenus from Brazil are
more slender, elongate forms, recalling Tetragnatha. Caloctenus includes a
number of Pardosa-like spiders found at a high elevation in South America.
The Ctenidae have the habits of the Lycosidae, and are wandering
spiders, some forming a burrow in the ground.
Fam. 34. Senoculidae.—The South American genus Senoculus
(Labdacus) alone constitutes this family. The species are probably
numerous, but ten only have been described. They are moderate-sized
spiders, spinning no web, but running with astonishing speed over the
leaves and stems of plants. The generic name is really inapplicable, as there
are eight eyes, but the anterior laterals are much reduced. The abdomen is
long, and the legs are long and unequal, the first pair much the longest and
the third much the shortest.
Fam. 35. Oxyopidae.—The Oxyopidae form a well-marked group, with
oval cephalothorax somewhat narrowed in front, and lanceolate abdomen.
The eight black eyes have a characteristic arrangement, and the anterior
medians are always very small. The legs are long and tapering, and not very
unequal, and are furnished with particularly long spines, which give these
spiders a very characteristic appearance. There are eight genera, of which
the most important are Pucetia and Oxyopes.
Page 464
Pucetia contains a number of rather large spiders, generally bright green,
often variegated with red. They affect particular plants. For instance, P.
viridis, which occurs in Spain, is always found on Ononis hispanica. There
are about thirty species of this genus distributed over the tropical and sub-
tropical regions of the world. Oxyopes numbers many species, certainly
more than fifty, and has a similar distribution, but some of its members
invade colder regions. They are of rather small size. O. lineatus is a very
rare spider in the south of England.
The Oxyopidae are diurnal spiders, running over plants in search of prey,
and often leaping, after the fashion of members of the following family.
Fam. 36. Attidae (Salticidae).—Wandering spiders with cephalothorax
broad anteriorly, and bearing eight homogeneous eyes in three rows. Four
eyes, largely developed, are directed forward; the remaining four eyes are
placed dorsally in two rows, the first pair being much reduced in size.
The Attidae or Jumping-spiders form the most extensive family of the
whole order, the known species amounting to something like four thousand.
It is only of late years that their vast numbers have begun to be realised, for
their vagabond habits and great activity enabled them to a great extent to
elude the earlier collectors, whose methods were not as thorough as those
now in vogue. Their real home is in the tropical regions, temperate fauna
being comparatively poor in Attid species. France boasts nearly 150, but
only 37 are recorded for the British Isles, and 2 at least of these are recent
introductions.
Some of the tropical forms are most brilliantly coloured, glowing with
vivid colours and metallic hues, and they have frequently excited the
admiration of travellers. The coloration is nearly always due to the hairs and
scales with which the spiders are clothed, and is, unfortunately, almost
incapable of preservation in the collector’s cabinet.
These spiders are all wanderers, spinning no snares, though they form a
sort of silken cell or retreat, in which the female lays her eggs. Their habits
are diurnal, and they delight in sunshine. They stalk their prey and leap
upon it with wonderful accuracy. They invariably attach a thread at intervals
in their course, and on the rare occasions when they miss their aim while
hunting on a perpendicular surface, they are saved from a fall by the silken
line proceeding from the spot whence the leap was made.
often variegated with red. They affect particular plants. For instance, P.
viridis, which occurs in Spain, is always found on Ononis hispanica. There
are about thirty species of this genus distributed over the tropical and sub-
tropical regions of the world. Oxyopes numbers many species, certainly
more than fifty, and has a similar distribution, but some of its members
invade colder regions. They are of rather small size. O. lineatus is a very
rare spider in the south of England.
The Oxyopidae are diurnal spiders, running over plants in search of prey,
and often leaping, after the fashion of members of the following family.
Fam. 36. Attidae (Salticidae).—Wandering spiders with cephalothorax
broad anteriorly, and bearing eight homogeneous eyes in three rows. Four
eyes, largely developed, are directed forward; the remaining four eyes are
placed dorsally in two rows, the first pair being much reduced in size.
The Attidae or Jumping-spiders form the most extensive family of the
whole order, the known species amounting to something like four thousand.
It is only of late years that their vast numbers have begun to be realised, for
their vagabond habits and great activity enabled them to a great extent to
elude the earlier collectors, whose methods were not as thorough as those
now in vogue. Their real home is in the tropical regions, temperate fauna
being comparatively poor in Attid species. France boasts nearly 150, but
only 37 are recorded for the British Isles, and 2 at least of these are recent
introductions.
Some of the tropical forms are most brilliantly coloured, glowing with
vivid colours and metallic hues, and they have frequently excited the
admiration of travellers. The coloration is nearly always due to the hairs and
scales with which the spiders are clothed, and is, unfortunately, almost
incapable of preservation in the collector’s cabinet.
These spiders are all wanderers, spinning no snares, though they form a
sort of silken cell or retreat, in which the female lays her eggs. Their habits
are diurnal, and they delight in sunshine. They stalk their prey and leap
upon it with wonderful accuracy. They invariably attach a thread at intervals
in their course, and on the rare occasions when they miss their aim while
hunting on a perpendicular surface, they are saved from a fall by the silken
line proceeding from the spot whence the leap was made.
Page 465
The movements of these spiders
are sufficient to indicate their
systematic position without entering
upon structural details, but their eyes
deserve a special mention. They are
all dark-coloured and very unequal in
size, and they occupy the whole area
of the caput, usually forming a large
quadrilateral figure. Four large eyes
occupy the facies or “forehead,” the
medians being especially large. Next
come two very small eyes, behind the
anterior laterals, and lastly two of
medium size at the posterior corners
of the caput.
This vast family does not lend
Fig. 215.—Attid Spiders. A, Salticus scenicus, itself easily to division into sub-
♂ ; B, Marpissa muscosa, ♀ ; C, Synemosyna families, and it will be impossible
formica, ♀; D, Ballus variegatus, ♀. here to do more than indicate a very
few of the multitudinous forms.
The most familiar British example is Salticus scenicus (Epiblemum
scenicum), the little black and white striped spider to be seen hunting on
walls and fences during the summer. Marpissa muscosa is the largest
English species, measuring about half an inch. It has a brownish-yellow
coloration, and is found, though not commonly, in similar situations. Attus
pubescens affects grey stone walls, on which it is nearly invisible except
when moving. The other British species are mostly to be found on trees and
shrubs or among herbage, or hunting over bare sandy spots in the sunshine.
A few (Marpissa pomatia, Hyctia nivoyi) are fen species. Hasarius falcatus
is a handsome spider, common in woods in some localities.
The species differ much in their jumping powers; the Marpissas, for
example, are not great leapers, but the little Attus saltator, found on
sandhills, jumps like a flea, and the North American species Saitis pulex has
a suggestive specific name.
Again, in this family there are mimetic forms resembling ants.
Myrmarachne formicaria (Salticus formicarius) is found very rarely in
are sufficient to indicate their
systematic position without entering
upon structural details, but their eyes
deserve a special mention. They are
all dark-coloured and very unequal in
size, and they occupy the whole area
of the caput, usually forming a large
quadrilateral figure. Four large eyes
occupy the facies or “forehead,” the
medians being especially large. Next
come two very small eyes, behind the
anterior laterals, and lastly two of
medium size at the posterior corners
of the caput.
This vast family does not lend
Fig. 215.—Attid Spiders. A, Salticus scenicus, itself easily to division into sub-
♂ ; B, Marpissa muscosa, ♀ ; C, Synemosyna families, and it will be impossible
formica, ♀; D, Ballus variegatus, ♀. here to do more than indicate a very
few of the multitudinous forms.
The most familiar British example is Salticus scenicus (Epiblemum
scenicum), the little black and white striped spider to be seen hunting on
walls and fences during the summer. Marpissa muscosa is the largest
English species, measuring about half an inch. It has a brownish-yellow
coloration, and is found, though not commonly, in similar situations. Attus
pubescens affects grey stone walls, on which it is nearly invisible except
when moving. The other British species are mostly to be found on trees and
shrubs or among herbage, or hunting over bare sandy spots in the sunshine.
A few (Marpissa pomatia, Hyctia nivoyi) are fen species. Hasarius falcatus
is a handsome spider, common in woods in some localities.
The species differ much in their jumping powers; the Marpissas, for
example, are not great leapers, but the little Attus saltator, found on
sandhills, jumps like a flea, and the North American species Saitis pulex has
a suggestive specific name.
Again, in this family there are mimetic forms resembling ants.
Myrmarachne formicaria (Salticus formicarius) is found very rarely in
Page 466
England, but is not uncommon on the Continent.
Synageles and Synemosyna are allied genera. Phidippus is a genus well
represented in America, and Ph. morsitans has already been mentioned (p.
365) in connexion with its poisonous reputation. Astia and Icius have
American representatives (see pp. 381, 382), though the type species
belongs to the Old World.
Synageles and Synemosyna are allied genera. Phidippus is a genus well
represented in America, and Ph. morsitans has already been mentioned (p.
365) in connexion with its poisonous reputation. Astia and Icius have
American representatives (see pp. 381, 382), though the type species
belongs to the Old World.
Page 467
CHAPTER XVI
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
PALPIGRADI—SOLIFUGAE = SOLPUGAE—
CHERNETIDEA = PSEUDOSCORPIONES
Order IV. Palpigradi.
Minute Arachnids with three-jointed chelate chelicerae, and with the last
two joints of the cephalothorax free. The abdomen consists of eleven
segments with a fifteen-jointed flagellum.
In 1885 Grassi discovered, at Catania, a minute Arachnid which did not
fall into any of the established orders of Arachnida. He named it Koenenia
mirabilis. In 1893 Hansen collected several specimens in Calabria, near
Palmi and Scilla, and carefully redescribed the species in conjunction with
Sörensen.[322] It has been studied still more minutely by Börner.[323]
There is a “head” portion, covered by a carapace, and bearing the
chelicerae, pedipalpi, and two pairs of legs. The two free thoracic segments
bear the third and fourth pairs of legs, recalling the Schizonotidae (see p.
312), where the portion of the thorax bearing these legs is separate, though
covered by a single dorsal plate. There are no eyes, but two hair-structures,
believed to be sensory, are present on the cephalothorax, and Börner has
observed openings in the second joint of the first pair of legs which have all
the appearance of “lyriform” organs, as found in Spiders (see p. 325).
The last three abdominal segments narrow rapidly, the last bearing the
anus. A fifteen-jointed caudal flagellum is carried, Scorpion-like, above the
animal’s back. The body and tail are each about a millimetre in length, and
the animal is of a translucent white colour.
The mouth is extremely simple, being merely a slit upon a slight
eminence. There are two sternal plates beneath the “head,” and one beneath
each free thoracic segment. The genital operculum is complicated, and is
situated beneath the second abdominal segment.
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
PALPIGRADI—SOLIFUGAE = SOLPUGAE—
CHERNETIDEA = PSEUDOSCORPIONES
Order IV. Palpigradi.
Minute Arachnids with three-jointed chelate chelicerae, and with the last
two joints of the cephalothorax free. The abdomen consists of eleven
segments with a fifteen-jointed flagellum.
In 1885 Grassi discovered, at Catania, a minute Arachnid which did not
fall into any of the established orders of Arachnida. He named it Koenenia
mirabilis. In 1893 Hansen collected several specimens in Calabria, near
Palmi and Scilla, and carefully redescribed the species in conjunction with
Sörensen.[322] It has been studied still more minutely by Börner.[323]
There is a “head” portion, covered by a carapace, and bearing the
chelicerae, pedipalpi, and two pairs of legs. The two free thoracic segments
bear the third and fourth pairs of legs, recalling the Schizonotidae (see p.
312), where the portion of the thorax bearing these legs is separate, though
covered by a single dorsal plate. There are no eyes, but two hair-structures,
believed to be sensory, are present on the cephalothorax, and Börner has
observed openings in the second joint of the first pair of legs which have all
the appearance of “lyriform” organs, as found in Spiders (see p. 325).
The last three abdominal segments narrow rapidly, the last bearing the
anus. A fifteen-jointed caudal flagellum is carried, Scorpion-like, above the
animal’s back. The body and tail are each about a millimetre in length, and
the animal is of a translucent white colour.
The mouth is extremely simple, being merely a slit upon a slight
eminence. There are two sternal plates beneath the “head,” and one beneath
each free thoracic segment. The genital operculum is complicated, and is
situated beneath the second abdominal segment.
Page 468
Since 1885 several other species
have been discovered in various parts
of the world. Two American forms
possess three pairs of lung-sacs on
segments 4, 5, and 6 of the abdomen.
Rucker[324] has suggested for them the
generic name of Prokoenenia,
including P. wheeleri, Rucker, from
Texas, and P. chilensis, Hansen, from
Chili. The others, styled by that
author Eukoenenia, have no lung-
sacs. There are about ten species,
mostly from the Mediterranean
region, but E. augusta, Hansen, is
found in Siam, E. florenciae, Rucker,
in Texas, and E. grassii, Hansen, in
Paraguay.
Fig. 216.—Koenenia mirabilis, much enlarged.
(After Hansen.)
Order V. Solifugae (Solpugae).
have been discovered in various parts
of the world. Two American forms
possess three pairs of lung-sacs on
segments 4, 5, and 6 of the abdomen.
Rucker[324] has suggested for them the
generic name of Prokoenenia,
including P. wheeleri, Rucker, from
Texas, and P. chilensis, Hansen, from
Chili. The others, styled by that
author Eukoenenia, have no lung-
sacs. There are about ten species,
mostly from the Mediterranean
region, but E. augusta, Hansen, is
found in Siam, E. florenciae, Rucker,
in Texas, and E. grassii, Hansen, in
Paraguay.
Fig. 216.—Koenenia mirabilis, much enlarged.
(After Hansen.)
Order V. Solifugae (Solpugae).
Page 469
Tracheate Arachnids, with the last three segments of the cephalothorax
free and the abdomen segmented. The chelicerae are largely developed and
chelate, and the pedipalpi are leg-like, possessing terminal sense-organs.
The Solifugae are, in some respects, the most primitive of the tracheate
Arachnida. Their general appearance is very spider-like, and by the old
writers they are uniformly alluded to as spiders. The segmented body and
the absence of spinning organs, however, make them readily distinguishable
on careful inspection. They are for the most part nocturnal creatures, though
some seem to rove about by day, and are even called “Sun-spiders” by the
Spaniards. The night-loving species are attracted by light. They are, as a
rule, exceedingly hairy. Some are extremely active, while the short-legged
forms (e.g. Rhagodes, see p. 429) move slowly. They are capable of
producing a hissing sound by the rubbing together of their chelicerae. Only
the last three pairs of legs are true ambulatory organs, the first being carried
aloft like the pedipalps, and used for feeling and manipulating the prey.
There has been much controversy as to the poisonous properties with
which these creatures have been very widely credited by both ancient and
modern writers. The people of Baku on the Caspian consider them
especially poisonous after their winter sleep. The Russians of that region
much dread the “Falangas,” as they call them, and keep a Falanga preserved
in oil as an antidote to the bite. The Somalis, on the other hand, have no fear
of them, and, though familiar with these animals, have not thought them
worthy of the dignity of a name.
Several investigators have allowed themselves to be bitten without any
special result. Some zoologists have found and described what they have
taken to be poison-glands, but these appear to be the coxal glands, which
have an excretory function. Bernard[325] suggests that, if the bite be
poisonous, the virus may exude from the numerous setal pores which are
found on the extremities of the chelicerae. The cutting powers of the
immensely-developed chelicerae are usually sufficient to ensure fatal results
on small animals without the agency of poison. Distant,[326] indeed, thinks
they cannot be poisonous, for when birds attack them they flee before their
assailants.
The Solifugae require a tolerably warm climate. In Europe they are only
found in Spain, Greece, and Southern Russia. They abound throughout
Africa, and are found in South-Western Asia, the southern United States,
free and the abdomen segmented. The chelicerae are largely developed and
chelate, and the pedipalpi are leg-like, possessing terminal sense-organs.
The Solifugae are, in some respects, the most primitive of the tracheate
Arachnida. Their general appearance is very spider-like, and by the old
writers they are uniformly alluded to as spiders. The segmented body and
the absence of spinning organs, however, make them readily distinguishable
on careful inspection. They are for the most part nocturnal creatures, though
some seem to rove about by day, and are even called “Sun-spiders” by the
Spaniards. The night-loving species are attracted by light. They are, as a
rule, exceedingly hairy. Some are extremely active, while the short-legged
forms (e.g. Rhagodes, see p. 429) move slowly. They are capable of
producing a hissing sound by the rubbing together of their chelicerae. Only
the last three pairs of legs are true ambulatory organs, the first being carried
aloft like the pedipalps, and used for feeling and manipulating the prey.
There has been much controversy as to the poisonous properties with
which these creatures have been very widely credited by both ancient and
modern writers. The people of Baku on the Caspian consider them
especially poisonous after their winter sleep. The Russians of that region
much dread the “Falangas,” as they call them, and keep a Falanga preserved
in oil as an antidote to the bite. The Somalis, on the other hand, have no fear
of them, and, though familiar with these animals, have not thought them
worthy of the dignity of a name.
Several investigators have allowed themselves to be bitten without any
special result. Some zoologists have found and described what they have
taken to be poison-glands, but these appear to be the coxal glands, which
have an excretory function. Bernard[325] suggests that, if the bite be
poisonous, the virus may exude from the numerous setal pores which are
found on the extremities of the chelicerae. The cutting powers of the
immensely-developed chelicerae are usually sufficient to ensure fatal results
on small animals without the agency of poison. Distant,[326] indeed, thinks
they cannot be poisonous, for when birds attack them they flee before their
assailants.
The Solifugae require a tolerably warm climate. In Europe they are only
found in Spain, Greece, and Southern Russia. They abound throughout
Africa, and are found in South-Western Asia, the southern United States,
Page 470
and the north of South America. They appear to be absent from Australia,
nor have any been found in Madagascar. Their usual food appears to be
insects, though they devour lizards with avidity. Some interesting
observations on their habits are recorded by Captain Hutton,[327] who kept
specimens in captivity in India. An imprisoned female made a burrow in the
earth with which her cage was provided, and laid fifty eggs, which hatched
in a fortnight, but the young remained motionless for three weeks longer,
when they underwent their first moult, and became active.
A sparrow and musk rats were at different times placed in the cage, and
were speedily killed, but not eaten. Two specimens placed in the same cage
tried to avoid each other, but, on coming into contact, fought desperately,
the one ultimately devouring the other. It was noteworthy that the one
which was first fairly seized immediately resigned itself to its fate without a
struggle. As is the case with some spiders, the female is said occasionally to
kill and devour the male. A Mashonaland species, Solpuga sericea, feeds on
termites,[328] while a South Californian Galeodes kills bees,[329] entering the
hives in search of them. They are fairly good climbers. In Egypt Galeodes
arabs climbs on to tables to catch flies, and some species have been
observed to climb trees.
That their pedipalps, in addition to their sensory function (see p. 426),
possess a sucking apparatus, is clear from an observation of Lönnberg,[330]
who kept specimens of Galeodes araneoides imprisoned in rectangular
glass boxes, up the perpendicular sides of which they were able to climb for
some distance by their palps, but, being able to obtain no hold by their legs,
they soon tired.
External Anatomy.—The body of Galeodes consists of a cephalothorax
and an abdomen, both portions being distinctly segmented. The
cephalothorax consists of six segments, the first thoracic segment being
fused with the two cephalic segments to form a sort of head, while the last
three thoracic segments are free, and there is almost as much freedom of
movement between the last two thoracic segments as between the thorax
and the abdomen. The “cephalic lobes,” which give the appearance of a
head, have been shown by Bernard[331] to be due to the enormous
development of the chelicerae, by the muscles of which they are entirely
occupied.
nor have any been found in Madagascar. Their usual food appears to be
insects, though they devour lizards with avidity. Some interesting
observations on their habits are recorded by Captain Hutton,[327] who kept
specimens in captivity in India. An imprisoned female made a burrow in the
earth with which her cage was provided, and laid fifty eggs, which hatched
in a fortnight, but the young remained motionless for three weeks longer,
when they underwent their first moult, and became active.
A sparrow and musk rats were at different times placed in the cage, and
were speedily killed, but not eaten. Two specimens placed in the same cage
tried to avoid each other, but, on coming into contact, fought desperately,
the one ultimately devouring the other. It was noteworthy that the one
which was first fairly seized immediately resigned itself to its fate without a
struggle. As is the case with some spiders, the female is said occasionally to
kill and devour the male. A Mashonaland species, Solpuga sericea, feeds on
termites,[328] while a South Californian Galeodes kills bees,[329] entering the
hives in search of them. They are fairly good climbers. In Egypt Galeodes
arabs climbs on to tables to catch flies, and some species have been
observed to climb trees.
That their pedipalps, in addition to their sensory function (see p. 426),
possess a sucking apparatus, is clear from an observation of Lönnberg,[330]
who kept specimens of Galeodes araneoides imprisoned in rectangular
glass boxes, up the perpendicular sides of which they were able to climb for
some distance by their palps, but, being able to obtain no hold by their legs,
they soon tired.
External Anatomy.—The body of Galeodes consists of a cephalothorax
and an abdomen, both portions being distinctly segmented. The
cephalothorax consists of six segments, the first thoracic segment being
fused with the two cephalic segments to form a sort of head, while the last
three thoracic segments are free, and there is almost as much freedom of
movement between the last two thoracic segments as between the thorax
and the abdomen. The “cephalic lobes,” which give the appearance of a
head, have been shown by Bernard[331] to be due to the enormous
development of the chelicerae, by the muscles of which they are entirely
occupied.
Page 471
The floor of the cephalothorax is
for the most part formed by the coxae
of the appendages, and the sternum is
hardly recognisable in many species.
In Solpuga, however (see p. 429), it
exists in the form of a long narrow
plate of three segments, ending
anteriorly in a lancet-shaped labium.
A pair of large simple eyes are
borne on a prominence in the middle
of the anterior portion of the
cephalothorax, and there are often
one or two pairs of vestigial lateral
eyes.
The first pair of tracheal stigmata
are to be found behind the coxae of
the second legs.
Fig. 217.—Rhagodes sp., ventral view. Nat.
size. a, Anus; ch, chelicerae; g.o, genital The mouth-parts take the form of a
operculum; n, racket organs; p, pedipalp; 1, 2, 3, characteristic beak, consisting of a
4, ambulatory legs. (After Bernard.)
labrum and a labium entirely fused
along their sides. The mouth is at the
extremity of the beak, and is furnished with a straining apparatus of
complicated hairs.
The abdomen possesses ten free segments, marked off by dorsal and
ventral plates, with a wide membranous lateral interval. The ventral plates
are paired, the first pair forming the genital opercula, while behind the
second and third are two pairs of stigmata. Some species have a single
median stigma on the fourth segment, but this is in some cases permanently
closed, and in the genus Rhagodes entirely absent, so that it would seem to
be a disappearing structure.
The appendages are the six pairs common to all Arachnids—chelicerae,
pedipalpi, and four pairs of legs. The chelicerae, which are enormously
developed, are two-jointed and chelate, the distal joint being articulated
beneath the produced basal joint. In the male there is nearly always present,
on the basal joint, a remarkable structure of modified hairs called the
“flagellum,” and believed to be sensory. It differs in the different genera,
for the most part formed by the coxae
of the appendages, and the sternum is
hardly recognisable in many species.
In Solpuga, however (see p. 429), it
exists in the form of a long narrow
plate of three segments, ending
anteriorly in a lancet-shaped labium.
A pair of large simple eyes are
borne on a prominence in the middle
of the anterior portion of the
cephalothorax, and there are often
one or two pairs of vestigial lateral
eyes.
The first pair of tracheal stigmata
are to be found behind the coxae of
the second legs.
Fig. 217.—Rhagodes sp., ventral view. Nat.
size. a, Anus; ch, chelicerae; g.o, genital The mouth-parts take the form of a
operculum; n, racket organs; p, pedipalp; 1, 2, 3, characteristic beak, consisting of a
4, ambulatory legs. (After Bernard.)
labrum and a labium entirely fused
along their sides. The mouth is at the
extremity of the beak, and is furnished with a straining apparatus of
complicated hairs.
The abdomen possesses ten free segments, marked off by dorsal and
ventral plates, with a wide membranous lateral interval. The ventral plates
are paired, the first pair forming the genital opercula, while behind the
second and third are two pairs of stigmata. Some species have a single
median stigma on the fourth segment, but this is in some cases permanently
closed, and in the genus Rhagodes entirely absent, so that it would seem to
be a disappearing structure.
The appendages are the six pairs common to all Arachnids—chelicerae,
pedipalpi, and four pairs of legs. The chelicerae, which are enormously
developed, are two-jointed and chelate, the distal joint being articulated
beneath the produced basal joint. In the male there is nearly always present,
on the basal joint, a remarkable structure of modified hairs called the
“flagellum,” and believed to be sensory. It differs in the different genera,
Page 472
and is only absent in the Eremobatinae (see p. 429). The pedipalpi are
strong, six-jointed, leg-like appendages, without terminal claw. They end in
a knob-like joint, sometimes movable, sometimes fixed, which contains a
very remarkable eversible sense-organ, which is probably olfactory. It is
concealed by a lid-like structure, and when protruded is seen to be
furnished, on its under surface, with a pile of velvet-like sensory hairs.
The legs differ in the number of their joints, as the third and fourth pairs
have the femora divided, and the tarsus jointed. The first pair has only a
very small terminal claw, but two well-developed claws are borne by the
tarsi of the other legs. Each of the last legs bears, on its under surface, five
“racket organs,” believed to be sensory.
Internal Structure.—The alimentary canal possesses a sucking chamber
within the beak, after which it narrows to pass through the nerve-mass, and
after an S-shaped fold, joins the mid-gut. This gives off four pairs of thin
diverticula towards the legs, the last two entering the coxae of the third and
fourth pairs.
At the constriction between the cephalothorax and the abdomen there is
no true pedicle, but there is a transverse septum or “diaphragm,” through
which the blood-vessel, tracheal nerves, and alimentary canal pass. The gut
narrows here, and, on entering the abdomen, proceeds straight to a stercoral
pocket at the hind end of the animal, but gives off, at the commencement,
two long lateral diverticula, which run backwards parallel with the main
trunk. These are furnished with innumerable secondary tube-like
diverticula, which proceed in all directions and fill every available portion
of the abdomen. The caeca, which are so characteristic of the Arachnidan
mid-gut, here reach their extreme development. A pair of Malpighian
tubules enter the main trunk in the fourth abdominal segment.
Other excretory organs are the coxal glands, which form many coils
behind the nerve-mass, and open between the coxae of the third and fourth
legs. They have been taken for poison-glands.
There is a small endosternite in the hinder portion of the cephalothorax
under the alimentary canal.
The vascular system is not completely understood. The heart is a very
long, narrow, dorsal tube, extending almost the entire length of the animal,
and possessing eight pairs of ostia, two in the cephalothorax and six in the
abdomen. It gives off an anterior and a posterior vessel, the latter apparently
strong, six-jointed, leg-like appendages, without terminal claw. They end in
a knob-like joint, sometimes movable, sometimes fixed, which contains a
very remarkable eversible sense-organ, which is probably olfactory. It is
concealed by a lid-like structure, and when protruded is seen to be
furnished, on its under surface, with a pile of velvet-like sensory hairs.
The legs differ in the number of their joints, as the third and fourth pairs
have the femora divided, and the tarsus jointed. The first pair has only a
very small terminal claw, but two well-developed claws are borne by the
tarsi of the other legs. Each of the last legs bears, on its under surface, five
“racket organs,” believed to be sensory.
Internal Structure.—The alimentary canal possesses a sucking chamber
within the beak, after which it narrows to pass through the nerve-mass, and
after an S-shaped fold, joins the mid-gut. This gives off four pairs of thin
diverticula towards the legs, the last two entering the coxae of the third and
fourth pairs.
At the constriction between the cephalothorax and the abdomen there is
no true pedicle, but there is a transverse septum or “diaphragm,” through
which the blood-vessel, tracheal nerves, and alimentary canal pass. The gut
narrows here, and, on entering the abdomen, proceeds straight to a stercoral
pocket at the hind end of the animal, but gives off, at the commencement,
two long lateral diverticula, which run backwards parallel with the main
trunk. These are furnished with innumerable secondary tube-like
diverticula, which proceed in all directions and fill every available portion
of the abdomen. The caeca, which are so characteristic of the Arachnidan
mid-gut, here reach their extreme development. A pair of Malpighian
tubules enter the main trunk in the fourth abdominal segment.
Other excretory organs are the coxal glands, which form many coils
behind the nerve-mass, and open between the coxae of the third and fourth
legs. They have been taken for poison-glands.
There is a small endosternite in the hinder portion of the cephalothorax
under the alimentary canal.
The vascular system is not completely understood. The heart is a very
long, narrow, dorsal tube, extending almost the entire length of the animal,
and possessing eight pairs of ostia, two in the cephalothorax and six in the
abdomen. It gives off an anterior and a posterior vessel, the latter apparently
Page 473
a vein, as it is guarded at its entrance by a valve. The blood seems to be
delivered by the anterior artery on to the nerve-mass, and, after percolating
the muscles and viscera, to divide into two streams—the one returning to
the heart by the thoracic ostia, the other passing through the diaphragm and
bathing the abdominal organs, finally to reach the heart either by the
abdominal ostia or by the posterior vein.
The nervous system,
notwithstanding the fact that the
three last thoracic segments are free,
is chiefly concentrated into a mass
surrounding the oesophagus. Nerves
are given off in front to the eyes, the
labrum, and the chelicerae, while
double nerves radiate to the
pedipalps and to the legs. From
behind the nerve-mass three nerves
emerge, and pass through the
diaphragm to enter the abdomen. The
median nerve swells into an
“abdominal ganglion” just behind the
diaphragm, and is then distributed to
the diverticula of the alimentary
canal. The lateral nerves innervate
the generative organs.
The respiratory system consists of
a connected network of tracheae
communicating with the exterior by
the stigmata, whose position has
already been described. There are
two main lateral trunks extending
nearly the whole length of the body,
and giving off numerous FAbdominal
ig. 218.—Nervous system of Galeodes. abd.g,
ganglion; ch, cheliceral nerve; ch.f,
ramifications, the most important of chitinous fold; ch.r, chitinous rod; g.n,
which are in the cephalothorax, and generative nerve; l, labial nerve; st, position of
supply the muscles of the chelicerae stigma. (After Bernard.)
and of the other appendages.
delivered by the anterior artery on to the nerve-mass, and, after percolating
the muscles and viscera, to divide into two streams—the one returning to
the heart by the thoracic ostia, the other passing through the diaphragm and
bathing the abdominal organs, finally to reach the heart either by the
abdominal ostia or by the posterior vein.
The nervous system,
notwithstanding the fact that the
three last thoracic segments are free,
is chiefly concentrated into a mass
surrounding the oesophagus. Nerves
are given off in front to the eyes, the
labrum, and the chelicerae, while
double nerves radiate to the
pedipalps and to the legs. From
behind the nerve-mass three nerves
emerge, and pass through the
diaphragm to enter the abdomen. The
median nerve swells into an
“abdominal ganglion” just behind the
diaphragm, and is then distributed to
the diverticula of the alimentary
canal. The lateral nerves innervate
the generative organs.
The respiratory system consists of
a connected network of tracheae
communicating with the exterior by
the stigmata, whose position has
already been described. There are
two main lateral trunks extending
nearly the whole length of the body,
and giving off numerous FAbdominal
ig. 218.—Nervous system of Galeodes. abd.g,
ganglion; ch, cheliceral nerve; ch.f,
ramifications, the most important of chitinous fold; ch.r, chitinous rod; g.n,
which are in the cephalothorax, and generative nerve; l, labial nerve; st, position of
supply the muscles of the chelicerae stigma. (After Bernard.)
and of the other appendages.
Page 474
The generative glands do not essentially differ from the usual Arachnid
type, though the paired ovaries do not fuse to form a ring. There are no
external organs, and the sexes can only be distinguished by secondary
characteristics, such as the “flagellum” already mentioned.
Classification.—There are about a hundred and seventy species of
Solifugae inhabiting the warm regions of the earth. No member of the group
is found in England, or in any except the most southern portions of Europe.
Kraepelin[332] has divided the group into three families—Galeodidae,
Solpugidae, and Hexisopodidae.
Fam. 1. Galeodidae.—The Galeodidae have a lancet-shaped flagellum,
directed backwards. There is a characteristic five-toothed plate or comb
covering the abdominal stigmata. The tarsus of the fourth leg is three-
jointed, and the terminal claws are hairy.
There are two genera, Galeodes,
with about twelve species, and
Paragaleodes, with six species,
scattered over the hot regions of the
Old World.
Fam. 2. Solpugidae.—The
Solpugidae comprise twenty-four
genera, distributed under five sub-
families. The toothed stigmatic plate
is absent, and the tarsal claws are
smooth. The ocular eminence is
Fig. 219.—Chelicera and flagellum of
Galeodes. (After Kraepelin.) furnished with irregular hairs. The
“flagellum” is very variable.
(i.) The Rhagodinae include the two genera, Rhagodes (Rhax) and
Dinorhax. The first has twenty-two species, which inhabit Africa and Asia.
The single species of Dinorhax belongs to East Asia. These creatures are
short-legged and sluggish.
(ii.) The Solpuginae contain two genera—Solpuga with about fifty
species, and Zeriana with three. They are all inhabitants of Africa, and
some occur on the African shore of the Mediterranean.
(iii.) The Daesiinae number about forty species, divided among several
genera, among which the principal are Daesia, Gluvia, and Gnosippus.
type, though the paired ovaries do not fuse to form a ring. There are no
external organs, and the sexes can only be distinguished by secondary
characteristics, such as the “flagellum” already mentioned.
Classification.—There are about a hundred and seventy species of
Solifugae inhabiting the warm regions of the earth. No member of the group
is found in England, or in any except the most southern portions of Europe.
Kraepelin[332] has divided the group into three families—Galeodidae,
Solpugidae, and Hexisopodidae.
Fam. 1. Galeodidae.—The Galeodidae have a lancet-shaped flagellum,
directed backwards. There is a characteristic five-toothed plate or comb
covering the abdominal stigmata. The tarsus of the fourth leg is three-
jointed, and the terminal claws are hairy.
There are two genera, Galeodes,
with about twelve species, and
Paragaleodes, with six species,
scattered over the hot regions of the
Old World.
Fam. 2. Solpugidae.—The
Solpugidae comprise twenty-four
genera, distributed under five sub-
families. The toothed stigmatic plate
is absent, and the tarsal claws are
smooth. The ocular eminence is
Fig. 219.—Chelicera and flagellum of
Galeodes. (After Kraepelin.) furnished with irregular hairs. The
“flagellum” is very variable.
(i.) The Rhagodinae include the two genera, Rhagodes (Rhax) and
Dinorhax. The first has twenty-two species, which inhabit Africa and Asia.
The single species of Dinorhax belongs to East Asia. These creatures are
short-legged and sluggish.
(ii.) The Solpuginae contain two genera—Solpuga with about fifty
species, and Zeriana with three. They are all inhabitants of Africa, and
some occur on the African shore of the Mediterranean.
(iii.) The Daesiinae number about forty species, divided among several
genera, among which the principal are Daesia, Gluvia, and Gnosippus.
Page 475
They are found in tropical regions of
both the Old and the New World.
(iv.) The Eremobatinae are North
American forms, the single genus
Eremobates numbering about twenty
species. The flagellum is here
entirely absent.
(v.) The Karshiinae include the
five genera Ceroma, Gylippus,
Barrus, Eusimonia, and Karshia.
They are universally distributed.
Fam. 3. Hexisopodidae.—This
family is formed for the reception of
a single aberrant African genus,
Hexisopus, of which five species
have been described.
There are no claws on the tarsus of
the fourth leg, which is beset with
short spine-like hairs, and in other
respects the genus is peculiar.
Fig. 220.—Chelicerae and flagella of A,
Rhagodes; B, Solpuga; and C, Daesia. (After
Kraepelin.)
both the Old and the New World.
(iv.) The Eremobatinae are North
American forms, the single genus
Eremobates numbering about twenty
species. The flagellum is here
entirely absent.
(v.) The Karshiinae include the
five genera Ceroma, Gylippus,
Barrus, Eusimonia, and Karshia.
They are universally distributed.
Fam. 3. Hexisopodidae.—This
family is formed for the reception of
a single aberrant African genus,
Hexisopus, of which five species
have been described.
There are no claws on the tarsus of
the fourth leg, which is beset with
short spine-like hairs, and in other
respects the genus is peculiar.
Fig. 220.—Chelicerae and flagella of A,
Rhagodes; B, Solpuga; and C, Daesia. (After
Kraepelin.)
Page 476
Fig. 221.—Chelicera and flagellum of
Hexisopus. (After Kraepelin.)
Order VI. Chernetidea.
(CHERNETES, PSEUDOSCORPIONES.)
Tracheate Arachnids, with the abdomen united to the cephalothorax by
its whole breadth. Eyeless, or with two or four simple eyes placed laterally.
Abdomen segmented, with four stigmata. Chelicerae chelate, bearing the
openings of the spinning organs. Pedipalpi large, six-jointed, and chelate.
Sternum absent or rudimentary.
The Chernetidea or “False-scorpions” constitute the most compact and
natural order of the Arachnida. There are no extreme variations within the
group as at present known, while all its members differ so markedly from
those of other Arachnidan orders that their true affinities are by no means
easy to determine.
The superficial resemblance to Scorpions which has won these animals
their popular name is almost entirely due to the comparative size and shape
of their pedipalpi, but it is probable that they are structurally much more
closely allied to the Solifugae.
Chernetidea are not creatures which obtrude themselves on the general
notice, and it is highly probable that many readers have never seen a living
specimen. This is largely due to their minute size. Garypus littoralis, a
Corsican species, nearly a quarter of an inch in length of body, is a veritable
Hexisopus. (After Kraepelin.)
Order VI. Chernetidea.
(CHERNETES, PSEUDOSCORPIONES.)
Tracheate Arachnids, with the abdomen united to the cephalothorax by
its whole breadth. Eyeless, or with two or four simple eyes placed laterally.
Abdomen segmented, with four stigmata. Chelicerae chelate, bearing the
openings of the spinning organs. Pedipalpi large, six-jointed, and chelate.
Sternum absent or rudimentary.
The Chernetidea or “False-scorpions” constitute the most compact and
natural order of the Arachnida. There are no extreme variations within the
group as at present known, while all its members differ so markedly from
those of other Arachnidan orders that their true affinities are by no means
easy to determine.
The superficial resemblance to Scorpions which has won these animals
their popular name is almost entirely due to the comparative size and shape
of their pedipalpi, but it is probable that they are structurally much more
closely allied to the Solifugae.
Chernetidea are not creatures which obtrude themselves on the general
notice, and it is highly probable that many readers have never seen a living
specimen. This is largely due to their minute size. Garypus littoralis, a
Corsican species, nearly a quarter of an inch in length of body, is a veritable
Page 477
giant of the tribe, while no British species boasts a length of more than one-
sixth of an inch.
Moreover, their habits are retiring. They are to be sought for under
stones, under the bark of trees, and among moss and débris. One species,
probably cosmopolitan, certainly lives habitually in houses, and is
occasionally noticed and recognised as the “book-scorpion,” and one or two
other species sometimes make themselves conspicuous by the remarkable
habit of seizing hold of the legs of flies and being carried about with them
in their flight. With these exceptions, the Chernetidea are not likely to be
seen unless specially sought for, or unless casually met with in the search
for small beetles or other creatures of similar habitat. Nevertheless they are
very widely distributed, and though more numerous in hot countries, are yet
to be found in quite cold regions.
Though comparatively little attention has been paid to them in this
country, twenty British species have been recorded, and the known
European species number about seventy.
As might be expected from their small size and retiring habits, little is
known of their mode of life. They are carnivorous, feeding apparently upon
any young insects which are too feeble to withstand their attacks. The writer
has on two or three occasions observed them preying upon Homopterous
larvae. As a rule they are sober-coloured, their livery consisting of various
shades of yellow and brown. Some species walk slowly, with their
relatively enormous pedipalps extended in front and gently waving, but all
can run swiftly backwards and sideways, and in some forms the motion is
almost exclusively retrograde and very rapid. A certain power of leaping is
said to be practised by some of the more active species. The Chernetidea
possess spinning organs, opening on the movable digit of the chelicera.
They do not, however, spin snares like the Spiders, nor do they anchor
themselves by lines, the sole use of the spinning apparatus being,
apparently, to form a silken retreat at the time of egg-laying or of
hibernation.
External Structure.—The Chernetid body consists of a cephalothorax,
and an abdomen composed of twelve segments. The segmentation of the
abdomen is emphasised by the presence of chitinous plates dorsally and
ventrally, but the last two dorsal plates and the last four ventral plates are
sixth of an inch.
Moreover, their habits are retiring. They are to be sought for under
stones, under the bark of trees, and among moss and débris. One species,
probably cosmopolitan, certainly lives habitually in houses, and is
occasionally noticed and recognised as the “book-scorpion,” and one or two
other species sometimes make themselves conspicuous by the remarkable
habit of seizing hold of the legs of flies and being carried about with them
in their flight. With these exceptions, the Chernetidea are not likely to be
seen unless specially sought for, or unless casually met with in the search
for small beetles or other creatures of similar habitat. Nevertheless they are
very widely distributed, and though more numerous in hot countries, are yet
to be found in quite cold regions.
Though comparatively little attention has been paid to them in this
country, twenty British species have been recorded, and the known
European species number about seventy.
As might be expected from their small size and retiring habits, little is
known of their mode of life. They are carnivorous, feeding apparently upon
any young insects which are too feeble to withstand their attacks. The writer
has on two or three occasions observed them preying upon Homopterous
larvae. As a rule they are sober-coloured, their livery consisting of various
shades of yellow and brown. Some species walk slowly, with their
relatively enormous pedipalps extended in front and gently waving, but all
can run swiftly backwards and sideways, and in some forms the motion is
almost exclusively retrograde and very rapid. A certain power of leaping is
said to be practised by some of the more active species. The Chernetidea
possess spinning organs, opening on the movable digit of the chelicera.
They do not, however, spin snares like the Spiders, nor do they anchor
themselves by lines, the sole use of the spinning apparatus being,
apparently, to form a silken retreat at the time of egg-laying or of
hibernation.
External Structure.—The Chernetid body consists of a cephalothorax,
and an abdomen composed of twelve segments. The segmentation of the
abdomen is emphasised by the presence of chitinous plates dorsally and
ventrally, but the last two dorsal plates and the last four ventral plates are
Page 478
fused, so that ordinarily only eleven segments can be counted above and
nine below.
The cephalothorax presents no trace of segmentation in the Obisiinae
(see p. 437), but in the other groups it is marked dorsally with one or two
transverse striae. The eyes, when present, are either two or four in number,
and are placed near the lateral borders of the carapace towards its anterior
end. They are whitish and only very slightly convex, and are never situated
on prominences. Except in Garypus there is no trace of a sternum, the coxae
of the legs and pedipalps forming the ventral floor of the cephalothorax.
In the Obisiinae a little triangular projection in front of the cephalothorax
is regarded by Simon[333] as an epistome. It is absent in the other sub-orders.
The abdomen is armed, dorsally and ventrally, with a series of chitinous
plates with membranous intervals. The dorsal plates are eleven in number
(except in Chiridium, which has only ten), and are frequently bisected by a
median dorsal membranous line. There are nine ventral plates. There is a
membranous interval down each side between the dorsal and ventral series
of plates.
The chitinous membrane between the plates is very extensible, rendering
measurements of the body in these animals of little value. In a female full of
eggs the dorsal plates may be separated by a considerable interval, while
after egg-laying they may actually overlap. The four stigmata are not
situated on the plates, but ventro-laterally, at the level of the hinder borders
of the first and second abdominal plates.
The first ventral abdominal plate bears the genital orifice. In the same
plate there are two other orifices, an anterior and a posterior, which belong
to the “abdominal glands.” They were taken by some authors for the
spinning organs, but their function is probably to supply material for the
capsule by which the eggs are suspended from the body of the mother (see
p. 434).
The Chernetidea possess chelicerae, pedipalpi, and four pairs of
ambulatory legs, all articulated to the cephalothorax.
The chelicerae are two-jointed, the upper portion of the first joint being
produced forward into a claw, curving downward. The second joint is
articulated beneath the first, and curves upward to a point, the appendage
being thus chelate. This second joint, or movable digit, bears, near its
extremity, the opening of the spinning organ, and is furnished, at all events
nine below.
The cephalothorax presents no trace of segmentation in the Obisiinae
(see p. 437), but in the other groups it is marked dorsally with one or two
transverse striae. The eyes, when present, are either two or four in number,
and are placed near the lateral borders of the carapace towards its anterior
end. They are whitish and only very slightly convex, and are never situated
on prominences. Except in Garypus there is no trace of a sternum, the coxae
of the legs and pedipalps forming the ventral floor of the cephalothorax.
In the Obisiinae a little triangular projection in front of the cephalothorax
is regarded by Simon[333] as an epistome. It is absent in the other sub-orders.
The abdomen is armed, dorsally and ventrally, with a series of chitinous
plates with membranous intervals. The dorsal plates are eleven in number
(except in Chiridium, which has only ten), and are frequently bisected by a
median dorsal membranous line. There are nine ventral plates. There is a
membranous interval down each side between the dorsal and ventral series
of plates.
The chitinous membrane between the plates is very extensible, rendering
measurements of the body in these animals of little value. In a female full of
eggs the dorsal plates may be separated by a considerable interval, while
after egg-laying they may actually overlap. The four stigmata are not
situated on the plates, but ventro-laterally, at the level of the hinder borders
of the first and second abdominal plates.
The first ventral abdominal plate bears the genital orifice. In the same
plate there are two other orifices, an anterior and a posterior, which belong
to the “abdominal glands.” They were taken by some authors for the
spinning organs, but their function is probably to supply material for the
capsule by which the eggs are suspended from the body of the mother (see
p. 434).
The Chernetidea possess chelicerae, pedipalpi, and four pairs of
ambulatory legs, all articulated to the cephalothorax.
The chelicerae are two-jointed, the upper portion of the first joint being
produced forward into a claw, curving downward. The second joint is
articulated beneath the first, and curves upward to a point, the appendage
being thus chelate. This second joint, or movable digit, bears, near its
extremity, the opening of the spinning organ, and is furnished, at all events
Page 479
in the Garypinae and Cheliferinae
(see p. 437), with a pectinate
projection, the “galea,” arising at its
base, and extending beyond the joint
in front. In the Obisiinae it is only
represented by a slight prominence.
Two other organs characterise the
chelicerae of all the Chernetidea;
these are the “serrula” and the
“flagellum.” Their minute size and
transparency make them very
difficult of observation, and for a
long time they escaped notice. The
serrula is a comb-like structure
attached to the inner side of the distal
joint. The flagellum is attached to the
outer side of the basal joint, and
recalls the antenna of a Lamellicorn
beetle, or the “pectines” of scorpions,
a resemblance which gave rise to the
supposition that they are olfactory Fig. 222.—A, Chernes sp., diagrammatic
ventral view, × about 12. a, Anus; ch, chelicera;
organs. It is more likely, however, g, generative opening; p, pedipalp; 1, 2, 3, 4,
that they are of use in manipulating legs. (The stigmata are at the postero-lateral
margins of the 1st and 2nd abdominal
the silk. segments.) B, Tarsus, with claws and sucking
The pedipalpi are six-jointed and disc.
are very large, giving these animals a
superficial resemblance to scorpions. According to Simon,[334] the patella is
absent, and the joints are coxa, trochanter, femur, tibia, tarsus, with an
apophysis forming the fixed digit of the chela, while the sixth joint is the
movable digit, and is articulated behind the tarsus. These joints, especially
the tarsus, are often much thickened, but however strongly developed, they
are always narrow and pediculate at the base. The coxae of the pedipalps
are closely approximated, and are enlarged and flattened. They probably
assist in mastication, but there is no true maxillary plate articulated to the
coxa as in some Arachnid groups.
(see p. 437), with a pectinate
projection, the “galea,” arising at its
base, and extending beyond the joint
in front. In the Obisiinae it is only
represented by a slight prominence.
Two other organs characterise the
chelicerae of all the Chernetidea;
these are the “serrula” and the
“flagellum.” Their minute size and
transparency make them very
difficult of observation, and for a
long time they escaped notice. The
serrula is a comb-like structure
attached to the inner side of the distal
joint. The flagellum is attached to the
outer side of the basal joint, and
recalls the antenna of a Lamellicorn
beetle, or the “pectines” of scorpions,
a resemblance which gave rise to the
supposition that they are olfactory Fig. 222.—A, Chernes sp., diagrammatic
ventral view, × about 12. a, Anus; ch, chelicera;
organs. It is more likely, however, g, generative opening; p, pedipalp; 1, 2, 3, 4,
that they are of use in manipulating legs. (The stigmata are at the postero-lateral
margins of the 1st and 2nd abdominal
the silk. segments.) B, Tarsus, with claws and sucking
The pedipalpi are six-jointed and disc.
are very large, giving these animals a
superficial resemblance to scorpions. According to Simon,[334] the patella is
absent, and the joints are coxa, trochanter, femur, tibia, tarsus, with an
apophysis forming the fixed digit of the chela, while the sixth joint is the
movable digit, and is articulated behind the tarsus. These joints, especially
the tarsus, are often much thickened, but however strongly developed, they
are always narrow and pediculate at the base. The coxae of the pedipalps
are closely approximated, and are enlarged and flattened. They probably
assist in mastication, but there is no true maxillary plate articulated to the
coxa as in some Arachnid groups.
Page 480
The legs are usually short and
feeble, and the number of their
articulations varies from five to eight,
so that it is not easy to be certain of
the homologies of the individual
joints to those of other Arachnids.
The coxae are large, and form the
floor of the cephalothorax. They are
succeeded by a short trochanter,
which may be followed by another
Fig. 223.—Chelicera of Garypus. f, Flagellum;
short joint, the “trochantin.” Then
g, galea; s, serrula. (After Simon.) come the femur and tibia, elongated
joints without any interposed patella,
and finally the tarsus of one or two
joints, terminated by two smooth curved claws, beneath which is situated a
trumpet-shaped membranous sucker.
Internal Structure.[335]—The internal structure of the Chernetidea, as far
as their small size has permitted it to be made out, bears a considerable
resemblance to that of the Phalangidea. The alimentary canal dilates into a
small sucking pharynx before passing through the nerve-mass into the large
many-lobed stomach, but the narrow intestine which terminates the canal is
convoluted or looped, and possesses a feebly-developed stercoral pocket.
Above the stomach are situated the spinning glands, the products of
which pass, by seven or more tubules, to the orifice already mentioned on
the distal joint of the chelicerae. The abdominal or cement-glands are in the
anterior ventral portion of the abdomen. No Malpighian tubes have been
found.
The tracheae from the anterior stigmata are directed forward; those from
the posterior stigmata backward. Bernard[336] has found rudimentary
stigmata on the remaining abdominal segments.
The heart is the usual dorsal tube, situated rather far forward, and
probably possessing only one pair of ostia. The nerve-cord is a double
series of ventral masses, united by transverse commissures. These undergo
great concentration in the last stages of development, but in the newly-
hatched Chernetid a cerebral mass and five pairs of post-oesophageal
ganglia can be distinguished.
feeble, and the number of their
articulations varies from five to eight,
so that it is not easy to be certain of
the homologies of the individual
joints to those of other Arachnids.
The coxae are large, and form the
floor of the cephalothorax. They are
succeeded by a short trochanter,
which may be followed by another
Fig. 223.—Chelicera of Garypus. f, Flagellum;
short joint, the “trochantin.” Then
g, galea; s, serrula. (After Simon.) come the femur and tibia, elongated
joints without any interposed patella,
and finally the tarsus of one or two
joints, terminated by two smooth curved claws, beneath which is situated a
trumpet-shaped membranous sucker.
Internal Structure.[335]—The internal structure of the Chernetidea, as far
as their small size has permitted it to be made out, bears a considerable
resemblance to that of the Phalangidea. The alimentary canal dilates into a
small sucking pharynx before passing through the nerve-mass into the large
many-lobed stomach, but the narrow intestine which terminates the canal is
convoluted or looped, and possesses a feebly-developed stercoral pocket.
Above the stomach are situated the spinning glands, the products of
which pass, by seven or more tubules, to the orifice already mentioned on
the distal joint of the chelicerae. The abdominal or cement-glands are in the
anterior ventral portion of the abdomen. No Malpighian tubes have been
found.
The tracheae from the anterior stigmata are directed forward; those from
the posterior stigmata backward. Bernard[336] has found rudimentary
stigmata on the remaining abdominal segments.
The heart is the usual dorsal tube, situated rather far forward, and
probably possessing only one pair of ostia. The nerve-cord is a double
series of ventral masses, united by transverse commissures. These undergo
great concentration in the last stages of development, but in the newly-
hatched Chernetid a cerebral mass and five pairs of post-oesophageal
ganglia can be distinguished.
Page 481
There are two peculiar eversible “ram’s-horn organs,” opening near the
genital opening. They are said to be present only in the male, and have been
taken for the male organs, though other writers consider them to be tracheal
in function.
Development.—Some points of peculiar interest are presented by the
embryology of these animals, the most striking facts being, first, that the
whole of the egg is, in some cases at all events, involved in the
segmentation; and, secondly, that there is a true metamorphosis, though the
larva is not free-living, but remains enclosed with others in a sac attached to
the mother.
At the beginning of winter the female immures herself in a silken retreat,
her body distended with eggs and accumulated nourishment. About
February the egg-laying commences, thirty eggs, perhaps, being extruded.
They are not, however, separated from the mother, but remain enclosed in a
sac attached to the genital aperture, and able, therefore, to receive the
nutritive fluids which she continues to supply throughout the whole period
of development.
The eggs, which line the periphery of the sac, develop into embryos
which presently become larvae, that is to say, instead of further
development at the expense of yolk-cells contained within themselves, they
develop a temporary stomach and a large sucking organ, and become for a
time independent sucking animals, imbibing the fluids in the common sac,
and arranged around its circumference with their mouths directed towards
the centre. Subsequently a second embryonic stage is entered upon, the
sucking organ being discarded, and the albuminous matter which the larva
has imbibed being treated anew like the original yolk of the egg.
It is an interesting fact that in this second embryonic stage a well-marked
“tail” or post-abdomen is formed, and the ganglionic nerve-masses increase
in number, a cerebral mass being followed by eight pairs of ganglia in the
body and eight in the tail. Subsequently a great concentration takes place
till, besides the cerebral mass, only five closely-applied pairs of ganglia
remain, corresponding to the pedipalpi and the four pairs of legs. Moreover,
the first pair advances, so as to lie on the sides of, and not behind, the
oesophagus.
genital opening. They are said to be present only in the male, and have been
taken for the male organs, though other writers consider them to be tracheal
in function.
Development.—Some points of peculiar interest are presented by the
embryology of these animals, the most striking facts being, first, that the
whole of the egg is, in some cases at all events, involved in the
segmentation; and, secondly, that there is a true metamorphosis, though the
larva is not free-living, but remains enclosed with others in a sac attached to
the mother.
At the beginning of winter the female immures herself in a silken retreat,
her body distended with eggs and accumulated nourishment. About
February the egg-laying commences, thirty eggs, perhaps, being extruded.
They are not, however, separated from the mother, but remain enclosed in a
sac attached to the genital aperture, and able, therefore, to receive the
nutritive fluids which she continues to supply throughout the whole period
of development.
The eggs, which line the periphery of the sac, develop into embryos
which presently become larvae, that is to say, instead of further
development at the expense of yolk-cells contained within themselves, they
develop a temporary stomach and a large sucking organ, and become for a
time independent sucking animals, imbibing the fluids in the common sac,
and arranged around its circumference with their mouths directed towards
the centre. Subsequently a second embryonic stage is entered upon, the
sucking organ being discarded, and the albuminous matter which the larva
has imbibed being treated anew like the original yolk of the egg.
It is an interesting fact that in this second embryonic stage a well-marked
“tail” or post-abdomen is formed, and the ganglionic nerve-masses increase
in number, a cerebral mass being followed by eight pairs of ganglia in the
body and eight in the tail. Subsequently a great concentration takes place
till, besides the cerebral mass, only five closely-applied pairs of ganglia
remain, corresponding to the pedipalpi and the four pairs of legs. Moreover,
the first pair advances, so as to lie on the sides of, and not behind, the
oesophagus.
Page 482
Fig. 224.—Three stages in the development of Chelifer. A, Segmenting ovum;
B, embryo, with post-abdomen, maximum number of ganglia, and developing
sucking apparatus; C, larva. (After Barrois.)
There are two ecdyses or moults during development, a partial moult,
concerning only the ventral surface of the “pro-embryo” as it assumes the
larval form, and a complete moult at the final stage, before emergence from
the incubating sac.
At the end of winter the mother cuts a hole in the silken web, and the
young brood issues forth.[337]
Classification.—The order Chernetidea consists of a single family,
Cheliferidae. Nine genera are recognised by most authors, but their
grouping has been the subject of a good deal of difference of opinion,
largely dependent on the different systemic value allowed by various
arachnologists to the absence or presence of eyes, and to their number when
present. Simon takes the extreme view that the eyes are only of specific
value, and he is thus led to suppress two ordinarily accepted genera,
Chernes and Roncus, which are separated chiefly by eye-characters from
Chelifer and Obisium respectively. He relies rather on such characters as the
presence or absence of galea, epistome, and trochantin, and establishes
three sub-families as follows:—
(i.) Cheliferinae.—Galea. No epistome. Trochantin on all legs. Eyes two
or none. Sole genus, Chelifer (Chelifer + Chernes).
(ii.) Garypinae.—Galea. No epistome. Trochantin on legs 3 and 4 only.
Eyes four or none. Genera Chiridium, Olpium, and Garypus.
B, embryo, with post-abdomen, maximum number of ganglia, and developing
sucking apparatus; C, larva. (After Barrois.)
There are two ecdyses or moults during development, a partial moult,
concerning only the ventral surface of the “pro-embryo” as it assumes the
larval form, and a complete moult at the final stage, before emergence from
the incubating sac.
At the end of winter the mother cuts a hole in the silken web, and the
young brood issues forth.[337]
Classification.—The order Chernetidea consists of a single family,
Cheliferidae. Nine genera are recognised by most authors, but their
grouping has been the subject of a good deal of difference of opinion,
largely dependent on the different systemic value allowed by various
arachnologists to the absence or presence of eyes, and to their number when
present. Simon takes the extreme view that the eyes are only of specific
value, and he is thus led to suppress two ordinarily accepted genera,
Chernes and Roncus, which are separated chiefly by eye-characters from
Chelifer and Obisium respectively. He relies rather on such characters as the
presence or absence of galea, epistome, and trochantin, and establishes
three sub-families as follows:—
(i.) Cheliferinae.—Galea. No epistome. Trochantin on all legs. Eyes two
or none. Sole genus, Chelifer (Chelifer + Chernes).
(ii.) Garypinae.—Galea. No epistome. Trochantin on legs 3 and 4 only.
Eyes four or none. Genera Chiridium, Olpium, and Garypus.
Page 483
(iii.) Obisiinae.—No galea. An epistome. No trochantin. Genera
Chthonius and Obisium (which includes Roncus).
Whatever be the value of the eyes in the classification of this group—and
Simon adduces strong arguments for his view—there can be no doubt of
their convenience in practical identification. Moreover, as Pickard-
Cambridge[338] points out, a grouping of the genera according to the eyes
results, as regards British species, in pretty much the same linear
arrangement as Simon’s classification, and it may therefore be convenient
to mention that, of the six genera represented in this country, Chthonius and
Obisium are four-eyed, Roncus and Chelifer two-eyed, while Chernes and
Chiridium are eyeless.
Sub-Fam. 1. Cheliferinae.—These Chernetidea have the cephalothorax
slightly narrowed in front, and generally marked dorsally with two
transverse striae, while the abdominal plates are bisected by a dorsal
longitudinal line. With the exception of Chelifer cancroides, which is
always found in houses, all the species are to be sought under bark, though
occasionally they are discovered under stones.
The two genera of this sub-family are Chelifer and Chernes, the species
of Chelifer being two-eyed, and those of Chernes blind.
As already stated, Simon does not consider the possession of the two—
often very feebly developed—eyes of generic importance, and admits only
the genus Chelifer.
Five species of Chelifer (including Ch. cancroides) and five of Chernes
have been recorded in England.
Sub-Fam. 2. Garypinae.—The Garypinae have the cephalothorax
greatly contracted in front and often projecting considerably.
There are three genera, Chiridium, Olpium, and Garypus. Chiridium is
eyeless, and appears to have only ten segments in the abdomen, the tergal
plates of which are bisected. C. museorum is found in England, and is the
only Chernetid except Chelifer cancroides which habitually lives in houses.
C. ferum is found under bark in the south of France.
Neither Olpium nor Garypus, which both possess four eyes and eleven
abdominal segments, have as yet been found in this country. Garypus, like
Chiridium, has the dorsal abdominal plates bisected. There is a transverse
Chthonius and Obisium (which includes Roncus).
Whatever be the value of the eyes in the classification of this group—and
Simon adduces strong arguments for his view—there can be no doubt of
their convenience in practical identification. Moreover, as Pickard-
Cambridge[338] points out, a grouping of the genera according to the eyes
results, as regards British species, in pretty much the same linear
arrangement as Simon’s classification, and it may therefore be convenient
to mention that, of the six genera represented in this country, Chthonius and
Obisium are four-eyed, Roncus and Chelifer two-eyed, while Chernes and
Chiridium are eyeless.
Sub-Fam. 1. Cheliferinae.—These Chernetidea have the cephalothorax
slightly narrowed in front, and generally marked dorsally with two
transverse striae, while the abdominal plates are bisected by a dorsal
longitudinal line. With the exception of Chelifer cancroides, which is
always found in houses, all the species are to be sought under bark, though
occasionally they are discovered under stones.
The two genera of this sub-family are Chelifer and Chernes, the species
of Chelifer being two-eyed, and those of Chernes blind.
As already stated, Simon does not consider the possession of the two—
often very feebly developed—eyes of generic importance, and admits only
the genus Chelifer.
Five species of Chelifer (including Ch. cancroides) and five of Chernes
have been recorded in England.
Sub-Fam. 2. Garypinae.—The Garypinae have the cephalothorax
greatly contracted in front and often projecting considerably.
There are three genera, Chiridium, Olpium, and Garypus. Chiridium is
eyeless, and appears to have only ten segments in the abdomen, the tergal
plates of which are bisected. C. museorum is found in England, and is the
only Chernetid except Chelifer cancroides which habitually lives in houses.
C. ferum is found under bark in the south of France.
Neither Olpium nor Garypus, which both possess four eyes and eleven
abdominal segments, have as yet been found in this country. Garypus, like
Chiridium, has the dorsal abdominal plates bisected. There is a transverse
Page 484
stria on the cephalothorax, and the
eyes are far from the anterior border.
In Olpium the dorsal plates are
undivided and the eyes more anterior.
Sub-Fam. 3. Obisiinae.—The
cephalothorax of the Obisiinae does
not narrow—and is, indeed,
sometimes broadest—anteriorly. The
chelicerae are notably large, and the
dorsal abdominal plates undivided.
They are the most active of the
Chernetidea, ordinarily running
backwards or sideways with their
pedipalpi closely folded up against
the body. Four genera usually
admitted fall within this group:—
Obisium, Roncus, Blothrus, and
Chthonius.
Fig. 225.—Chelifer cyrneus, enlarged. (After Obisium has four eyes, parallel-
Simon.) sided cephalothorax, and curved
chelae on the palps. Roncus is like
Obisium except in having only two eyes, and is therefore disallowed by
Simon, who also considers Blothrus to comprise merely eyeless species of
Obisium. In Chthonius the cephalothorax is broadest in front, and the digits
of the chelae are straight.
The Obisiinae are found in moss and débris, and under stones. Three
species of Obisium, two of Roncus, and four of Chthonius are recorded in
England.
The subjoined list of British species of Chernetidea is taken from the
monograph of the Rev. O. P. Cambridge, cited above:—
eyes are far from the anterior border.
In Olpium the dorsal plates are
undivided and the eyes more anterior.
Sub-Fam. 3. Obisiinae.—The
cephalothorax of the Obisiinae does
not narrow—and is, indeed,
sometimes broadest—anteriorly. The
chelicerae are notably large, and the
dorsal abdominal plates undivided.
They are the most active of the
Chernetidea, ordinarily running
backwards or sideways with their
pedipalpi closely folded up against
the body. Four genera usually
admitted fall within this group:—
Obisium, Roncus, Blothrus, and
Chthonius.
Fig. 225.—Chelifer cyrneus, enlarged. (After Obisium has four eyes, parallel-
Simon.) sided cephalothorax, and curved
chelae on the palps. Roncus is like
Obisium except in having only two eyes, and is therefore disallowed by
Simon, who also considers Blothrus to comprise merely eyeless species of
Obisium. In Chthonius the cephalothorax is broadest in front, and the digits
of the chelae are straight.
The Obisiinae are found in moss and débris, and under stones. Three
species of Obisium, two of Roncus, and four of Chthonius are recorded in
England.
The subjoined list of British species of Chernetidea is taken from the
monograph of the Rev. O. P. Cambridge, cited above:—
Page 485
Fig. 226.—Chiridium museorum, enlarged.
(After Simon.)
(After Simon.)
Page 486
Fig. 227.—Olpium pallipes, enlarged. (After
Simon.)
Group I.—Four eyes.
Chthonius orthodactylus, Leach.
„ rayi, L. Koch.
„ tetrachelatus, Preyssler.
„ tenuis, L. Koch.
Obisium muscorum, Leach.
„ sylvaticum, C. L. Koch.
„ maritimum, Leach.
Group II.—Two eyes.
Roncus cambridgii, L. Koch.
„ lubricus, L. Koch.
Chelifer hermannii, Leach.
„ cancroides, Linn.
„ meridianus, L. Koch.
Simon.)
Group I.—Four eyes.
Chthonius orthodactylus, Leach.
„ rayi, L. Koch.
„ tetrachelatus, Preyssler.
„ tenuis, L. Koch.
Obisium muscorum, Leach.
„ sylvaticum, C. L. Koch.
„ maritimum, Leach.
Group II.—Two eyes.
Roncus cambridgii, L. Koch.
„ lubricus, L. Koch.
Chelifer hermannii, Leach.
„ cancroides, Linn.
„ meridianus, L. Koch.
Page 487
„ subruber, Simon.
„ latreillii, Leach.
Group III.—No eyes.
Chernes nodosus, Schr.
„ insuetus, Camb.
„ cimicoides, Fabr.
„ dubius, Camb.
„ phaleratus, Simon.
Chiridium museorum, Leach.
„ latreillii, Leach.
Group III.—No eyes.
Chernes nodosus, Schr.
„ insuetus, Camb.
„ cimicoides, Fabr.
„ dubius, Camb.
„ phaleratus, Simon.
Chiridium museorum, Leach.
Page 488
CHAPTER XVII
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
PODOGONA—PHALANGIDEA = OPILIONES—HABITS—
STRUCTURE—CLASSIFICATION
Order VII. Podogona (Ricinulei).
Tracheate Arachnids with two-jointed chelate chelicerae and prehensile
pedipalpi. The tarsus of the third leg of the male bears a copulatory organ.
In 1838 Guérin-Méneville[339]
described an Arachnid from West
Africa which he named
Cryptostemma westermannii. At rare
intervals occasional specimens of
allied forms have been taken in the
same region until six species of
Cryptostemma have been established.
In South America, also, two unique
examples of very similar creatures
are the only known representatives of
the two species of the allied genus
Cryptocellus. All the examples
hitherto found are of fair size
(between ⅕ inch and ½ inch in
length), and bear some general,
Fig. 228.—Cryptocellus simonis, × 4. (After
Hansen and Sörensen.) though superficial, resemblance to
the Trogulidae, which has led to their
being placed among the Phalangidea
by almost all the Arachnologists who have noticed them. Their claim to this
systematic position, however, is extremely doubtful, and Hansen and
Sörensen, who have had the opportunity of studying the group much more
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
PODOGONA—PHALANGIDEA = OPILIONES—HABITS—
STRUCTURE—CLASSIFICATION
Order VII. Podogona (Ricinulei).
Tracheate Arachnids with two-jointed chelate chelicerae and prehensile
pedipalpi. The tarsus of the third leg of the male bears a copulatory organ.
In 1838 Guérin-Méneville[339]
described an Arachnid from West
Africa which he named
Cryptostemma westermannii. At rare
intervals occasional specimens of
allied forms have been taken in the
same region until six species of
Cryptostemma have been established.
In South America, also, two unique
examples of very similar creatures
are the only known representatives of
the two species of the allied genus
Cryptocellus. All the examples
hitherto found are of fair size
(between ⅕ inch and ½ inch in
length), and bear some general,
Fig. 228.—Cryptocellus simonis, × 4. (After
Hansen and Sörensen.) though superficial, resemblance to
the Trogulidae, which has led to their
being placed among the Phalangidea
by almost all the Arachnologists who have noticed them. Their claim to this
systematic position, however, is extremely doubtful, and Hansen and
Sörensen, who have had the opportunity of studying the group much more
Page 489
minutely than previous writers, are of the opinion that they ought to
constitute a separate order of Arachnids, more nearly allied to the Pedipalpi
than to the Phalangidea. In this place it is only possible to indicate some of
their peculiar characteristics. Their integuments are particularly hard and
coriaceous. The cephalothorax is united to the abdomen by a rather broad
pedicle, but there is also a remarkable coupling apparatus which makes the
constriction between cephalothorax and abdomen appear very slight. There
is a movable anterior projection of the cephalothorax, the “cucullus.” The
two-jointed chelicerae terminate in minute chelae, as also do the five-
jointed pedipalps. There are no spiracles on the abdomen, but two are
situated on the thorax above the coxae of the third pair of legs. Perhaps the
most remarkable fact is that, as in the Araneae, a modified limb is used by
the male for the fertilisation of the female; but in this case it is not the tarsus
of the pedipalp, but of the third leg of the male, which is specially
developed as an intromittent organ.
Ordinal rank is not universally accorded to the group, but whatever its
true position, the known forms fall under a single family
Cryptostemmatidae, including the two genera Cryptostemma and
Cryptocellus.
Order VIII. Phalangidea (Opiliones).
Tracheate Arachnids, with abdomen united to the cephalothorax by its
whole breadth. They are oviparous, and undergo no metamorphosis.
Abdomen always segmented. A pair of odoriferous glands opening on the
thorax. Two simple eyes; three-jointed chelate chelicerae; pedipalpi not
chelate. Spinning organs absent.
“Harvesters,” “Harvestmen,” or “Harvest-spiders,” as these animals are
popularly called, need never be confounded with true Spiders if the absence
of a constriction between the cephalothorax and abdomen be noted. They
are more difficult to distinguish from Mites, members of which group have
sometimes been described as Phalangids. The Phalangid is, however,
generally recognisable by its segmented abdomen, and as a further point of
distinction, it may be noted that, whereas the anal orifice is always
transverse or circular in Phalangids, it is uniformly longitudinal in the
Acarines.
constitute a separate order of Arachnids, more nearly allied to the Pedipalpi
than to the Phalangidea. In this place it is only possible to indicate some of
their peculiar characteristics. Their integuments are particularly hard and
coriaceous. The cephalothorax is united to the abdomen by a rather broad
pedicle, but there is also a remarkable coupling apparatus which makes the
constriction between cephalothorax and abdomen appear very slight. There
is a movable anterior projection of the cephalothorax, the “cucullus.” The
two-jointed chelicerae terminate in minute chelae, as also do the five-
jointed pedipalps. There are no spiracles on the abdomen, but two are
situated on the thorax above the coxae of the third pair of legs. Perhaps the
most remarkable fact is that, as in the Araneae, a modified limb is used by
the male for the fertilisation of the female; but in this case it is not the tarsus
of the pedipalp, but of the third leg of the male, which is specially
developed as an intromittent organ.
Ordinal rank is not universally accorded to the group, but whatever its
true position, the known forms fall under a single family
Cryptostemmatidae, including the two genera Cryptostemma and
Cryptocellus.
Order VIII. Phalangidea (Opiliones).
Tracheate Arachnids, with abdomen united to the cephalothorax by its
whole breadth. They are oviparous, and undergo no metamorphosis.
Abdomen always segmented. A pair of odoriferous glands opening on the
thorax. Two simple eyes; three-jointed chelate chelicerae; pedipalpi not
chelate. Spinning organs absent.
“Harvesters,” “Harvestmen,” or “Harvest-spiders,” as these animals are
popularly called, need never be confounded with true Spiders if the absence
of a constriction between the cephalothorax and abdomen be noted. They
are more difficult to distinguish from Mites, members of which group have
sometimes been described as Phalangids. The Phalangid is, however,
generally recognisable by its segmented abdomen, and as a further point of
distinction, it may be noted that, whereas the anal orifice is always
transverse or circular in Phalangids, it is uniformly longitudinal in the
Acarines.
Page 490
Members of this group vary
considerably in habit. The best
known forms are exceedingly active,
and trust to their speed in
endeavouring to escape from danger,
at the same time emitting an odorous
fluid from two apertures situated just
above the coxae of the first pair of
legs. These active Harvestmen are
only found in the mature state at
certain seasons of the year, and are
believed, therefore, to live only for a
single season. Slow-moving forms,
like the Nemastomatidae and the
Trogulidae, which live amidst grass
and herbage, have a much longer
duration of life. In danger they
remain perfectly still, and trust to
their earthy appearance to escape
observation.
They are stated to be extremely FPickard-Cambridge.)
ig. 229.—Oligolophus spinosus. (After
thirsty animals, and have been
observed drinking from the dewdrops
on herbage. It is probably on this account that they are sometimes seen
attacking juicy vegetable matter, for without doubt they are essentially
carnivorous. The larvae of insects, young spiders, mites, and myriapods are
their customary food. It is not requisite that the prey should be alive, but
they will not touch anything mouldy.
Notwithstanding their apparently weak mouth-parts, they do not merely
suck the juices of their victims, but masticate and swallow solid particles.
Cannibalism is frequently observed among them.
The males fight fiercely with one another at the breeding time. The
females, with their long extrusible ovipositors, place groups of twenty to
forty eggs in small holes in the ground or under stones or bark, unprotected
by any form of cocoon. The eggs hatch into fully-formed Phalangids, which
considerably in habit. The best
known forms are exceedingly active,
and trust to their speed in
endeavouring to escape from danger,
at the same time emitting an odorous
fluid from two apertures situated just
above the coxae of the first pair of
legs. These active Harvestmen are
only found in the mature state at
certain seasons of the year, and are
believed, therefore, to live only for a
single season. Slow-moving forms,
like the Nemastomatidae and the
Trogulidae, which live amidst grass
and herbage, have a much longer
duration of life. In danger they
remain perfectly still, and trust to
their earthy appearance to escape
observation.
They are stated to be extremely FPickard-Cambridge.)
ig. 229.—Oligolophus spinosus. (After
thirsty animals, and have been
observed drinking from the dewdrops
on herbage. It is probably on this account that they are sometimes seen
attacking juicy vegetable matter, for without doubt they are essentially
carnivorous. The larvae of insects, young spiders, mites, and myriapods are
their customary food. It is not requisite that the prey should be alive, but
they will not touch anything mouldy.
Notwithstanding their apparently weak mouth-parts, they do not merely
suck the juices of their victims, but masticate and swallow solid particles.
Cannibalism is frequently observed among them.
The males fight fiercely with one another at the breeding time. The
females, with their long extrusible ovipositors, place groups of twenty to
forty eggs in small holes in the ground or under stones or bark, unprotected
by any form of cocoon. The eggs hatch into fully-formed Phalangids, which
Page 491
are at first white, but attain their coloration after the first moult. They
subsequently moult from five to nine times.
The distribution of this group is world-wide, and some of the exotic
species are very remarkable in form. Only twenty-four species have as yet
been recorded in this country.
External Structure.—In the Phalangidea there is no constriction
between the cephalothorax and the abdomen, and in the Ischyropsalidae
alone is the distinction between them readily observable. This is due to the
partial or complete fusion of the first five segments of the abdomen with the
carapace or cephalothoracic shield in most species, these segments being
indicated, if at all, merely by faint striae or successive transverse rows of
spines or tubercles. In the forms possessing hard integuments
(Gonyleptidae, Nemastomatidae, Trogulidae) this fusion results in a dorsal
“scutum,” the component parts of which cannot easily be distinguished.
The cephalothorax is often surmounted by a turret—usually grooved
dorsally, and beset on its edges with a spiny armature—on the sides of
which are the two simple eyes. The position and shape of this turret and the
arrangement of its spines are of importance in the classification of the
group.
In the Trogulidae the base of the
turret gives rise to a remarkable,
forwardly-directed, bifurcate
structure, furnished with numerous
strong tubular bristles. This is called
the “hood,” and its hollowed-out
under surface forms a chamber, the
“camerostome,” in which lie the
basal joints of the pedipalpi.
In most European Phalangids the
under surface of the cephalothorax is
almost entirely concealed by the
forwardly-projecting portion of the
Fig. 230.—Hood of Metopoctea. (After Simon.) abdomen bearing the generative
opening, and by the gnathobases, not
only of the pedipalpi, but of the first
and sometimes of the second legs. As in Spiders, however, there is always
subsequently moult from five to nine times.
The distribution of this group is world-wide, and some of the exotic
species are very remarkable in form. Only twenty-four species have as yet
been recorded in this country.
External Structure.—In the Phalangidea there is no constriction
between the cephalothorax and the abdomen, and in the Ischyropsalidae
alone is the distinction between them readily observable. This is due to the
partial or complete fusion of the first five segments of the abdomen with the
carapace or cephalothoracic shield in most species, these segments being
indicated, if at all, merely by faint striae or successive transverse rows of
spines or tubercles. In the forms possessing hard integuments
(Gonyleptidae, Nemastomatidae, Trogulidae) this fusion results in a dorsal
“scutum,” the component parts of which cannot easily be distinguished.
The cephalothorax is often surmounted by a turret—usually grooved
dorsally, and beset on its edges with a spiny armature—on the sides of
which are the two simple eyes. The position and shape of this turret and the
arrangement of its spines are of importance in the classification of the
group.
In the Trogulidae the base of the
turret gives rise to a remarkable,
forwardly-directed, bifurcate
structure, furnished with numerous
strong tubular bristles. This is called
the “hood,” and its hollowed-out
under surface forms a chamber, the
“camerostome,” in which lie the
basal joints of the pedipalpi.
In most European Phalangids the
under surface of the cephalothorax is
almost entirely concealed by the
forwardly-projecting portion of the
Fig. 230.—Hood of Metopoctea. (After Simon.) abdomen bearing the generative
opening, and by the gnathobases, not
only of the pedipalpi, but of the first
and sometimes of the second legs. As in Spiders, however, there is always
Page 492
present a “sternum” and generally a “labium.” The sternum is long and
narrow in the Mecostethi, and Cyphophthalmi, but in the Plagiostethi,
which include most of the forms found in temperate regions, it is very short
and transverse, and is hidden by the abdominal prolongation before
mentioned.
The anterior wall of the mouth is
formed by a beak-like plate, the
“epistome,” the basal portion of
which is covered externally by a
second plate, for which Simon[340]
proposes the name “pre-epistome.”
In some Phalangids there are three
little chitinous plates, one median
and two lateral, on the clypeus,
between the anterior border of the
carapace and the insertion of the
chelicerae. They are best seen in
Nemastoma.
The abdomen always presents Fig. 231.—Mouth-parts of Phalangium. A, B,
evidences of segmentation, though C, Gnathobases of pedipalp and first and second
legs; ch, chelicera; ep, epistome; lab, labium; m,
there is a difference of opinion as to mouth; ped, pedipalp; pre.ep, pre-epistome; st,
the number of segments of which it is sternum, shown by the removal of the anterior
part of the genital process, which extends to the
composed. This is due to the already dotted line; 1, 2, 3, 4, legs.
mentioned partial or complete fusion
of the anterior segments with the
cephalothorax. From the admirable researches of Hansen and Sörensen[341] it
seems likely that the normal number of abdominal segments is ten.
Ventrally, the abdomen is produced forward into a “sternal process” which
is capped by a genital plate, hardly distinguishable in the Phalangidae, but
readily visible in the other families, which surrounds and masks the
unpaired genital orifice. Two stigmata or breathing pores are situated on the
sides of the first ventral plate, which these authors consider to be composed
of two fused sternites.
As in other Arachnids there are six pairs of appendages articulated to the
cephalothorax. They are the chelicerae, the pedipalpi, and the four pairs of
ambulatory legs.
narrow in the Mecostethi, and Cyphophthalmi, but in the Plagiostethi,
which include most of the forms found in temperate regions, it is very short
and transverse, and is hidden by the abdominal prolongation before
mentioned.
The anterior wall of the mouth is
formed by a beak-like plate, the
“epistome,” the basal portion of
which is covered externally by a
second plate, for which Simon[340]
proposes the name “pre-epistome.”
In some Phalangids there are three
little chitinous plates, one median
and two lateral, on the clypeus,
between the anterior border of the
carapace and the insertion of the
chelicerae. They are best seen in
Nemastoma.
The abdomen always presents Fig. 231.—Mouth-parts of Phalangium. A, B,
evidences of segmentation, though C, Gnathobases of pedipalp and first and second
legs; ch, chelicera; ep, epistome; lab, labium; m,
there is a difference of opinion as to mouth; ped, pedipalp; pre.ep, pre-epistome; st,
the number of segments of which it is sternum, shown by the removal of the anterior
part of the genital process, which extends to the
composed. This is due to the already dotted line; 1, 2, 3, 4, legs.
mentioned partial or complete fusion
of the anterior segments with the
cephalothorax. From the admirable researches of Hansen and Sörensen[341] it
seems likely that the normal number of abdominal segments is ten.
Ventrally, the abdomen is produced forward into a “sternal process” which
is capped by a genital plate, hardly distinguishable in the Phalangidae, but
readily visible in the other families, which surrounds and masks the
unpaired genital orifice. Two stigmata or breathing pores are situated on the
sides of the first ventral plate, which these authors consider to be composed
of two fused sternites.
As in other Arachnids there are six pairs of appendages articulated to the
cephalothorax. They are the chelicerae, the pedipalpi, and the four pairs of
ambulatory legs.
Page 493
The chelicerae are three-jointed and chelate, the second joint having its
inner portion produced into an apophysis to which the final joint is apposed.
In certain forms (Gonyleptidae, Ischyropsalis) the chelicerae are remarkably
long, and may considerably exceed the total length of the trunk.
The pedipalpi are six-jointed, possessing coxa, trochanter, femur, patella,
tibia, and tarsus. They are leg-like and are never chelate, but in some forms
terminate in a single movable claw. The coxal joints are provided with
maxillary plates.
The legs are normally seven-jointed, as in Spiders, the penultimate joint
being the metatarsus. The tarsus is always multi-articulate, the number of its
joints being variable. It bears terminally one or two simple claws. “False
articulations” (where the parts are not inserted one into the other, but are
only marked off by a membranous ring) are of frequent occurrence in the
legs of these creatures. The first legs, like the pedipalps, bear maxillary
plates, as do also the second in most Phalangids. The maxillae of the second
legs are, however, entirely absent in Nemastoma, and rudimentary in the
Gonyleptidae and the Ischyropsalidae. The coxae of the legs are all largely
developed, but are not capable of free motion, being soldered to, and
practically forming part of, the cephalothoracic floor. In some forms they
are only separated from one another by slight grooves. The extreme length
of the legs, and their hard and brittle nature, are characteristic features of
the Phalangids, though in some species (Trogulidae) they are comparatively
short. The first pair of legs are always the shortest, and the second the
longest.
The sexual organs of Phalangids are ordinarily concealed, and the sexes
can only be distinguished by certain very variable secondary characters, the
males being usually smaller of body and longer of leg than the females,
besides being more distinctly coloured and being armed with more
numerous and longer spines. Sometimes the male chelicerae are highly
characteristic.
Phalangids are usually destitute of spinning organs, but such have been
discovered, in a rudimentary state, in the Cyphophthalmi, which are said to
spin slight webs.
Internal Structure.—In Phalangium the mouth leads upwards into a
membranous pharynx, wider than that of Spiders, but narrowing into an
oesophagus which passes between the cerebral and thoracic ganglionic
inner portion produced into an apophysis to which the final joint is apposed.
In certain forms (Gonyleptidae, Ischyropsalis) the chelicerae are remarkably
long, and may considerably exceed the total length of the trunk.
The pedipalpi are six-jointed, possessing coxa, trochanter, femur, patella,
tibia, and tarsus. They are leg-like and are never chelate, but in some forms
terminate in a single movable claw. The coxal joints are provided with
maxillary plates.
The legs are normally seven-jointed, as in Spiders, the penultimate joint
being the metatarsus. The tarsus is always multi-articulate, the number of its
joints being variable. It bears terminally one or two simple claws. “False
articulations” (where the parts are not inserted one into the other, but are
only marked off by a membranous ring) are of frequent occurrence in the
legs of these creatures. The first legs, like the pedipalps, bear maxillary
plates, as do also the second in most Phalangids. The maxillae of the second
legs are, however, entirely absent in Nemastoma, and rudimentary in the
Gonyleptidae and the Ischyropsalidae. The coxae of the legs are all largely
developed, but are not capable of free motion, being soldered to, and
practically forming part of, the cephalothoracic floor. In some forms they
are only separated from one another by slight grooves. The extreme length
of the legs, and their hard and brittle nature, are characteristic features of
the Phalangids, though in some species (Trogulidae) they are comparatively
short. The first pair of legs are always the shortest, and the second the
longest.
The sexual organs of Phalangids are ordinarily concealed, and the sexes
can only be distinguished by certain very variable secondary characters, the
males being usually smaller of body and longer of leg than the females,
besides being more distinctly coloured and being armed with more
numerous and longer spines. Sometimes the male chelicerae are highly
characteristic.
Phalangids are usually destitute of spinning organs, but such have been
discovered, in a rudimentary state, in the Cyphophthalmi, which are said to
spin slight webs.
Internal Structure.—In Phalangium the mouth leads upwards into a
membranous pharynx, wider than that of Spiders, but narrowing into an
oesophagus which passes between the cerebral and thoracic ganglionic
Page 494
nerve-masses. It then turns backwards over the thoracic ganglion, being
slightly dilated at that point. Immediately afterwards it dilates into a flask-
like gastric sac which occupies almost the whole width of the abdomen, and
proceeds straight to the anus. Viewed from above, the shape of this sac is
entirely concealed by the large number of caeca (thirty) to which it gives
rise dorsally and laterally. The two largest of these caeca extend, parallel to
each other, over the whole of the abdominal portion of the gastric sac, and
are flanked by four lateral pairs of smaller caeca, while there is a cluster of
small caeca covering the anterior and narrower portion of the flask-like
stomach.
The large hepatic mass so conspicuous on opening dorsally the abdomen
of a Spider is here entirely absent, but its functions are believed to be
performed by certain wrinkled, tubular, longitudinally parallel bodies, about
seven in number, closely applied to the under surface of the flask.
The masticating portions of the maxillae of the pedipalpi and the first
pair of legs are hollow distensible sacs, often seen in a swollen condition in
specimens kept in spirits. They are furnished, on the inner surface, with a
horny ridge.
Owing to the fixity of the coxae of the legs, their maxillary plates are
incapable of much lateral motion, but are rubbed against each other
vertically.
Beyond the fact that the heart is a dorsal tube lying along the anterior
two-thirds of the alimentary canal, and divided by constrictions into three
well-marked and equal portions, little is known of the blood-system of these
animals. It is probably essentially like that of Spiders, but the presence of a
pericardial sac has not yet been established, nor has the course of the blood-
vessels been described in detail.
As in other Arachnids, the principal ganglionic nerve-masses closely
embrace the oesophagus. Immediately anterior to it, forming a conical mass
with its base on the oesophagus, is the cerebral ganglion, while just behind
it is the transverse portion of the large thoracic nerve-centre. In Phalangium
opilio, according to Tulk,[342] a median nerve is given off from the apex of
the cerebral mass (the paired nature of which is apparent) and bifurcates to
the two eyes. Two lateral nerves proceed to certain organs near the origin of
the second pair of legs, which were thought by the old writers to be lateral
slightly dilated at that point. Immediately afterwards it dilates into a flask-
like gastric sac which occupies almost the whole width of the abdomen, and
proceeds straight to the anus. Viewed from above, the shape of this sac is
entirely concealed by the large number of caeca (thirty) to which it gives
rise dorsally and laterally. The two largest of these caeca extend, parallel to
each other, over the whole of the abdominal portion of the gastric sac, and
are flanked by four lateral pairs of smaller caeca, while there is a cluster of
small caeca covering the anterior and narrower portion of the flask-like
stomach.
The large hepatic mass so conspicuous on opening dorsally the abdomen
of a Spider is here entirely absent, but its functions are believed to be
performed by certain wrinkled, tubular, longitudinally parallel bodies, about
seven in number, closely applied to the under surface of the flask.
The masticating portions of the maxillae of the pedipalpi and the first
pair of legs are hollow distensible sacs, often seen in a swollen condition in
specimens kept in spirits. They are furnished, on the inner surface, with a
horny ridge.
Owing to the fixity of the coxae of the legs, their maxillary plates are
incapable of much lateral motion, but are rubbed against each other
vertically.
Beyond the fact that the heart is a dorsal tube lying along the anterior
two-thirds of the alimentary canal, and divided by constrictions into three
well-marked and equal portions, little is known of the blood-system of these
animals. It is probably essentially like that of Spiders, but the presence of a
pericardial sac has not yet been established, nor has the course of the blood-
vessels been described in detail.
As in other Arachnids, the principal ganglionic nerve-masses closely
embrace the oesophagus. Immediately anterior to it, forming a conical mass
with its base on the oesophagus, is the cerebral ganglion, while just behind
it is the transverse portion of the large thoracic nerve-centre. In Phalangium
opilio, according to Tulk,[342] a median nerve is given off from the apex of
the cerebral mass (the paired nature of which is apparent) and bifurcates to
the two eyes. Two lateral nerves proceed to certain organs near the origin of
the second pair of legs, which were thought by the old writers to be lateral
Page 495
eyes, but which are now known to be glands for the manufacture of the
odorous fluid which these animals can exude.
The thoracic ganglion expands, on
either side of the oesophagus, into a
mass which extends nearly as far
forward as the apex of the cerebral
ganglion. These lateral masses give
off nerves to the appendages. From
the back of the transverse portion
proceed three nerves. The median
nerve passes above the generative
organs, and soon branches into two
nerves which presently swell out to
form ganglia of considerable size,
beyond which they soon join again
and give off an anastomosing
network of nerve-fibres. The lateral
nerves immediately branch. The
outer branch dilates into a ganglion
Fig. 232.—Nervous and respiratory systems of a which supplies the external part of
Phalangid. Nerves black, tracheae white. c.g,
Cerebral ganglion; g′, g″, g‴, ganglia supplying the generative organ. The inner
viscera; m.n, median abdominal nerve; oe, branch, which is longer, also forms a
passage for oesophagus; st, stigma; th.g,
thoracic ganglion; tr, main trunk of tracheae.
ganglion the nerves from which are
chiefly distributed to the under
surface of the alimentary canal.
The respiratory organs consist of two large tracheal tubes with numerous
branches, having their external openings or “stigmata” near the base of the
fourth pair of legs. The two main tubes are directed forwards, and are
mainly concerned with supplying the largely developed muscles of the legs.
The distribution of branches to the abdomen is comparatively feeble. The
particular arrangement of tubes in P. opilio, according to Tulk, may be seen
in the accompanying figure. There are a pair of coxal glands, of excretory
function, opening in the neighbourhood of the coxae of the third pair of
legs.
The Phalangidea are remarkable among Arachnids in the possession of
large protrusible external organs of generation. The ovipositor of the female
odorous fluid which these animals can exude.
The thoracic ganglion expands, on
either side of the oesophagus, into a
mass which extends nearly as far
forward as the apex of the cerebral
ganglion. These lateral masses give
off nerves to the appendages. From
the back of the transverse portion
proceed three nerves. The median
nerve passes above the generative
organs, and soon branches into two
nerves which presently swell out to
form ganglia of considerable size,
beyond which they soon join again
and give off an anastomosing
network of nerve-fibres. The lateral
nerves immediately branch. The
outer branch dilates into a ganglion
Fig. 232.—Nervous and respiratory systems of a which supplies the external part of
Phalangid. Nerves black, tracheae white. c.g,
Cerebral ganglion; g′, g″, g‴, ganglia supplying the generative organ. The inner
viscera; m.n, median abdominal nerve; oe, branch, which is longer, also forms a
passage for oesophagus; st, stigma; th.g,
thoracic ganglion; tr, main trunk of tracheae.
ganglion the nerves from which are
chiefly distributed to the under
surface of the alimentary canal.
The respiratory organs consist of two large tracheal tubes with numerous
branches, having their external openings or “stigmata” near the base of the
fourth pair of legs. The two main tubes are directed forwards, and are
mainly concerned with supplying the largely developed muscles of the legs.
The distribution of branches to the abdomen is comparatively feeble. The
particular arrangement of tubes in P. opilio, according to Tulk, may be seen
in the accompanying figure. There are a pair of coxal glands, of excretory
function, opening in the neighbourhood of the coxae of the third pair of
legs.
The Phalangidea are remarkable among Arachnids in the possession of
large protrusible external organs of generation. The ovipositor of the female
Page 496
may be as long as the whole body of the animal, and the intromittent organ
of the male is of almost equal length. The pedipalpi take no part in the
fertilisation of the female, which is accomplished directly.
The protrusible organs are concealed under the forwardly-projecting
anterior segment of the abdomen beneath, the genital orifice being thus in
many cases quite near the head region. The internal sexual organs are not
very complex. The ovary re-enters upon itself, forming a ring, and from the
point of re-entry a tube proceeds towards the centre of the ring, dilating to
form an ovisac. It then narrows, turns forward, dilates once more into a
second ovisac, from which the oviduct proceeds to the base of the
ovipositor. This is a flattened organ, grooved on its upper surface and bifid
at its extremity. The testis of the male is a single sac-like gland, from either
end of which proceeds a vas deferens, which, after several convolutions,
unite into a sperm-sac which opens at the base of the penis.
Partial hermaphroditism is a very frequent phenomenon among the
Phalangids, the testis often producing ova as well as spermatozoa.
Though the males fight fiercely at the breeding time, the animals for the
most part live peacefully together. Henking[343] found that the eggs of
Liobunum, which were about half a millimetre in diameter, were laid during
October and hatched out in the following April.
Classification.—The Order Phalangidea is divided into three Sub-orders:
1, Cyphophthalmi; 2, Mecostethi; 3, Plagiostethi.
Sub-Order 1. Cyphophthalmi
Phalangids with dorsal and ventral scutum, only the last abdominal
segment remaining free. Eyes two or absent. Maxillary lobe on coxae of
first pair of legs rudimentary. Sternum long and narrow. Anterior segment
of abdomen not projecting ventrally beyond the coxae of the fourth pair.
Odoriferous glands open on prominences.
In 1875 Stecker published a description of a remarkable creature which
he said he had found in Bohemia, and which he named Gibocellum
sudeticum. Among other points it possessed four eyes and four spinning
mammillae, and it differed so much from other Cyphophthalmi as to
necessitate the foundation of a family, Gibocellidae, for its reception. No
one else appears to have seen the animal, or any of Stecker’s preparations of
of the male is of almost equal length. The pedipalpi take no part in the
fertilisation of the female, which is accomplished directly.
The protrusible organs are concealed under the forwardly-projecting
anterior segment of the abdomen beneath, the genital orifice being thus in
many cases quite near the head region. The internal sexual organs are not
very complex. The ovary re-enters upon itself, forming a ring, and from the
point of re-entry a tube proceeds towards the centre of the ring, dilating to
form an ovisac. It then narrows, turns forward, dilates once more into a
second ovisac, from which the oviduct proceeds to the base of the
ovipositor. This is a flattened organ, grooved on its upper surface and bifid
at its extremity. The testis of the male is a single sac-like gland, from either
end of which proceeds a vas deferens, which, after several convolutions,
unite into a sperm-sac which opens at the base of the penis.
Partial hermaphroditism is a very frequent phenomenon among the
Phalangids, the testis often producing ova as well as spermatozoa.
Though the males fight fiercely at the breeding time, the animals for the
most part live peacefully together. Henking[343] found that the eggs of
Liobunum, which were about half a millimetre in diameter, were laid during
October and hatched out in the following April.
Classification.—The Order Phalangidea is divided into three Sub-orders:
1, Cyphophthalmi; 2, Mecostethi; 3, Plagiostethi.
Sub-Order 1. Cyphophthalmi
Phalangids with dorsal and ventral scutum, only the last abdominal
segment remaining free. Eyes two or absent. Maxillary lobe on coxae of
first pair of legs rudimentary. Sternum long and narrow. Anterior segment
of abdomen not projecting ventrally beyond the coxae of the fourth pair.
Odoriferous glands open on prominences.
In 1875 Stecker published a description of a remarkable creature which
he said he had found in Bohemia, and which he named Gibocellum
sudeticum. Among other points it possessed four eyes and four spinning
mammillae, and it differed so much from other Cyphophthalmi as to
necessitate the foundation of a family, Gibocellidae, for its reception. No
one else appears to have seen the animal, or any of Stecker’s preparations of
Page 497
it, and Hansen and Sörensen[344] adduce grave reasons for believing that it
never existed at all. If this species is to be disallowed, the Cyphophthalmi
all fall into a single family.
Fam. Sironidae.—These
somewhat Mite-like Phalangids are
rarely met with, partly, no doubt,
because of their retiring habits and
small size, the known forms ranging
from 6 mm. to less than 2 mm. in
length. Of the seven genera which
have been established, Stylocellus
numbers eight species from Borneo
and Sumatra, and Pettalus two
species from Ceylon. Ogovia,
Miopsalis, and Purcellia have one
species each, from South Africa,
Further India, and the Cape,
respectively. The only European
forms are the two species of Siro
(France and Austria), and Parasiro
corsicus. No species has yet been
Fig. 233.—Parasiro corsicus, enlarged. (After
found in England. Simon.)
Sub-Order 2. Mecostethi.[345]
(LANIATORES).
Sternum long and narrow. Dorsal scutum leaving at least the last three
segments free. Openings of odoriferous glands not on prominences. The
fourth pair of legs usually long and powerful. One terminal claw on each of
the first two pairs of legs; two on the last two pairs.
The Mecostethi are essentially tropical forms, though a few
representatives are found in the caves of Southern Europe. One family
(Phalangodidae) has its headquarters in the hot regions of the Old World,
while the other two (Cosmetidae, Gonyleptidae) are confined to Central and
South America.
never existed at all. If this species is to be disallowed, the Cyphophthalmi
all fall into a single family.
Fam. Sironidae.—These
somewhat Mite-like Phalangids are
rarely met with, partly, no doubt,
because of their retiring habits and
small size, the known forms ranging
from 6 mm. to less than 2 mm. in
length. Of the seven genera which
have been established, Stylocellus
numbers eight species from Borneo
and Sumatra, and Pettalus two
species from Ceylon. Ogovia,
Miopsalis, and Purcellia have one
species each, from South Africa,
Further India, and the Cape,
respectively. The only European
forms are the two species of Siro
(France and Austria), and Parasiro
corsicus. No species has yet been
Fig. 233.—Parasiro corsicus, enlarged. (After
found in England. Simon.)
Sub-Order 2. Mecostethi.[345]
(LANIATORES).
Sternum long and narrow. Dorsal scutum leaving at least the last three
segments free. Openings of odoriferous glands not on prominences. The
fourth pair of legs usually long and powerful. One terminal claw on each of
the first two pairs of legs; two on the last two pairs.
The Mecostethi are essentially tropical forms, though a few
representatives are found in the caves of Southern Europe. One family
(Phalangodidae) has its headquarters in the hot regions of the Old World,
while the other two (Cosmetidae, Gonyleptidae) are confined to Central and
South America.
Page 498
Fam. 1. Phalangodidae.—Body piriform or triangular, broadest behind.
Last ventral segment of abdomen much the largest. Very narrow sternum.
Eye-turret near anterior border of cephalothorax. Chelicerae narrow at
base. Pedipalpi long and strong. Maxillary plates on first pair of legs
rudimentary. No stigmata visible.
The only European forms of this family belong to the genus
Phalangodes. They all avoid the light, and are usually found in caves.
Simon[346] records six species found in France. A North American species, P.
armata, is entirely destitute of eyes.
The family has representatives in Australia and in tropical Africa and
Asia. Mermerus, Epidanus, Maracaudus, and Sitalces are some of the
exotic genera.
The other two families of this Sub-order—Fam. 2, Cosmetidae; Fam. 3,
Gonyleptidae—include a large number of species, some of considerable
size (up to an inch in length of body), found in Central and South America.
Last ventral segment of abdomen much the largest. Very narrow sternum.
Eye-turret near anterior border of cephalothorax. Chelicerae narrow at
base. Pedipalpi long and strong. Maxillary plates on first pair of legs
rudimentary. No stigmata visible.
The only European forms of this family belong to the genus
Phalangodes. They all avoid the light, and are usually found in caves.
Simon[346] records six species found in France. A North American species, P.
armata, is entirely destitute of eyes.
The family has representatives in Australia and in tropical Africa and
Asia. Mermerus, Epidanus, Maracaudus, and Sitalces are some of the
exotic genera.
The other two families of this Sub-order—Fam. 2, Cosmetidae; Fam. 3,
Gonyleptidae—include a large number of species, some of considerable
size (up to an inch in length of body), found in Central and South America.
Page 499
Fig. 234.—Phalangodes terricola, enlarged.
(After Simon.)
Sub-Order 3. Plagiostethi.[347]
(PALPATORES.)
First abdominal segment produced forward ventrally to the level of the
first pair of legs, bringing the mouth and the genital opening very near
together. Sternum consequently much reduced. Pedipalpi thin, with terminal
claw absent or rudimentary. Terminal claws of the legs single.
(After Simon.)
Sub-Order 3. Plagiostethi.[347]
(PALPATORES.)
First abdominal segment produced forward ventrally to the level of the
first pair of legs, bringing the mouth and the genital opening very near
together. Sternum consequently much reduced. Pedipalpi thin, with terminal
claw absent or rudimentary. Terminal claws of the legs single.
Page 500
The Plagiostethi include most of the Harvestmen of temperate regions,
the most familiar examples of these creatures belonging to the large family
Phalangidae, and being much more in evidence than the slow-moving and
ground-living forms included in the other families.
Fam. 1. Phalangiidae.—Eye-turret always far removed from anterior
border of cephalothorax. Second pair of legs with well-marked maxillary
lobes. Legs similar, without the false joint called “trochantin.”
Multiarticulate tarsi. Simple pedipalpi, with tarsus much longer than tibia,
and possessing terminal claw. Some have soft, some coriaceous
integuments.
The Phalangidae fall naturally into two groups or sub-families, named by
Simon Sclerosomatinae and Phalangiinae. The first group consists of more
or less coriaceous forms living among moss and herbage. They are not very
numerous, there being only about twelve known European species divided
among the three genera, Sclerosoma, Mastobunus, and Astrobunus.
Two species of Sclerosoma are
found in England, S. quadridentatum
occurring not uncommonly among
moss or under stones in various parts
of the country. Its back is studded
with wart-like tubercles, which give
it a characteristic appearance.
The Phalangiinae are soft-bodied
Harvestmen, always with long legs,
which in the genus Liobunum attain
an inordinate length. There are nine
European genera, Liobunum,
Prosalpia, Gyas, Oligolophus,
Acantholophus, Phalangium,
Fig. 235.—Sclerosoma quadridentatum. (After
Dasylobus, Platybunus, and Pickard-Cambridge.)
Megabunus, comprising in all about
fifty species. Five of these genera are
represented in England.
The familiar Phalangids, with small, almost spherical bodies and
ridiculously long legs, belong to the genus Liobunum, L. rotundum being
the common species. It is mature in autumn, when it may be seen
the most familiar examples of these creatures belonging to the large family
Phalangidae, and being much more in evidence than the slow-moving and
ground-living forms included in the other families.
Fam. 1. Phalangiidae.—Eye-turret always far removed from anterior
border of cephalothorax. Second pair of legs with well-marked maxillary
lobes. Legs similar, without the false joint called “trochantin.”
Multiarticulate tarsi. Simple pedipalpi, with tarsus much longer than tibia,
and possessing terminal claw. Some have soft, some coriaceous
integuments.
The Phalangidae fall naturally into two groups or sub-families, named by
Simon Sclerosomatinae and Phalangiinae. The first group consists of more
or less coriaceous forms living among moss and herbage. They are not very
numerous, there being only about twelve known European species divided
among the three genera, Sclerosoma, Mastobunus, and Astrobunus.
Two species of Sclerosoma are
found in England, S. quadridentatum
occurring not uncommonly among
moss or under stones in various parts
of the country. Its back is studded
with wart-like tubercles, which give
it a characteristic appearance.
The Phalangiinae are soft-bodied
Harvestmen, always with long legs,
which in the genus Liobunum attain
an inordinate length. There are nine
European genera, Liobunum,
Prosalpia, Gyas, Oligolophus,
Acantholophus, Phalangium,
Fig. 235.—Sclerosoma quadridentatum. (After
Dasylobus, Platybunus, and Pickard-Cambridge.)
Megabunus, comprising in all about
fifty species. Five of these genera are
represented in England.
The familiar Phalangids, with small, almost spherical bodies and
ridiculously long legs, belong to the genus Liobunum, L. rotundum being
the common species. It is mature in autumn, when it may be seen
Page 501
scampering at a great pace among the herbage. It very readily parts with its
limbs, and Pickard-Cambridge[348] relates that he once “saw one running
with very fair speed and facility, having lost all but two legs, an anterior one
on one side and a posterior one on the other.”
The Harvestmen so frequently seen on walls belong, as a rule, to the
genus Phalangium. The best known example is Phalangium opilio (the P.
cornutum of Linnaeus), the male of which possesses a remarkable
development of the chelicerae.
The genus Oligolophus is well represented in this country, nine species
having been recorded. They do not differ greatly from Phalangium, but
have, as a rule, more massive bodies, and rather stout, though tolerably long
legs. The largest English Harvestman, not rare under stones at Cambridge,
is O. spinosus, whose body measures half an inch in length. O. agrestis is
perhaps the commonest British Phalangid, and is abundant in woods and
among herbage, and on low trees.
Platybunus has two, and Megabunus one British representative. They are
of small size, and are to be sought for among heather or dead leaves in
spring or early summer.
Fam. 2. Ischyropsalidae.—Coriaceous Phalangids, with eye-turret far
removed from anterior border of cephalothorax. Maxillary lobes of second
pair of legs rudimentary, in the form of tubercles. Legs similar, without
“trochantin.” Multiarticulate tarsi. Tarsus of pedipalp without claw, and
shorter than metatarsus. Pedipalps long and horizontal.
This family includes a small number of large or moderate-sized
Phalangids, which are found occasionally in thick moss, or in caves, in
mountainous regions of the south of Europe, and belong to the genera
Ischyropsalis and Sabacon. There is a North American genus, Taracus.
Fam. 3. Nemastomatidae.—Coriaceous Phalangids, with cephalothorax
fused with the first five segments of the abdomen, forming a scutum. Eye-
turret near anterior border. No maxillary lobe on second coxae. Similar
legs, without “trochantin.” Multiarticulate tarsi. Tarsus of pedipalp without
claw, and shorter than metatarsus.
There is but one genus, Nemastoma, in this family, and the members of it
are, as a rule, rather small and dark Phalangids, which live under stones or
in moss or débris, and are found in the mature state at all seasons of the
year. There are about twenty European species, but only two of these, N.
limbs, and Pickard-Cambridge[348] relates that he once “saw one running
with very fair speed and facility, having lost all but two legs, an anterior one
on one side and a posterior one on the other.”
The Harvestmen so frequently seen on walls belong, as a rule, to the
genus Phalangium. The best known example is Phalangium opilio (the P.
cornutum of Linnaeus), the male of which possesses a remarkable
development of the chelicerae.
The genus Oligolophus is well represented in this country, nine species
having been recorded. They do not differ greatly from Phalangium, but
have, as a rule, more massive bodies, and rather stout, though tolerably long
legs. The largest English Harvestman, not rare under stones at Cambridge,
is O. spinosus, whose body measures half an inch in length. O. agrestis is
perhaps the commonest British Phalangid, and is abundant in woods and
among herbage, and on low trees.
Platybunus has two, and Megabunus one British representative. They are
of small size, and are to be sought for among heather or dead leaves in
spring or early summer.
Fam. 2. Ischyropsalidae.—Coriaceous Phalangids, with eye-turret far
removed from anterior border of cephalothorax. Maxillary lobes of second
pair of legs rudimentary, in the form of tubercles. Legs similar, without
“trochantin.” Multiarticulate tarsi. Tarsus of pedipalp without claw, and
shorter than metatarsus. Pedipalps long and horizontal.
This family includes a small number of large or moderate-sized
Phalangids, which are found occasionally in thick moss, or in caves, in
mountainous regions of the south of Europe, and belong to the genera
Ischyropsalis and Sabacon. There is a North American genus, Taracus.
Fam. 3. Nemastomatidae.—Coriaceous Phalangids, with cephalothorax
fused with the first five segments of the abdomen, forming a scutum. Eye-
turret near anterior border. No maxillary lobe on second coxae. Similar
legs, without “trochantin.” Multiarticulate tarsi. Tarsus of pedipalp without
claw, and shorter than metatarsus.
There is but one genus, Nemastoma, in this family, and the members of it
are, as a rule, rather small and dark Phalangids, which live under stones or
in moss or débris, and are found in the mature state at all seasons of the
year. There are about twenty European species, but only two of these, N.
Page 502
lugubre and N. chrysomelas, have as
yet been found in Britain. N. lugubre
is a very common animal, and though
it does not obtrude itself upon public
notice, its little black body with two
pearly white spots must be a familiar
object to all insect collectors who
have occasion to search under stones
or among moss in damp places. Its
legs are short and stout, but those of
N. chrysomelas, which is a brighter
coloured Harvestman with spots of
dull gold colour, are long and slender.
Fam. 4. Trogulidae.—Coriaceous
and very hard integument. Anterior
part of cephalothorax produced into
a bifurcate “hood.” Often a
“trochantin.”
The Trogulidae are very slow-
Fig. 236.—Oligolophus spinosus. (After moving Phalangids of moderate or
Pickard-Cambridge.) large size (a sixth to half an inch in
body), found under stones or in damp
moss and débris. They are Mite-like in general appearance, and may readily
be distinguished from all other Harvestmen by the presence of the “hood”
(Fig. 230, p. 442), the hollowed-out under surface of which forms a
chamber, called by Simon the “camerostome,” in which lie the basal
portions of the pedipalps.
Only a single immature specimen has been found in England, belonging
probably to the species Trogulus tricarinatus. It was found in Dorsetshire.
Some members of the family are not uncommon in various regions of the
Continent. There are four genera, Dicranolasma, Anelasmocephalus,
Calathocratus, and Trogulus. Two other genera, Amopaum and Metopoctea,
have been established, but the former is probably the young of
Dicranolasma and the latter of Trogulus.
According to the monograph on the British Phalangidea by the Rev. O.
Pickard-Cambridge, cited above, the following species have been recorded
yet been found in Britain. N. lugubre
is a very common animal, and though
it does not obtrude itself upon public
notice, its little black body with two
pearly white spots must be a familiar
object to all insect collectors who
have occasion to search under stones
or among moss in damp places. Its
legs are short and stout, but those of
N. chrysomelas, which is a brighter
coloured Harvestman with spots of
dull gold colour, are long and slender.
Fam. 4. Trogulidae.—Coriaceous
and very hard integument. Anterior
part of cephalothorax produced into
a bifurcate “hood.” Often a
“trochantin.”
The Trogulidae are very slow-
Fig. 236.—Oligolophus spinosus. (After moving Phalangids of moderate or
Pickard-Cambridge.) large size (a sixth to half an inch in
body), found under stones or in damp
moss and débris. They are Mite-like in general appearance, and may readily
be distinguished from all other Harvestmen by the presence of the “hood”
(Fig. 230, p. 442), the hollowed-out under surface of which forms a
chamber, called by Simon the “camerostome,” in which lie the basal
portions of the pedipalps.
Only a single immature specimen has been found in England, belonging
probably to the species Trogulus tricarinatus. It was found in Dorsetshire.
Some members of the family are not uncommon in various regions of the
Continent. There are four genera, Dicranolasma, Anelasmocephalus,
Calathocratus, and Trogulus. Two other genera, Amopaum and Metopoctea,
have been established, but the former is probably the young of
Dicranolasma and the latter of Trogulus.
According to the monograph on the British Phalangidea by the Rev. O.
Pickard-Cambridge, cited above, the following species have been recorded
Page 503
in this country. They all fall under the
sub-order Plagiostethi:—
Fig. 237.—Nemastoma lugubre.
sub-order Plagiostethi:—
Fig. 237.—Nemastoma lugubre.
Page 504
BRITISH PHALANGIDEA.
Phalangiidae.
Sclerosoma quadridentatum, Cuvier.
„ romanum, L. Koch.
Liobunum rotundum, Latr.
„ blackwallii, Meade.
Phalangium opilio, Linn.
„ parietinum, De Geer.
„ saxatile, C. L. Koch.
„ minutum, Meade.
Platybunus corniger, Meade.
„ triangularis, Herbst.
Megabunus insignis, Meade.
Oligolophus morio, Fabr.
„ alpinus, Herbst.
„ cinerascens, C. L. Koch.
„ agrestis, Meade.
„ tridens, C. L. Koch.
„ palpinalis, Herbst.
„ ephippiatus, C. L. Koch.
„ spinosus, Bosc.
Nemastomatidae.
Nemastoma lugubre, Müller.
„ chrysomelas, Hermann.
Trogulidae.
Anelasmocephalus cambridgii, Westwood.
Trogulus tricarinatus, Linn.
Phalangiidae.
Sclerosoma quadridentatum, Cuvier.
„ romanum, L. Koch.
Liobunum rotundum, Latr.
„ blackwallii, Meade.
Phalangium opilio, Linn.
„ parietinum, De Geer.
„ saxatile, C. L. Koch.
„ minutum, Meade.
Platybunus corniger, Meade.
„ triangularis, Herbst.
Megabunus insignis, Meade.
Oligolophus morio, Fabr.
„ alpinus, Herbst.
„ cinerascens, C. L. Koch.
„ agrestis, Meade.
„ tridens, C. L. Koch.
„ palpinalis, Herbst.
„ ephippiatus, C. L. Koch.
„ spinosus, Bosc.
Nemastomatidae.
Nemastoma lugubre, Müller.
„ chrysomelas, Hermann.
Trogulidae.
Anelasmocephalus cambridgii, Westwood.
Trogulus tricarinatus, Linn.
Page 505
CHAPTER XVIII
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ACARINA—HARVEST-BUGS—PARASITIC MITES—
TICKS—SPINNING MITES—STRUCTURE—
METAMORPHOSIS—CLASSIFICATION
Order IX. Acarina (Acari, Acaridea).
Arachnids with unsegmented,[349] non-pediculated abdomen. Respiration
by tracheae, or by the general surface of the body. Month parts suctorial,
but frequently capable of biting or piercing. Metamorphosis always
observable.
The Acarina or Mites are remarkable not so much for the number of their
species, which is very considerable, as for the vast multitude of individuals
of the Order, which is far in excess of that of any other Arachnid group.
This fact is correlated with their minute size. Very few Mites exceed half an
inch in length, while very many are microscopic creatures, often measuring
less than the hundredth of an inch. Taken all round, a millimetre may be
considered a large size for a Mite.
There is much variety of habit within the Order. All Mites live principally
on fluid nutriment, but it may be obtained from living animals or plants or
from decaying organic matter. Some are entirely parasitic upon plants or
animals; others attach themselves to animals in their larval stage, but are
free when adults; while others, again, live an entirely independent and
predaceous life.
The greater number of the Mites are too small to strike the eye. Some of
them have, however, contrived to attract attention, in no very agreeable
manner. Every one knows the Mite popularly called the “Harvest-bug,” but
to this day there is some uncertainty as to its identity. It was described as a
separate species under the name of Leptus autumnalis, and Mégnin was the
first to show that it was the larval form of one of the Trombidiidae (see p.
ARACHNIDA EMBOLOBRANCHIATA (CONTINUED)—
ACARINA—HARVEST-BUGS—PARASITIC MITES—
TICKS—SPINNING MITES—STRUCTURE—
METAMORPHOSIS—CLASSIFICATION
Order IX. Acarina (Acari, Acaridea).
Arachnids with unsegmented,[349] non-pediculated abdomen. Respiration
by tracheae, or by the general surface of the body. Month parts suctorial,
but frequently capable of biting or piercing. Metamorphosis always
observable.
The Acarina or Mites are remarkable not so much for the number of their
species, which is very considerable, as for the vast multitude of individuals
of the Order, which is far in excess of that of any other Arachnid group.
This fact is correlated with their minute size. Very few Mites exceed half an
inch in length, while very many are microscopic creatures, often measuring
less than the hundredth of an inch. Taken all round, a millimetre may be
considered a large size for a Mite.
There is much variety of habit within the Order. All Mites live principally
on fluid nutriment, but it may be obtained from living animals or plants or
from decaying organic matter. Some are entirely parasitic upon plants or
animals; others attach themselves to animals in their larval stage, but are
free when adults; while others, again, live an entirely independent and
predaceous life.
The greater number of the Mites are too small to strike the eye. Some of
them have, however, contrived to attract attention, in no very agreeable
manner. Every one knows the Mite popularly called the “Harvest-bug,” but
to this day there is some uncertainty as to its identity. It was described as a
separate species under the name of Leptus autumnalis, and Mégnin was the
first to show that it was the larval form of one of the Trombidiidae (see p.
Page 506
472). Most authors have considered it the larva of Trombidium
holosericeum, but Murray referred it to the genus Tetranychus. The
difficulty is that the minute creature cannot be removed from its victim
without such injury as to prevent it from being bred out and the mature
form determined. Brucker[350] has recently compared a large number of
“Harvest-bugs” taken from human beings with the figures and descriptions
of the larvae of certain Trombidiidae given by Henking and Berlese, and he
determined them as the larvae of T. gynopterorum. Quite possibly, however,
more than one genus is concerned in the production of this pest.
That certain skin-diseases are due to Mites (Demodicidae, Sarcoptidae) is
a fact which is widely known. The fruit-grower, too, has to take cognisance
of the Order, for his trees may suffer from “Red-spider” (Tetranychus
telarius), and his black-currant bushes fail under the attack of the “Gall-
mite” (Eriophyes or Phytoptus ribis). The curious swellings or galls which
disfigure the leaves of many trees are sometimes of insect origin, but they
are often due to Mites.
Domestic pets suffer greatly from Acarine parasites. A large number of
species confine their attention exclusively to the feathers of birds (Analges,
etc., see p. 466). One curious genus, Syringophilus, is parasitic within the
feathers, feeding upon the pith of the quill. Heller of Kiel discovered them
in 1879, but the researches of Trouessart first showed their frequent
presence and very wide distribution. He found that they entered by the
superior umbilicus of the feather, and disappeared by the inferior umbilicus
when the feathers moulted or the infested bird died.
It is probable that the comparatively large Mites of the group Ixodoidea
(see p. 468), commonly called “Ticks,” are the most widely known of the
order. They attack wild and domestic animals and man, and are nearly
always acquired from vegetables, such as brush or herbage. It would seem
likely that many of these creatures can never have the chance of attaching
themselves to animals, and it has been suggested that animal juices are a
luxury but not a necessity to them, and that they can live, if need be, on
vegetable sap, but further investigations have quite dispelled this view.
The suspected connection between the North American Tick, Boophilus
annulatus, and the cattle disease known as Texas fever or “red water,” since
clearly proved by the researches of Smith and Kilborne, led to the careful
holosericeum, but Murray referred it to the genus Tetranychus. The
difficulty is that the minute creature cannot be removed from its victim
without such injury as to prevent it from being bred out and the mature
form determined. Brucker[350] has recently compared a large number of
“Harvest-bugs” taken from human beings with the figures and descriptions
of the larvae of certain Trombidiidae given by Henking and Berlese, and he
determined them as the larvae of T. gynopterorum. Quite possibly, however,
more than one genus is concerned in the production of this pest.
That certain skin-diseases are due to Mites (Demodicidae, Sarcoptidae) is
a fact which is widely known. The fruit-grower, too, has to take cognisance
of the Order, for his trees may suffer from “Red-spider” (Tetranychus
telarius), and his black-currant bushes fail under the attack of the “Gall-
mite” (Eriophyes or Phytoptus ribis). The curious swellings or galls which
disfigure the leaves of many trees are sometimes of insect origin, but they
are often due to Mites.
Domestic pets suffer greatly from Acarine parasites. A large number of
species confine their attention exclusively to the feathers of birds (Analges,
etc., see p. 466). One curious genus, Syringophilus, is parasitic within the
feathers, feeding upon the pith of the quill. Heller of Kiel discovered them
in 1879, but the researches of Trouessart first showed their frequent
presence and very wide distribution. He found that they entered by the
superior umbilicus of the feather, and disappeared by the inferior umbilicus
when the feathers moulted or the infested bird died.
It is probable that the comparatively large Mites of the group Ixodoidea
(see p. 468), commonly called “Ticks,” are the most widely known of the
order. They attack wild and domestic animals and man, and are nearly
always acquired from vegetables, such as brush or herbage. It would seem
likely that many of these creatures can never have the chance of attaching
themselves to animals, and it has been suggested that animal juices are a
luxury but not a necessity to them, and that they can live, if need be, on
vegetable sap, but further investigations have quite dispelled this view.
The suspected connection between the North American Tick, Boophilus
annulatus, and the cattle disease known as Texas fever or “red water,” since
clearly proved by the researches of Smith and Kilborne, led to the careful
Page 507
investigation of the life-history of that creature, and this was undertaken by
Curtice.[351]
The female Ticks laid eggs a few days after dropping off the cattle, egg-
laying lasting a week or more. The eggs took from three to five weeks to
hatch, and the larvae attached themselves to cattle, on which they remained
a fortnight, becoming mature and fertilised before they again sought the
ground. The whole cycle occupied a time varying from six to ten weeks, a
period apparently much exceeded by some members of the family.
Lounsbury[352] has recently made out the life-history of the South African
“Bont” tick, Amblyomma hebraeum.
The eggs are deposited in the soil, ten to twenty thousand eggs in all
being laid by one female. The larvae climb neighbouring plants and seize
passing animals. After the third day of attachment they begin to distend, and
they generally fall off, fully distended, on the sixth day, immediately
seeking a place of concealment, where they become torpid. Under natural
conditions the nymph does not emerge for at least eleven weeks, and then it
behaves in the same way as the larva, again attaching itself to an animal for
six days. A new time of torpidity and concealment ensues, again of at least
eleven weeks’ duration, when the final moult takes place and the mature
tick emerges. The males at once attach themselves to animals, but the
females hesitate to fix themselves, except close by a male. For four days
after fixation the male appears to exercise no attraction for the female, but
after that period he shows great excitement at her approach. She, however,
does all the courting, the male remaining fixed in the skin of the host. After
pairing, the female distends greatly, attaining her maximum size (nearly one
inch in length) in about a week, when she lets go and descends to the earth
to lay eggs. If unmated, she detaches herself within a week, and seeks
another host. Oviposition lasts from three to nine weeks, and the
development of the egg from eleven weeks to six months. At least a year is
occupied in the whole cycle. These ticks, and many others, communicate
disease[353] by inoculation, conveying it from one animal to another.
No poison-glands have been demonstrated in the Acari, the function of
the salivary glands of the Ticks being probably to prevent the coagulation of
the blood of their victims.
It is an important point in the mode of life of the Ticks that they can live
for a long time without food. Mégnin[354] states that he kept an Argas alive
Curtice.[351]
The female Ticks laid eggs a few days after dropping off the cattle, egg-
laying lasting a week or more. The eggs took from three to five weeks to
hatch, and the larvae attached themselves to cattle, on which they remained
a fortnight, becoming mature and fertilised before they again sought the
ground. The whole cycle occupied a time varying from six to ten weeks, a
period apparently much exceeded by some members of the family.
Lounsbury[352] has recently made out the life-history of the South African
“Bont” tick, Amblyomma hebraeum.
The eggs are deposited in the soil, ten to twenty thousand eggs in all
being laid by one female. The larvae climb neighbouring plants and seize
passing animals. After the third day of attachment they begin to distend, and
they generally fall off, fully distended, on the sixth day, immediately
seeking a place of concealment, where they become torpid. Under natural
conditions the nymph does not emerge for at least eleven weeks, and then it
behaves in the same way as the larva, again attaching itself to an animal for
six days. A new time of torpidity and concealment ensues, again of at least
eleven weeks’ duration, when the final moult takes place and the mature
tick emerges. The males at once attach themselves to animals, but the
females hesitate to fix themselves, except close by a male. For four days
after fixation the male appears to exercise no attraction for the female, but
after that period he shows great excitement at her approach. She, however,
does all the courting, the male remaining fixed in the skin of the host. After
pairing, the female distends greatly, attaining her maximum size (nearly one
inch in length) in about a week, when she lets go and descends to the earth
to lay eggs. If unmated, she detaches herself within a week, and seeks
another host. Oviposition lasts from three to nine weeks, and the
development of the egg from eleven weeks to six months. At least a year is
occupied in the whole cycle. These ticks, and many others, communicate
disease[353] by inoculation, conveying it from one animal to another.
No poison-glands have been demonstrated in the Acari, the function of
the salivary glands of the Ticks being probably to prevent the coagulation of
the blood of their victims.
It is an important point in the mode of life of the Ticks that they can live
for a long time without food. Mégnin[354] states that he kept an Argas alive
Page 508
for four years, entirely without nutriment.
In the Tetranychinae (see p. 472), glands apparently homologous with the
salivary glands of the Ticks have taken on the function of spinning organs.
According to Donnadieu,[355] these glands, which resemble bunches of
grapes, and are possessed by both sexes, open into the buccal cavity at the
base of the chelicerae. The gummy fluid exudes from the mouth, and is
combed into threads by the pedipalps. The legs of these mites are furnished
terminally with curious hairs ending in a round knob, which are supposed to
have some relation to their spinning habits.
The males are the busiest spinners, the time of the females being largely
occupied in laying eggs among the excessively fine threads of silk with
which the Mites cover the under surface of leaves. In the Eriophyidae (see
p. 464) corresponding glands are thought to furnish an irritant fluid which
causes abnormal growths or galls upon vegetable tissues.
External Structure.—It is often stated, but erroneously, that there is no
distinction between cephalothorax and abdomen in the Mites. Certainly no
such division can be made out in the Hydrachnidae (see p. 472) or in some
other forms, but in the majority of Acari the cephalothorax is clearly
marked off by a transverse groove or suture. In some cases the anterior
portion of the cephalothorax is movably articulated with the rest, and forms
a sort of false head called a “capitulum.” In most Mites the chitinous
integument is soft and non-resistant, but it is otherwise with the Oribatidae
or “Beetle-mites” (see p. 467), which are nearly all covered by an extremely
hard and coriaceous armature.
Eyes are sometimes absent, sometimes present in varying numbers. They
seem here to be of remarkably little systematic importance, as otherwise
closely allied species may be either eyed or eyeless.
Normally Mites possess the usual Arachnid appendages, chelicerae,
pedipalpi, and four pairs of ambulatory legs. The anterior appendages are,
however, subject to a very great degree of modification, while in one
Family, the Eriophyidae (Phytoptidae), the legs are apparently reduced to
two pairs.
The chelicerae are sometimes chelate, in which case they are two-jointed,
the distal joint or movable finger being always articulated below the
immovable finger. Sometimes they terminate in a single claw or blade, the
In the Tetranychinae (see p. 472), glands apparently homologous with the
salivary glands of the Ticks have taken on the function of spinning organs.
According to Donnadieu,[355] these glands, which resemble bunches of
grapes, and are possessed by both sexes, open into the buccal cavity at the
base of the chelicerae. The gummy fluid exudes from the mouth, and is
combed into threads by the pedipalps. The legs of these mites are furnished
terminally with curious hairs ending in a round knob, which are supposed to
have some relation to their spinning habits.
The males are the busiest spinners, the time of the females being largely
occupied in laying eggs among the excessively fine threads of silk with
which the Mites cover the under surface of leaves. In the Eriophyidae (see
p. 464) corresponding glands are thought to furnish an irritant fluid which
causes abnormal growths or galls upon vegetable tissues.
External Structure.—It is often stated, but erroneously, that there is no
distinction between cephalothorax and abdomen in the Mites. Certainly no
such division can be made out in the Hydrachnidae (see p. 472) or in some
other forms, but in the majority of Acari the cephalothorax is clearly
marked off by a transverse groove or suture. In some cases the anterior
portion of the cephalothorax is movably articulated with the rest, and forms
a sort of false head called a “capitulum.” In most Mites the chitinous
integument is soft and non-resistant, but it is otherwise with the Oribatidae
or “Beetle-mites” (see p. 467), which are nearly all covered by an extremely
hard and coriaceous armature.
Eyes are sometimes absent, sometimes present in varying numbers. They
seem here to be of remarkably little systematic importance, as otherwise
closely allied species may be either eyed or eyeless.
Normally Mites possess the usual Arachnid appendages, chelicerae,
pedipalpi, and four pairs of ambulatory legs. The anterior appendages are,
however, subject to a very great degree of modification, while in one
Family, the Eriophyidae (Phytoptidae), the legs are apparently reduced to
two pairs.
The chelicerae are sometimes chelate, in which case they are two-jointed,
the distal joint or movable finger being always articulated below the
immovable finger. Sometimes they terminate in a single claw or blade, the
Page 509
movable joint being obsolete. In the Ticks they exist as two long styles or
piercing weapons, serrate on the outer edge.
The pedipalpi vary very much in structure, according to the habits of the
particular form to which they belong. In the Sarcoptidae (see p. 466) they
are hardly recognisable owing to the extent to which they have coalesced
with the maxillary plate. In many of the free-living forms they are leg-like
feeling organs, but in others they are raptorial, being not precisely chelate,
but terminating in a “finger-and-thumb” arrangement which is of use in
holding prey. The extreme development of the raptorial palp is found in
Cheyletus (see p. 473), in which the whole appendage is remarkably thick
and strong, and the “finger” is a powerful chitinous claw, while the “thumb”
is replaced by movable pectinated spines of chitin. The Water-mites have a
palpus adapted for anchoring themselves to water-weeds, the last joint
being articulated terminally with the penultimate joint, and bending down
upon it. Finally, in the “Snouted mites” (Bdellidae, see p. 471) the palpi are
tactile or antenniform, often strongly recalling the antennae of weevils.
The maxillary plates which arise from the basal joints of the pedipalps
are always more or less fused, in the Mites, to form a single median
transverse plate, constituting the lower lip or “labium” of some authors. In
some of the Oribatidae the fusion of the maxillae is only complete at the
base, and the free points are still of some use as masticating organs. In those
free living Mites which have undergone no great modification of the mouth-
parts two other portions can be distinguished, the upper lip or “epipharynx,”
and the “lingua,” which forms the floor of the mouth, and is for the most
part concealed by the maxillary plate.
The legs are usually six- or seven-jointed, and are subject to great
variation, especially as regards the tarsus or terminal joint. This may bear
claws (1–3) or sucking disks, or a combination of the two, or may simply
take the form of a long bristle or hair.
The Cheese-mite has a claw surrounded by a sucker—like Captain
Cuttle’s hook within his sleeve. The claws of those species which are
parasitic on the hairs of animals are sometimes most remarkably modified.
Internal Structure.—The minute size of most Mites has rendered
research upon their internal structure a matter of great difficulty, and there
are still many obscurities to be removed. Those forms which have been
subjected to examination present a tolerable uniformity in the structure of
piercing weapons, serrate on the outer edge.
The pedipalpi vary very much in structure, according to the habits of the
particular form to which they belong. In the Sarcoptidae (see p. 466) they
are hardly recognisable owing to the extent to which they have coalesced
with the maxillary plate. In many of the free-living forms they are leg-like
feeling organs, but in others they are raptorial, being not precisely chelate,
but terminating in a “finger-and-thumb” arrangement which is of use in
holding prey. The extreme development of the raptorial palp is found in
Cheyletus (see p. 473), in which the whole appendage is remarkably thick
and strong, and the “finger” is a powerful chitinous claw, while the “thumb”
is replaced by movable pectinated spines of chitin. The Water-mites have a
palpus adapted for anchoring themselves to water-weeds, the last joint
being articulated terminally with the penultimate joint, and bending down
upon it. Finally, in the “Snouted mites” (Bdellidae, see p. 471) the palpi are
tactile or antenniform, often strongly recalling the antennae of weevils.
The maxillary plates which arise from the basal joints of the pedipalps
are always more or less fused, in the Mites, to form a single median
transverse plate, constituting the lower lip or “labium” of some authors. In
some of the Oribatidae the fusion of the maxillae is only complete at the
base, and the free points are still of some use as masticating organs. In those
free living Mites which have undergone no great modification of the mouth-
parts two other portions can be distinguished, the upper lip or “epipharynx,”
and the “lingua,” which forms the floor of the mouth, and is for the most
part concealed by the maxillary plate.
The legs are usually six- or seven-jointed, and are subject to great
variation, especially as regards the tarsus or terminal joint. This may bear
claws (1–3) or sucking disks, or a combination of the two, or may simply
take the form of a long bristle or hair.
The Cheese-mite has a claw surrounded by a sucker—like Captain
Cuttle’s hook within his sleeve. The claws of those species which are
parasitic on the hairs of animals are sometimes most remarkably modified.
Internal Structure.—The minute size of most Mites has rendered
research upon their internal structure a matter of great difficulty, and there
are still many obscurities to be removed. Those forms which have been
subjected to examination present a tolerable uniformity in the structure of
Page 510
the principal organs, but the brief
description here given will not, of
course, apply to aberrant groups like
the Vermiformia. A marked
concentration is noticeable
throughout the Order, and is best
exemplified by the nervous system.
The mouth leads into a sucking
pharynx, which narrows to form the
oesophagus. This passes through the
nerve-mass in the usual Arachnid
fashion, and widens to form the
ventriculus or stomach. The
oesophagus varies considerably in
width in the various groups, being
Fig. 239.—Diagram of the viscera of an
very narrow in those Mites which Oribatid Mite, greatly enlarged. C, C, Lateral
merely suck blood, but wider in caeca of stomach; g, cerebral ganglion; od, od,
vegetable-feeders like the Oribatidae. oviducts; oe, oesophagus; pr.g, pro-ventricular
gland; ps, pseudo-stigmatic organ; st, stomach;
The stomach is always provided tr, tr, tracheae. (Partly after Michael.)
with caeca, but these are not nearly
so numerous as in some other Orders of Arachnida. There are always two
large caeca directed backwards, and there may be others. They are most
numerous in the Gamasidae (see p. 470), which sometimes possess eight,
some being prolonged into the coxae of the legs, as in Spiders. At the sides
of the anterior part of the stomach there are usually two glandular bodies,
the pro-ventricular glands. In those Mites in which the alimentary canal is
most differentiated (e.g. Oribatidae) three parts are distinguishable behind
the stomach, a small intestine, a colon, and a rectum, but in most groups the
small intestine is practically absent. The Malpighian tubes, very variable in
length, enter at the constriction between colon and rectum.
In some of the Trombidiidae there appears to be a doubt as to the
existence of a hind-gut at all. A body having the appearance of the hind-gut,
and occupying its usual position, is found to contain, not faecal matter, but a
white excretory substance, and all efforts to discover any passage into it
from the stomach have been unsuccessful. Both Croneberg[356] and
Henking[357] came to the conclusion that the stomach ended blindly, and that
description here given will not, of
course, apply to aberrant groups like
the Vermiformia. A marked
concentration is noticeable
throughout the Order, and is best
exemplified by the nervous system.
The mouth leads into a sucking
pharynx, which narrows to form the
oesophagus. This passes through the
nerve-mass in the usual Arachnid
fashion, and widens to form the
ventriculus or stomach. The
oesophagus varies considerably in
width in the various groups, being
Fig. 239.—Diagram of the viscera of an
very narrow in those Mites which Oribatid Mite, greatly enlarged. C, C, Lateral
merely suck blood, but wider in caeca of stomach; g, cerebral ganglion; od, od,
vegetable-feeders like the Oribatidae. oviducts; oe, oesophagus; pr.g, pro-ventricular
gland; ps, pseudo-stigmatic organ; st, stomach;
The stomach is always provided tr, tr, tracheae. (Partly after Michael.)
with caeca, but these are not nearly
so numerous as in some other Orders of Arachnida. There are always two
large caeca directed backwards, and there may be others. They are most
numerous in the Gamasidae (see p. 470), which sometimes possess eight,
some being prolonged into the coxae of the legs, as in Spiders. At the sides
of the anterior part of the stomach there are usually two glandular bodies,
the pro-ventricular glands. In those Mites in which the alimentary canal is
most differentiated (e.g. Oribatidae) three parts are distinguishable behind
the stomach, a small intestine, a colon, and a rectum, but in most groups the
small intestine is practically absent. The Malpighian tubes, very variable in
length, enter at the constriction between colon and rectum.
In some of the Trombidiidae there appears to be a doubt as to the
existence of a hind-gut at all. A body having the appearance of the hind-gut,
and occupying its usual position, is found to contain, not faecal matter, but a
white excretory substance, and all efforts to discover any passage into it
from the stomach have been unsuccessful. Both Croneberg[356] and
Henking[357] came to the conclusion that the stomach ended blindly, and that
Page 511
the apparent hind-gut was an excretory organ. Michael,[358] in his research
upon a Water-mite, Thyas petrophilus, met with precisely the same
difficulty, and was led to the belief that what was originally hind-gut had
become principally or entirely an excretory organ.
The nervous system chiefly consists of a central ganglionic mass, usually
transversely oval, and presenting little or no indication of the parts which
have coalesced in its formation. Nerves proceed from it in a radiate manner,
but no double nerve-cord passes towards the posterior end of the body. As
above stated, it is perforated by the oesophagus.
The vascular system is little understood. In 1876 Kramer[359] wrote that he
was able to perceive an actively pulsating heart in the posterior third of the
abdomen in specimens of Gamasus which had recently moulted, and were
therefore moderately transparent. No other investigator has been equally
fortunate, though many capable workers have sought diligently for any
trace of a dorsal vessel in various Acarine groups.
It would appear that the blood-flow in most Mites is lacunar and
indefinite, aided incidentally by the movements of the muscles, and perhaps
by a certain rhythmic motion of the alimentary canal, which has been
observed to be most marked during the more quiescent stages of the life-
history.
The internal reproductive organs have the ringed arrangement generally
observed in the Arachnida. The two testes, which are sometimes bi-lobed,
are connected by a median structure which may serve as a vesicula
seminalis, and there are two vasa deferentia which proceed to the
intromittent organ, which is sometimes situated quite in the anterior part of
the ventral surface, but at others towards its centre. The male Mite is often
provided with a pair of suckers towards the posterior end of the abdomen,
and sometimes accessory clasping organs are present.
In some Mites there is no intromittent organ, and Michael[360] has
described some remarkable cases in which the chelicerae are used in the
fertilisation of the female, a spermatophore, or bag containing spermatozoa,
being removed by them from the male opening and deposited in that of the
female. The most remarkable instance is that of Gamasus terribilis, the
movable joint of whose chelicera is perforated by a foramen through which
the spermatophore is, so to speak, blown and carried as a bi-lobed bag,
upon a Water-mite, Thyas petrophilus, met with precisely the same
difficulty, and was led to the belief that what was originally hind-gut had
become principally or entirely an excretory organ.
The nervous system chiefly consists of a central ganglionic mass, usually
transversely oval, and presenting little or no indication of the parts which
have coalesced in its formation. Nerves proceed from it in a radiate manner,
but no double nerve-cord passes towards the posterior end of the body. As
above stated, it is perforated by the oesophagus.
The vascular system is little understood. In 1876 Kramer[359] wrote that he
was able to perceive an actively pulsating heart in the posterior third of the
abdomen in specimens of Gamasus which had recently moulted, and were
therefore moderately transparent. No other investigator has been equally
fortunate, though many capable workers have sought diligently for any
trace of a dorsal vessel in various Acarine groups.
It would appear that the blood-flow in most Mites is lacunar and
indefinite, aided incidentally by the movements of the muscles, and perhaps
by a certain rhythmic motion of the alimentary canal, which has been
observed to be most marked during the more quiescent stages of the life-
history.
The internal reproductive organs have the ringed arrangement generally
observed in the Arachnida. The two testes, which are sometimes bi-lobed,
are connected by a median structure which may serve as a vesicula
seminalis, and there are two vasa deferentia which proceed to the
intromittent organ, which is sometimes situated quite in the anterior part of
the ventral surface, but at others towards its centre. The male Mite is often
provided with a pair of suckers towards the posterior end of the abdomen,
and sometimes accessory clasping organs are present.
In some Mites there is no intromittent organ, and Michael[360] has
described some remarkable cases in which the chelicerae are used in the
fertilisation of the female, a spermatophore, or bag containing spermatozoa,
being removed by them from the male opening and deposited in that of the
female. The most remarkable instance is that of Gamasus terribilis, the
movable joint of whose chelicera is perforated by a foramen through which
the spermatophore is, so to speak, blown and carried as a bi-lobed bag,
Page 512
united by the narrow stalk which passes through the foramen, to the female
aperture.
The ovaries are fused in the middle line, and connected by oviducts with
the tube (vagina or uterus) which passes to the exterior. There is often an
ovipositor.
Professor Gené of Turin[361] described, in 1844, some remarkable
phenomena in connection with the reproduction of Ticks. The male Ixodes
introduced his rostrum into the female aperture, two small white fusiform
bodies emerging right and left from the labium at the moment of
introduction. On retraction they had disappeared. When the female laid
eggs, a bi-lobed vesicle was protruded from beneath the anterior border of
the scutum and grasped the egg delivered to it by the ovipositor, appearing
to manipulate it for some minutes. Then the vesicle was withdrawn, and the
egg was left on the rostrum, and deposited by it in front of the animal.
When the vesicle was punctured, and so rendered useless, the
unmanipulated eggs quickly shrivelled and dried up.
Lounsbury[362] has recently confirmed Professor Gené’s observation as to
oviposition in the case of a South African Tick, Amblyomma hebraeum.
The respiratory organs, if present, are always in the form of tracheae.
These are usually long and convoluted, but not branching. The spiral
structure is difficult to make out in these animals, and in the Oribatidae at
least, instead of the external sheath being fortified with a spiral filament of
chitin, there is a very delicate enveloping membrane with an apparently
unbroken chitinous lining, which can, however, by suitable treatment, be
resolved into a ribbon-like spiral band.[363] The position of the stigmata is
very variable, and is utilised to indicate the main groups into which the
Mites have been divided.
The Oribatidae possess two curious cephalothoracic organs which were
for a long time considered respiratory. These are in the form of two bodies,
like modified hairs, which protrude from sockets on the dorsal surface of
the cephalothoracic shield. Michael[364] has shown that these have no
connection with the tracheae, and he regards them as sensory organs—
possibly olfactory. They are generally referred to as the “pseudo-stigmatic”
organs.
In the Oribatidae, at all events, well-developed coxal glands are present.
In many Mites, especially the Ixodoidea or Ticks, the salivary glands are
aperture.
The ovaries are fused in the middle line, and connected by oviducts with
the tube (vagina or uterus) which passes to the exterior. There is often an
ovipositor.
Professor Gené of Turin[361] described, in 1844, some remarkable
phenomena in connection with the reproduction of Ticks. The male Ixodes
introduced his rostrum into the female aperture, two small white fusiform
bodies emerging right and left from the labium at the moment of
introduction. On retraction they had disappeared. When the female laid
eggs, a bi-lobed vesicle was protruded from beneath the anterior border of
the scutum and grasped the egg delivered to it by the ovipositor, appearing
to manipulate it for some minutes. Then the vesicle was withdrawn, and the
egg was left on the rostrum, and deposited by it in front of the animal.
When the vesicle was punctured, and so rendered useless, the
unmanipulated eggs quickly shrivelled and dried up.
Lounsbury[362] has recently confirmed Professor Gené’s observation as to
oviposition in the case of a South African Tick, Amblyomma hebraeum.
The respiratory organs, if present, are always in the form of tracheae.
These are usually long and convoluted, but not branching. The spiral
structure is difficult to make out in these animals, and in the Oribatidae at
least, instead of the external sheath being fortified with a spiral filament of
chitin, there is a very delicate enveloping membrane with an apparently
unbroken chitinous lining, which can, however, by suitable treatment, be
resolved into a ribbon-like spiral band.[363] The position of the stigmata is
very variable, and is utilised to indicate the main groups into which the
Mites have been divided.
The Oribatidae possess two curious cephalothoracic organs which were
for a long time considered respiratory. These are in the form of two bodies,
like modified hairs, which protrude from sockets on the dorsal surface of
the cephalothoracic shield. Michael[364] has shown that these have no
connection with the tracheae, and he regards them as sensory organs—
possibly olfactory. They are generally referred to as the “pseudo-stigmatic”
organs.
In the Oribatidae, at all events, well-developed coxal glands are present.
In many Mites, especially the Ixodoidea or Ticks, the salivary glands are
Page 513
large and conspicuous.
Metamorphosis.—All Mites undergo a metamorphosis, varying in
completeness in the different groups. Altogether six stages can be
recognised, though they are seldom or never all exhibited in the
development of a single species. These are ovum, deutovum, larva, nymph,
hypopial stage, and imago.
The Ovum.—All Mites lay eggs. It is frequently stated that the Oribatidae
are viviparous exceptions, but though some of them are perhaps
ovoviviparous, most deposit eggs like the rest of the Order. A phenomenon
which has probably helped to foster this erroneous view is the occasional
emergence from the dead body of the mother of fully-formed larvae.
Towards winter it is not unusual for the mother to die at a time when her
abdomen contains a few ripe eggs, and these are able to complete their
development internally.
The Deutovum.[365]—In a few cases (Atax, Damaeus) a stage has been
observed in which the outer envelope of the egg becomes brown and hard,
and splits longitudinally, so as to allow the thin inner membrane to become
visible through the fissure. More room is thus obtained for the developing
larva, which is, moreover, protected, over most of its surface, by a hard
shell. The deutovum stage may occur either within the body of the mother,
or after the egg has been laid.
The Larva.—Omitting, for the moment, the very aberrant Vermiformia
(see p. 464), it is the almost universal rule for the egg to hatch out as a
hexapod larva. The larvae of the genus Pteroptus are said to be eight-
legged. Winkler has stated that the early embryo of Gamasus possesses
eight legs, of which the last pair subsequently atrophy, but this observation
requires confirmation.
The Nymph.—The nymph-stage commences on the acquisition of eight
legs, and lasts until the final ecdysis which produces the imago. This is the
most important period of Acarine life, and is divided into a prolonged active
period, during which the animal feeds and grows, and an inert period,
sometimes prolonged, but at others very short, and differing little from the
quiescence observable at an ordinary moult, during which the imago is
elaborated. In many species the nymph is strikingly different from the
imago; in others there is a close resemblance between them. It would
appear, from the cases which have been most thoroughly investigated, that
Metamorphosis.—All Mites undergo a metamorphosis, varying in
completeness in the different groups. Altogether six stages can be
recognised, though they are seldom or never all exhibited in the
development of a single species. These are ovum, deutovum, larva, nymph,
hypopial stage, and imago.
The Ovum.—All Mites lay eggs. It is frequently stated that the Oribatidae
are viviparous exceptions, but though some of them are perhaps
ovoviviparous, most deposit eggs like the rest of the Order. A phenomenon
which has probably helped to foster this erroneous view is the occasional
emergence from the dead body of the mother of fully-formed larvae.
Towards winter it is not unusual for the mother to die at a time when her
abdomen contains a few ripe eggs, and these are able to complete their
development internally.
The Deutovum.[365]—In a few cases (Atax, Damaeus) a stage has been
observed in which the outer envelope of the egg becomes brown and hard,
and splits longitudinally, so as to allow the thin inner membrane to become
visible through the fissure. More room is thus obtained for the developing
larva, which is, moreover, protected, over most of its surface, by a hard
shell. The deutovum stage may occur either within the body of the mother,
or after the egg has been laid.
The Larva.—Omitting, for the moment, the very aberrant Vermiformia
(see p. 464), it is the almost universal rule for the egg to hatch out as a
hexapod larva. The larvae of the genus Pteroptus are said to be eight-
legged. Winkler has stated that the early embryo of Gamasus possesses
eight legs, of which the last pair subsequently atrophy, but this observation
requires confirmation.
The Nymph.—The nymph-stage commences on the acquisition of eight
legs, and lasts until the final ecdysis which produces the imago. This is the
most important period of Acarine life, and is divided into a prolonged active
period, during which the animal feeds and grows, and an inert period,
sometimes prolonged, but at others very short, and differing little from the
quiescence observable at an ordinary moult, during which the imago is
elaborated. In many species the nymph is strikingly different from the
imago; in others there is a close resemblance between them. It would
appear, from the cases which have been most thoroughly investigated, that
Page 514
the imago is not developed, part for part, from the nymph, but that there is
an “histolysis” and “histogenesis” similar to that which occurs among
certain insects (see vol. v. p. 165). There may be more than one nymphal
stage.
The hypopial stage occurs in the Tyroglyphinae, the “Cheese-mite” sub-
family. Here some of the young nymphs assume an entirely different form,
so different that it was for a long time considered to constitute a separate
genus, and was named Hypopus. The animal acquires a hard dorsal
covering. The mouth-parts are in the form of a flat blade with two terminal
bristles, but with no discernible orifice. The legs are single-clawed, and all
more or less directed forward, and they are articulated near the middle line
of the ventral surface. Suckers are always present under the hind part of the
abdomen.
It appears that these remarkably modified nymphs are entrusted with the
wider distribution of the species, and that they are analogous to the winged
individuals which occur in the parthenogenetic generations of the Aphidae.
The ordinary Tyroglyphus is soft-bodied, and requires a moist environment,
and exposure to the sun or prolonged passage through the air would be fatal
to it. The hypopial form is much more independent of external conditions,
and its habit is to attach itself by its suckers to various insects, and by this
means to seek a new locality, when it resumes the ordinary nymph-form and
proceeds with its development.
Classification.—There is no generally accepted classification of the
Acarina, though several eminent Arachnologists have attempted of late
years to reduce the group to order. Widely different views are held
concerning the affinities of certain groups, and there is no agreement as to
the value to be accorded to the characters which all recognise. Thus
Canestrini[366] allows thirty-four families, while according to Trouessart[367]
there are only ten.
Trouessart’s scheme of classification is in the main followed in the
present chapter.
Sub-Order 1. Vermiformia.
This Sub-order includes the lowest and most aberrant forms of the Mites.
They are entirely parasitic, and of very small size. The abdomen is much
an “histolysis” and “histogenesis” similar to that which occurs among
certain insects (see vol. v. p. 165). There may be more than one nymphal
stage.
The hypopial stage occurs in the Tyroglyphinae, the “Cheese-mite” sub-
family. Here some of the young nymphs assume an entirely different form,
so different that it was for a long time considered to constitute a separate
genus, and was named Hypopus. The animal acquires a hard dorsal
covering. The mouth-parts are in the form of a flat blade with two terminal
bristles, but with no discernible orifice. The legs are single-clawed, and all
more or less directed forward, and they are articulated near the middle line
of the ventral surface. Suckers are always present under the hind part of the
abdomen.
It appears that these remarkably modified nymphs are entrusted with the
wider distribution of the species, and that they are analogous to the winged
individuals which occur in the parthenogenetic generations of the Aphidae.
The ordinary Tyroglyphus is soft-bodied, and requires a moist environment,
and exposure to the sun or prolonged passage through the air would be fatal
to it. The hypopial form is much more independent of external conditions,
and its habit is to attach itself by its suckers to various insects, and by this
means to seek a new locality, when it resumes the ordinary nymph-form and
proceeds with its development.
Classification.—There is no generally accepted classification of the
Acarina, though several eminent Arachnologists have attempted of late
years to reduce the group to order. Widely different views are held
concerning the affinities of certain groups, and there is no agreement as to
the value to be accorded to the characters which all recognise. Thus
Canestrini[366] allows thirty-four families, while according to Trouessart[367]
there are only ten.
Trouessart’s scheme of classification is in the main followed in the
present chapter.
Sub-Order 1. Vermiformia.
This Sub-order includes the lowest and most aberrant forms of the Mites.
They are entirely parasitic, and of very small size. The abdomen is much
Page 515
elongated, and is transversely striated. There are two families,
Eriophyidae[368] (Phytoptidae) and Demodicidae.
Fam. 1. Eriophyidae (Phytoptidae).—These are the so-called Gall-
mites. The curious excrescences and abnormal growths which occur on the
leaves and buds of plants are familiar to every one. Various creatures are
responsible for these deformities, many being the work of insects,
especially the Cynipidae among the Hymenoptera, and the Cecidomyiidae
among the Diptera. Others, again, are due to Eriophyid Mites.
Though the galls originated by Mites are often outwardly extremely
similar to those of insect origin, they can be at once distinguished on close
examination. Mite-galls contain a single chamber, communicating with the
exterior by a pore, usually guarded with hairs, and the Mites live
gregariously within it, apparently feeding upon the hairs which grow
abundantly on its inner surface. In Insect-galls each insect larva lives in a
separate closed chamber.
The Eriophyidae are unique among Mites in possessing only two pairs of
legs, situated quite at the anterior part of the body. The mouth-parts are very
simple.
There are three genera, Eriophyes (Phyptoptus) with about one hundred
and fifty known species, Monochetus with a single species, and
Phyllocoptes with about fifty species.
Among the best known examples are Eriophyes tiliae, which produces
the “nail-galls” on lime-leaves, and E. ribis, the “black-currant Gall-mite,”
which feeds between the folded leaves of the leaf-buds, and gives rise to
swelling and distortion.
Fam. 2. Demodicidae.—The single genus Demodex which constitutes
this family consists of a few species of microscopic Mites which inhabit the
hair-follicles of mammals, and are the cause of what is known as “follicular
mange,” some other forms of mange being due to members of the
succeeding family. Demodex possesses eight short, three-jointed legs, each
terminated by two claws. The abdomen is much produced, and is
transversely striated. About ten species have been described, but of these
five are probably varieties of D. folliculorum (Fig. 240, A), which infests
Man.
Eriophyidae[368] (Phytoptidae) and Demodicidae.
Fam. 1. Eriophyidae (Phytoptidae).—These are the so-called Gall-
mites. The curious excrescences and abnormal growths which occur on the
leaves and buds of plants are familiar to every one. Various creatures are
responsible for these deformities, many being the work of insects,
especially the Cynipidae among the Hymenoptera, and the Cecidomyiidae
among the Diptera. Others, again, are due to Eriophyid Mites.
Though the galls originated by Mites are often outwardly extremely
similar to those of insect origin, they can be at once distinguished on close
examination. Mite-galls contain a single chamber, communicating with the
exterior by a pore, usually guarded with hairs, and the Mites live
gregariously within it, apparently feeding upon the hairs which grow
abundantly on its inner surface. In Insect-galls each insect larva lives in a
separate closed chamber.
The Eriophyidae are unique among Mites in possessing only two pairs of
legs, situated quite at the anterior part of the body. The mouth-parts are very
simple.
There are three genera, Eriophyes (Phyptoptus) with about one hundred
and fifty known species, Monochetus with a single species, and
Phyllocoptes with about fifty species.
Among the best known examples are Eriophyes tiliae, which produces
the “nail-galls” on lime-leaves, and E. ribis, the “black-currant Gall-mite,”
which feeds between the folded leaves of the leaf-buds, and gives rise to
swelling and distortion.
Fam. 2. Demodicidae.—The single genus Demodex which constitutes
this family consists of a few species of microscopic Mites which inhabit the
hair-follicles of mammals, and are the cause of what is known as “follicular
mange,” some other forms of mange being due to members of the
succeeding family. Demodex possesses eight short, three-jointed legs, each
terminated by two claws. The abdomen is much produced, and is
transversely striated. About ten species have been described, but of these
five are probably varieties of D. folliculorum (Fig. 240, A), which infests
Man.
Page 516
Fig. 240.—Vermiform Mites, highly magnified.
A, Demodex folliculorum; B, Eriophyes
(Phyptoptus) ribis.
Sub-Order 2. Astigmata.
The Astigmata are Mites of more or less globular form, with chelate
chelicerae and five-jointed legs. All members of the group are eyeless.
Their habits are very various, some feeding on vegetable matter and others
on carrion, while a large number are parasitic on animals. Tracheae are
absent. There is only one family.
Fam. 1. Sarcoptidae.—No tracheae or stigmata. Apical rostrum.
Oviparous or ovoviviparous. The seventy genera and 530 odd species of
this family are divided into a number of sub-families, of which the principal
are the Sarcoptinae, the Analgesinae, and the Tyroglyphinae.
A, Demodex folliculorum; B, Eriophyes
(Phyptoptus) ribis.
Sub-Order 2. Astigmata.
The Astigmata are Mites of more or less globular form, with chelate
chelicerae and five-jointed legs. All members of the group are eyeless.
Their habits are very various, some feeding on vegetable matter and others
on carrion, while a large number are parasitic on animals. Tracheae are
absent. There is only one family.
Fam. 1. Sarcoptidae.—No tracheae or stigmata. Apical rostrum.
Oviparous or ovoviviparous. The seventy genera and 530 odd species of
this family are divided into a number of sub-families, of which the principal
are the Sarcoptinae, the Analgesinae, and the Tyroglyphinae.
Page 517
(i.) The Sarcoptinae are the so-
called “Itch-mites.” They are minute
animals, with bodies transversely
wrinkled and legs terminating in
suckers or bristles. The genus
Sarcoptes, which includes about
fifteen species, lives in tunnels which
it burrows in the skin of mammals.
(ii.) The Analgesinae are the
“Birds’-feather Mites.” The principal
genera are Pterolichus (120 species),
Pteronyssus (33 species), Analges
(23 species), Megninia (42 species),
and Alloptes (33 species).
(iii.) The Tyroglyphinae[369] have
received the popular name of
“Cheese-mites,” from the best known
example of the group. They are
smooth-bodied, soft-skinned white
Mites, with legs usually terminating
in a single claw, sometimes
accompanied by a sucker. They are
for the most part carrion-feeders,
living upon decaying animal or
vegetable matter, but a few are
parasitic on mammals, insects, and
worms.
There are sixteen genera, including
about fifty species. Tyroglyphus siro
and T. longior are common Cheese-
mites. Other species live in decaying
vegetables and food-stuffs. Some of
the genus Glycyphagus (G. palmifer,
G. plumiger) are very remarkable for
the palmate or plumose hairs which
decorate their bodies. The remarkable
called “Itch-mites.” They are minute
animals, with bodies transversely
wrinkled and legs terminating in
suckers or bristles. The genus
Sarcoptes, which includes about
fifteen species, lives in tunnels which
it burrows in the skin of mammals.
(ii.) The Analgesinae are the
“Birds’-feather Mites.” The principal
genera are Pterolichus (120 species),
Pteronyssus (33 species), Analges
(23 species), Megninia (42 species),
and Alloptes (33 species).
(iii.) The Tyroglyphinae[369] have
received the popular name of
“Cheese-mites,” from the best known
example of the group. They are
smooth-bodied, soft-skinned white
Mites, with legs usually terminating
in a single claw, sometimes
accompanied by a sucker. They are
for the most part carrion-feeders,
living upon decaying animal or
vegetable matter, but a few are
parasitic on mammals, insects, and
worms.
There are sixteen genera, including
about fifty species. Tyroglyphus siro
and T. longior are common Cheese-
mites. Other species live in decaying
vegetables and food-stuffs. Some of
the genus Glycyphagus (G. palmifer,
G. plumiger) are very remarkable for
the palmate or plumose hairs which
decorate their bodies. The remarkable
Page 518
hypopial stage in the development of
Tyroglyphus has been mentioned on
p. 463. The Tyroglyphinae are the
lowest of the free-living Acarine
forms.
Tyroglyphus has been mentioned on
p. 463. The Tyroglyphinae are the
lowest of the free-living Acarine
forms.
Page 519
Fig. 241.—A, Leg of a fowl infested with “leg-
scab”; B, female of Sarcoptes mutans, greatly
magnified. (After Neumann.)
Sub-Order 3. Metastigmata.
The four families which constitute this sub-order comprise a large
number of Mites in which the tracheae open near the articulation of the
legs, and consequently in a somewhat posterior situation. The families are
Oribatidae, Argasidae, Ixodidae, and Gamasidae.
Fam. 1. Oribatidae.—The Oribatidae or “Beetle-mites” are free-living
Acari, with tracheae of which the stigmata are concealed by the articulation
of the legs. The cephalothorax is distinctly marked off from the abdomen,
and bears dorsally two “pseudo-stigmatic” organs. The rostrum is inserted
below the cephalothorax. These Mites gain their popular name from the
beetle-like hardness of their integuments. They are oviparous or
ovoviviparous. Eyes are always absent.
These are small creatures, seldom
attaining the twentieth of an inch in
length. They are vegetable-feeders
(except, perhaps, Pelops), and are to
be found in dead wood or vegetable
débris, under bark, or among moss
and lichen. In winter they often take
refuge under stones. It is impossible
Fig. 242.—Oribatid Mites. A, Cepheus
at present to estimate the number of
ocellatus, × 24; B, ventral view of Hoploderma existing species, for only a few
magnum, closed, × 20. (After Michael.) localities have been systematically
worked for them, and their small size
has prevented their inclusion, in any numbers, in the collections of scientific
expeditions. Our knowledge of the group is likely, however, to be largely
extended, for it has been found that they reach England alive and in good
condition from the most remote regions if moss or other material in which
they live is collected when not too dry, and hermetically sealed up in tin
cases.
About twenty genera and more than 220 species are at present known.
Pelops has much elongated chelicerae, with very small chelae at the end.
There are ten species, found in moss and on bushes. Oribata numbers about
scab”; B, female of Sarcoptes mutans, greatly
magnified. (After Neumann.)
Sub-Order 3. Metastigmata.
The four families which constitute this sub-order comprise a large
number of Mites in which the tracheae open near the articulation of the
legs, and consequently in a somewhat posterior situation. The families are
Oribatidae, Argasidae, Ixodidae, and Gamasidae.
Fam. 1. Oribatidae.—The Oribatidae or “Beetle-mites” are free-living
Acari, with tracheae of which the stigmata are concealed by the articulation
of the legs. The cephalothorax is distinctly marked off from the abdomen,
and bears dorsally two “pseudo-stigmatic” organs. The rostrum is inserted
below the cephalothorax. These Mites gain their popular name from the
beetle-like hardness of their integuments. They are oviparous or
ovoviviparous. Eyes are always absent.
These are small creatures, seldom
attaining the twentieth of an inch in
length. They are vegetable-feeders
(except, perhaps, Pelops), and are to
be found in dead wood or vegetable
débris, under bark, or among moss
and lichen. In winter they often take
refuge under stones. It is impossible
Fig. 242.—Oribatid Mites. A, Cepheus
at present to estimate the number of
ocellatus, × 24; B, ventral view of Hoploderma existing species, for only a few
magnum, closed, × 20. (After Michael.) localities have been systematically
worked for them, and their small size
has prevented their inclusion, in any numbers, in the collections of scientific
expeditions. Our knowledge of the group is likely, however, to be largely
extended, for it has been found that they reach England alive and in good
condition from the most remote regions if moss or other material in which
they live is collected when not too dry, and hermetically sealed up in tin
cases.
About twenty genera and more than 220 species are at present known.
Pelops has much elongated chelicerae, with very small chelae at the end.
There are ten species, found in moss and on bushes. Oribata numbers about
Page 520
fifty species, found in moss and on trees. Notaspis, in which the last three
legs are inserted at the margin of the body, has about thirty species, found
among moss and dead leaves. Nothrus is a short-legged genus with flat or
concave dorsal plate, often produced into very remarkable spiny processes.
There are twenty-two species found under bark and among moss and lichen.
Hoploderma (Hoplophora) is remarkable for its power of shutting down its
rostrum and withdrawing its legs in a manner which leaves it as
unassailable as a tortoise or an armadillo.
Though the Oribatidae are all eyeless, they are distinctly sensitive to
light, not wandering aimlessly till they reach a shadow, but apparently
making straight for a dark spot when subjected to strong illumination. Some
species have a curious habit of collecting dirt and débris on their backs, so
as entirely to obscure the often very remarkable disposition of the spines
and processes with which they are furnished.
The next two families include the
animals commonly known as Ticks,
the largest and most familiar of the
Mite tribe. Of recent years they have
attracted much attention as the
conveyers, to man and domestic
animals, of certain diseases due to
blood-parasites (see p. 457, n.), and
our knowledge of their structure and
habits has greatly increased in
consequence. Hitherto they have Fig. 243.—Capitulum of Boophilus australis;
generally been considered to ventral view. p1, p2, p3, p4, The four articles of
constitute a single family, the the palp; m, the mandible or chelicera; d, its
digit; n, the hypostome.
Ixodidae, but a section of them so
differ from the rest as to require their
removal to another family, the Argasidae, so that it is necessary to employ a
super-family name—Ixodoidea—to embrace the whole group.
Ticks are parasitic on mammals, birds, and reptiles, some shewing a
marked partiality for a particular host, others being much more catholic in
their tastes. Both sexes in the Argasidae, but the females only of the
Ixodidae, are capable of great distension, but when unfed they are all
legs are inserted at the margin of the body, has about thirty species, found
among moss and dead leaves. Nothrus is a short-legged genus with flat or
concave dorsal plate, often produced into very remarkable spiny processes.
There are twenty-two species found under bark and among moss and lichen.
Hoploderma (Hoplophora) is remarkable for its power of shutting down its
rostrum and withdrawing its legs in a manner which leaves it as
unassailable as a tortoise or an armadillo.
Though the Oribatidae are all eyeless, they are distinctly sensitive to
light, not wandering aimlessly till they reach a shadow, but apparently
making straight for a dark spot when subjected to strong illumination. Some
species have a curious habit of collecting dirt and débris on their backs, so
as entirely to obscure the often very remarkable disposition of the spines
and processes with which they are furnished.
The next two families include the
animals commonly known as Ticks,
the largest and most familiar of the
Mite tribe. Of recent years they have
attracted much attention as the
conveyers, to man and domestic
animals, of certain diseases due to
blood-parasites (see p. 457, n.), and
our knowledge of their structure and
habits has greatly increased in
consequence. Hitherto they have Fig. 243.—Capitulum of Boophilus australis;
generally been considered to ventral view. p1, p2, p3, p4, The four articles of
constitute a single family, the the palp; m, the mandible or chelicera; d, its
digit; n, the hypostome.
Ixodidae, but a section of them so
differ from the rest as to require their
removal to another family, the Argasidae, so that it is necessary to employ a
super-family name—Ixodoidea—to embrace the whole group.
Ticks are parasitic on mammals, birds, and reptiles, some shewing a
marked partiality for a particular host, others being much more catholic in
their tastes. Both sexes in the Argasidae, but the females only of the
Ixodidae, are capable of great distension, but when unfed they are all
Page 521
somewhat flat animals with laterally extended legs and rather crab-like
movement.
All Ticks possess a small, movable “false head” or capitulum bearing
mouth-parts which are exceedingly characteristic of the group. The
chelicerae are cutting instruments with their distal ends serrated outwardly,
and there is always present a hypostome beset with recurved teeth which
serve to maintain a firm hold on the tissues into which it is thrust. On either
side of the chelicerae are the four-jointed palps, leg-like in the Argasidae,
but more rigid and rod-like in the Ixodidae, where their inner margin is
often hollowed so as to enclose the chelicerae and hypostome when the
palps are apposed. There is a conspicuous pair of spiracles near the coxae of
the fourth pair of legs.
Fam. 2. Argasidae.—The
Argasidae are leathery Ticks without
a shield or scutum, and with free, leg-
like palps. The capitulum is never
more than partially visible when the
adult animal is viewed dorsally. Their
hosts are always warm-blooded
animals. Two genera are usually
recognised, Argas and Ornithodoros,
though recent discoveries of new
forms have tended towards their
fusion. Argas reflexus and A. persicus
have been proved to convey a
Spirochaete disease to fowls, and the
latter, under the name of the “Mianeh
Bug” has long possessed an evil
Fig. 244.—Ornithodoros talaje, under surface, × reputation for the “poisonous” effect
5. (After Canestrini.) of its bite on human beings. In
Mexico the “Turicata” (Ornithodoros
turicata) and the “Garapata” (O. megnini) are greatly dreaded, while human
“tick fever” on the Congo has been traced to the instrumentality of O.
moubata.
Fam. 3. Ixodidae.—These are the more familiar Ticks, possessing a
scutum or shield, which covers the whole back of the male, which is
movement.
All Ticks possess a small, movable “false head” or capitulum bearing
mouth-parts which are exceedingly characteristic of the group. The
chelicerae are cutting instruments with their distal ends serrated outwardly,
and there is always present a hypostome beset with recurved teeth which
serve to maintain a firm hold on the tissues into which it is thrust. On either
side of the chelicerae are the four-jointed palps, leg-like in the Argasidae,
but more rigid and rod-like in the Ixodidae, where their inner margin is
often hollowed so as to enclose the chelicerae and hypostome when the
palps are apposed. There is a conspicuous pair of spiracles near the coxae of
the fourth pair of legs.
Fam. 2. Argasidae.—The
Argasidae are leathery Ticks without
a shield or scutum, and with free, leg-
like palps. The capitulum is never
more than partially visible when the
adult animal is viewed dorsally. Their
hosts are always warm-blooded
animals. Two genera are usually
recognised, Argas and Ornithodoros,
though recent discoveries of new
forms have tended towards their
fusion. Argas reflexus and A. persicus
have been proved to convey a
Spirochaete disease to fowls, and the
latter, under the name of the “Mianeh
Bug” has long possessed an evil
Fig. 244.—Ornithodoros talaje, under surface, × reputation for the “poisonous” effect
5. (After Canestrini.) of its bite on human beings. In
Mexico the “Turicata” (Ornithodoros
turicata) and the “Garapata” (O. megnini) are greatly dreaded, while human
“tick fever” on the Congo has been traced to the instrumentality of O.
moubata.
Fam. 3. Ixodidae.—These are the more familiar Ticks, possessing a
scutum or shield, which covers the whole back of the male, which is
Page 522
capable, therefore, of little
distension, whereas it forms only a
small patch on the front part of the
body of the distended female. There
are ten genera, Ixodes,
Haemaphysalis, Dermacentor,
Rhipicentor, Rhipicephalus,
Boophilus, Margaropus, Hyalomma,
Amblyomma, and Aponomma.
Ixodes ricinus is the common
English sheep-tick. Species of
Boophilus are parasitic on cattle the
world over, and B. annulatus is the
transmitter of Texas fever. Fig. 245.—Female Sheep-tick, Ixodes ricinus.
Rhipicephalus and Amblyomma are
large genera which include several
species of economic importance. For example, R. sanguineus conveys
canine piroplasmosis, and A. hebraeum causes “heart-water” in South
African cattle. The genus Aponomma confines its attention to reptiles, and
some of its species are exceedingly ornate.
Neglecting Margaropus and Rhipicentor, which include only a very few
aberrant forms, the following entirely artificial key will serve to
differentiate the genera of the Ixodidae:—
distension, whereas it forms only a
small patch on the front part of the
body of the distended female. There
are ten genera, Ixodes,
Haemaphysalis, Dermacentor,
Rhipicentor, Rhipicephalus,
Boophilus, Margaropus, Hyalomma,
Amblyomma, and Aponomma.
Ixodes ricinus is the common
English sheep-tick. Species of
Boophilus are parasitic on cattle the
world over, and B. annulatus is the
transmitter of Texas fever. Fig. 245.—Female Sheep-tick, Ixodes ricinus.
Rhipicephalus and Amblyomma are
large genera which include several
species of economic importance. For example, R. sanguineus conveys
canine piroplasmosis, and A. hebraeum causes “heart-water” in South
African cattle. The genus Aponomma confines its attention to reptiles, and
some of its species are exceedingly ornate.
Neglecting Margaropus and Rhipicentor, which include only a very few
aberrant forms, the following entirely artificial key will serve to
differentiate the genera of the Ixodidae:—
Page 523
1. A pair of eyes on the lateral borders of the scutum 2
No eyes 6
2. Capitulum long, much longer than broad 3
Capitulum short 4
3. Unicolorous, ♂ with chitinous plates near anus Hyalomma
Generally ornate, ♂ without anal plates Amblyomma
4. Generally ornate, ♂ without anal plates, but with enlarged 4th coxae Dermacentor
Unicolorous, ♂ with anal plates and normal coxae 5
5. Palpi very short, spiracle circular Boophilus
Palpi medium, spiracle comma-shaped Rhipicephalus
6. Capitulum short; 2nd article of palp projecting laterally Haemaphysalis
Capitulum long 7
7. Unicolorous, elongate, on birds or mammals Ixodes
Generally ornate, broad-oval, on reptiles Aponomma
Neumann has recently revised the Ixodoidea in a series of papers
published in the Mémoires de la Société zoologique de France,[370] but the
work is not obtainable as a whole. A monograph, by Nuttall, Warburton,
Cooper, and Robinson, is now in course of publication at the Cambridge
University Press.[371]
Fam. 4. Gamasidae.—The Gamasidae are carnivorous Mites, either
free-living or parasitic on animals. The chelicerae are chelate, and the palps
are free. The tarsi have two claws, accompanied by a “caruncle” or sucking
disc. They are mostly pale-coloured Mites, with a smooth, more or less
scutate covering. The three principal sub-families are Gamasinae,
Uropodinae, and Dermanyssinae.
Of the Gamasinae, Gamasus coleoptratorum is the well-known Beetle-
parasite so frequently seen on Geotrupes. It is often confounded with
another species of similar habits, G. crassipes.
The curious Beetle-parasites attached to their victim by a thread belong
to the genus Uropoda of the Uropodinae. The connecting filament, which
the Mite can sever at will, for a long time puzzled observers. It was
variously construed as a silken cord of attachment, and as a sort of
umbilical cord, through which the Mite drew nourishment from the Beetle.
On more careful investigation it proved to be connected with the anus of the
Mite, and to consist of its consolidated excrement.
No eyes 6
2. Capitulum long, much longer than broad 3
Capitulum short 4
3. Unicolorous, ♂ with chitinous plates near anus Hyalomma
Generally ornate, ♂ without anal plates Amblyomma
4. Generally ornate, ♂ without anal plates, but with enlarged 4th coxae Dermacentor
Unicolorous, ♂ with anal plates and normal coxae 5
5. Palpi very short, spiracle circular Boophilus
Palpi medium, spiracle comma-shaped Rhipicephalus
6. Capitulum short; 2nd article of palp projecting laterally Haemaphysalis
Capitulum long 7
7. Unicolorous, elongate, on birds or mammals Ixodes
Generally ornate, broad-oval, on reptiles Aponomma
Neumann has recently revised the Ixodoidea in a series of papers
published in the Mémoires de la Société zoologique de France,[370] but the
work is not obtainable as a whole. A monograph, by Nuttall, Warburton,
Cooper, and Robinson, is now in course of publication at the Cambridge
University Press.[371]
Fam. 4. Gamasidae.—The Gamasidae are carnivorous Mites, either
free-living or parasitic on animals. The chelicerae are chelate, and the palps
are free. The tarsi have two claws, accompanied by a “caruncle” or sucking
disc. They are mostly pale-coloured Mites, with a smooth, more or less
scutate covering. The three principal sub-families are Gamasinae,
Uropodinae, and Dermanyssinae.
Of the Gamasinae, Gamasus coleoptratorum is the well-known Beetle-
parasite so frequently seen on Geotrupes. It is often confounded with
another species of similar habits, G. crassipes.
The curious Beetle-parasites attached to their victim by a thread belong
to the genus Uropoda of the Uropodinae. The connecting filament, which
the Mite can sever at will, for a long time puzzled observers. It was
variously construed as a silken cord of attachment, and as a sort of
umbilical cord, through which the Mite drew nourishment from the Beetle.
On more careful investigation it proved to be connected with the anus of the
Mite, and to consist of its consolidated excrement.
Page 524
The Dermanyssinae are all parasitic on warm-blooded animals,
principally birds and bats. Dermanyssus avium is the common parasite
infesting fowls and cage-birds.
Sub-Order 4. Heterostigmata.
Fam. Tarsonemidae.—This is the sole family of the sub-order. It
comprises a number of minute vegetable-feeding Mites which have been
little studied, though they are probably the cause of considerable injury to
the leaves and buds of plants.
Sub-Order 5. Prostigmata.
In these Mites the stigmata are situated anteriorly, in the rostrum or the
thorax. In the Water-mites the tracheae have atrophied, but these creatures
are clearly Trombidiidae which have taken to an aquatic life.
Fam. 1. Bdellidae.—The Bdellidae are sometimes known as the
“Snouted Mites” on account of the very prominent forwardly-directed
“capitulum” or false head. They have chelate chelicerae and tactile palps,
which are often “elbowed,” like the antennae of weevils. Eyes may be
present or absent. They are usually of a bright red colour, and are free-living
and predaceous, though in their larval stages they may often be found
attached to the limbs of insects and spiders.
The minute active scarlet Mites of the genus Eupodes and its allies
perhaps come within this family. Their legs are six-jointed.
The remaining families of the Prostigmata (Halacaridae, Hydrachnidae,
and Trombidiidae) all have raptorial palps, and clawed or piercing
chelicerae.
Fam. 2. Halacaridae.—This is a small group of marine Mites. In their
usually prominent capitulum they resemble the Bdellidae. In some respects
they recall the Oribatidae, having hard integuments, and their legs being
articulated near the margin of the body. They do not swim, but crawl upon
weeds and zoophytes, or burrow in the mud.
Fam. 3. Hydrachnidae.—The Hydrachnidae are the Fresh-water Mites.
Their legs are provided with long close-set hairs, and thus adapted for
swimming. They are predaceous, and in their young stages are often
principally birds and bats. Dermanyssus avium is the common parasite
infesting fowls and cage-birds.
Sub-Order 4. Heterostigmata.
Fam. Tarsonemidae.—This is the sole family of the sub-order. It
comprises a number of minute vegetable-feeding Mites which have been
little studied, though they are probably the cause of considerable injury to
the leaves and buds of plants.
Sub-Order 5. Prostigmata.
In these Mites the stigmata are situated anteriorly, in the rostrum or the
thorax. In the Water-mites the tracheae have atrophied, but these creatures
are clearly Trombidiidae which have taken to an aquatic life.
Fam. 1. Bdellidae.—The Bdellidae are sometimes known as the
“Snouted Mites” on account of the very prominent forwardly-directed
“capitulum” or false head. They have chelate chelicerae and tactile palps,
which are often “elbowed,” like the antennae of weevils. Eyes may be
present or absent. They are usually of a bright red colour, and are free-living
and predaceous, though in their larval stages they may often be found
attached to the limbs of insects and spiders.
The minute active scarlet Mites of the genus Eupodes and its allies
perhaps come within this family. Their legs are six-jointed.
The remaining families of the Prostigmata (Halacaridae, Hydrachnidae,
and Trombidiidae) all have raptorial palps, and clawed or piercing
chelicerae.
Fam. 2. Halacaridae.—This is a small group of marine Mites. In their
usually prominent capitulum they resemble the Bdellidae. In some respects
they recall the Oribatidae, having hard integuments, and their legs being
articulated near the margin of the body. They do not swim, but crawl upon
weeds and zoophytes, or burrow in the mud.
Fam. 3. Hydrachnidae.—The Hydrachnidae are the Fresh-water Mites.
Their legs are provided with long close-set hairs, and thus adapted for
swimming. They are predaceous, and in their young stages are often
Page 525
parasitic on water insects. A familiar
example is Atax bonzi, which lives
within the shell of the fresh-water
mussel.
Fam. 4. Trombidiidae.—The
predaceous palps of the Trombidiidae
are generally of the “finger-and-
thumb” type. The tarsi are two-
clawed, without caruncle. This group
may be divided into six sub-families.
(i.) The Limnocharinae or “Mud-
mites” connect the Hydrachnidae
with the typical Trombidiidae. They
are usually velvety and of a red
colour. They do not swim, but creep.
The larva of Limnocharis aquaticus
is parasitic on Gerris lacustris.
(ii.) The Caeculinae bear a strong
general resemblance to the
Harvestmen or Phalangidae.
Caeculus is so similar to the
Phalangid genus Trogulus that it was
Fig. 246.—Bdella lignicola, x about 50. (After considered by Dufour to belong to
Canestrini.) the same order.
(iii.) The Tetranychinae or
“Spinning mites” are phytophagous, and do much injury to plants, sucking
the sap from the leaves and giving them a blistered appearance. Tetranychus
telarius is the “Red-spider” of popular nomenclature.
(iv.) The Cheyletinae are remarkable Mites with fleshy, semi-transparent
body, and enormously developed raptorial pedipalpi, which are extremely
formidable weapons of attack. They do not creep or run like most Mites but
proceed by a series of short leaps. Cheyletus is the principal genus.
The curious genus Syringophilus, which is parasitic in the interior of
birds’ feathers, appears to be a degenerate Cheyletine.
(v.) The Erythraeinae are minute, active Mites, usually red in colour,
free-living and predaceous.
example is Atax bonzi, which lives
within the shell of the fresh-water
mussel.
Fam. 4. Trombidiidae.—The
predaceous palps of the Trombidiidae
are generally of the “finger-and-
thumb” type. The tarsi are two-
clawed, without caruncle. This group
may be divided into six sub-families.
(i.) The Limnocharinae or “Mud-
mites” connect the Hydrachnidae
with the typical Trombidiidae. They
are usually velvety and of a red
colour. They do not swim, but creep.
The larva of Limnocharis aquaticus
is parasitic on Gerris lacustris.
(ii.) The Caeculinae bear a strong
general resemblance to the
Harvestmen or Phalangidae.
Caeculus is so similar to the
Phalangid genus Trogulus that it was
Fig. 246.—Bdella lignicola, x about 50. (After considered by Dufour to belong to
Canestrini.) the same order.
(iii.) The Tetranychinae or
“Spinning mites” are phytophagous, and do much injury to plants, sucking
the sap from the leaves and giving them a blistered appearance. Tetranychus
telarius is the “Red-spider” of popular nomenclature.
(iv.) The Cheyletinae are remarkable Mites with fleshy, semi-transparent
body, and enormously developed raptorial pedipalpi, which are extremely
formidable weapons of attack. They do not creep or run like most Mites but
proceed by a series of short leaps. Cheyletus is the principal genus.
The curious genus Syringophilus, which is parasitic in the interior of
birds’ feathers, appears to be a degenerate Cheyletine.
(v.) The Erythraeinae are minute, active Mites, usually red in colour,
free-living and predaceous.
Page 526
(vi.) The Trombidiinae include
most of the moderate-sized, velvety
red Mites which are commonly
known as “Harvest-mites,” and their
larvae, the so-called Harvest-bugs,
frequently attack man. Trombidium
holosericeum is a well-known
example.
Fig. 247.—Atax alticola, x 16. (After
Canestrini.)
Fig. 248.—Tetranychus gibbosus, x 50. (After
Canestrini.)
Sub-Order 6. Notostigmata.[372]
This sub-order has been established for the reception of the curious genus
Opilioacarus.
most of the moderate-sized, velvety
red Mites which are commonly
known as “Harvest-mites,” and their
larvae, the so-called Harvest-bugs,
frequently attack man. Trombidium
holosericeum is a well-known
example.
Fig. 247.—Atax alticola, x 16. (After
Canestrini.)
Fig. 248.—Tetranychus gibbosus, x 50. (After
Canestrini.)
Sub-Order 6. Notostigmata.[372]
This sub-order has been established for the reception of the curious genus
Opilioacarus.
Page 527
Fam. Opilioacaridae.—Mites with segmented abdomen, leg-like palps,
chelate chelicerae, and two pairs of eyes. There are four dorsal abdominal
stigmata. Four species of the sole genus Opilioacarus have been recorded,
O. segmentatus from Algeria, O. italicus from Italy, O. arabicus from
Arabia, and O. platensis[373] from South America.
chelate chelicerae, and two pairs of eyes. There are four dorsal abdominal
stigmata. Four species of the sole genus Opilioacarus have been recorded,
O. segmentatus from Algeria, O. italicus from Italy, O. arabicus from
Arabia, and O. platensis[373] from South America.
Page 528
APPENDICES TO ARACHNIDA
I. and II.
TARDIGRADA AND PENTASTOMIDA
BY
ARTHUR E. SHIPLEY, M.A., F.R.S.
Fellow and Tutor of Christ’s College, Cambridge, and Reader in Zoology in the University
I. and II.
TARDIGRADA AND PENTASTOMIDA
BY
ARTHUR E. SHIPLEY, M.A., F.R.S.
Fellow and Tutor of Christ’s College, Cambridge, and Reader in Zoology in the University
Page 529
CHAPTER XIX
TARDIGRADA
OCCURRENCE—ECDYSIS—STRUCTURE—DEVELOPMENT—
AFFINITIES—BIOLOGY—DESICCATION—PARASITES—
SYSTEMATIC
The animals dealt with in this chapter lead obscure lives, remote from the
world, and few but the specialist have any first-hand acquaintance with
them. Structurally they are thought to show affinities with the Arachnida,
but their connexion with this Phylum is at best a remote one.
Tardigrades are amongst the most minute multicellular animals which
exist, and their small size—averaging from ⅓ to 1 mm. in length—and
retiring habits render them very inconspicuous, so that as a rule they are
overlooked; yet Max Schultze[374] asserts that without any doubt they are the
most widely distributed of all segmented animals. They are found amongst
moss, etc., growing in gutters, on roofs, trees or in ditches, and in such
numbers that Schultze states that almost any piece of moss the size of a pea
will, if closely examined, yield some members of this group, but they are
very difficult to see. The genus Macrobiotus especially affects the roots of
moss growing on stones and old walls. M. macronyx lives entirely in fresh
water, and Lydella dujardini and Echiniscoides sigismundi are marine; all
other species are practically terrestrial, though inhabiting very damp places.
In searching amongst the heather of the Scotch moors for the ova and
embryos of the Nematodes which infest the alimentary canal of the grouse,
I have recently adopted a method not, as far as I am aware, in use before,
and one which in every case has yielded a good supply of Tardigrades
otherwise so difficult to find. The method is to soak the heather in water for
some hours and then thoroughly shake it, or to shake it gently in a rocking
machine for some hours. The sediment is allowed to settle, and is then
removed with a pipette and placed in a centrifugaliser. A few turns of the
TARDIGRADA
OCCURRENCE—ECDYSIS—STRUCTURE—DEVELOPMENT—
AFFINITIES—BIOLOGY—DESICCATION—PARASITES—
SYSTEMATIC
The animals dealt with in this chapter lead obscure lives, remote from the
world, and few but the specialist have any first-hand acquaintance with
them. Structurally they are thought to show affinities with the Arachnida,
but their connexion with this Phylum is at best a remote one.
Tardigrades are amongst the most minute multicellular animals which
exist, and their small size—averaging from ⅓ to 1 mm. in length—and
retiring habits render them very inconspicuous, so that as a rule they are
overlooked; yet Max Schultze[374] asserts that without any doubt they are the
most widely distributed of all segmented animals. They are found amongst
moss, etc., growing in gutters, on roofs, trees or in ditches, and in such
numbers that Schultze states that almost any piece of moss the size of a pea
will, if closely examined, yield some members of this group, but they are
very difficult to see. The genus Macrobiotus especially affects the roots of
moss growing on stones and old walls. M. macronyx lives entirely in fresh
water, and Lydella dujardini and Echiniscoides sigismundi are marine; all
other species are practically terrestrial, though inhabiting very damp places.
In searching amongst the heather of the Scotch moors for the ova and
embryos of the Nematodes which infest the alimentary canal of the grouse,
I have recently adopted a method not, as far as I am aware, in use before,
and one which in every case has yielded a good supply of Tardigrades
otherwise so difficult to find. The method is to soak the heather in water for
some hours and then thoroughly shake it, or to shake it gently in a rocking
machine for some hours. The sediment is allowed to settle, and is then
removed with a pipette and placed in a centrifugaliser. A few turns of the
Page 530
handle are sufficient to concentrate at the bottom of the test-tubes a
perfectly amazing amount of cryptozoic animal life, and amongst other
forms I have never failed to find Tardigrades.
Many Tardigrades are very
transparent; their cells are large, and
arranged in a beautifully symmetrical
manner; and since those of them that
live in moss, and at times undergo
desiccation, are readily thrown into a
perfectly motionless state, during
which they may be examined at
leisure, it is not surprising that these
little creatures have been a favourite
object for histological research. One
way to produce the above-mentioned
stillness is partly to asphyxiate the
animals by placing them in water
which has been boiled, and covering
the surface of the water with a film of
oil.
The whole body is enclosed in a
thin transparent cuticle, which must
be pierced by a needle if it be desired
to stain the tissues of the interior. As
a rule the cuticle is of the same
thickness all over the body, but in the
Fig. 249.—Dorsal view of Echiniscus testudo,
genus Echiniscus the cuticle of the
C. Sch., × 200, showing the four segments 1, 2, dorsal surface is arranged in
3, 4. (From Doyère.) thickened plates, and these plates are
finely granulated. From time to time
the cuticle is cast, and this is a lengthy process, so that it is not unusual to
find a Tardigrade ensheathed in two cuticles, the outer of which is being
rubbed off. The Macrobioti lay their eggs in their cast cuticle (Fig. 250).
The end of each of the eight legs bears forked claws of cuticular origin. The
legs are not jointed except in the genus Lydella, where two divisions are
apparent.
perfectly amazing amount of cryptozoic animal life, and amongst other
forms I have never failed to find Tardigrades.
Many Tardigrades are very
transparent; their cells are large, and
arranged in a beautifully symmetrical
manner; and since those of them that
live in moss, and at times undergo
desiccation, are readily thrown into a
perfectly motionless state, during
which they may be examined at
leisure, it is not surprising that these
little creatures have been a favourite
object for histological research. One
way to produce the above-mentioned
stillness is partly to asphyxiate the
animals by placing them in water
which has been boiled, and covering
the surface of the water with a film of
oil.
The whole body is enclosed in a
thin transparent cuticle, which must
be pierced by a needle if it be desired
to stain the tissues of the interior. As
a rule the cuticle is of the same
thickness all over the body, but in the
Fig. 249.—Dorsal view of Echiniscus testudo,
genus Echiniscus the cuticle of the
C. Sch., × 200, showing the four segments 1, 2, dorsal surface is arranged in
3, 4. (From Doyère.) thickened plates, and these plates are
finely granulated. From time to time
the cuticle is cast, and this is a lengthy process, so that it is not unusual to
find a Tardigrade ensheathed in two cuticles, the outer of which is being
rubbed off. The Macrobioti lay their eggs in their cast cuticle (Fig. 250).
The end of each of the eight legs bears forked claws of cuticular origin. The
legs are not jointed except in the genus Lydella, where two divisions are
apparent.
Page 531
Within the cuticle is the epidermis,
a single layer of cells arranged in
regular longitudinal and transverse
rows along the upper and under
surface, where the cells are as
uniformly arranged and as
rectangular as bricks. The cells on the
sides of the body are polygonal, and
not in such definite rows. The nuclei
show the same diagrammatic
symmetry as the cells which contain
them, and lie in the same relative
position in neighbouring cells. In a
few places, such as the end of each
limb and around the mouth and arms,
the cells of the epidermis are heaped
up and form a clump or ridge. In
some genera a deposit of pigment in
the epidermis, which increases as the
animal grows old, obscures the
internal structures. It is generally
brown, black, or red in colour.
The cuticle and epidermis enclose
a space in which the various internal
organs lie. This space is traversed by
numerous symmetrically disposed
muscle-fibres, and contains a clear
Fig. 250.—Cast-off cuticle of Macrobiotus
fluid—the blood—which everywhere tetradactylus, Gr., × about 150, containing four
bathes these organs. This fluid eggs in which the boring apparatus of the
evaporates when desiccation takes embryo can be distinguished. (From R. Greeff.)
place, and is soon replaced after rain;
it forms no coagulum when reagents are added to it, and it probably differs
but little from water. Floating in it are numerous corpuscles, whose number
increases with age. In well-fed Tardigrades the corpuscles are packed with
food-reserves, often of the same colour—green or brown—as the contents
of the stomach, which soon disappear when the little creatures are starved.
a single layer of cells arranged in
regular longitudinal and transverse
rows along the upper and under
surface, where the cells are as
uniformly arranged and as
rectangular as bricks. The cells on the
sides of the body are polygonal, and
not in such definite rows. The nuclei
show the same diagrammatic
symmetry as the cells which contain
them, and lie in the same relative
position in neighbouring cells. In a
few places, such as the end of each
limb and around the mouth and arms,
the cells of the epidermis are heaped
up and form a clump or ridge. In
some genera a deposit of pigment in
the epidermis, which increases as the
animal grows old, obscures the
internal structures. It is generally
brown, black, or red in colour.
The cuticle and epidermis enclose
a space in which the various internal
organs lie. This space is traversed by
numerous symmetrically disposed
muscle-fibres, and contains a clear
Fig. 250.—Cast-off cuticle of Macrobiotus
fluid—the blood—which everywhere tetradactylus, Gr., × about 150, containing four
bathes these organs. This fluid eggs in which the boring apparatus of the
evaporates when desiccation takes embryo can be distinguished. (From R. Greeff.)
place, and is soon replaced after rain;
it forms no coagulum when reagents are added to it, and it probably differs
but little from water. Floating in it are numerous corpuscles, whose number
increases with age. In well-fed Tardigrades the corpuscles are packed with
food-reserves, often of the same colour—green or brown—as the contents
of the stomach, which soon disappear when the little creatures are starved.
Page 532
The alimentary canal begins with
an oral cavity, which is in many
species surrounded by chitinous
rings. The number of these rings and
their general arrangement are of
systematic importance. The oral
cavity opens behind into a fine tube
Fig. 251.—Echiniscus spinulosus, C. Sch., × lined with chitin, very characteristic
about 200, seen from the side. (From Doyère.) of the Tardigrada, which has been
termed the mouth-tube. By its side,
converging anteriorly, lie the two chitinous teeth, which may open ventrally
into the mouth-tube, as in Macrobiotus hufelandi and Doyeria simplex, or
may open directly into the oral cavity, as in Echiniscus, Milnesium, and
some species of Macrobiotus. In some of the last named the tips of the teeth
are hardened by a calcareous deposit. The hinder end of each stylet or tooth
is supported by a second chitinous tooth-bearer,[375] and the movement of
each is controlled by three muscles, one of which, running forwards to the
mouth, helps to protrude the tooth, whilst the other two running upwards
and downwards to the sheath of the pharynx, direct in what plane the tooth
shall be moved.
The mouth-tube passes suddenly into the muscular sucking pharynx,
which is pierced by a continuation of its chitinous tube. Roughly speaking,
the pharynx is spherical; the great thickness of its walls is due to radially
arranged muscles which run from the chitinous tube to a surrounding
membrane. When the muscles contract, the lumen of the tube is enlarged,
and food, for the most part liquid, is sucked in. Two large glands, composed
of cells with conspicuous nuclei, but with ill-defined cell outlines, pour
their contents into the mouth in close proximity to the exit of the teeth. The
secretion of the glands—often termed salivary glands—is said in many
cases to be poisonous.
The pharynx may be followed by a distinct oesophagus, or it may pass
almost immediately into the stomach, which consists of a layer of six-sided
cells arranged in very definite rows. In fully-fed specimens these cells
project into the lumen with a well-rounded contour. Posteriorly the stomach
contracts and passes into the narrow rectum, which receives anteriorly the
products of the excretory canals and the reproductive organs, and thus
forms a cloaca. Its transversely placed orifice lies between the last pair of
an oral cavity, which is in many
species surrounded by chitinous
rings. The number of these rings and
their general arrangement are of
systematic importance. The oral
cavity opens behind into a fine tube
Fig. 251.—Echiniscus spinulosus, C. Sch., × lined with chitin, very characteristic
about 200, seen from the side. (From Doyère.) of the Tardigrada, which has been
termed the mouth-tube. By its side,
converging anteriorly, lie the two chitinous teeth, which may open ventrally
into the mouth-tube, as in Macrobiotus hufelandi and Doyeria simplex, or
may open directly into the oral cavity, as in Echiniscus, Milnesium, and
some species of Macrobiotus. In some of the last named the tips of the teeth
are hardened by a calcareous deposit. The hinder end of each stylet or tooth
is supported by a second chitinous tooth-bearer,[375] and the movement of
each is controlled by three muscles, one of which, running forwards to the
mouth, helps to protrude the tooth, whilst the other two running upwards
and downwards to the sheath of the pharynx, direct in what plane the tooth
shall be moved.
The mouth-tube passes suddenly into the muscular sucking pharynx,
which is pierced by a continuation of its chitinous tube. Roughly speaking,
the pharynx is spherical; the great thickness of its walls is due to radially
arranged muscles which run from the chitinous tube to a surrounding
membrane. When the muscles contract, the lumen of the tube is enlarged,
and food, for the most part liquid, is sucked in. Two large glands, composed
of cells with conspicuous nuclei, but with ill-defined cell outlines, pour
their contents into the mouth in close proximity to the exit of the teeth. The
secretion of the glands—often termed salivary glands—is said in many
cases to be poisonous.
The pharynx may be followed by a distinct oesophagus, or it may pass
almost immediately into the stomach, which consists of a layer of six-sided
cells arranged in very definite rows. In fully-fed specimens these cells
project into the lumen with a well-rounded contour. Posteriorly the stomach
contracts and passes into the narrow rectum, which receives anteriorly the
products of the excretory canals and the reproductive organs, and thus
forms a cloaca. Its transversely placed orifice lies between the last pair of
Page 533
legs. The food of Tardigrades is
mainly the sap of mosses and other
humble plants, the cell-walls of
which are pierced by the teeth of the
little creatures.
The organs to which an excretory
function has been attributed are a pair
of lateral caeca, which vary much in
size according as the possessor is
well or ill nourished. They recall the
Malpighian tubules of such Mites as
Tyroglyphus. Nothing comparable in
structure to nephridia or to coxal
glands has been found.
The muscles show a beautiful
symmetry. There are ventral, dorsal,
and lateral bundles, and others that
move the limbs and teeth, but the
reader must be referred to the works
of Basse, Doyère,[376] and Plate[377] for
the details of their arrangement. The
muscle-fibres are smooth.
The nervous system consists of a
brain or supra-oesophageal ganglion,
whose structure was first elucidated F(Modified
ig. 252.—Macrobiotus schultzei, Gr., × 150.
from Greeff.) a, The six inner
by Plate, and a ventral chain of four papillae of the mouth; b, the chitin-lined
ganglia. Anteriorly the brain is oesophagus; c, calcareous spicule; d, muscle
rounded, and gives off a nerve to the which moves the spicule; e, muscular pharynx
with masticating plates; f, salivary glands; g,
skin; posteriorly each half divides stomach; h, ovary; i, median dorsal accessory
into two lobes, an inner and an outer. gland; k, diverticula of rectum.
The latter bears the eye-spot when
this is present. Just below this eye a slender nerve passes straight to the first
ventral ganglion. The brain is continued round the oral cavity as a thick
nerve-ring, the ventral part of which forms the sub-oesophageal ganglion,
united by two longitudinal commissures to the first ventral ganglion. Thus
the brain has two channels of communication between it and the ventral
mainly the sap of mosses and other
humble plants, the cell-walls of
which are pierced by the teeth of the
little creatures.
The organs to which an excretory
function has been attributed are a pair
of lateral caeca, which vary much in
size according as the possessor is
well or ill nourished. They recall the
Malpighian tubules of such Mites as
Tyroglyphus. Nothing comparable in
structure to nephridia or to coxal
glands has been found.
The muscles show a beautiful
symmetry. There are ventral, dorsal,
and lateral bundles, and others that
move the limbs and teeth, but the
reader must be referred to the works
of Basse, Doyère,[376] and Plate[377] for
the details of their arrangement. The
muscle-fibres are smooth.
The nervous system consists of a
brain or supra-oesophageal ganglion,
whose structure was first elucidated F(Modified
ig. 252.—Macrobiotus schultzei, Gr., × 150.
from Greeff.) a, The six inner
by Plate, and a ventral chain of four papillae of the mouth; b, the chitin-lined
ganglia. Anteriorly the brain is oesophagus; c, calcareous spicule; d, muscle
rounded, and gives off a nerve to the which moves the spicule; e, muscular pharynx
with masticating plates; f, salivary glands; g,
skin; posteriorly each half divides stomach; h, ovary; i, median dorsal accessory
into two lobes, an inner and an outer. gland; k, diverticula of rectum.
The latter bears the eye-spot when
this is present. Just below this eye a slender nerve passes straight to the first
ventral ganglion. The brain is continued round the oral cavity as a thick
nerve-ring, the ventral part of which forms the sub-oesophageal ganglion,
united by two longitudinal commissures to the first ventral ganglion. Thus
the brain has two channels of communication between it and the ventral
Page 534
nerve-cord on each side, one by
means of the slender nerve above
mentioned, and one through the sub-
oesophageal ganglion. The ventral
chain is composed of four ganglia
connected together by widely
divaricated commissures. Each
ganglion gives off three pairs of
nerves, two to the ventral
musculature, and one to the dorsal.
The terminations of these nerves in
Fig. 253.—Brain of Macrobiotus hufelandi, C.
the muscles are very clearly seen in
Sch., × about 350. (From Plate.) Seen from the these transparent little creatures,
side. ap, Lobe of brain bearing the eye; ce, though there is still much dispute as
supra-oesophageal ganglion; d, tooth; Ga, first
ventral ganglion; ga’, sub-oesophageal
to their exact nature.
ganglion; k, thickening of the epidermis round The older writers considered the
the mouth; oc, eye-spot; oe, oesophagus; op,
nerve running from the ocular lobe of the brain
Tardigrada as hermaphrodites, but
to the first ventral ganglion; ph, pharynx. Plate and others have conclusively
shown that they are bisexual, at any
rate in the genus Macrobiotus. The
males are, however, much rarer than the females. The reproductive organs
of both sexes are alike. Both ovary and testis are unpaired structures
opening into the intestine, and each is provided with a dorsal accessory
gland placed near its orifice. In the ovary many of the eggs are not destined
to be fertilised, but serve as nourishment for the more successful ova which
survive.
No special circulatory or respiratory organs exist, and, as in many other
simple organisms, there is no connective tissue.
The segmentation of the egg in M. macronyx is total and equal, according
to the observations of von Erlanger.[378] A blastula, followed by a gastrula, is
formed. The blastopore closes, but later the anus appears at the same spot.
There are four pairs of mesodermic diverticula which give rise to the
coelom and the chief muscles. The reproductive organs arise as an unpaired
diverticulum of the alimentary canal, which also gives origin to the
Malpighian tubules. The development is thus very primitive and simple, and
affords no evidence of degeneration.
means of the slender nerve above
mentioned, and one through the sub-
oesophageal ganglion. The ventral
chain is composed of four ganglia
connected together by widely
divaricated commissures. Each
ganglion gives off three pairs of
nerves, two to the ventral
musculature, and one to the dorsal.
The terminations of these nerves in
Fig. 253.—Brain of Macrobiotus hufelandi, C.
the muscles are very clearly seen in
Sch., × about 350. (From Plate.) Seen from the these transparent little creatures,
side. ap, Lobe of brain bearing the eye; ce, though there is still much dispute as
supra-oesophageal ganglion; d, tooth; Ga, first
ventral ganglion; ga’, sub-oesophageal
to their exact nature.
ganglion; k, thickening of the epidermis round The older writers considered the
the mouth; oc, eye-spot; oe, oesophagus; op,
nerve running from the ocular lobe of the brain
Tardigrada as hermaphrodites, but
to the first ventral ganglion; ph, pharynx. Plate and others have conclusively
shown that they are bisexual, at any
rate in the genus Macrobiotus. The
males are, however, much rarer than the females. The reproductive organs
of both sexes are alike. Both ovary and testis are unpaired structures
opening into the intestine, and each is provided with a dorsal accessory
gland placed near its orifice. In the ovary many of the eggs are not destined
to be fertilised, but serve as nourishment for the more successful ova which
survive.
No special circulatory or respiratory organs exist, and, as in many other
simple organisms, there is no connective tissue.
The segmentation of the egg in M. macronyx is total and equal, according
to the observations of von Erlanger.[378] A blastula, followed by a gastrula, is
formed. The blastopore closes, but later the anus appears at the same spot.
There are four pairs of mesodermic diverticula which give rise to the
coelom and the chief muscles. The reproductive organs arise as an unpaired
diverticulum of the alimentary canal, which also gives origin to the
Malpighian tubules. The development is thus very primitive and simple, and
affords no evidence of degeneration.
Page 535
With regard to their position in the
animal kingdom, writers on the
Tardigrada are by no means agreed.
O. F. Müller placed them with the
Mites; Schultze and Ehrenberg near
the Crustacea; Dujardin and Doyère
with the Rotifers near the Annelids;
and von Graff with the
Myzostomidae and the Pentastomida.
Plate regards them as the lowest of
all air-breathing Arthropods, but he
carefully guards himself against the
view that they retain the structure of
the original Tracheates from which
later forms have been derived. He
looks upon Tardigrades as a side twig
of the great Tracheate branch, but a Fig. 254.—Male reproductive organs of
twig which arises nearer the base of Macrobiotus hufelandi, C. Sch., × about 350.
(From Plate.) a.ep, Epidermal thickening round
the branch than any other existing anus; cl, cloaca; gl.d, accessory gland; gl.l,
forms. These animals seem certainly Malpighian gland; st, stomach; te, testis; x,
to belong to the Arthropod phylum, mother-cells of spermatozoa.
inasmuch as they are segmented,
have feet ending in claws, Malpighian tubules, and an entire absence of
cilia. The second and third of these features indicate a relationship with the
Tracheate groups; on the other hand there is an absence of paired sensory
appendages, and of mouth-parts. Von Erlanger has pointed out that the
Malpighian tubules, arising as they do from the mid-gut, are not
homologous with the Malpighian tubules of most Tracheates, and he is
inclined to place this group at the base or near the base of the whole
Arthropod phylum. They, however, show little resemblance to any of the
more primitive Crustacea. The matter must remain to a large extent a matter
of opinion, but there can be no doubt that the Tardigrades show more
marked affinities to the Arthropods than to any other group of the animal
kingdom.
Biology.—Spallanzani, who published in the year 1776 his Opuscules de
physique animale et végétale, was the first satisfactorily to describe the
phenomena of the desiccation of Tardigrades, though the subject of the
animal kingdom, writers on the
Tardigrada are by no means agreed.
O. F. Müller placed them with the
Mites; Schultze and Ehrenberg near
the Crustacea; Dujardin and Doyère
with the Rotifers near the Annelids;
and von Graff with the
Myzostomidae and the Pentastomida.
Plate regards them as the lowest of
all air-breathing Arthropods, but he
carefully guards himself against the
view that they retain the structure of
the original Tracheates from which
later forms have been derived. He
looks upon Tardigrades as a side twig
of the great Tracheate branch, but a Fig. 254.—Male reproductive organs of
twig which arises nearer the base of Macrobiotus hufelandi, C. Sch., × about 350.
(From Plate.) a.ep, Epidermal thickening round
the branch than any other existing anus; cl, cloaca; gl.d, accessory gland; gl.l,
forms. These animals seem certainly Malpighian gland; st, stomach; te, testis; x,
to belong to the Arthropod phylum, mother-cells of spermatozoa.
inasmuch as they are segmented,
have feet ending in claws, Malpighian tubules, and an entire absence of
cilia. The second and third of these features indicate a relationship with the
Tracheate groups; on the other hand there is an absence of paired sensory
appendages, and of mouth-parts. Von Erlanger has pointed out that the
Malpighian tubules, arising as they do from the mid-gut, are not
homologous with the Malpighian tubules of most Tracheates, and he is
inclined to place this group at the base or near the base of the whole
Arthropod phylum. They, however, show little resemblance to any of the
more primitive Crustacea. The matter must remain to a large extent a matter
of opinion, but there can be no doubt that the Tardigrades show more
marked affinities to the Arthropods than to any other group of the animal
kingdom.
Biology.—Spallanzani, who published in the year 1776 his Opuscules de
physique animale et végétale, was the first satisfactorily to describe the
phenomena of the desiccation of Tardigrades, though the subject of the
Page 536
desiccation of Rotifers, Nematodes, and Infusoria had attracted much
notice, since Leeuwenhoek had first drawn attention to it at the very
beginning of the century. In its natural state and in a damp atmosphere
Tardigrades live and move and have their being like other animals, but if the
surroundings dry up, or if one be isolated on a microscopic slide and slowly
allowed to dry, its movements cease, its body shrinks, its skin becomes
wrinkled, and at length it takes on the appearance of a much weathered
grain of sand in which no parts are distinguishable. In this state, in which it
may remain for years, its only vital action must be respiration, and this must
be reduced to a minimum. When water is added it slowly revives, the body
swells, fills out, the legs project, and gradually it assumes its former plump
appearance. For a time it remains still, and is then in a very favourable
condition for observation, but soon it begins to move and resumes its
ordinary life which has been so curiously interrupted.
All Tardigrades have not this peculiar power of revivification—anabiosis,
Preyer calls it—it is confined to those species which live amongst moss,
and the process of desiccation must be slow and, according to Lance,[379] the
animal must be protected as much as possible from direct contact with the
air.
According to Plate, the Tardigrada are free from parasitic Metazoa, which
indeed could hardly find room in their minute bodies. They are, however,
freely attacked by Bacteria and other lowly vegetable organisms, and these
seem to flourish in the blood without apparently producing any deleterious
effects on the host. Plate also records the occurrence of certain enigmatical
spherical bodies which were found in the blood or more usually in the cells
of the stomach. These bodies generally appeared when the Tardigrades were
kept in the same unchanged water for some weeks. Nothing certain is
known as to their nature or origin.
Systematic.—A good deal of work has recently been done by Mr. James
Murray on the Polar Tardigrades and on the Tardigrades of Scotland, many
of which have been collected by the staff of the Lake Survey.[380] Over forty
species have been described from North Britain.
The following table of Classification is based on that drawn up by Plate:
—
notice, since Leeuwenhoek had first drawn attention to it at the very
beginning of the century. In its natural state and in a damp atmosphere
Tardigrades live and move and have their being like other animals, but if the
surroundings dry up, or if one be isolated on a microscopic slide and slowly
allowed to dry, its movements cease, its body shrinks, its skin becomes
wrinkled, and at length it takes on the appearance of a much weathered
grain of sand in which no parts are distinguishable. In this state, in which it
may remain for years, its only vital action must be respiration, and this must
be reduced to a minimum. When water is added it slowly revives, the body
swells, fills out, the legs project, and gradually it assumes its former plump
appearance. For a time it remains still, and is then in a very favourable
condition for observation, but soon it begins to move and resumes its
ordinary life which has been so curiously interrupted.
All Tardigrades have not this peculiar power of revivification—anabiosis,
Preyer calls it—it is confined to those species which live amongst moss,
and the process of desiccation must be slow and, according to Lance,[379] the
animal must be protected as much as possible from direct contact with the
air.
According to Plate, the Tardigrada are free from parasitic Metazoa, which
indeed could hardly find room in their minute bodies. They are, however,
freely attacked by Bacteria and other lowly vegetable organisms, and these
seem to flourish in the blood without apparently producing any deleterious
effects on the host. Plate also records the occurrence of certain enigmatical
spherical bodies which were found in the blood or more usually in the cells
of the stomach. These bodies generally appeared when the Tardigrades were
kept in the same unchanged water for some weeks. Nothing certain is
known as to their nature or origin.
Systematic.—A good deal of work has recently been done by Mr. James
Murray on the Polar Tardigrades and on the Tardigrades of Scotland, many
of which have been collected by the staff of the Lake Survey.[380] Over forty
species have been described from North Britain.
The following table of Classification is based on that drawn up by Plate:
—
Page 537
Table of Genera.
I. The claws of the legs are simple, without a second hook. If there are
several on the same foot they are alike in structure and size.
A. The legs are short and broad, each with at least two claws.
2–4 claws Gen. 1. ECHINISCUS, C. Sch. (Fig. 249).
7–9 claws Sub-gen. 1a. ECHINISCOIDES, Plate.
B. The legs are long and slender; each bears only one small claw.
Gen. 2. LYDELLA, Doy.
II. The claws of the legs are all or partly two- or three-hooked.
Frequently they are of different lengths.
A. There are no processes or palps around the mouth.
I. The muscular sucking pharynx follows closely on the mouth-
tube.
α. The oral armature consists on each side of a stout tooth
and a transversely placed support.
Gen. 3. MACROBIOTUS, C. Sch. (Fig.
252).
β. The oral armature consists on each side of a stylet-like
tooth without support.
Gen. 4. DOYERIA, Plate.
II. The mouth-tube is separated from the muscular sucking
pharynx by a short oesophagus.
Gen. 5. DIPHASCON, Plate (Fig. 255).
B. Six short processes or palps surround the mouth, and two
others are placed a little farther back.
Gen. 6. MILNESIUM, Doy.
I. The claws of the legs are simple, without a second hook. If there are
several on the same foot they are alike in structure and size.
A. The legs are short and broad, each with at least two claws.
2–4 claws Gen. 1. ECHINISCUS, C. Sch. (Fig. 249).
7–9 claws Sub-gen. 1a. ECHINISCOIDES, Plate.
B. The legs are long and slender; each bears only one small claw.
Gen. 2. LYDELLA, Doy.
II. The claws of the legs are all or partly two- or three-hooked.
Frequently they are of different lengths.
A. There are no processes or palps around the mouth.
I. The muscular sucking pharynx follows closely on the mouth-
tube.
α. The oral armature consists on each side of a stout tooth
and a transversely placed support.
Gen. 3. MACROBIOTUS, C. Sch. (Fig.
252).
β. The oral armature consists on each side of a stylet-like
tooth without support.
Gen. 4. DOYERIA, Plate.
II. The mouth-tube is separated from the muscular sucking
pharynx by a short oesophagus.
Gen. 5. DIPHASCON, Plate (Fig. 255).
B. Six short processes or palps surround the mouth, and two
others are placed a little farther back.
Gen. 6. MILNESIUM, Doy.
Page 538
1. Genus ECHINISCUS (= EURYDIUM, Doy.).—The dorsal cuticle is
thick, and divided into a varying number of shields, which bear thread- or
spike-like projections. The anterior end forms a proboscis-like extension of
the body. Two red eye-spots. There are many species, and the number has
increased so rapidly in the last few years that specialists are talking of
splitting up the genus. E. arctomys, Ehrb.; E. mutabilis, Murray; E.
islandicus, Richters; E. gladiator, Murray; E. wendti, Richters; E.
reticulatus, Murray; E. oihonnae, Richters; E. granulatus, Doy.; E.
spitzbergensis, Scourfield;[381] E. quadrispinosus, Richters; and E.
muscicola, Plate, are all British. More than one-half of these species are
also Arctic, and E. arctomys is in addition Antarctic. In fact, the group is a
very cosmopolitan one. The genus is also widely distributed vertically,
specimens being found in cities on the sea level and on mountains up to a
height of over 11,000 feet.
1a. Sub-genus ECHINISCOIDES differs from the preceding in the
number of the claws, the want of definition in the dorsal plates, and in being
marine. The single species E. sigismundi, M. Sch., is found amongst algae
in the North Sea (Ostend and Heligoland).
2. Genus LYDELLA.[382]—The long, thin legs of this genus have two
segments, and in other respects approach the Arthropod limb. Marine. Plate
suggests the name L. dujardini for the single species known.
3. Genus MACROBIOTUS has a pigmented epidermis, but eye-spots may
be present or absent. The eggs are laid one at a time, or many leave the
body at once. They are either quite free or enclosed in a cast-off cuticle. The
genus is divided into many species and shows signs of disruption. They
mostly live amongst moss; but M. macronyx, Doy., is said to live in fresh
water. The following species are recorded from North Britain: M.
oberhäuseri, Doy.; M. hufelandi, Schultze; M. zetlandicus, Murray; M.
intermedius, Plate; M. angusti, Murray; M. annulatus, Murray; M.
tuberculatus, Plate; M. sattleri, Richters; M. papillifer, Murray; M.
coronifer, Richters; M. crenulatus, Richters; M. harmsworthi, Murray; M.
orcadensis, Murray; M. islandicus, Richters; M. dispar, Murray; M.
ambiguus, Murray; M. pullari, Murray; M. hastatus, Murray; M. dubius,
Murray; M. echinogenitus, Richters; M. ornatus, Richters; M. macronyx?,
Doy.
thick, and divided into a varying number of shields, which bear thread- or
spike-like projections. The anterior end forms a proboscis-like extension of
the body. Two red eye-spots. There are many species, and the number has
increased so rapidly in the last few years that specialists are talking of
splitting up the genus. E. arctomys, Ehrb.; E. mutabilis, Murray; E.
islandicus, Richters; E. gladiator, Murray; E. wendti, Richters; E.
reticulatus, Murray; E. oihonnae, Richters; E. granulatus, Doy.; E.
spitzbergensis, Scourfield;[381] E. quadrispinosus, Richters; and E.
muscicola, Plate, are all British. More than one-half of these species are
also Arctic, and E. arctomys is in addition Antarctic. In fact, the group is a
very cosmopolitan one. The genus is also widely distributed vertically,
specimens being found in cities on the sea level and on mountains up to a
height of over 11,000 feet.
1a. Sub-genus ECHINISCOIDES differs from the preceding in the
number of the claws, the want of definition in the dorsal plates, and in being
marine. The single species E. sigismundi, M. Sch., is found amongst algae
in the North Sea (Ostend and Heligoland).
2. Genus LYDELLA.[382]—The long, thin legs of this genus have two
segments, and in other respects approach the Arthropod limb. Marine. Plate
suggests the name L. dujardini for the single species known.
3. Genus MACROBIOTUS has a pigmented epidermis, but eye-spots may
be present or absent. The eggs are laid one at a time, or many leave the
body at once. They are either quite free or enclosed in a cast-off cuticle. The
genus is divided into many species and shows signs of disruption. They
mostly live amongst moss; but M. macronyx, Doy., is said to live in fresh
water. The following species are recorded from North Britain: M.
oberhäuseri, Doy.; M. hufelandi, Schultze; M. zetlandicus, Murray; M.
intermedius, Plate; M. angusti, Murray; M. annulatus, Murray; M.
tuberculatus, Plate; M. sattleri, Richters; M. papillifer, Murray; M.
coronifer, Richters; M. crenulatus, Richters; M. harmsworthi, Murray; M.
orcadensis, Murray; M. islandicus, Richters; M. dispar, Murray; M.
ambiguus, Murray; M. pullari, Murray; M. hastatus, Murray; M. dubius,
Murray; M. echinogenitus, Richters; M. ornatus, Richters; M. macronyx?,
Doy.
Page 539
4. Genus DOYERIA.—The teeth of
this genus have no support, and the
large salivary glands of the foregoing
genus are absent; in other respects
Doyeria, with the single species
Doyeria simplex, Plate, resembles
Macrobiotus, and is usually to be
found in consort with M. hufelandi,
C. Sch.
5. Genus DIPHASCON resembles
M. oberhäuseri, Doy., but an
oesophagus separates the mouth-tube
from the sucking pharynx, and the
oral armature is weak. The following
species are British, the first named
being very cosmopolitan, being
found at both Poles, in Chili, Europe,
and Asia: D. chilenense, Plate; D.
scoticum, Murray; D. bullatum,
Murray; D. angustatum, Murray; D.
oculatum, Murray; D. alpinum,
Murray; D. spitzbergense, Murray.
6. Genus MILNESIUM has a soft
oral armature, and the teeth open
straight into the mouth. A lens can
usually be distinguished in the eyes.
Two species have been described, M.
Fig. 255.—Diphascon chilenense, Plate, × about
tardigradum, Doy., British, and M.
100. (From Plate.) ce, Brain; k, thickening of the alpigenum, Ehrb. Bruce and Richters
epidermis above the mouth; o, egg; oe, consider that these two species are
oesophagus; p,?salivary glands; ph, pharynx; sa,
blood corpuscles; st, stomach.
identical.
this genus have no support, and the
large salivary glands of the foregoing
genus are absent; in other respects
Doyeria, with the single species
Doyeria simplex, Plate, resembles
Macrobiotus, and is usually to be
found in consort with M. hufelandi,
C. Sch.
5. Genus DIPHASCON resembles
M. oberhäuseri, Doy., but an
oesophagus separates the mouth-tube
from the sucking pharynx, and the
oral armature is weak. The following
species are British, the first named
being very cosmopolitan, being
found at both Poles, in Chili, Europe,
and Asia: D. chilenense, Plate; D.
scoticum, Murray; D. bullatum,
Murray; D. angustatum, Murray; D.
oculatum, Murray; D. alpinum,
Murray; D. spitzbergense, Murray.
6. Genus MILNESIUM has a soft
oral armature, and the teeth open
straight into the mouth. A lens can
usually be distinguished in the eyes.
Two species have been described, M.
Fig. 255.—Diphascon chilenense, Plate, × about
tardigradum, Doy., British, and M.
100. (From Plate.) ce, Brain; k, thickening of the alpigenum, Ehrb. Bruce and Richters
epidermis above the mouth; o, egg; oe, consider that these two species are
oesophagus; p,?salivary glands; ph, pharynx; sa,
blood corpuscles; st, stomach.
identical.
Page 540
CHAPTER XX
PENTASTOMIDA[383]
OCCURRENCE—ECONOMIC IMPORTANCE—STRUCTURE—
DEVELOPMENT AND LIFE-HISTORY—SYSTEMATIC
Pentastomids are unpleasant-looking, fluke-like or worm-like animals,
which pass their adult lives in the nasal cavities, frontal sinuses, and lungs
of flesh-eating animals, such as the Carnivora, Crocodiles, and Snakes;
more rarely in Lizards, Birds, or Fishes. From these retreats their eggs or
larvae are sneezed out or coughed up, or in some other way expelled from
the body of their primary host, and then if they are eaten, as they may well
be if they fall on grass, by some vegetable-feeding or omnivorous animal,
they undergo a further development. If uneaten the eggs die. When once in
the stomach of the second host, the egg-shell is dissolved and a larva
emerges (Fig. 260, p. 494), which bores through the stomach-wall and
comes to rest in a cyst in some of the neighbouring viscera. Here, with
occasional wanderings which may prove fatal to the host, it matures, and
should the second host be eaten by one of the first, the encysted form
escapes, makes its way to the nasal chambers or lungs, and attaching itself
by means of its two pairs of hooks, comes to rest on some surface capable
of affording nutriment. Having once taken up its position the female seldom
moves, but the males, which are smaller than the females, are more active.
They move about in search of a mate. Further, should the host die, both
sexes, after the manner of parasites, attempt to leave the body. Like most
animals who live entirely in the dark they develop no pigment, and have a
whitish, blanched appearance.
The only species of Pentastomid which has any economic importance is
Linguatula taenioides of Lamarck, which is found in the nose of the dog,
and much more rarely in the same position in the horse, mule, goat, sheep,
and man. It is a comparatively rare parasite, but occurred in about 10 per
cent of the 630 dogs in which it was sought at the laboratory of Alfort, near
PENTASTOMIDA[383]
OCCURRENCE—ECONOMIC IMPORTANCE—STRUCTURE—
DEVELOPMENT AND LIFE-HISTORY—SYSTEMATIC
Pentastomids are unpleasant-looking, fluke-like or worm-like animals,
which pass their adult lives in the nasal cavities, frontal sinuses, and lungs
of flesh-eating animals, such as the Carnivora, Crocodiles, and Snakes;
more rarely in Lizards, Birds, or Fishes. From these retreats their eggs or
larvae are sneezed out or coughed up, or in some other way expelled from
the body of their primary host, and then if they are eaten, as they may well
be if they fall on grass, by some vegetable-feeding or omnivorous animal,
they undergo a further development. If uneaten the eggs die. When once in
the stomach of the second host, the egg-shell is dissolved and a larva
emerges (Fig. 260, p. 494), which bores through the stomach-wall and
comes to rest in a cyst in some of the neighbouring viscera. Here, with
occasional wanderings which may prove fatal to the host, it matures, and
should the second host be eaten by one of the first, the encysted form
escapes, makes its way to the nasal chambers or lungs, and attaching itself
by means of its two pairs of hooks, comes to rest on some surface capable
of affording nutriment. Having once taken up its position the female seldom
moves, but the males, which are smaller than the females, are more active.
They move about in search of a mate. Further, should the host die, both
sexes, after the manner of parasites, attempt to leave the body. Like most
animals who live entirely in the dark they develop no pigment, and have a
whitish, blanched appearance.
The only species of Pentastomid which has any economic importance is
Linguatula taenioides of Lamarck, which is found in the nose of the dog,
and much more rarely in the same position in the horse, mule, goat, sheep,
and man. It is a comparatively rare parasite, but occurred in about 10 per
cent of the 630 dogs in which it was sought at the laboratory of Alfort, near
Page 541
Paris, and in 5 out of 60 dogs examined at Toulouse. The symptoms caused
by the presence of these parasites are not usually very severe, though cases
have been recorded where they have caused asphyxia. The larval stages
occur in the rabbit, sheep, ox, deer, guinea-pig, hare, rat, horse, camel, and
man, and by their wandering through the tissues may set up peritonitis and
other troubles.
As in the Cestoda, which they so closely resemble in their life-history,
the nomenclature of the Pentastomids has been complicated by their double
life. For long the larval form of L. taenioides was known by different names
in different hosts, e.g. Pentastoma denticulatum, Rud., when found in the
goat, P. serratum, Fröhlich, when found in the hare, P. emarginatum when
found in the guinea-pig, and so on. In the systematic section of this article
some of the species mentioned are known in the adult state, some in the
larval, and in only a few has the life-history been fully worked out.
Structure.[384]—The body of a Pentastomid is usually white, though in
the living condition it may be tinged red by the colour of the blood upon
which it lives. The anterior end, which bears the mouth and the hooks (Fig.
256), has no rings; this has been termed the cephalothorax. The rest of the
body, sometimes called the abdomen, is ringed, and each annulus is divided
into an anterior half dotted with the pores of certain epidermal glands and a
hinder part of the ring in which these are absent.
On the ventral surface of the cephalothorax, in the middle line, lies the
mouth, elevated on an oral papilla, and on each side of the mouth are a pair
of hooks whose bases are sunk in pits. The hooks can be protruded from the
pits, and serve as organs of attachment. Their shape has some systematic
value.
There are a pair of peculiar papillae which bear the openings of the
“hook-glands,” lying just in front of the pairs of hooks, and other smaller
papillae are arranged in pairs on the cephalothorax and anterior annuli. The
entire body is covered by a cuticle which is tucked in at the several orifices.
This is secreted by a continuous layer of ectoderm cells. Some of these
subcuticular cells are aggregated together to form very definite glands
opening through the cuticle by pores which have somewhat unfortunately
received the name of stigmata. Spencer attributes to these glands a general
excretory function. There is, however, a very special pair of glands, the
hook-glands, which extend almost from one end to the other of the body;
by the presence of these parasites are not usually very severe, though cases
have been recorded where they have caused asphyxia. The larval stages
occur in the rabbit, sheep, ox, deer, guinea-pig, hare, rat, horse, camel, and
man, and by their wandering through the tissues may set up peritonitis and
other troubles.
As in the Cestoda, which they so closely resemble in their life-history,
the nomenclature of the Pentastomids has been complicated by their double
life. For long the larval form of L. taenioides was known by different names
in different hosts, e.g. Pentastoma denticulatum, Rud., when found in the
goat, P. serratum, Fröhlich, when found in the hare, P. emarginatum when
found in the guinea-pig, and so on. In the systematic section of this article
some of the species mentioned are known in the adult state, some in the
larval, and in only a few has the life-history been fully worked out.
Structure.[384]—The body of a Pentastomid is usually white, though in
the living condition it may be tinged red by the colour of the blood upon
which it lives. The anterior end, which bears the mouth and the hooks (Fig.
256), has no rings; this has been termed the cephalothorax. The rest of the
body, sometimes called the abdomen, is ringed, and each annulus is divided
into an anterior half dotted with the pores of certain epidermal glands and a
hinder part of the ring in which these are absent.
On the ventral surface of the cephalothorax, in the middle line, lies the
mouth, elevated on an oral papilla, and on each side of the mouth are a pair
of hooks whose bases are sunk in pits. The hooks can be protruded from the
pits, and serve as organs of attachment. Their shape has some systematic
value.
There are a pair of peculiar papillae which bear the openings of the
“hook-glands,” lying just in front of the pairs of hooks, and other smaller
papillae are arranged in pairs on the cephalothorax and anterior annuli. The
entire body is covered by a cuticle which is tucked in at the several orifices.
This is secreted by a continuous layer of ectoderm cells. Some of these
subcuticular cells are aggregated together to form very definite glands
opening through the cuticle by pores which have somewhat unfortunately
received the name of stigmata. Spencer attributes to these glands a general
excretory function. There is, however, a very special pair of glands, the
hook-glands, which extend almost from one end to the other of the body;
Page 542
anteriorly these two lateral glands
unite and form the head-gland (Fig.
257). From this on each side three
ducts pass, one of which opens to the
surface on the primary papilla; the
other two ducts open at the base of
the two hooks which lie on each side
of the mouth. Leuckart has suggested
that these important glands secrete
some fluid like the irritating saliva of
a Mosquito which induces an
increased flow of blood to the place
where it is of use to the parasite.
Spencer, however, regards the
secretion as having, like the secretion
of the so-called salivary cells of the
Leech, a retarding action on the
coagulation of the blood of the host.
The muscles of Pentastomids are
striated. There is a circular layer
within the subcuticular cells, and
within this a longitudinal layer and
an oblique layer which runs across
the body-cavity from the dorso-
lateral surface to the mid-ventral line,
a primitive arrangement which Fig. 256.—Porocephalus annulatus, Baird. A,
Ventral view of head, × 6; B, ventral view of
recalls the similar division of the animal, × 2.
body-cavity into three chambers in
Peripatus and in many Chaetopods.
Besides these there are certain muscles which move the hooks and other
structures.
The mouth opens into a pharynx which runs upwards and then backwards
to open into the oesophagus (Fig. 257). Certain muscles attached to these
parts enlarge their cavities, and thus give rise to a sucking action by whose
force the blood of the host is taken into the alimentary canal. The
oesophagus opens by a funnel-shaped valve into the capacious stomach or
unite and form the head-gland (Fig.
257). From this on each side three
ducts pass, one of which opens to the
surface on the primary papilla; the
other two ducts open at the base of
the two hooks which lie on each side
of the mouth. Leuckart has suggested
that these important glands secrete
some fluid like the irritating saliva of
a Mosquito which induces an
increased flow of blood to the place
where it is of use to the parasite.
Spencer, however, regards the
secretion as having, like the secretion
of the so-called salivary cells of the
Leech, a retarding action on the
coagulation of the blood of the host.
The muscles of Pentastomids are
striated. There is a circular layer
within the subcuticular cells, and
within this a longitudinal layer and
an oblique layer which runs across
the body-cavity from the dorso-
lateral surface to the mid-ventral line,
a primitive arrangement which Fig. 256.—Porocephalus annulatus, Baird. A,
Ventral view of head, × 6; B, ventral view of
recalls the similar division of the animal, × 2.
body-cavity into three chambers in
Peripatus and in many Chaetopods.
Besides these there are certain muscles which move the hooks and other
structures.
The mouth opens into a pharynx which runs upwards and then backwards
to open into the oesophagus (Fig. 257). Certain muscles attached to these
parts enlarge their cavities, and thus give rise to a sucking action by whose
force the blood of the host is taken into the alimentary canal. The
oesophagus opens by a funnel-shaped valve into the capacious stomach or
Page 543
mid-gut, which stretches through the body to end in a short rectum or hind-
gut. The anus is terminal.
Fig. 257.—Diagrammatic representation of the alimentary, secretory, nervous,
and reproductive systems of a male Porocephalus teretiusculus, seen from the
side. The nerves are represented by solid black lines. (From W. Baldwin
Spencer.)
1, Head-gland; 2, testis; 3, hook-gland; 4, hind-gut; 5, mid-gut; 6, ejaculatory
duct; 7, vesicula seminalis; 8, vas deferens; 9, dilator-rod sac; 10, cirrus-bulb;
11, cirrus-sac; 12, fore-gut; 13, oral papillae.
There appears to be no trace of circulatory or respiratory organs, whilst
the function usually exercised by the nephridia or Malpighian tubules or by
coxal glands, of removing waste nitrogenous matter, seems, according to
Spencer, to be transferred to the skin-glands.
The nervous system is aggregated into a large ventral ganglion which lies
behind the oesophagus. It gives off a narrow band devoid of ganglion-cells,
which encircles that tube. It also gives off eight nerves supplying various
parts, and is continued backward as a ninth pair of prolongations which,
running along the ventral surface, reach almost to the end of the body (Fig.
257). The only sense-organs known are certain paired papillae on the head,
which is the portion that most closely comes in contact with the tissues of
the host.
Pentastomids are bisexual. The males are as a rule much less numerous
and considerably smaller than the females, although the number of annuli
may be greater.
The ovary consists of a single tube closed behind. This is supported by a
median mesentery. Anteriorly the ovary passes into a right and left oviduct,
which, traversing the large hook-gland, encircle the alimentary canal and
the two posterior nerves (Fig. 258). They then unite, and at their point of
union they receive the ducts of the two spermathecae, usually found packed
gut. The anus is terminal.
Fig. 257.—Diagrammatic representation of the alimentary, secretory, nervous,
and reproductive systems of a male Porocephalus teretiusculus, seen from the
side. The nerves are represented by solid black lines. (From W. Baldwin
Spencer.)
1, Head-gland; 2, testis; 3, hook-gland; 4, hind-gut; 5, mid-gut; 6, ejaculatory
duct; 7, vesicula seminalis; 8, vas deferens; 9, dilator-rod sac; 10, cirrus-bulb;
11, cirrus-sac; 12, fore-gut; 13, oral papillae.
There appears to be no trace of circulatory or respiratory organs, whilst
the function usually exercised by the nephridia or Malpighian tubules or by
coxal glands, of removing waste nitrogenous matter, seems, according to
Spencer, to be transferred to the skin-glands.
The nervous system is aggregated into a large ventral ganglion which lies
behind the oesophagus. It gives off a narrow band devoid of ganglion-cells,
which encircles that tube. It also gives off eight nerves supplying various
parts, and is continued backward as a ninth pair of prolongations which,
running along the ventral surface, reach almost to the end of the body (Fig.
257). The only sense-organs known are certain paired papillae on the head,
which is the portion that most closely comes in contact with the tissues of
the host.
Pentastomids are bisexual. The males are as a rule much less numerous
and considerably smaller than the females, although the number of annuli
may be greater.
The ovary consists of a single tube closed behind. This is supported by a
median mesentery. Anteriorly the ovary passes into a right and left oviduct,
which, traversing the large hook-gland, encircle the alimentary canal and
the two posterior nerves (Fig. 258). They then unite, and at their point of
union they receive the ducts of the two spermathecae, usually found packed
Page 544
with spermatozoa. Having received the orifices of the spermatheca, the
united oviducts are continued backward as the uterus, a highly-coiled tube
in which the fertilised eggs are stored. These are very numerous; Leuckart
estimated that a single female may contain half a million eggs. The uterus
opens to the exterior in the mid-ventral line a short distance—in P.
teretiusculus on the last ring but seven—in front of the terminal anus. In L.
taenioides the eggs begin to be laid in the mucus of the nose some six
months after the parasite has taken up its position.
Fig. 258.—Diagrammatic representation of the alimentary, secretory, nervous,
and reproductive systems of a female Porocephalus teretiusculus, seen from the
side. The nerves are represented by solid black lines. (From W. Baldwin
Spencer.)
1, Head-gland; 2, oviduct; 3, hook-gland; 4, mid-gut; 5, ovary; 6, hind-gut; 7,
vagina; 8, uterus; 9, accessory gland; 10, spermatheca.
The testis is a single tube occupying in the male a position similar to that
of the ovary in the female. Anteriorly it opens into two vesiculae seminales,
which, like the oviducts, pierce the hook-glands and encircle the alimentary
canal (Fig. 257). Each vesicula passes into a vas deferens with a cuticular
lining. Each vas deferens also receives the orifice of a muscular caecal
ejaculatory duct, which, crowded with mature spermatozoa, stretches back
through the body. Anteriorly the vas deferens passes into a cirrus-bulb,
which is joined by a cirrus-sac on one side and a dilator-rod sac on the
other, structures containing organs that assist in introducing the
spermatozoa into the female. The two tubes then unite, and having received
a dorsally-placed accessory gland, open to the exterior by a median aperture
placed ventrally a little way behind the mouth.
Life-history.—The egg undergoes a large portion of its development
within the body of the mother. In Linguatula taenioides, which lives in the
nasal cavities of the dog, the eggs pass away with the nasal excretions. If
united oviducts are continued backward as the uterus, a highly-coiled tube
in which the fertilised eggs are stored. These are very numerous; Leuckart
estimated that a single female may contain half a million eggs. The uterus
opens to the exterior in the mid-ventral line a short distance—in P.
teretiusculus on the last ring but seven—in front of the terminal anus. In L.
taenioides the eggs begin to be laid in the mucus of the nose some six
months after the parasite has taken up its position.
Fig. 258.—Diagrammatic representation of the alimentary, secretory, nervous,
and reproductive systems of a female Porocephalus teretiusculus, seen from the
side. The nerves are represented by solid black lines. (From W. Baldwin
Spencer.)
1, Head-gland; 2, oviduct; 3, hook-gland; 4, mid-gut; 5, ovary; 6, hind-gut; 7,
vagina; 8, uterus; 9, accessory gland; 10, spermatheca.
The testis is a single tube occupying in the male a position similar to that
of the ovary in the female. Anteriorly it opens into two vesiculae seminales,
which, like the oviducts, pierce the hook-glands and encircle the alimentary
canal (Fig. 257). Each vesicula passes into a vas deferens with a cuticular
lining. Each vas deferens also receives the orifice of a muscular caecal
ejaculatory duct, which, crowded with mature spermatozoa, stretches back
through the body. Anteriorly the vas deferens passes into a cirrus-bulb,
which is joined by a cirrus-sac on one side and a dilator-rod sac on the
other, structures containing organs that assist in introducing the
spermatozoa into the female. The two tubes then unite, and having received
a dorsally-placed accessory gland, open to the exterior by a median aperture
placed ventrally a little way behind the mouth.
Life-history.—The egg undergoes a large portion of its development
within the body of the mother. In Linguatula taenioides, which lives in the
nasal cavities of the dog, the eggs pass away with the nasal excretions. If
Page 545
these, scattered about in the grass, etc., be eaten by a rabbit, the egg-shell is
dissolved in the stomach of the second host and a small larva is set free. In
Porocephalus proboscideus and others, which inhabit the lungs of snakes,
the eggs pass along the alimentary canal and leave the body with the faeces.
They also must be eaten by a second host if development is to proceed.
The larva which emerges when the
egg-shell is dissolved has a rounded
body provided with two pairs of
hooked appendages, and a tail which
is more or less prominent in different
species (Figs. 259, 260). Each
appendage bears a claw, and is
strengthened by a supporting rod or
skeleton. Anteriorly the head bears a
boring apparatus of several chitinous
stylets. The various internal organs
are in this stage already formed,
though in a somewhat rudimentary Fig. 259.—A late larval stage of Porocephalus
state, and it is doubtful if the anus proboscideus, seen from the side. Highly
magnified. (From Stiles.) 1, primordium of first
has yet appeared. pair of chitinous processes; 2, primordium of
By means of its boring apparatus, second pair of chitinous processes; 3, mouth; 4,
ventral ganglion; 5, receptaculum seminis; 6,
and aided by its hooked limbs, the oviduct; 7, ovary; 8, anus; 9, vagina.
larva now works its way through the
stomach-walls of its second host, and
comes to rest in the liver or in some other viscus. Its presence in the tissues
of its second host causes the formation of a cyst, and within this the larva
rests and develops. In man, at least, the cysts often undergo a calcareous
degeneration, and Virchow states “dass beim Menschen das Pentastomum
am häufigsten von allen Entozoen zu Verwechselungen mit echten
Tuberkeln Veranlassungen giebt.” The larva moults several times, and loses
its limbs, which seem to have no connexion with the paired hooks in the
adult (Fig. 256). The internal organs slowly assume the form they possess in
the adult. The larva is at first quite smooth, but as it grows the annulations
make their appearance, arising in the middle and spreading forward and
backward (Fig. 259). In this encysted condition the larva remains coiled up
for some months, according to Leuckart; six in the case of L. taenioides,
dissolved in the stomach of the second host and a small larva is set free. In
Porocephalus proboscideus and others, which inhabit the lungs of snakes,
the eggs pass along the alimentary canal and leave the body with the faeces.
They also must be eaten by a second host if development is to proceed.
The larva which emerges when the
egg-shell is dissolved has a rounded
body provided with two pairs of
hooked appendages, and a tail which
is more or less prominent in different
species (Figs. 259, 260). Each
appendage bears a claw, and is
strengthened by a supporting rod or
skeleton. Anteriorly the head bears a
boring apparatus of several chitinous
stylets. The various internal organs
are in this stage already formed,
though in a somewhat rudimentary Fig. 259.—A late larval stage of Porocephalus
state, and it is doubtful if the anus proboscideus, seen from the side. Highly
magnified. (From Stiles.) 1, primordium of first
has yet appeared. pair of chitinous processes; 2, primordium of
By means of its boring apparatus, second pair of chitinous processes; 3, mouth; 4,
ventral ganglion; 5, receptaculum seminis; 6,
and aided by its hooked limbs, the oviduct; 7, ovary; 8, anus; 9, vagina.
larva now works its way through the
stomach-walls of its second host, and
comes to rest in the liver or in some other viscus. Its presence in the tissues
of its second host causes the formation of a cyst, and within this the larva
rests and develops. In man, at least, the cysts often undergo a calcareous
degeneration, and Virchow states “dass beim Menschen das Pentastomum
am häufigsten von allen Entozoen zu Verwechselungen mit echten
Tuberkeln Veranlassungen giebt.” The larva moults several times, and loses
its limbs, which seem to have no connexion with the paired hooks in the
adult (Fig. 256). The internal organs slowly assume the form they possess in
the adult. The larva is at first quite smooth, but as it grows the annulations
make their appearance, arising in the middle and spreading forward and
backward (Fig. 259). In this encysted condition the larva remains coiled up
for some months, according to Leuckart; six in the case of L. taenioides,
Page 546
and a somewhat shorter period,
according to Stiles,[385] in the case of
P. proboscideus.
The frequency of what used to be
called Pentastoma denticulatum (=
the larval form of L. taenioides) in
the body of man depends on the
familiarity of man with dogs. Klebs
and Zaeslin found one larva in 900
and two in 1914 autopsies.
Laenger[386] found the larva fifteen
times in about 400 dissections, once
in the mesentery, seven times in the
liver, and seven times in the wall of
the intestine. After remaining
Fig. 260.—Larva of Porocephalus encysted for some time it may
proboscideus, seen from below. Highly escape, and begins wandering
magnified. (From Stiles.) 1, Boring, anterior
end; 2, first pair of chitinous processes seen through the tissues, aided by its
between the forks of the second pair; 3, ventral hooks and annulations, a proceeding
nerve-ganglion; 4, alimentary canal; 5, mouth; 6 not unaccompanied by danger to its
and 7, gland-cells.
host. Should the latter be eaten by
some carnivorous animal, the larva
makes its way into the nasal cavities or sinuses, or into the lungs of the
flesh-eating creature, and there after another ecdysis it becomes adult. If,
however, the second host escapes this fate, the larvae re-encyst themselves,
and then if swallowed they are said to bore through the intestine of the
flesh-eater, and so make their way to their adult abode.
Systematic.[387]—The Pentastomida are a group much modified by
parasitism, which has so deeply moulded their structure as to obscure to a
great extent their origin and affinities. The larva, with its clawed limbs,
recalls the Tardigrades and certain Mites, e.g. Phytoptus, where only two
pairs of limbs persist, and where the abdomen is elongated and forms a
large proportion of the body. The resemblances to a single and somewhat
aberrant genus must not, however, be pressed too far. The striated muscles,
the ring-like nature of the reproductive organs and their ducts, perhaps even
the disproportion both in size and number of the females to the males, are
also characters common to many Arachnids.
according to Stiles,[385] in the case of
P. proboscideus.
The frequency of what used to be
called Pentastoma denticulatum (=
the larval form of L. taenioides) in
the body of man depends on the
familiarity of man with dogs. Klebs
and Zaeslin found one larva in 900
and two in 1914 autopsies.
Laenger[386] found the larva fifteen
times in about 400 dissections, once
in the mesentery, seven times in the
liver, and seven times in the wall of
the intestine. After remaining
Fig. 260.—Larva of Porocephalus encysted for some time it may
proboscideus, seen from below. Highly escape, and begins wandering
magnified. (From Stiles.) 1, Boring, anterior
end; 2, first pair of chitinous processes seen through the tissues, aided by its
between the forks of the second pair; 3, ventral hooks and annulations, a proceeding
nerve-ganglion; 4, alimentary canal; 5, mouth; 6 not unaccompanied by danger to its
and 7, gland-cells.
host. Should the latter be eaten by
some carnivorous animal, the larva
makes its way into the nasal cavities or sinuses, or into the lungs of the
flesh-eating creature, and there after another ecdysis it becomes adult. If,
however, the second host escapes this fate, the larvae re-encyst themselves,
and then if swallowed they are said to bore through the intestine of the
flesh-eater, and so make their way to their adult abode.
Systematic.[387]—The Pentastomida are a group much modified by
parasitism, which has so deeply moulded their structure as to obscure to a
great extent their origin and affinities. The larva, with its clawed limbs,
recalls the Tardigrades and certain Mites, e.g. Phytoptus, where only two
pairs of limbs persist, and where the abdomen is elongated and forms a
large proportion of the body. The resemblances to a single and somewhat
aberrant genus must not, however, be pressed too far. The striated muscles,
the ring-like nature of the reproductive organs and their ducts, perhaps even
the disproportion both in size and number of the females to the males, are
also characters common to many Arachnids.
Page 547
The Pentastomida include three
genera, Linguatula, Fröhlich,
Porocephalus, Humboldt, and
[388]
Reighardia, Ward. The first two
were regarded by Leuckart as but
sub-genera, but Railliet[389] and
Hoyle[390] have raised them to the
rank of genera. They are
characterised as follows:—
Linguatula, body flattened, but
dorsal surface arched; the edges of
the fluke-like body crenelated; the
body-cavity extends as diverticula
into the edges of the body. Fig. 261.—Encysted form of Porocephalus
protelis, × 1, lying in the mesentery of its host.
Porocephalus, body cylindrical, (From Hoyle.)
with no diverticula of the body-
cavity.
Reighardia, devoid of annulations, transparent, with poorly developed
hooks and a mouth-armature.
The following is a list of the species with their primary and secondary or
larval hosts:—
i. Linguatula pusilla, Diesing, found in the intestine of the fresh-water
fish Acara, a South American genus of the Cichlidae. This is possibly
the immature form of L. subtriquetra.
ii. L. recurvata, Diesing, found in the frontal sinuses and the trachea of
Felis onca.
iii. L. subtriquetra, Diesing, found in the throat of Caiman latirostris and
C. sclerops, perhaps the mature form of L. pusilla.
iv. L. taenioides, Lamarck, found in the frontal sinuses and nasal
chambers of the dog and ounce, and in the nasal cavities of the wolf,
fox, goat, horse, mule, sheep, and man, and in the trachea of the ounce.
The immature form has been found in or on the liver of the cat, guinea-
pig, and horse; in the lungs of the ox, cat, guinea-pig, porcupine, hare,
and rabbit; in the liver and connective tissue of the small intestine of
genera, Linguatula, Fröhlich,
Porocephalus, Humboldt, and
[388]
Reighardia, Ward. The first two
were regarded by Leuckart as but
sub-genera, but Railliet[389] and
Hoyle[390] have raised them to the
rank of genera. They are
characterised as follows:—
Linguatula, body flattened, but
dorsal surface arched; the edges of
the fluke-like body crenelated; the
body-cavity extends as diverticula
into the edges of the body. Fig. 261.—Encysted form of Porocephalus
protelis, × 1, lying in the mesentery of its host.
Porocephalus, body cylindrical, (From Hoyle.)
with no diverticula of the body-
cavity.
Reighardia, devoid of annulations, transparent, with poorly developed
hooks and a mouth-armature.
The following is a list of the species with their primary and secondary or
larval hosts:—
i. Linguatula pusilla, Diesing, found in the intestine of the fresh-water
fish Acara, a South American genus of the Cichlidae. This is possibly
the immature form of L. subtriquetra.
ii. L. recurvata, Diesing, found in the frontal sinuses and the trachea of
Felis onca.
iii. L. subtriquetra, Diesing, found in the throat of Caiman latirostris and
C. sclerops, perhaps the mature form of L. pusilla.
iv. L. taenioides, Lamarck, found in the frontal sinuses and nasal
chambers of the dog and ounce, and in the nasal cavities of the wolf,
fox, goat, horse, mule, sheep, and man, and in the trachea of the ounce.
The immature form has been found in or on the liver of the cat, guinea-
pig, and horse; in the lungs of the ox, cat, guinea-pig, porcupine, hare,
and rabbit; in the liver and connective tissue of the small intestine of
Page 548
man; and in the mesenteric glands of the ox, camel, goat, sheep,
antelope, fallow-deer, and mouse.
v. Porocephalus annulatus, Baird, found in the lungs of the Egyptian
cobra, Naja haje; the immature form is thought to live encapsuled in a
species of Porphyrio[391] and in the Numidian Crane.
vi. P. aonycis, Macalister, from the lungs of an Indian otter taken in the
Indus.
vii. P. armillatus, Wyman, found in the adult state in the lungs of certain
African pythons, and in the lion; in the larval form it occurs encysted in
the abdomen of the Aard-wolf, the mandril, and man—usually in
negroes. Its migrations in the body of its second host sometimes cause
fatal results.
viii. P. bifurcatus, Diesing, found in the body-cavity of certain snakes,
and in the lungs of boa-constrictors and the legless lizard, Amphisbaena
alba. Possibly an immature form.
ix. P. clavatus, Lohrmann, found in the lungs of the Monitor lizard.
x. P. crocidura, Parona, found in the peritoneum of the “musk-rat”
Crocidura in Burmah. Probably a larval form.
xi. P. crotali, Humboldt, found in the lungs, body-cavity, kidneys, spleen,
and mesentery of many snakes and lizards, and of the lion and leopard.
The immature forms occur in the liver and abdominal cavity of species
of opossum, armadillo, mouse, raccoon, bat, and marmoset.
xii. P. geckonis, Dujardin, found in the lungs of a Siamese gecko.
xiii. P. gracilis, Diesing, found free in the body-cavity or encapsuled on
the viscera and mesenteries of South American fishes, snakes, and
lizards,
xiv. P. heterodontis; Leuckart, found encapsuled in the abdominal
muscles and mesentery of a species of Heterodon.
xv. P. indicus,[392] v. Linst., found in the trachea and lungs of Gavialis
gangeticus.
xvi. P. lari, Mégnin, found in the air-sacs of the Burgomaster or Glaucous
gull, Larus glaucus of the Polar seas.
antelope, fallow-deer, and mouse.
v. Porocephalus annulatus, Baird, found in the lungs of the Egyptian
cobra, Naja haje; the immature form is thought to live encapsuled in a
species of Porphyrio[391] and in the Numidian Crane.
vi. P. aonycis, Macalister, from the lungs of an Indian otter taken in the
Indus.
vii. P. armillatus, Wyman, found in the adult state in the lungs of certain
African pythons, and in the lion; in the larval form it occurs encysted in
the abdomen of the Aard-wolf, the mandril, and man—usually in
negroes. Its migrations in the body of its second host sometimes cause
fatal results.
viii. P. bifurcatus, Diesing, found in the body-cavity of certain snakes,
and in the lungs of boa-constrictors and the legless lizard, Amphisbaena
alba. Possibly an immature form.
ix. P. clavatus, Lohrmann, found in the lungs of the Monitor lizard.
x. P. crocidura, Parona, found in the peritoneum of the “musk-rat”
Crocidura in Burmah. Probably a larval form.
xi. P. crotali, Humboldt, found in the lungs, body-cavity, kidneys, spleen,
and mesentery of many snakes and lizards, and of the lion and leopard.
The immature forms occur in the liver and abdominal cavity of species
of opossum, armadillo, mouse, raccoon, bat, and marmoset.
xii. P. geckonis, Dujardin, found in the lungs of a Siamese gecko.
xiii. P. gracilis, Diesing, found free in the body-cavity or encapsuled on
the viscera and mesenteries of South American fishes, snakes, and
lizards,
xiv. P. heterodontis; Leuckart, found encapsuled in the abdominal
muscles and mesentery of a species of Heterodon.
xv. P. indicus,[392] v. Linst., found in the trachea and lungs of Gavialis
gangeticus.
xvi. P. lari, Mégnin, found in the air-sacs of the Burgomaster or Glaucous
gull, Larus glaucus of the Polar seas.
Page 549
xvii. P. megacephalus, Baird, found embedded in the flesh of the head of
an Indian crocodile, C. palustris, the “Mugger.” Probably a larval form.
xviii. P. megastomus, Diesing, found in the lungs of a fresh-water
tortoise, Hydraspis geoffroyana.
xix. P. moniliformis, Diesing, found in the lungs of pythons.
xx. P. najae sputatricis, Leuckart, found encapsuled in the abdominal
muscles and peritoneum of the cobra, Naja tripudians. Probably a
larval form.
xxi. P. oxycephalus, Diesing, found in the lungs of crocodiles and
alligators.
xxii. P. platycephalus, Lohrmann, habitat unknown.
xxiii. P. subuliferus, Leuckart, in the lungs of the cobra Naja haje.
xxiv. P. teretiusculus, Baird, found in the lungs and mouth of certain
Australian snakes.
xxv. P. tortus, Shipley, found in the body-cavity of a snake,
Dipsadomorphus irregularis, taken in New Britain.
xxvi. Reighardia, sp., Ward, found in the air-sacs of Bonaparte’s gull and
the common North American tern.
an Indian crocodile, C. palustris, the “Mugger.” Probably a larval form.
xviii. P. megastomus, Diesing, found in the lungs of a fresh-water
tortoise, Hydraspis geoffroyana.
xix. P. moniliformis, Diesing, found in the lungs of pythons.
xx. P. najae sputatricis, Leuckart, found encapsuled in the abdominal
muscles and peritoneum of the cobra, Naja tripudians. Probably a
larval form.
xxi. P. oxycephalus, Diesing, found in the lungs of crocodiles and
alligators.
xxii. P. platycephalus, Lohrmann, habitat unknown.
xxiii. P. subuliferus, Leuckart, in the lungs of the cobra Naja haje.
xxiv. P. teretiusculus, Baird, found in the lungs and mouth of certain
Australian snakes.
xxv. P. tortus, Shipley, found in the body-cavity of a snake,
Dipsadomorphus irregularis, taken in New Britain.
xxvi. Reighardia, sp., Ward, found in the air-sacs of Bonaparte’s gull and
the common North American tern.
Page 550
PYCNOGONIDA
BY
D’ARCY W. THOMPSON, C.B., M.A. Trinity College
Professor of Natural History in University College, Dundee
BY
D’ARCY W. THOMPSON, C.B., M.A. Trinity College
Professor of Natural History in University College, Dundee
Page 551
CHAPTER XXI
PYCNOGONIDA[393]
Remote, so far as we at present see, from all other Arthropods, while yet
manifesting the most patent features of the Arthropod type, the Pycnogons
constitute a little group, easily recognised and characterised, abundant and
omnipresent in the sea. The student of the foreshore finds few species and
seldom many individuals, but the dredger in deep waters meets at times
with prodigious numbers, lending a character to the fauna over great areas.
The commonest of our native
species, or that at least which we find
the oftenest, is Pycnogonum littorale
(Phalangium littorale, Ström, 1762).
We find it under stones near low
water, or often clinging louse-like to
a large Anemone. The squat
segmented trunk carries, on four
pairs of strong lateral processes, as
many legs, long, robust, eight-
jointed, furnished each with a sharp
terminal claw. In front the trunk bears
a long, stout, tubular proboscis, at the
apex of which is the mouth, suctorial,
devoid of jaws; the body terminates Fig. 262.—Pycnogonum littorale, Ström, × 2.
in a narrow, limbless, unsegmented
process, the so-called “abdomen,” at
the end of which is the anal orifice. The body-ring to which is attached the
first pair of legs, bears a tubercle carrying four eye-spots; and below, it
carries, in the male sex, a pair of small limbs, whose function is to grasp
and hold the eggs, of which the male animal assumes the burden, carrying
them beneath his body in a flattened coherent mass. In either sex a pair of
sexual apertures open on the second joints of the last pair of legs. The
PYCNOGONIDA[393]
Remote, so far as we at present see, from all other Arthropods, while yet
manifesting the most patent features of the Arthropod type, the Pycnogons
constitute a little group, easily recognised and characterised, abundant and
omnipresent in the sea. The student of the foreshore finds few species and
seldom many individuals, but the dredger in deep waters meets at times
with prodigious numbers, lending a character to the fauna over great areas.
The commonest of our native
species, or that at least which we find
the oftenest, is Pycnogonum littorale
(Phalangium littorale, Ström, 1762).
We find it under stones near low
water, or often clinging louse-like to
a large Anemone. The squat
segmented trunk carries, on four
pairs of strong lateral processes, as
many legs, long, robust, eight-
jointed, furnished each with a sharp
terminal claw. In front the trunk bears
a long, stout, tubular proboscis, at the
apex of which is the mouth, suctorial,
devoid of jaws; the body terminates Fig. 262.—Pycnogonum littorale, Ström, × 2.
in a narrow, limbless, unsegmented
process, the so-called “abdomen,” at
the end of which is the anal orifice. The body-ring to which is attached the
first pair of legs, bears a tubercle carrying four eye-spots; and below, it
carries, in the male sex, a pair of small limbs, whose function is to grasp
and hold the eggs, of which the male animal assumes the burden, carrying
them beneath his body in a flattened coherent mass. In either sex a pair of
sexual apertures open on the second joints of the last pair of legs. The
Page 552
integument of body and limbs is very strongly chitinised, brown in colour,
and raised into strong bosses or tubercles along the middle line of the back,
over the lateral processes, and from joint to joint of the limbs. The whole
animal has a singular likeness to the Whale-louse, Cyamus mysticeti (well
described by Fr. Martins in 1675), that clings to the skin of the Greenland
Whale as does Pycnogonum to the Anemone, a resemblance close enough
to mislead some of the older naturalists, and so close that Linnaeus, though
in no way misled thereby, named it Phalangium balaenarum. The substance
of the above account, and the perplexity attending the classification of the
animal, are all included in Linnaeus’s short description:[394] “Simillimus
Onisco Ceti, sed pedes omnes pluribus articulis, omnes perfecti, nec plures
quam octo. Dorsum rubrum, pluribus segmentis; singulis tribus mucronibus.
Cauda cylindrica, brevissima, truncata. Rostrum membranaceum,
subsubulatum, longitudine pedum. Genus dubium, facie Onisci ceti; rostro a
reliquis diversum. Cum solo rostro absque maxillis sit forte aptius Acaris
aut proprio generi subjiciendum.... Habitat in mari norvegico sub
lapidibus.”[395]
The common Pycnogonum is, by reason of the suppression of certain
limbs, rather an outlying member than a typical representative of the Order,
whose common characters are more strikingly and more perfectly shown in
species, for instance, of Nymphon. Of this multiform genus we have many
British species, some of the smaller being common below tide-marks,
creeping among weeds or clinging like Caprellae with skeleton limbs to the
branches of Zoophytes, where their slender forms are not easily seen. In
contrast to the stouter body and limbs of Pycnogonum, the whole fabric of
Nymphon tends to elongation; the body is drawn out so that the successive
lateral processes stand far apart, and a slender neck intervenes between the
oculiferous tubercle and the proboscis; the legs are produced to an amazing
length and an extreme degree of attenuation: “mirum tam parvum corpus
regere tam magnos pedes,” says Linnaeus. Above the base of the proboscis
are a pair of three-jointed appendages, the two terminal joints of which
compose a forcipate claw; below and behind these come a pair of delicate,
palp-like limbs of five joints; and lastly, on the ventral side, some little way
behind these, we find the ovigerous legs that we have already seen in the
male Pycnogonum, but which are present in both sexes in the case of
Nymphon. At the base of the claw which terminates each of the eight long
ambulatory legs stands a pair of smaller accessory or “auxiliary” claws. The
and raised into strong bosses or tubercles along the middle line of the back,
over the lateral processes, and from joint to joint of the limbs. The whole
animal has a singular likeness to the Whale-louse, Cyamus mysticeti (well
described by Fr. Martins in 1675), that clings to the skin of the Greenland
Whale as does Pycnogonum to the Anemone, a resemblance close enough
to mislead some of the older naturalists, and so close that Linnaeus, though
in no way misled thereby, named it Phalangium balaenarum. The substance
of the above account, and the perplexity attending the classification of the
animal, are all included in Linnaeus’s short description:[394] “Simillimus
Onisco Ceti, sed pedes omnes pluribus articulis, omnes perfecti, nec plures
quam octo. Dorsum rubrum, pluribus segmentis; singulis tribus mucronibus.
Cauda cylindrica, brevissima, truncata. Rostrum membranaceum,
subsubulatum, longitudine pedum. Genus dubium, facie Onisci ceti; rostro a
reliquis diversum. Cum solo rostro absque maxillis sit forte aptius Acaris
aut proprio generi subjiciendum.... Habitat in mari norvegico sub
lapidibus.”[395]
The common Pycnogonum is, by reason of the suppression of certain
limbs, rather an outlying member than a typical representative of the Order,
whose common characters are more strikingly and more perfectly shown in
species, for instance, of Nymphon. Of this multiform genus we have many
British species, some of the smaller being common below tide-marks,
creeping among weeds or clinging like Caprellae with skeleton limbs to the
branches of Zoophytes, where their slender forms are not easily seen. In
contrast to the stouter body and limbs of Pycnogonum, the whole fabric of
Nymphon tends to elongation; the body is drawn out so that the successive
lateral processes stand far apart, and a slender neck intervenes between the
oculiferous tubercle and the proboscis; the legs are produced to an amazing
length and an extreme degree of attenuation: “mirum tam parvum corpus
regere tam magnos pedes,” says Linnaeus. Above the base of the proboscis
are a pair of three-jointed appendages, the two terminal joints of which
compose a forcipate claw; below and behind these come a pair of delicate,
palp-like limbs of five joints; and lastly, on the ventral side, some little way
behind these, we find the ovigerous legs that we have already seen in the
male Pycnogonum, but which are present in both sexes in the case of
Nymphon. At the base of the claw which terminates each of the eight long
ambulatory legs stands a pair of smaller accessory or “auxiliary” claws. The
Page 553
generative orifices are on the second
joint of the legs as in Pycnogonum,
but as a rule they are present on all
the eight legs in the female sex, and
on the two hindmost pairs in the
male. One of the Antarctic
Nymphonidae (Pentanymphon) and
one other Antarctic genus less closely
related (Decolopoda) have an extra
pair of legs. No other Pycnogon, save
these, exhibits a greater number of
appendages than Nymphon nor a less
number than Pycnogonum, nor are
any other conspicuous organs to be
discovered in other genera that are
not represented in these two: within
so narrow limits lie the varying
characters of the group.
In framing a terminology for the
parts and members of the body, we
encounter an initial difficulty due to
Fig. 263.—Dorsal view of Nymphon brevirostre, the ease with which terms seem
Hodge, × 6. Britain. applicable, that are used of more or
less analogous parts in the Insect or
the Crustacean, without warrant of homology. Thus the first two pairs of
appendages in Nymphon have been commonly called, since Latreille’s time,
the mandibles and the palps (Linnaeus had called them the palps and the
antennae), though the comparison that Latreille intended to denote is long
abandoned; or, by those who leaned, with Kröyer and Milne-Edwards, to
the Crustacean analogy, mandibles and maxillae. Dohrn eludes the
difficulty by denominating the appendages by simple numbers, I., II., III., ...
VII., and this method has its own advantages; but it is better to frame, as
Sars has done, a new nomenclature. With him we shall speak of the
Pycnogon’s body as constituted of a trunk, whose first (composite) segment
is the cephalic segment or head, better perhaps the cephalothorax, and
which terminates in a caudal segment or abdomen; the “head” bears the
proboscis, the first appendages or “chelophores,” the second or “palps,” the
joint of the legs as in Pycnogonum,
but as a rule they are present on all
the eight legs in the female sex, and
on the two hindmost pairs in the
male. One of the Antarctic
Nymphonidae (Pentanymphon) and
one other Antarctic genus less closely
related (Decolopoda) have an extra
pair of legs. No other Pycnogon, save
these, exhibits a greater number of
appendages than Nymphon nor a less
number than Pycnogonum, nor are
any other conspicuous organs to be
discovered in other genera that are
not represented in these two: within
so narrow limits lie the varying
characters of the group.
In framing a terminology for the
parts and members of the body, we
encounter an initial difficulty due to
Fig. 263.—Dorsal view of Nymphon brevirostre, the ease with which terms seem
Hodge, × 6. Britain. applicable, that are used of more or
less analogous parts in the Insect or
the Crustacean, without warrant of homology. Thus the first two pairs of
appendages in Nymphon have been commonly called, since Latreille’s time,
the mandibles and the palps (Linnaeus had called them the palps and the
antennae), though the comparison that Latreille intended to denote is long
abandoned; or, by those who leaned, with Kröyer and Milne-Edwards, to
the Crustacean analogy, mandibles and maxillae. Dohrn eludes the
difficulty by denominating the appendages by simple numbers, I., II., III., ...
VII., and this method has its own advantages; but it is better to frame, as
Sars has done, a new nomenclature. With him we shall speak of the
Pycnogon’s body as constituted of a trunk, whose first (composite) segment
is the cephalic segment or head, better perhaps the cephalothorax, and
which terminates in a caudal segment or abdomen; the “head” bears the
proboscis, the first appendages or “chelophores,” the second or “palps,” the
Page 554
third, the false or “ovigerous” legs,
and the first of the four pairs of
“ambulatory” legs. The chelophores
bear their chela, or “hand,” on a stalk
or scape; the ambulatory legs are
constituted of three coxal joints, a
femur, two tibial joints, a tarsus, and
a propodus, with its claws, and with
or without auxiliary claws.
The Body.—The trunk with its
lateral processes may be still more
compact than in Pycnogonum, still
more attenuated than in Nymphon.
In a few forms (e.g. Pallene,
Ammothea, Tanystylum,
Colossendeis) the last two, or even
more, segments of the trunk are more Fig. 264.—Nymphon brevirostre, Hodge. Head,
or less coalescent. In Rhynchothorax from below, showing chelophores, palps, and
the cephalic segment is produced into ovigerous leg.
a sharp-pointed rostrum that juts
forward over the base of the proboscis. The whole body and limbs may be
smooth, tuberculated, furnished with scattered hairs, or sometimes densely
hispid.
and the first of the four pairs of
“ambulatory” legs. The chelophores
bear their chela, or “hand,” on a stalk
or scape; the ambulatory legs are
constituted of three coxal joints, a
femur, two tibial joints, a tarsus, and
a propodus, with its claws, and with
or without auxiliary claws.
The Body.—The trunk with its
lateral processes may be still more
compact than in Pycnogonum, still
more attenuated than in Nymphon.
In a few forms (e.g. Pallene,
Ammothea, Tanystylum,
Colossendeis) the last two, or even
more, segments of the trunk are more Fig. 264.—Nymphon brevirostre, Hodge. Head,
or less coalescent. In Rhynchothorax from below, showing chelophores, palps, and
the cephalic segment is produced into ovigerous leg.
a sharp-pointed rostrum that juts
forward over the base of the proboscis. The whole body and limbs may be
smooth, tuberculated, furnished with scattered hairs, or sometimes densely
hispid.
Page 555
Fig. 265.—A, Colossendeis proboscidea, Sabine, Britain; B, Ammothea
echinata, Hodge, Britain; C, Phoxichilus spinosus, Mont., Arctic Ocean. (The
legs omitted.)
The proboscis varies much in shape and size. It may be much longer or
much shorter than the body, cylindrical or tumid, blunt or pointed, straight
or (e.g. Decolopoda) decurved; usually firmly affixed to the head and
pointing straight forwards; sometimes (Eurycide, Ascorhynchus) articulated
on a mobile stalk and borne deflexed beneath the body.
Chelophores.—The first pair of appendages or chelophores are wanting
in the adult Pycnogonum, Phoxichilus, Rhynchothorax, and Colossendeis.
[396]
In Ammothea and its allies they are extremely rudimentary in the adult,
being reduced to tiny knobs in Tanystylum and Trygaeus, and present as
small two-jointed appendages in Ammothea; in this last, if not in the others
also, they are present in complete chelate form in the later larval stages.
echinata, Hodge, Britain; C, Phoxichilus spinosus, Mont., Arctic Ocean. (The
legs omitted.)
The proboscis varies much in shape and size. It may be much longer or
much shorter than the body, cylindrical or tumid, blunt or pointed, straight
or (e.g. Decolopoda) decurved; usually firmly affixed to the head and
pointing straight forwards; sometimes (Eurycide, Ascorhynchus) articulated
on a mobile stalk and borne deflexed beneath the body.
Chelophores.—The first pair of appendages or chelophores are wanting
in the adult Pycnogonum, Phoxichilus, Rhynchothorax, and Colossendeis.
[396]
In Ammothea and its allies they are extremely rudimentary in the adult,
being reduced to tiny knobs in Tanystylum and Trygaeus, and present as
small two-jointed appendages in Ammothea; in this last, if not in the others
also, they are present in complete chelate form in the later larval stages.
Page 556
Fig. 266.—A, B, Chelophores of Ascorhynchus abyssi, G.O.S. A, Young; B,
adult. (After Sars.) C, Anterior portion of Ammothea hispida, Hodge, Jersey: late
larval stage (= Achelia longipes, Hodge), showing complete chelae. D, Chela of
Eurycide hispida, Kr.
In Eurycide, Ascorhynchus, and Barana they are usually less atrophied,
but yet comparatively small and with imperfect chelae, while in some
Ascorhynchi (A. minutus, Hoek) they are reduced to stumps.
Fig. 267.—Chelae of species of Nymphonidae: A, Nymphon brevirostre, Hodge;
B, Boreonymphon robustum, Bell; C, Chaetonymphon macronyx, G.O.S.; D,
Nymphon elegans, Hansen.
In Pallenopsis the scape of the chelophore consists of two joints, as also
in Decolopoda and some Ascorhynchus: in Nymphon, Phoxichilidium,
Pallene, and Cordylochele of one only; in all these the terminal portion or
“hand” forms a forcipate “chela,” of which the ultimate joint forms the
adult. (After Sars.) C, Anterior portion of Ammothea hispida, Hodge, Jersey: late
larval stage (= Achelia longipes, Hodge), showing complete chelae. D, Chela of
Eurycide hispida, Kr.
In Eurycide, Ascorhynchus, and Barana they are usually less atrophied,
but yet comparatively small and with imperfect chelae, while in some
Ascorhynchi (A. minutus, Hoek) they are reduced to stumps.
Fig. 267.—Chelae of species of Nymphonidae: A, Nymphon brevirostre, Hodge;
B, Boreonymphon robustum, Bell; C, Chaetonymphon macronyx, G.O.S.; D,
Nymphon elegans, Hansen.
In Pallenopsis the scape of the chelophore consists of two joints, as also
in Decolopoda and some Ascorhynchus: in Nymphon, Phoxichilidium,
Pallene, and Cordylochele of one only; in all these the terminal portion or
“hand” forms a forcipate “chela,” of which the ultimate joint forms the
Page 557
“movable finger.” In some species of
Nymphon the chela is greatly
produced and attenuated, and armed
with formidable serrate teeth on its
opposing edges; in others it is
shortened, with blunter teeth; in
Boreonymphon robustum the claws
are greatly curved, with a wide gap
between. In this last, and in
Phoxichilidium, the opposing edges
are smooth and toothless. In
Cordylochele the hand is almost
globular, the movable finger being
shortened down, and half enclosed by
the other.
Fig. 268.—Proboscis and chelophores of
Palpi.—The second pair of Cordylochele longicollis, G.O.S. (After Sars.)
appendages, or palps, are absent, or
all but absent, in the adult
Pycnogonum, Phoxichilus, Phoxichilidium, Pallene, and their allies. In
certain of these cases, e.g. Phoxichilidium, a knob remains to mark their
place; in others, e.g. Pallenopsis, a single joint remains; in a few Pallenidae
a sexual difference is manifested, reduction of the appendage being carried
further in the female than in the male. The composition of the palps varies
in the genera that possess them. In Nymphon there are five joints, and their
relative lengths (especially of the terminal ones) are much used by Sars in
defining the many species of the genus. The recently described
Paranymphon, Caullery, has palps of six or seven joints. In the
Ammotheidae the number of joints ranges from five or six in Tanystylum to
nine (as a rule) in Ammothea and Oorhynchus, or ten, according to Dohrn,
in certain species of Ammothea. Colossendeis and the Eurycididae have a
ten-jointed palp, which in this last family is very long and bent in zigzag
fashion, as it is, by the way, also in Ammothea. The terminal joints of the
palp are in all cases more or less setose, and their function is conjecturally
tactile.
Ovigerous Legs.—Custom sanctions for these organs an inappropriate
name, inasmuch as it is only in the males that they perform the function
Nymphon the chela is greatly
produced and attenuated, and armed
with formidable serrate teeth on its
opposing edges; in others it is
shortened, with blunter teeth; in
Boreonymphon robustum the claws
are greatly curved, with a wide gap
between. In this last, and in
Phoxichilidium, the opposing edges
are smooth and toothless. In
Cordylochele the hand is almost
globular, the movable finger being
shortened down, and half enclosed by
the other.
Fig. 268.—Proboscis and chelophores of
Palpi.—The second pair of Cordylochele longicollis, G.O.S. (After Sars.)
appendages, or palps, are absent, or
all but absent, in the adult
Pycnogonum, Phoxichilus, Phoxichilidium, Pallene, and their allies. In
certain of these cases, e.g. Phoxichilidium, a knob remains to mark their
place; in others, e.g. Pallenopsis, a single joint remains; in a few Pallenidae
a sexual difference is manifested, reduction of the appendage being carried
further in the female than in the male. The composition of the palps varies
in the genera that possess them. In Nymphon there are five joints, and their
relative lengths (especially of the terminal ones) are much used by Sars in
defining the many species of the genus. The recently described
Paranymphon, Caullery, has palps of six or seven joints. In the
Ammotheidae the number of joints ranges from five or six in Tanystylum to
nine (as a rule) in Ammothea and Oorhynchus, or ten, according to Dohrn,
in certain species of Ammothea. Colossendeis and the Eurycididae have a
ten-jointed palp, which in this last family is very long and bent in zigzag
fashion, as it is, by the way, also in Ammothea. The terminal joints of the
palp are in all cases more or less setose, and their function is conjecturally
tactile.
Ovigerous Legs.—Custom sanctions for these organs an inappropriate
name, inasmuch as it is only in the males that they perform the function
Page 558
which the name connotes.[397] They
probably also take some part, as
Hodgson suggests, in the act of
feeding.
Fig. 269.—Eurycide hispida, Kr., showing
stalked proboscis and zigzag palps.
Fig. 270.—Ovigerous legs of A, Phoxichilus spinosus, Mont.; B, Phoxichilidium
femoratum, Rathke; C, Anoplodactylus petiolatus, Kr.; D, Colossendeis
proboscideus, Sab.
probably also take some part, as
Hodgson suggests, in the act of
feeding.
Fig. 269.—Eurycide hispida, Kr., showing
stalked proboscis and zigzag palps.
Fig. 270.—Ovigerous legs of A, Phoxichilus spinosus, Mont.; B, Phoxichilidium
femoratum, Rathke; C, Anoplodactylus petiolatus, Kr.; D, Colossendeis
proboscideus, Sab.
Page 559
In Pycnogonum, Phoxichilus,
Phoxichilidium, and their immediate
allies they are absent in the female;
in all the rest they are alike present in
both sexes, though often somewhat
smaller in the female than in the
Fig. 271.—Terminal joints of ovigerous leg of male. They are always turned
Rhynchothorax mediterraneus, Costa. towards the lower side of the body,
and in many cases even their point of
origin is wholly ventral. The number
of joints varies: in Phoxichilidium
five, Anoplodactylus six, Phoxichilus
seven; in Paranymphon eight; in
Pycnogonum nine, with, in addition,
a terminal claw; in the Ammotheidae
from seven (Trygaeus) to ten, without
a claw; in Pallenidae ten, with or
without a claw; in Rhynchothorax,
Colossendeis, Eurycide,
Ascorhynchus, Nymphon, ten and a
Fig. 272.—Nymphon brevirostre, Hodge.
claw. The appendage, especially Terminal joints of ovigerous leg, with magnified
when long, is apt to be wound “tooth.”
towards its extremity into a spiral,
and its last four joints usually possess a peculiar armature. In
Rhynchothorax this takes the form of a stout toothed tubercle on each joint;
in Colossendeis of several rows of small imbricated denticles; in Nymphon
and Pallene of a single row of curious serrate and pointed spines, each set
in a little membranous socket.
Phoxichilidium, and their immediate
allies they are absent in the female;
in all the rest they are alike present in
both sexes, though often somewhat
smaller in the female than in the
Fig. 271.—Terminal joints of ovigerous leg of male. They are always turned
Rhynchothorax mediterraneus, Costa. towards the lower side of the body,
and in many cases even their point of
origin is wholly ventral. The number
of joints varies: in Phoxichilidium
five, Anoplodactylus six, Phoxichilus
seven; in Paranymphon eight; in
Pycnogonum nine, with, in addition,
a terminal claw; in the Ammotheidae
from seven (Trygaeus) to ten, without
a claw; in Pallenidae ten, with or
without a claw; in Rhynchothorax,
Colossendeis, Eurycide,
Ascorhynchus, Nymphon, ten and a
Fig. 272.—Nymphon brevirostre, Hodge.
claw. The appendage, especially Terminal joints of ovigerous leg, with magnified
when long, is apt to be wound “tooth.”
towards its extremity into a spiral,
and its last four joints usually possess a peculiar armature. In
Rhynchothorax this takes the form of a stout toothed tubercle on each joint;
in Colossendeis of several rows of small imbricated denticles; in Nymphon
and Pallene of a single row of curious serrate and pointed spines, each set
in a little membranous socket.
Page 560
Fig. 273.—Nymphon strömii, Kr. Male carrying egg-masses on his ovigerous
legs.
Fig. 274.—Terminal joints (tarsus and propodus) of legs. 1, Chaetonymphon
hirtum, Fabr.; 2, N. strömii, Kr.; 3, Nymphon brevirostre, Hodge; 4, Ammothea
echinata, Hodge; 5, Ascorhynchus abyssi, G.O.S. (All after Sars.)
Legs.—The four pairs of ambulatory legs are composed, in all cases
without exception, of eight joints if we exclude, or nine if we include, the
terminal claw. They vary from a length about equal to that of the body
(Pycnogonum, Rhynchothorax, Ammothea) to six or seven times as much,
perhaps more, in Nymphon and Colossendeis, the fourth, fifth, and sixth
legs.
Fig. 274.—Terminal joints (tarsus and propodus) of legs. 1, Chaetonymphon
hirtum, Fabr.; 2, N. strömii, Kr.; 3, Nymphon brevirostre, Hodge; 4, Ammothea
echinata, Hodge; 5, Ascorhynchus abyssi, G.O.S. (All after Sars.)
Legs.—The four pairs of ambulatory legs are composed, in all cases
without exception, of eight joints if we exclude, or nine if we include, the
terminal claw. They vary from a length about equal to that of the body
(Pycnogonum, Rhynchothorax, Ammothea) to six or seven times as much,
perhaps more, in Nymphon and Colossendeis, the fourth, fifth, and sixth
Page 561
joints being those that suffer the greatest elongation. The seventh joint, or
tarsus, is usually short, but in some Nymphonidae is much elongated; the
eighth, or propodus, is usually somewhat curved, and usually possesses a
special armature of simple or serrate spines. The auxiliary claws, sometimes
large, sometimes small, lie at the base of the terminal claw in
Ammotheidae, Phoxichilidae, in Phoxichilidium, in most Pallenidae, in
nearly all Nymphonidae. Their presence or absence is often used as a
generic character, helping to separate, e.g., Pallene from Pseudopallene and
Pallenopsis, and Phoxichilidium from Anoplodactylus; nevertheless they
may often be detected in a rudimentary state when apparently absent. The
legs are smooth or hirsute as the body may happen to be.
tarsus, is usually short, but in some Nymphonidae is much elongated; the
eighth, or propodus, is usually somewhat curved, and usually possesses a
special armature of simple or serrate spines. The auxiliary claws, sometimes
large, sometimes small, lie at the base of the terminal claw in
Ammotheidae, Phoxichilidae, in Phoxichilidium, in most Pallenidae, in
nearly all Nymphonidae. Their presence or absence is often used as a
generic character, helping to separate, e.g., Pallene from Pseudopallene and
Pallenopsis, and Phoxichilidium from Anoplodactylus; nevertheless they
may often be detected in a rudimentary state when apparently absent. The
legs are smooth or hirsute as the body may happen to be.
Page 562
Fig. 275.—Legs of A, Pallene brevirostris, Johnston; B, Anoplodactylus
petiolatus, Kr.; C, Phoxichilus spinosus, Mont.; D, Colossendeis proboscidea,
Sabine; E, Ammothea echinata, Hodge, ♂.
petiolatus, Kr.; C, Phoxichilus spinosus, Mont.; D, Colossendeis proboscidea,
Sabine; E, Ammothea echinata, Hodge, ♂.
Page 563
Fig. 276.—Boreonymphon robustum, Bell. Male with young, slightly enlarged.
Faeroe Channel.
Glands.—In some or all of the appendages of the Pycnogonida may be
found special glands with varying and sometimes obscure functions. The
glands of the chelophores (Fig. 280, p. 522) are present in the larval stages
only. They consist of a number of flask-shaped cells[398] lying within the
basal joint of the appendage, and generally opening at the extremity of a
long, conspicuous, often mobile, spine (e.g. Ammothea (Dohrn), Pallene,
Tanystylum (Morgan), Nymphon brevicollum and N. gracile (Hoek)). They
secrete a sticky thread, by means of which the larvae attach themselves to
one another and to the ovigerous legs of the male parent. In Nymphon
hamatum, Hoek, the several filaments secreted by the separate sacculi of the
gland issue separately. In Pycnogonum the spine on which the gland opens
is itself prolonged into a long fine filament, and here, according to Hoek,
the gland is in all probability functionless and rudimentary. Hoek has failed
to find the gland in Ascorhynchus, and also in certain Nymphonidae (e.g.
Boreonymphon robustum, Bell), in which the young are more than usually
Faeroe Channel.
Glands.—In some or all of the appendages of the Pycnogonida may be
found special glands with varying and sometimes obscure functions. The
glands of the chelophores (Fig. 280, p. 522) are present in the larval stages
only. They consist of a number of flask-shaped cells[398] lying within the
basal joint of the appendage, and generally opening at the extremity of a
long, conspicuous, often mobile, spine (e.g. Ammothea (Dohrn), Pallene,
Tanystylum (Morgan), Nymphon brevicollum and N. gracile (Hoek)). They
secrete a sticky thread, by means of which the larvae attach themselves to
one another and to the ovigerous legs of the male parent. In Nymphon
hamatum, Hoek, the several filaments secreted by the separate sacculi of the
gland issue separately. In Pycnogonum the spine on which the gland opens
is itself prolonged into a long fine filament, and here, according to Hoek,
the gland is in all probability functionless and rudimentary. Hoek has failed
to find the gland in Ascorhynchus, and also in certain Nymphonidae (e.g.
Boreonymphon robustum, Bell), in which the young are more than usually
Page 564
advanced at the time of hatching. The gland has also been described by
Lendenfeld and others in Phoxichilidium, whose larvae do not cling
together but live a parasitic life; in this genus the long spine or tubercle is
absent on which the orifice is usually situated, and, according to
Lendenfeld, the secretion issues from many small orifices set along the
opposing edges of the chela. Of the two species described by Dohrn as
Barana castelli and B. arenicola, the former has the spine of inordinate
length, more than twice as long as the whole body, chelophore and all;
while in the latter (which species rather resembles Ascorhynchus) the spine
is altogether absent.
In the palps and ovigerous legs of the adult are found glandular bodies of
a hollow vesicular form with a simple lining of cells, the vesicle being
divided within by a septum with a central orifice, the outer and smaller half
opening to the exterior. These glands are probably of general occurrence,
but they have been but little investigated. They lie usually in the fourth and
fifth joints of the palp, and the third and fourth joints of the ovigerous leg.
Hoek describes them in Discoarachne (Tanystylum) as lying within the
elongated third joint of the palp, and opening by a sieve-plate at the end of
the second joint. In Ammothea (Dohrn) and Ascorhynchus (Hoek) they open
on a small tubercle situated on the fifth joint of the palp. In Nymphon, Hoek
describes them as opening by a small pore on the fourth joint of the
ovigerous leg. Dohrn failed to find them in Pycnogonum, but in
Phoxichilus, Phoxichilidium and Pallene he discovered the glands
appertaining to the palps, though the palps themselves have disappeared in
those genera; he has found the glands also in Ammothea, in larvae that have
not yet attained their full complement of legs.
The males in nearly all cases are known to possess glands in the fourth
joints or thighs of all the ambulatory legs, and these glands without doubt
act as cement-glands, emitting, like the chelophoral glands of the larvae, a
sticky thread or threads by which the eggs and young are anchored to the
ovigerous legs. In some species of Nymphon and of Colossendeis Hoek
could not find these, and he conjectures them to be conspicuous only in the
breeding season. While in most cases these glands open by a single orifice
or by a few pores grouped closely together, in Barana, according to Dohrn,
and especially in B. arenicola, the pores are distributed over a wide area of
the femoral joint.[399] In Discoarachne (Loman) and Trygaeus they open into
a wide chitinised sac with tubular orifice. While the function of these last
Lendenfeld and others in Phoxichilidium, whose larvae do not cling
together but live a parasitic life; in this genus the long spine or tubercle is
absent on which the orifice is usually situated, and, according to
Lendenfeld, the secretion issues from many small orifices set along the
opposing edges of the chela. Of the two species described by Dohrn as
Barana castelli and B. arenicola, the former has the spine of inordinate
length, more than twice as long as the whole body, chelophore and all;
while in the latter (which species rather resembles Ascorhynchus) the spine
is altogether absent.
In the palps and ovigerous legs of the adult are found glandular bodies of
a hollow vesicular form with a simple lining of cells, the vesicle being
divided within by a septum with a central orifice, the outer and smaller half
opening to the exterior. These glands are probably of general occurrence,
but they have been but little investigated. They lie usually in the fourth and
fifth joints of the palp, and the third and fourth joints of the ovigerous leg.
Hoek describes them in Discoarachne (Tanystylum) as lying within the
elongated third joint of the palp, and opening by a sieve-plate at the end of
the second joint. In Ammothea (Dohrn) and Ascorhynchus (Hoek) they open
on a small tubercle situated on the fifth joint of the palp. In Nymphon, Hoek
describes them as opening by a small pore on the fourth joint of the
ovigerous leg. Dohrn failed to find them in Pycnogonum, but in
Phoxichilus, Phoxichilidium and Pallene he discovered the glands
appertaining to the palps, though the palps themselves have disappeared in
those genera; he has found the glands also in Ammothea, in larvae that have
not yet attained their full complement of legs.
The males in nearly all cases are known to possess glands in the fourth
joints or thighs of all the ambulatory legs, and these glands without doubt
act as cement-glands, emitting, like the chelophoral glands of the larvae, a
sticky thread or threads by which the eggs and young are anchored to the
ovigerous legs. In some species of Nymphon and of Colossendeis Hoek
could not find these, and he conjectures them to be conspicuous only in the
breeding season. While in most cases these glands open by a single orifice
or by a few pores grouped closely together, in Barana, according to Dohrn,
and especially in B. arenicola, the pores are distributed over a wide area of
the femoral joint.[399] In Discoarachne (Loman) and Trygaeus they open into
a wide chitinised sac with tubular orifice. While the function of these last
Page 565
glands and of the larval glands seems plain enough, that of those which
occur in the palps and ovigerous legs of both sexes remains doubtful.
In their morphological nature the two groups of glands are likewise in
contrast, the former being unicellular glands, such as occur in various parts
of the integument of the body and limbs of many Crustacea; while the latter
are segmentally arranged and doubtless mesoblastic in origin, like the many
other segmental excretory organs (or coelomoducts) of various Arthropods.
By adding colouring matters (acid-fuchsin, etc.) to the water in which the
animals were living, Kowalevsky demonstrated the presence of what he
believed to be excretory organs in Phoxichilus, Ammothea, and Pallene.
These are small groups of cells, lying symmetrically near the posterior
borders of the first three body-segments, and also near the bases of the first
joints of the legs, dorsal to the alimentary canal.[400]
Alimentary System.—The proboscis is a very complicated organ, and
has been elaborately described by Dohrn.[401] It is a prolongation of the oral
cavity, containing a highly developed stomodaeum, but showing no sign of
being built up of limbs or gnathites. The mouth, situated at its apex, is a
three-sided orifice, formed by a dorsal[402] and two lateral lobes; and hence
the proboscis has been assumed by some, on no competent evidence, to be
constituted of a degenerate pair of appendages and a labrum or upper lip.
Each of the three lobes which bounds the mouth shows the following
structures: firstly, a lappet of external chitinised integument, overlapping, as
the finger-nail overlaps the finger, a cushion-like lip, ridged after the
fashion of a fine-cut file in some species, hairy in others, on the inner
surface where the three lips meet to close the orifice of the mouth. Below
this again is a prominent tooth (Fig. 277, mt), supported, as are the lips, by a
system of chitinous rods, which are but little developed in the genus here
figured, though conspicuous and complicated in others. Transverse ridges
run across the angles where adjacent lips meet, and the whole mechanism
constitutes an efficient valve, preventing the escape of swallowed food. The
greater portion of the proboscis is occupied by a masticating or triturating
apparatus, the oesophageal cavity expanding somewhat and having its walls
densely covered, in three bands corresponding to the antimeres, with
innumerable minute spines (h) or needles, sometimes supplemented by
large teeth (t) that point forwards somewhat obliquely to the axis of the
proboscis.[403]
occur in the palps and ovigerous legs of both sexes remains doubtful.
In their morphological nature the two groups of glands are likewise in
contrast, the former being unicellular glands, such as occur in various parts
of the integument of the body and limbs of many Crustacea; while the latter
are segmentally arranged and doubtless mesoblastic in origin, like the many
other segmental excretory organs (or coelomoducts) of various Arthropods.
By adding colouring matters (acid-fuchsin, etc.) to the water in which the
animals were living, Kowalevsky demonstrated the presence of what he
believed to be excretory organs in Phoxichilus, Ammothea, and Pallene.
These are small groups of cells, lying symmetrically near the posterior
borders of the first three body-segments, and also near the bases of the first
joints of the legs, dorsal to the alimentary canal.[400]
Alimentary System.—The proboscis is a very complicated organ, and
has been elaborately described by Dohrn.[401] It is a prolongation of the oral
cavity, containing a highly developed stomodaeum, but showing no sign of
being built up of limbs or gnathites. The mouth, situated at its apex, is a
three-sided orifice, formed by a dorsal[402] and two lateral lobes; and hence
the proboscis has been assumed by some, on no competent evidence, to be
constituted of a degenerate pair of appendages and a labrum or upper lip.
Each of the three lobes which bounds the mouth shows the following
structures: firstly, a lappet of external chitinised integument, overlapping, as
the finger-nail overlaps the finger, a cushion-like lip, ridged after the
fashion of a fine-cut file in some species, hairy in others, on the inner
surface where the three lips meet to close the orifice of the mouth. Below
this again is a prominent tooth (Fig. 277, mt), supported, as are the lips, by a
system of chitinous rods, which are but little developed in the genus here
figured, though conspicuous and complicated in others. Transverse ridges
run across the angles where adjacent lips meet, and the whole mechanism
constitutes an efficient valve, preventing the escape of swallowed food. The
greater portion of the proboscis is occupied by a masticating or triturating
apparatus, the oesophageal cavity expanding somewhat and having its walls
densely covered, in three bands corresponding to the antimeres, with
innumerable minute spines (h) or needles, sometimes supplemented by
large teeth (t) that point forwards somewhat obliquely to the axis of the
proboscis.[403]
Page 566
In the curious East Indian genus
Pipetta (Loman) the sucking and
sifting mechanism is low down in the
proboscis, and the organ is prolonged
into a very fine tube, the lips growing
together till they leave an aperture of
only ·007 mm. for the absorption of
liquids.
In some cases, where the proboscis
itself is short, as in Pallene, this
mechanism is carried backwards into
the fore-part of the body; and, in the
latter genus, the narrow oesophagus
which succeeds the masticatory
apparatus is likewise provided with
extrinsic muscles.
Fig. 277.—Longitudinal section through one
“antimere” of the proboscis in Phoxichilus
charybdaeus. G, g′, Principal and secondary
ganglia; h, sieve-hairs; L, lip; mt, oral tooth; N,
Pipetta (Loman) the sucking and
sifting mechanism is low down in the
proboscis, and the organ is prolonged
into a very fine tube, the lips growing
together till they leave an aperture of
only ·007 mm. for the absorption of
liquids.
In some cases, where the proboscis
itself is short, as in Pallene, this
mechanism is carried backwards into
the fore-part of the body; and, in the
latter genus, the narrow oesophagus
which succeeds the masticatory
apparatus is likewise provided with
extrinsic muscles.
Fig. 277.—Longitudinal section through one
“antimere” of the proboscis in Phoxichilus
charybdaeus. G, g′, Principal and secondary
ganglia; h, sieve-hairs; L, lip; mt, oral tooth; N,
Page 567
N′, inner and outer nerve-cords; t, proboscis-
teeth. (After Dohrn.)
Fig. 278.—Transverse sections through the proboscis of Ph. charybdaeus. A,
Anterior, through the principal ganglionic mass (G); B, posterior, at the level of
the sieve-hairs (h). Coec, Intestinal caeca; Dil. M, dilator muscles; N, inner
nerve-ganglion, with circular commissure; N′, outer nerve; or, chitinous lining of
oral cavity; R M, Ret.M, retractor muscles. (After Dohrn.)
The oesophagus is followed by a
long gastric cavity, which sends forth
caecal diverticula into the
chelophores (when these are present),
and four immensely long ones into
the ambulatory legs. The caeca are
attached to the walls of the limb
cavities, especially at their
extremities in the tarsi, by suspensory
threads of connective tissue, and the
whole gut, central and diverticular, is
further supported by a horizontal
Fig. 279.—Transverse section through the basal
septal membrane, running through joint of the third leg in Phoxichilus
body and legs, which separates the charybdaeus, ♀. Cut, Cuticle; Hyp, hypodermis;
dorsal blood-vessel and sinus from Int, intestinal caecum; N, nerve-cord; Ov, ovary;
Sept, septum. (After Dohrn.)
the gut, the nervous system and the
ventral sinus, giving support also to
the reproductive glands. A short and simple rectum follows the gastric
cavity.
teeth. (After Dohrn.)
Fig. 278.—Transverse sections through the proboscis of Ph. charybdaeus. A,
Anterior, through the principal ganglionic mass (G); B, posterior, at the level of
the sieve-hairs (h). Coec, Intestinal caeca; Dil. M, dilator muscles; N, inner
nerve-ganglion, with circular commissure; N′, outer nerve; or, chitinous lining of
oral cavity; R M, Ret.M, retractor muscles. (After Dohrn.)
The oesophagus is followed by a
long gastric cavity, which sends forth
caecal diverticula into the
chelophores (when these are present),
and four immensely long ones into
the ambulatory legs. The caeca are
attached to the walls of the limb
cavities, especially at their
extremities in the tarsi, by suspensory
threads of connective tissue, and the
whole gut, central and diverticular, is
further supported by a horizontal
Fig. 279.—Transverse section through the basal
septal membrane, running through joint of the third leg in Phoxichilus
body and legs, which separates the charybdaeus, ♀. Cut, Cuticle; Hyp, hypodermis;
dorsal blood-vessel and sinus from Int, intestinal caecum; N, nerve-cord; Ov, ovary;
Sept, septum. (After Dohrn.)
the gut, the nervous system and the
ventral sinus, giving support also to
the reproductive glands. A short and simple rectum follows the gastric
cavity.
Page 568
In Phoxichilus, which lacks the three anterior appendages in the female
and the two anterior in the male, two pairs of caeca run from the gut into the
cavity of the proboscis (Fig. 278, B, coec.).[404]
Circulatory System.—The heart has been especially studied by Dohrn in
Phoxichilus. It consists of a median vessel running from the level of the
eyes to the abdomen, furnished with two pairs of lateral valvular openings,
and sometimes, though not always, with an unpaired one at the posterior
end. The walls are muscular, but with this peculiarity that the muscular
walls do not extend around the heart dorsally, in which region its lumen is
only covered by the hypodermis and cuticle of the back. The blood-spaces
of the body are separated into dorsal and ventral halves by the septal
membrane already referred to, which is perforated in the region of the
lateral processes by slits placing the two cavities in communication; this
septal membrane runs through the limbs to their tips, and far into the
proboscis, where it is attached to the edge of the superior antimere. The
blood is a colourless plasma with several kinds of corpuscles, of which the
most remarkable are amoeboid, actively mobile, often coalescing into
plasmodia. The course of the circulation is on the whole outwards in the
inferior or ventral sinus, inwards towards the heart in the superior, save in
the proboscis, where the systole of the heart drives the blood forwards in
the dorsal channel. The beat is rapid, two or three times in a second,
according to Loman, in Phoxichilidium. Especially in the species with small
body and exaggerated legs, the movement of the circulatory fluid is
actuated more by the movements of the limbs and the contractions of the
intestinal caeca than by the direct impulse of the heart.
Nervous System.—The nerve-chain consists of a fused pair of supra-
oesophageal ganglia, which innervate (at least in the adult) the chelophores,
and of ventral ganglia, whence proceed the nerves to the other limbs. The
ganglia of the second and third appendages are fused with one another,
sometimes also with the ganglia of the first ambulatory legs; the ganglia of
the three posterior pairs of legs are always independent (though the
development of their longitudinal commissures varies with the body-form),
and they are succeeded by one or two pairs of ganglia, much reduced in
size, situated in the abdomen, of which the posterior one innervates the
muscles of the abdomen and of the anal orifice. Each lateral nerve divides
into two main branches, which supply the parts above and below the septal
membrane. The nerve-supply of the proboscis is very complicated. Its upper
and the two anterior in the male, two pairs of caeca run from the gut into the
cavity of the proboscis (Fig. 278, B, coec.).[404]
Circulatory System.—The heart has been especially studied by Dohrn in
Phoxichilus. It consists of a median vessel running from the level of the
eyes to the abdomen, furnished with two pairs of lateral valvular openings,
and sometimes, though not always, with an unpaired one at the posterior
end. The walls are muscular, but with this peculiarity that the muscular
walls do not extend around the heart dorsally, in which region its lumen is
only covered by the hypodermis and cuticle of the back. The blood-spaces
of the body are separated into dorsal and ventral halves by the septal
membrane already referred to, which is perforated in the region of the
lateral processes by slits placing the two cavities in communication; this
septal membrane runs through the limbs to their tips, and far into the
proboscis, where it is attached to the edge of the superior antimere. The
blood is a colourless plasma with several kinds of corpuscles, of which the
most remarkable are amoeboid, actively mobile, often coalescing into
plasmodia. The course of the circulation is on the whole outwards in the
inferior or ventral sinus, inwards towards the heart in the superior, save in
the proboscis, where the systole of the heart drives the blood forwards in
the dorsal channel. The beat is rapid, two or three times in a second,
according to Loman, in Phoxichilidium. Especially in the species with small
body and exaggerated legs, the movement of the circulatory fluid is
actuated more by the movements of the limbs and the contractions of the
intestinal caeca than by the direct impulse of the heart.
Nervous System.—The nerve-chain consists of a fused pair of supra-
oesophageal ganglia, which innervate (at least in the adult) the chelophores,
and of ventral ganglia, whence proceed the nerves to the other limbs. The
ganglia of the second and third appendages are fused with one another,
sometimes also with the ganglia of the first ambulatory legs; the ganglia of
the three posterior pairs of legs are always independent (though the
development of their longitudinal commissures varies with the body-form),
and they are succeeded by one or two pairs of ganglia, much reduced in
size, situated in the abdomen, of which the posterior one innervates the
muscles of the abdomen and of the anal orifice. Each lateral nerve divides
into two main branches, which supply the parts above and below the septal
membrane. The nerve-supply of the proboscis is very complicated. Its upper
Page 569
antimere is supplied from the pre-oral, its two lateral antimeres from the
first post-oral, ganglion, and each of these three nerves divides into two
branches, of which the inner bears six to eight or more small ganglia, which
annular commissures passing round the pharynx connect one to another. Of
these ganglia and commissures the anterior are the largest, and with these
the outer lateral nerve-branches of the proboscis merge. The immediate
origin of the nerves to the chelophores is from the median nerve that springs
from the under side of the supra-oesophageal ganglion to run forward into
the proboscis, but it is noteworthy that the chelophores receive twigs also
from the lateral nerves of the proboscis which arise from the post-oral
ganglia.
Eyes.—Eyes are the only organs of special sense known in the
Pycnogons. The deep-water Pycnogons, in general those inhabiting depths
below four or five hundred fathoms, have in most cases imperfect organs,
destitute of lens and of pigment, so imperfect in many cases as to be
described as wanting. It is rare for the eyes to be lacking in shallow-water
species, as they are, for instance, in Ascorhynchus minutus, Hoek, dredged
by the Challenger in 38 fathoms, but, on the other hand, it is no small
minority of deep-water species that possess them of normal character and
size, even to depths of about 2000 fathoms.
In all cases where eyes are present, they are simple or “monomeniscous”
eyes, four in number, and are situated in two pairs on an “oculiferous
tubercle,” sometimes blunt and low, sometimes high and pointed, placed on
the so-called cephalothorax, or first, compound, segment of the body. The
anterior pair are frequently a little larger, sometimes, as in Phoxichilidium
mollissimum, Hoek, very much larger, than the posterior. The minute
structure of the eye has been investigated by Dohrn, Grenacher, Hoek, and
Morgan. The following account is drawn in the first instance from Morgan’s
descriptions.[405]
The eye of a Pycnogon (Phoxichilidium) is composed of three layers, an
outer layer of specialised ectoderm cells (hypodermis) that secrete the
cuticular lens, a middle layer of visual or retinal elements, and an inner
layer of pigment-cells. The elements of the middle layer consist of much
elongated cells, whose branching outer ends are connected with nerve-
fibrils and interwoven in a protoplasmic syncytium, whose middle parts are
occupied by the nuclei and whose inwardly directed ends form the retinal
first post-oral, ganglion, and each of these three nerves divides into two
branches, of which the inner bears six to eight or more small ganglia, which
annular commissures passing round the pharynx connect one to another. Of
these ganglia and commissures the anterior are the largest, and with these
the outer lateral nerve-branches of the proboscis merge. The immediate
origin of the nerves to the chelophores is from the median nerve that springs
from the under side of the supra-oesophageal ganglion to run forward into
the proboscis, but it is noteworthy that the chelophores receive twigs also
from the lateral nerves of the proboscis which arise from the post-oral
ganglia.
Eyes.—Eyes are the only organs of special sense known in the
Pycnogons. The deep-water Pycnogons, in general those inhabiting depths
below four or five hundred fathoms, have in most cases imperfect organs,
destitute of lens and of pigment, so imperfect in many cases as to be
described as wanting. It is rare for the eyes to be lacking in shallow-water
species, as they are, for instance, in Ascorhynchus minutus, Hoek, dredged
by the Challenger in 38 fathoms, but, on the other hand, it is no small
minority of deep-water species that possess them of normal character and
size, even to depths of about 2000 fathoms.
In all cases where eyes are present, they are simple or “monomeniscous”
eyes, four in number, and are situated in two pairs on an “oculiferous
tubercle,” sometimes blunt and low, sometimes high and pointed, placed on
the so-called cephalothorax, or first, compound, segment of the body. The
anterior pair are frequently a little larger, sometimes, as in Phoxichilidium
mollissimum, Hoek, very much larger, than the posterior. The minute
structure of the eye has been investigated by Dohrn, Grenacher, Hoek, and
Morgan. The following account is drawn in the first instance from Morgan’s
descriptions.[405]
The eye of a Pycnogon (Phoxichilidium) is composed of three layers, an
outer layer of specialised ectoderm cells (hypodermis) that secrete the
cuticular lens, a middle layer of visual or retinal elements, and an inner
layer of pigment-cells. The elements of the middle layer consist of much
elongated cells, whose branching outer ends are connected with nerve-
fibrils and interwoven in a protoplasmic syncytium, whose middle parts are
occupied by the nuclei and whose inwardly directed ends form the retinal
Page 570
rods or bacilli. The pigment-cells of the inner layer are of various forms,
those towards the middle of the eye being small and flattened, those at the
sides being, for the most part, long and attenuated, so seeming, as Morgan
remarks, to approximate in character to the retinal elements. The pigment-
layer is easily dispersed and reveals beneath it a median vertical raphe,
caused by the convergence of the cells of the middle layer from either side,
and along the line of this raphe the optic nerve joins the eye, though its
subsequent course to its connection with the retinal elements is obscure. It
is at least clear that the retina is an “inverted” retina, with the nerve-
connected bases of its cells lying outwards and their bacillar extremities
directed inwards.
In a longitudinal vertical section of the eye of a larva (Tanystylum), at a
stage when three pairs of walking legs are present, Morgan shows us the
pigment-layer apparently continuous with the hypodermis just below the
eye, and in close connection with the middle layer at the upper part of the
eye. From this we are permitted to infer a development by invagination, in
which the long invaginated sac is bent and pushed upwards till it comes into
secondary contact with the hypoderm, so giving us the three layers of the
developed eye. This manner of formation is precisely akin to that described
by Parker, Patten, Locy, and others for the median eyes of Scorpions and of
Spiders, and the organ is structurally comparable to the Nauplius- or median
eye of Crustacea. But neither in these cases nor in that of the Pycnogon is
the whole process clear, in consequence chiefly of the obscurity that attends
the course of the optic nerve in both embryo and adult. For various
discussions and accounts, frequently contradictory, of these phenomena, the
reader is referred to the authors quoted, or to Korschelt and Heider’s
judicious summary.[406]
There seems to be a small structure, of some sort or other, between the
ocelli on either side. Dohrn thought it might be auditory, Loman that it
might be secretory, but its use is unknown.
Integument.—The chitinised integument is perforated by many little
cavities, some of them conical and tapering to a minute external pore, the
others more regularly tubular. Sometimes, but according to Hoek rarely, the
tubular pore-canals communicate with, or arise from, the conical cavities.
The pore-canals transmit a nerve for the supply of sensory hairs, often
forked, which arise from the orifice of the canal in little groups of two or
those towards the middle of the eye being small and flattened, those at the
sides being, for the most part, long and attenuated, so seeming, as Morgan
remarks, to approximate in character to the retinal elements. The pigment-
layer is easily dispersed and reveals beneath it a median vertical raphe,
caused by the convergence of the cells of the middle layer from either side,
and along the line of this raphe the optic nerve joins the eye, though its
subsequent course to its connection with the retinal elements is obscure. It
is at least clear that the retina is an “inverted” retina, with the nerve-
connected bases of its cells lying outwards and their bacillar extremities
directed inwards.
In a longitudinal vertical section of the eye of a larva (Tanystylum), at a
stage when three pairs of walking legs are present, Morgan shows us the
pigment-layer apparently continuous with the hypodermis just below the
eye, and in close connection with the middle layer at the upper part of the
eye. From this we are permitted to infer a development by invagination, in
which the long invaginated sac is bent and pushed upwards till it comes into
secondary contact with the hypoderm, so giving us the three layers of the
developed eye. This manner of formation is precisely akin to that described
by Parker, Patten, Locy, and others for the median eyes of Scorpions and of
Spiders, and the organ is structurally comparable to the Nauplius- or median
eye of Crustacea. But neither in these cases nor in that of the Pycnogon is
the whole process clear, in consequence chiefly of the obscurity that attends
the course of the optic nerve in both embryo and adult. For various
discussions and accounts, frequently contradictory, of these phenomena, the
reader is referred to the authors quoted, or to Korschelt and Heider’s
judicious summary.[406]
There seems to be a small structure, of some sort or other, between the
ocelli on either side. Dohrn thought it might be auditory, Loman that it
might be secretory, but its use is unknown.
Integument.—The chitinised integument is perforated by many little
cavities, some of them conical and tapering to a minute external pore, the
others more regularly tubular. Sometimes, but according to Hoek rarely, the
tubular pore-canals communicate with, or arise from, the conical cavities.
The pore-canals transmit a nerve for the supply of sensory hairs, often
forked, which arise from the orifice of the canal in little groups of two or
Page 571
more, sometimes in rosettes of eight or nine. These setae are small or
rudimentary in Ascorhynchus and totally wanting in Colossendeis; they
appear to be extremely large and stellate in Paranymphon. The conical
cavities contain proliferated epithelial cells, blood corpuscles, and cells of
more doubtful nature that are perhaps glandular. According to Dohrn,
glands exist in connection with both kinds of integumentary perforations,
and he suspects that they secrete a poisonous fluid in response to stimuli
affecting the sensory hairs; Hoek, on the other hand, is inclined to ascribe a
respiratory function to the cavities; but indeed, as yet, we must confess that
their use is undetermined.
Reproductive Organs.—In each sex the generative organs consist of a
pair of ovaries or testes lying above the gut on either side of the heart; in the
adult they are fused together posteriorly at the base of the abdomen, and
send long diverticula into the ambulatory legs. In the female
Phoxichilidium, at least, as Loman has lately shown, the fusion is complete,
and the ovary forms a thin broad plate, spreading through the body and
giving off its lateral diverticula. The diverticula of the testes reach to the
third joint of the legs, those of the ovaries to the fourth, or sometimes
farther. The ova ripen within the lateral diverticula, chiefly, and sometimes
(Pallene) exclusively, in the femora or fourth joints of the legs,[407] which, in
many forms, are greatly swollen to accommodate them; the spermatozoa,
on the other hand, are said to develop both within the legs and within the
thoracic portions of the testis. The genital diverticula may end blindly
within the leg, or communicate through a duct with the exterior by a
valvular aperture placed on the second coxal joint. Such apertures occur, as
a rule, on all the legs in the females, in Rhynchothorax and Pycnogonum on
the last only. In the males an aperture is present on all the legs in
Decolopoda and Phoxichilidium; on the last three in Nymphon and
Phoxichilus; in most genera on the last two; in Pycnogonum and
Rhynchothorax on the last only.
Very commonly the female individuals are somewhat larger than the
males, and in some species (Ammothea, Trygaeus) the latter are
distinguished by a greater development of spines or tubercles on the body
and basal joints of the legs (Dohrn).
The act of fecundation has been observed by Cole[408] in Anoplodactylus.
The animal reproduces towards the end of August. Consorting on their
rudimentary in Ascorhynchus and totally wanting in Colossendeis; they
appear to be extremely large and stellate in Paranymphon. The conical
cavities contain proliferated epithelial cells, blood corpuscles, and cells of
more doubtful nature that are perhaps glandular. According to Dohrn,
glands exist in connection with both kinds of integumentary perforations,
and he suspects that they secrete a poisonous fluid in response to stimuli
affecting the sensory hairs; Hoek, on the other hand, is inclined to ascribe a
respiratory function to the cavities; but indeed, as yet, we must confess that
their use is undetermined.
Reproductive Organs.—In each sex the generative organs consist of a
pair of ovaries or testes lying above the gut on either side of the heart; in the
adult they are fused together posteriorly at the base of the abdomen, and
send long diverticula into the ambulatory legs. In the female
Phoxichilidium, at least, as Loman has lately shown, the fusion is complete,
and the ovary forms a thin broad plate, spreading through the body and
giving off its lateral diverticula. The diverticula of the testes reach to the
third joint of the legs, those of the ovaries to the fourth, or sometimes
farther. The ova ripen within the lateral diverticula, chiefly, and sometimes
(Pallene) exclusively, in the femora or fourth joints of the legs,[407] which, in
many forms, are greatly swollen to accommodate them; the spermatozoa,
on the other hand, are said to develop both within the legs and within the
thoracic portions of the testis. The genital diverticula may end blindly
within the leg, or communicate through a duct with the exterior by a
valvular aperture placed on the second coxal joint. Such apertures occur, as
a rule, on all the legs in the females, in Rhynchothorax and Pycnogonum on
the last only. In the males an aperture is present on all the legs in
Decolopoda and Phoxichilidium; on the last three in Nymphon and
Phoxichilus; in most genera on the last two; in Pycnogonum and
Rhynchothorax on the last only.
Very commonly the female individuals are somewhat larger than the
males, and in some species (Ammothea, Trygaeus) the latter are
distinguished by a greater development of spines or tubercles on the body
and basal joints of the legs (Dohrn).
The act of fecundation has been observed by Cole[408] in Anoplodactylus.
The animal reproduces towards the end of August. Consorting on their
Page 572
Eudendrium (Hydroid) colony, the male climbs upon the female and crawls
over her head to lie beneath her, head to tail; and then, fertilisation taking
place the while, the hooked ovigerous legs of the male fasten into the
extruding egg-masses and tear them away. The whole process is over in five
minutes. The fresh egg-masses are more or less irregular in shape, and
white in colour like little tufts of cotton.
Each ball of eggs that the male carries represents the entire brood of one
female, and in Phoxichilidium Loman has seen a male carrying as many as
fourteen balls. Fertilisation is external, taking place while the eggs are being
laid. The spermatozoa have small rounded heads and long tails, and are thus
unlike the spermatozoa of most Crustacea.
Development.—Until the hatching of the embryo, the eggs of the
Pycnogons are carried about, agglutinated by cement-substance into
coherent packets, on the ovigerous legs of the males. They are larger or
smaller according to the amount of yolk-substance present, very small in
Phoxichilidium and Tanystylum (Morgan), where they measure only ·05
mm. in diameter; larger in Pallene (·25 mm.); larger still (·5–·7 mm.) in
Nymphon. In Pallene each egg-mass commonly contains only two eggs; in
the other genera they are much more numerous, rising to a hundred or more
in Ammothea (Dohrn). The egg-masses may be one or more on each
ovigerous leg, sometimes (Phoxichilidium angulatum, Dohrn) a single egg-
mass is held by both legs; they are extremely numerous in Phoxichilus, and
in Pycnogonum they coalesce to form a broad pad beneath the body. The
fact that it is the male and not the female that carries the eggs was only
announced in 1877 by Cavanna;[409] before, and by some even after his time,
the two sexes were constantly confused.[410]
Segmentation is complete, symmetrical in the forms with smaller eggs,
unequal in those burdened with a preponderance of yolk (Morgan). In
Pallene, as in the Spider’s egg, what is described as at first a total
segmentation passes into a superficial or centrolecithal one by the migration
outwards of the nuclei and the breaking down of the inner ends of the
wedge-shaped segmentation-cells. The blastoderm so formed becomes
concentrated at the germinal pole of the egg. A thickened portion of the
blastoderm (which Morgan compares to the “cumulus primitivus” of the
Spider’s egg) forms an apparently blastoporal invagination (though Morgan
calls it the stomodaeum), and from its sides are budded off the mesodermal
over her head to lie beneath her, head to tail; and then, fertilisation taking
place the while, the hooked ovigerous legs of the male fasten into the
extruding egg-masses and tear them away. The whole process is over in five
minutes. The fresh egg-masses are more or less irregular in shape, and
white in colour like little tufts of cotton.
Each ball of eggs that the male carries represents the entire brood of one
female, and in Phoxichilidium Loman has seen a male carrying as many as
fourteen balls. Fertilisation is external, taking place while the eggs are being
laid. The spermatozoa have small rounded heads and long tails, and are thus
unlike the spermatozoa of most Crustacea.
Development.—Until the hatching of the embryo, the eggs of the
Pycnogons are carried about, agglutinated by cement-substance into
coherent packets, on the ovigerous legs of the males. They are larger or
smaller according to the amount of yolk-substance present, very small in
Phoxichilidium and Tanystylum (Morgan), where they measure only ·05
mm. in diameter; larger in Pallene (·25 mm.); larger still (·5–·7 mm.) in
Nymphon. In Pallene each egg-mass commonly contains only two eggs; in
the other genera they are much more numerous, rising to a hundred or more
in Ammothea (Dohrn). The egg-masses may be one or more on each
ovigerous leg, sometimes (Phoxichilidium angulatum, Dohrn) a single egg-
mass is held by both legs; they are extremely numerous in Phoxichilus, and
in Pycnogonum they coalesce to form a broad pad beneath the body. The
fact that it is the male and not the female that carries the eggs was only
announced in 1877 by Cavanna;[409] before, and by some even after his time,
the two sexes were constantly confused.[410]
Segmentation is complete, symmetrical in the forms with smaller eggs,
unequal in those burdened with a preponderance of yolk (Morgan). In
Pallene, as in the Spider’s egg, what is described as at first a total
segmentation passes into a superficial or centrolecithal one by the migration
outwards of the nuclei and the breaking down of the inner ends of the
wedge-shaped segmentation-cells. The blastoderm so formed becomes
concentrated at the germinal pole of the egg. A thickened portion of the
blastoderm (which Morgan compares to the “cumulus primitivus” of the
Spider’s egg) forms an apparently blastoporal invagination (though Morgan
calls it the stomodaeum), and from its sides are budded off the mesodermal
Page 573
bands. Meisenheimer has recently
given a minute account of the early
development of Ammothea, a form
with small yolkless eggs. Here
certain cells of the uniform and
almost solid blastosphere grow
inwards till their nuclei arrange
themselves in an inner layer of what
(so far as they are concerned) is a
typical gastrula, but without any
central cavity. The inner layer
subsequently, but slowly,
differentiates into the mid-gut, and
into dorsal and lateral offshoots, the
sources of the heart and of the
muscles and connective tissues
respectively. The further
Fig. 280.—Young larva (nat. size ·1 mm.) of development of the egg takes place,
Ammothea fibulifera, Dohrn. C.G, Brain; gl, gld,
gland and duct of chelophore; pr, proboscis; I,
as is usual in Arthropods, by the
II, III, IV, appendages. (After Dohrn.) appearance, in a longitudinal strip or
germ-band which enwraps the yolk,
of paired thickenings which represent
the cerebral and post-oral ganglia, and of others from which arise the limbs.
Of these latter, the chelophores are the first to appear, on either side of the
mouth; in Pallene the fourth pair appears next in order, followed by the fifth
and sixth, and by the third and seventh just before the hatching out of the
embryo; the second is lacking in this particular genus. Thus in Pallene
(Dohrn, Morgan), and in some others, e.g. Nymphon brevicollum (Hoek),
the free larva is from the first provided with its full complement of limbs.
Certain other species of Nymphon hatch out in possession of four or five
pairs of limbs, but in the great majority of cases studied the larval Pycnogon
is at first provided with three pairs only, the three anterior pairs of the
typical adult.[411] Numerical coincidence, and that alone, has often led this
“Protonymphon” larva to be compared with the Crustacean Nauplius. In the
annexed figure of a young larval Ammothea (Achelia), we see the
unsegmented body, the already chelate chelophores (furnished with the
provisional cement-glands already described), the other two pairs of
given a minute account of the early
development of Ammothea, a form
with small yolkless eggs. Here
certain cells of the uniform and
almost solid blastosphere grow
inwards till their nuclei arrange
themselves in an inner layer of what
(so far as they are concerned) is a
typical gastrula, but without any
central cavity. The inner layer
subsequently, but slowly,
differentiates into the mid-gut, and
into dorsal and lateral offshoots, the
sources of the heart and of the
muscles and connective tissues
respectively. The further
Fig. 280.—Young larva (nat. size ·1 mm.) of development of the egg takes place,
Ammothea fibulifera, Dohrn. C.G, Brain; gl, gld,
gland and duct of chelophore; pr, proboscis; I,
as is usual in Arthropods, by the
II, III, IV, appendages. (After Dohrn.) appearance, in a longitudinal strip or
germ-band which enwraps the yolk,
of paired thickenings which represent
the cerebral and post-oral ganglia, and of others from which arise the limbs.
Of these latter, the chelophores are the first to appear, on either side of the
mouth; in Pallene the fourth pair appears next in order, followed by the fifth
and sixth, and by the third and seventh just before the hatching out of the
embryo; the second is lacking in this particular genus. Thus in Pallene
(Dohrn, Morgan), and in some others, e.g. Nymphon brevicollum (Hoek),
the free larva is from the first provided with its full complement of limbs.
Certain other species of Nymphon hatch out in possession of four or five
pairs of limbs, but in the great majority of cases studied the larval Pycnogon
is at first provided with three pairs only, the three anterior pairs of the
typical adult.[411] Numerical coincidence, and that alone, has often led this
“Protonymphon” larva to be compared with the Crustacean Nauplius. In the
annexed figure of a young larval Ammothea (Achelia), we see the
unsegmented body, the already chelate chelophores (furnished with the
provisional cement-glands already described), the other two pairs of
Page 574
appendages each with a curious spine at its base, the gut beginning to send
out diverticula (of which the first pair approach the chelophores) but still
destitute of the anus (which is only to be formed after the development of
the abdomen), the proboscis, and one pair of eyes situated close over the
pre-oral ganglia. The subsequent changes are in this genus extremely
protracted, and terminate with the loss of the chelae, a process which occurs
so late in life that the chelate individuals were long looked upon as
belonging to a separate genus, the original Ammothea of Hodge, until Hoek
proved their identity with the clawless Achelia.
The developmental history of Phoxichilidium and Anoplodactylus is
peculiar. The young larvae have the claws of the second and third
appendages hypertrophied to form enormous stiff tendril-like organs, with
which they affix themselves to the bodies of Hydroid Zoophytes (Coryne,
Eudendrium, Tubularia, Hydractinia, etc.), feeding as the adults do:
afterwards losing these elongated tendrils in a moult, they pass into the
gastral cavity of the Hydroid; in our native species the larva issues from the
Hydroid and begins its independent life at a stage when three pairs of
ambulatory legs are present and the fourth is in bud.[412] The Phoxichilidium
larvae were first noticed by Gegenbaur in Eudendrium,[413] again by Allman
in Coryne eximia.[414] George Hodge made detailed and important
observations,[415] and showed, in opposition to Gegenbaur, that it was the
larva which entered the Hydroid and not the egg that was laid therein.[416]
out diverticula (of which the first pair approach the chelophores) but still
destitute of the anus (which is only to be formed after the development of
the abdomen), the proboscis, and one pair of eyes situated close over the
pre-oral ganglia. The subsequent changes are in this genus extremely
protracted, and terminate with the loss of the chelae, a process which occurs
so late in life that the chelate individuals were long looked upon as
belonging to a separate genus, the original Ammothea of Hodge, until Hoek
proved their identity with the clawless Achelia.
The developmental history of Phoxichilidium and Anoplodactylus is
peculiar. The young larvae have the claws of the second and third
appendages hypertrophied to form enormous stiff tendril-like organs, with
which they affix themselves to the bodies of Hydroid Zoophytes (Coryne,
Eudendrium, Tubularia, Hydractinia, etc.), feeding as the adults do:
afterwards losing these elongated tendrils in a moult, they pass into the
gastral cavity of the Hydroid; in our native species the larva issues from the
Hydroid and begins its independent life at a stage when three pairs of
ambulatory legs are present and the fourth is in bud.[412] The Phoxichilidium
larvae were first noticed by Gegenbaur in Eudendrium,[413] again by Allman
in Coryne eximia.[414] George Hodge made detailed and important
observations,[415] and showed, in opposition to Gegenbaur, that it was the
larva which entered the Hydroid and not the egg that was laid therein.[416]
Page 575
Fig. 281.—Larva of Phoxichilidium sp., showing tendril-like appendages of the
larval palps and ovigerous legs. (After Dohrn.)
Moseley has the following interesting note in his Challenger Report:[417]
“The most interesting parasite observed was a form found in the gastric
cavities of the gastrozoids of Pliobothrus symmetricus (West Indies, 450 f.),
contained in small capsules. These capsules were badly preserved, but there
seemed little doubt that they contained the remains of larvae of a
Pycnogonid, so that the deep-sea Pycnogonids, which are so abundant, very
possibly pass through their early stages in deep-sea Stylasteridae.... The
gastrozoids containing the larvae were partly aborted.”
A Pycnogon larva, doubtfully ascribed to Nymphon, has been found
living in abundance ectoparasitically on Tethys in the Bay of Naples.[418]
Habits.—Of the intimate habits of the Pycnogons we can say little.
Pycnogonum we often find clinging, as has been said, close appressed to
some large Anemone (Tealia, Bolocera, etc.), whose living juices it very
probably imbibes. The more slender species we find climbing over sea-
weeds and Zoophytes, where sometimes similarity of colour as well as
delicacy of form helps to conceal them; thus Phoxichilidium femoratum
(Orithyia coccinea, Johnston) is red like the Corallines among which we
often find it, P. virescens green like the filamentous Ulvae, the Nymphons
yellowish like the Hydrallmania and other Zoophytes which they affect. On
the New England coast, according to Cole, the dark purple Anoplodactylus
larval palps and ovigerous legs. (After Dohrn.)
Moseley has the following interesting note in his Challenger Report:[417]
“The most interesting parasite observed was a form found in the gastric
cavities of the gastrozoids of Pliobothrus symmetricus (West Indies, 450 f.),
contained in small capsules. These capsules were badly preserved, but there
seemed little doubt that they contained the remains of larvae of a
Pycnogonid, so that the deep-sea Pycnogonids, which are so abundant, very
possibly pass through their early stages in deep-sea Stylasteridae.... The
gastrozoids containing the larvae were partly aborted.”
A Pycnogon larva, doubtfully ascribed to Nymphon, has been found
living in abundance ectoparasitically on Tethys in the Bay of Naples.[418]
Habits.—Of the intimate habits of the Pycnogons we can say little.
Pycnogonum we often find clinging, as has been said, close appressed to
some large Anemone (Tealia, Bolocera, etc.), whose living juices it very
probably imbibes. The more slender species we find climbing over sea-
weeds and Zoophytes, where sometimes similarity of colour as well as
delicacy of form helps to conceal them; thus Phoxichilidium femoratum
(Orithyia coccinea, Johnston) is red like the Corallines among which we
often find it, P. virescens green like the filamentous Ulvae, the Nymphons
yellowish like the Hydrallmania and other Zoophytes which they affect. On
the New England coast, according to Cole, the dark purple Anoplodactylus
Page 576
lentus, Wilson (Phoxichilidium maxillare, Stimpson), is especially abundant
on colonies of Eudendrium, whose colour matches its own, the yellowish
Tanystylum orbiculare frequents a certain yellowish Hydroid, and of these
two species neither is ever found on the Hydroid affected by the other;
while, on the other hand, Pallene brevirostris, whose whitish, almost
transparent body is difficult to see, is more generally distributed.[419] The
deep-sea Pycnogons (Colossendeis, Nymphon) are generally (if not
universally) of a deep orange-scarlet colour, a common dress of many deep-
sea Crustacea.
The movements of the Pycnogons are singularly slow and deliberate;
they are manifestly not adapted to capture or to kill a living prey. Linnaeus
accepted from J. C. König the singular statement that they enter and feed
upon bivalve shells, “Mytilorum testes penetrat et exhaurit”; but the
statement has never been reaffirmed.[420]
Loman describes Phoxichilidium as feeding greedily on Tubularia larynx,
and especially on the gonophores. It grasps them with its claws, sucks them
in bit by bit till the proboscis is filled as far as the sieve, whereupon that
part of the proboscis squeezes and kneads the mass, letting only juices and
fine particles pass through into the alimentary canal. The lateral caeca and
the rectum are separated by sphincter muscles from the stomach; the former
are in turn filled with food and again emptied; the contents of the
alimentary canal are in constant rolling movement, and the faeces are
eliminated by the action of a pair of levatores ani, in round pellets.
The Pycnogons, or some of them, can swim by “treading water,” and
Pallene is said by Cole to swim especially well; they more often progress
half by swimming, half by kicking on the bottom. They move promptly
towards the light, unless they have Hydroids to cling to, and Cole points out
that when they crawl with all their legs on the bottom they move forwards
towards the light,[421] but backwards when they swim in part or whole. The
legs move mostly in a vertical plane, horizontal movements taking place
chiefly between the first and second joints. Tanystylum is uncommonly
sluggish and inert; it sinks to the bottom, draws its legs over its back and
remains quiet, while Pallene, by vigorous kicks, remains suspended.
The long legs of the Pycnogons are easily injured or lost, and easily
repaired or regenerated. This observation, often repeated, is as old as
Fabricius: “Mutilatur etiam in libertate sua, redintegrandum tamen; vidi
on colonies of Eudendrium, whose colour matches its own, the yellowish
Tanystylum orbiculare frequents a certain yellowish Hydroid, and of these
two species neither is ever found on the Hydroid affected by the other;
while, on the other hand, Pallene brevirostris, whose whitish, almost
transparent body is difficult to see, is more generally distributed.[419] The
deep-sea Pycnogons (Colossendeis, Nymphon) are generally (if not
universally) of a deep orange-scarlet colour, a common dress of many deep-
sea Crustacea.
The movements of the Pycnogons are singularly slow and deliberate;
they are manifestly not adapted to capture or to kill a living prey. Linnaeus
accepted from J. C. König the singular statement that they enter and feed
upon bivalve shells, “Mytilorum testes penetrat et exhaurit”; but the
statement has never been reaffirmed.[420]
Loman describes Phoxichilidium as feeding greedily on Tubularia larynx,
and especially on the gonophores. It grasps them with its claws, sucks them
in bit by bit till the proboscis is filled as far as the sieve, whereupon that
part of the proboscis squeezes and kneads the mass, letting only juices and
fine particles pass through into the alimentary canal. The lateral caeca and
the rectum are separated by sphincter muscles from the stomach; the former
are in turn filled with food and again emptied; the contents of the
alimentary canal are in constant rolling movement, and the faeces are
eliminated by the action of a pair of levatores ani, in round pellets.
The Pycnogons, or some of them, can swim by “treading water,” and
Pallene is said by Cole to swim especially well; they more often progress
half by swimming, half by kicking on the bottom. They move promptly
towards the light, unless they have Hydroids to cling to, and Cole points out
that when they crawl with all their legs on the bottom they move forwards
towards the light,[421] but backwards when they swim in part or whole. The
legs move mostly in a vertical plane, horizontal movements taking place
chiefly between the first and second joints. Tanystylum is uncommonly
sluggish and inert; it sinks to the bottom, draws its legs over its back and
remains quiet, while Pallene, by vigorous kicks, remains suspended.
The long legs of the Pycnogons are easily injured or lost, and easily
repaired or regenerated. This observation, often repeated, is as old as
Fabricius: “Mutilatur etiam in libertate sua, redintegrandum tamen; vidi
Page 577
enim in quo pedes brevissimi juxta longiores enascentes, velut in asteriis
cancris aliisque redintegratis.” In such cases of redintegration of a leg, the
reproductive organ, the genital orifice, and the cement-gland are not
restored until the next moult.[422]
Systematic Position.—To bring this little group into closer accord with
one or other of the greater groups of Arthropods is a problem seemingly
simple but really full of difficulty.
The larval Pycnogon, with its three pairs of appendages, resembles the
Crustacean Nauplius in no single feature save this unimportant numerical
coincidence; nor is there any significance in the apparent outward
resemblance to isolated forms (e.g. Cyamus) that induced some of the older
writers, from Fabricius downwards and including Kröyer and the elder
Milne-Edwards, to connect the Pycnogons with the Crustacea. To refer
them, or to approximate them to the Arachnids, has been a stronger and a
more lasting tendency.[423] Linnaeus (1767) included the two species of
which he was cognisant in the genus Phalangium, together with P. opilio.
Lamarck, who first formulated the group Arachnida (1802), let it embrace
the Pycnogons; and Latreille (1804, 1810), who immediately followed him,
defined more clearly the Pycnogonida as a subdivision of the greater group,
side by side with the subdivision that corresponds to our modern Arachnida
(“Arachnides acères”), and together with a medley of lower Crustacea,
Myriapoda, Thysanura, and Parasitic Insects; he was so cautious as to add
“j’observerai seulement, que je ne connais pas encore bien la place naturelle
des Pycnogonides et des Parasites,” and Cuvier, setting them in a similar
position, adds a similar qualification.[424]
Leach (1814), whose great service it was to dissociate the
Edriophthalmata and the Myriapoda from the Latreillian medley, left the
group Arachnida as we still have it (save for the inclusion of the Dipterous
Insect Nycteribia), and divided the group (with the same exception) into
four Orders of which the Podosomata, i.e. the Pycnogonida, are one.
Savigny (1816), less philosophical in this case than was his wont, assumed
the Crustacean type to pass to the Arachnidan by a loss of several anterior
pairs of appendages, and appears to set the Pycnogons in an intermediate
grade, marking the pathway of the change. He considered the seven pairs of
limbs of the Pycnogons to represent thoracic limbs of a Malacostracan, and,
like so many of his contemporaries, was much biased by the apparent
cancris aliisque redintegratis.” In such cases of redintegration of a leg, the
reproductive organ, the genital orifice, and the cement-gland are not
restored until the next moult.[422]
Systematic Position.—To bring this little group into closer accord with
one or other of the greater groups of Arthropods is a problem seemingly
simple but really full of difficulty.
The larval Pycnogon, with its three pairs of appendages, resembles the
Crustacean Nauplius in no single feature save this unimportant numerical
coincidence; nor is there any significance in the apparent outward
resemblance to isolated forms (e.g. Cyamus) that induced some of the older
writers, from Fabricius downwards and including Kröyer and the elder
Milne-Edwards, to connect the Pycnogons with the Crustacea. To refer
them, or to approximate them to the Arachnids, has been a stronger and a
more lasting tendency.[423] Linnaeus (1767) included the two species of
which he was cognisant in the genus Phalangium, together with P. opilio.
Lamarck, who first formulated the group Arachnida (1802), let it embrace
the Pycnogons; and Latreille (1804, 1810), who immediately followed him,
defined more clearly the Pycnogonida as a subdivision of the greater group,
side by side with the subdivision that corresponds to our modern Arachnida
(“Arachnides acères”), and together with a medley of lower Crustacea,
Myriapoda, Thysanura, and Parasitic Insects; he was so cautious as to add
“j’observerai seulement, que je ne connais pas encore bien la place naturelle
des Pycnogonides et des Parasites,” and Cuvier, setting them in a similar
position, adds a similar qualification.[424]
Leach (1814), whose great service it was to dissociate the
Edriophthalmata and the Myriapoda from the Latreillian medley, left the
group Arachnida as we still have it (save for the inclusion of the Dipterous
Insect Nycteribia), and divided the group (with the same exception) into
four Orders of which the Podosomata, i.e. the Pycnogonida, are one.
Savigny (1816), less philosophical in this case than was his wont, assumed
the Crustacean type to pass to the Arachnidan by a loss of several anterior
pairs of appendages, and appears to set the Pycnogons in an intermediate
grade, marking the pathway of the change. He considered the seven pairs of
limbs of the Pycnogons to represent thoracic limbs of a Malacostracan, and,
like so many of his contemporaries, was much biased by the apparent
Page 578
resemblance of Cyamus to Pycnogonum. The reader may find in Dohrn’s
Monograph a guide to many other opinions and judgments, some of them of
no small morphological interest and historical value[425]; but it behoves us to
pass them by, and to inspect, in brief, the case as it stands at present. The
obvious features in which a Pycnogon resembles a Spider or other typical
Arachnid, are the possession of four pairs of walking legs, and the pre-oral
position and chelate form of the first pair of appendages; we may perhaps
also add, as a more general feature of resemblance, the imperfect
subservience of limbs to the mouth as compared with any of the Crustacea.
The resemblance would still be striking, in spite of the presence of an
additional pair of legs in a few Pycnogons, were it not for the presence of
the third pair of appendages or ovigerous legs of the Pycnogon, whose
intercalation spoils the apparent harmony. We are neither at liberty to
suppose, with Claus, that these members, so important in the larva, have
been interpolated, as it were, anew in the Pycnogon; nor that they have
arisen by subdivision of the second pair, as Schimkewitsch is inclined to
suppose; nor that they have dropped out of the series in the Arachnid,
whose body presents no trace of them in embryo or adult. In a word, their
presence precludes us from assuming a direct homology between the
apparently similar limbs of the two groups,[426] and at best leaves it only
open to us to compare the last legs of the Pycnogon with the first
abdominal, or genital, appendages of the Scorpion and the Spider. On the
other hand, if we admit the seventh (as we must admit the occasional
eighth) pair of appendages of Pycnogons to be unrepresented in the
prosoma of the Arachnids, then, in the cephalothorax of the former, with its
four pairs of appendages, we may find the homologue of the more or less
free and separate part of the cephalothorax in Koenenia, Galeodes, and the
Tartaridae. There is a resemblance between the two groups in the presence
of intestinal diverticula that run towards or into the limbs, as in Spiders and
some Mites, and there are certain histological and embryological
resemblances that have been in part referred to above; but these, such as
they are, are not adequate guides to morphological classification. We must
bear in mind that such resemblances as the Pycnogons seem to show are not
with the lower Arachnids but with the higher; they are either degenerates
from very advanced and specialised Arachnida, or they are lower than the
lowest. Confronted with such an issue, we cannot but conclude to let the
Pycnogons stand apart, an independent group of Arthropods[427]; and I am
Monograph a guide to many other opinions and judgments, some of them of
no small morphological interest and historical value[425]; but it behoves us to
pass them by, and to inspect, in brief, the case as it stands at present. The
obvious features in which a Pycnogon resembles a Spider or other typical
Arachnid, are the possession of four pairs of walking legs, and the pre-oral
position and chelate form of the first pair of appendages; we may perhaps
also add, as a more general feature of resemblance, the imperfect
subservience of limbs to the mouth as compared with any of the Crustacea.
The resemblance would still be striking, in spite of the presence of an
additional pair of legs in a few Pycnogons, were it not for the presence of
the third pair of appendages or ovigerous legs of the Pycnogon, whose
intercalation spoils the apparent harmony. We are neither at liberty to
suppose, with Claus, that these members, so important in the larva, have
been interpolated, as it were, anew in the Pycnogon; nor that they have
arisen by subdivision of the second pair, as Schimkewitsch is inclined to
suppose; nor that they have dropped out of the series in the Arachnid,
whose body presents no trace of them in embryo or adult. In a word, their
presence precludes us from assuming a direct homology between the
apparently similar limbs of the two groups,[426] and at best leaves it only
open to us to compare the last legs of the Pycnogon with the first
abdominal, or genital, appendages of the Scorpion and the Spider. On the
other hand, if we admit the seventh (as we must admit the occasional
eighth) pair of appendages of Pycnogons to be unrepresented in the
prosoma of the Arachnids, then, in the cephalothorax of the former, with its
four pairs of appendages, we may find the homologue of the more or less
free and separate part of the cephalothorax in Koenenia, Galeodes, and the
Tartaridae. There is a resemblance between the two groups in the presence
of intestinal diverticula that run towards or into the limbs, as in Spiders and
some Mites, and there are certain histological and embryological
resemblances that have been in part referred to above; but these, such as
they are, are not adequate guides to morphological classification. We must
bear in mind that such resemblances as the Pycnogons seem to show are not
with the lower Arachnids but with the higher; they are either degenerates
from very advanced and specialised Arachnida, or they are lower than the
lowest. Confronted with such an issue, we cannot but conclude to let the
Pycnogons stand apart, an independent group of Arthropods[427]; and I am
Page 579
inclined to think that they conserve primitive features in the usual presence
of generative apertures on several pairs of limbs, and probably also in the
non-development of any special respiratory organs. But inasmuch as the
weight of evidence goes to show that subservience of limbs to mouth is a
primitive Arthropodan character, the fact that the basal elements of the
anterior appendages have here (as in Koenenia) no such relation to the
mouth must be taken as evidence, not of antiquity, but of specialisation. In
like manner the suctorial proboscis cannot be deemed a primitive character,
and the much reduced abdomen also is obviously secondary and not
primitive.
Classification.—No single genus more than another shows signs of
affinity with other groups, and no single organ gives us, within the group, a
clear picture of advancing stages of complexity. On the contrary, the
differences between one genus and another depend very much on degrees of
degeneration of the anterior appendages, and we have no reason to suppose
that these stages of degeneration form a single continuous series, but have
rather reason to believe that degeneration has set in independently in
various ways and at various points in the series. But while we are unable at
present to form a natural classification[428] of the Pycnogons, yet at the same
time a purely arbitrary or artificial classification, conveniently based on the
presence or absence of certain limbs, would run counter to such natural
relationships as we can already discern.
The classification here adopted is a compromise between a natural
system, so far as we can detect it, and an artificial one.
Two forms, separated from one another by many differences, show a
minimum of degeneration, namely Decolopoda on the one hand, and the
Nymphonidae on the other. The former genus has five pairs of legs, and this
peculiarity is shared by Pentanymphon. In both groups the three anterior
limbs are all present and well formed, save only that the ovigerous legs,
which have ten joints in Decolopoda, are reduced to five joints in the
Nymphons, and their denticulate spines, of which several rows are present
in the former, are reduced to one row in the latter; on the other hand, a
greater or a less degeneration of these limbs marks each and all of the other
families.
Decolopoda is very probably the most primitive form known, though it
has characters which seem to be the reverse of primitive in the dwarfish size
of generative apertures on several pairs of limbs, and probably also in the
non-development of any special respiratory organs. But inasmuch as the
weight of evidence goes to show that subservience of limbs to mouth is a
primitive Arthropodan character, the fact that the basal elements of the
anterior appendages have here (as in Koenenia) no such relation to the
mouth must be taken as evidence, not of antiquity, but of specialisation. In
like manner the suctorial proboscis cannot be deemed a primitive character,
and the much reduced abdomen also is obviously secondary and not
primitive.
Classification.—No single genus more than another shows signs of
affinity with other groups, and no single organ gives us, within the group, a
clear picture of advancing stages of complexity. On the contrary, the
differences between one genus and another depend very much on degrees of
degeneration of the anterior appendages, and we have no reason to suppose
that these stages of degeneration form a single continuous series, but have
rather reason to believe that degeneration has set in independently in
various ways and at various points in the series. But while we are unable at
present to form a natural classification[428] of the Pycnogons, yet at the same
time a purely arbitrary or artificial classification, conveniently based on the
presence or absence of certain limbs, would run counter to such natural
relationships as we can already discern.
The classification here adopted is a compromise between a natural
system, so far as we can detect it, and an artificial one.
Two forms, separated from one another by many differences, show a
minimum of degeneration, namely Decolopoda on the one hand, and the
Nymphonidae on the other. The former genus has five pairs of legs, and this
peculiarity is shared by Pentanymphon. In both groups the three anterior
limbs are all present and well formed, save only that the ovigerous legs,
which have ten joints in Decolopoda, are reduced to five joints in the
Nymphons, and their denticulate spines, of which several rows are present
in the former, are reduced to one row in the latter; on the other hand, a
greater or a less degeneration of these limbs marks each and all of the other
families.
Decolopoda is very probably the most primitive form known, though it
has characters which seem to be the reverse of primitive in the dwarfish size
Page 580
of its chelophores and the crowded coalescent segmentation of the trunk.
Colossendeis, in spite of its vanished chelophores, is probably closely
allied: the shape and segmentation of the body and the several rows of
smooth denticles on the ovigerous legs are points in common. The
Eurycydidae are closely allied to Colossendeidae; they agree with
Decolopoda in the two-jointed scape of the chelophore, and with
Ammotheidae in the deflexed mobile proboscis. The true position of
Rhynchothorax is very doubtful.
The Nymphonidae and Pallenidae are closely allied, and the
Phoxichilidiidae have points of resemblance, especially with the latter.
Nymphon compares with Decolopoda in the completeness of its parts, and
is more typical in its long well-segmented body, and in its highly-developed
chelae; but it already shows reduction in the scape of the chelophore, in the
palps, and in the armature of the ovigerous legs.
The Phoxichilidae and Pycnogonidae (Agnathonia, Leach; Achelata,
Sars), though differing greatly in aspect, are not improbably allied to one
another; and whether this be so or not, the complete absence of chelophores
and of palps affords an arbitrary character by which they are conveniently
separated from all the rest.
The following table epitomises the chief characters of the several
families:—
Colossendeis, in spite of its vanished chelophores, is probably closely
allied: the shape and segmentation of the body and the several rows of
smooth denticles on the ovigerous legs are points in common. The
Eurycydidae are closely allied to Colossendeidae; they agree with
Decolopoda in the two-jointed scape of the chelophore, and with
Ammotheidae in the deflexed mobile proboscis. The true position of
Rhynchothorax is very doubtful.
The Nymphonidae and Pallenidae are closely allied, and the
Phoxichilidiidae have points of resemblance, especially with the latter.
Nymphon compares with Decolopoda in the completeness of its parts, and
is more typical in its long well-segmented body, and in its highly-developed
chelae; but it already shows reduction in the scape of the chelophore, in the
palps, and in the armature of the ovigerous legs.
The Phoxichilidae and Pycnogonidae (Agnathonia, Leach; Achelata,
Sars), though differing greatly in aspect, are not improbably allied to one
another; and whether this be so or not, the complete absence of chelophores
and of palps affords an arbitrary character by which they are conveniently
separated from all the rest.
The following table epitomises the chief characters of the several
families:—
Page 581
Pycnogonida. Proboscis. Chelophores. Palps. Ovigerous Teeth on Legs. Trunk- Genital
legs. do. segments. Openings.
♂ ♀
(Cryptochelata,
Sars)—
Decolopodidae Fixed, Complete, 10 joints 10 joints Four 5 Condensed, 1, 1,
decurved small, scape ♂, ♀ rows, coalescent 2, 2,
2–jointed simple 3, 3,
4, 4, 5
5,
Colossendeidae Somewhat 0 10 10 ♂, ♀ Many 4 Coalescent 1, 1,
mobile, rows, 2, 2,
sometimes simple 3, 4 3, 4
decurved
Eurycididae Mobile, Scape 2– 10 10 ♂, ♀ More 4 Well 3, 4 1,
stalked, jointed, than one segmented 2,
deflexed chelae row, 3, 4
rudimentary serrate
Hannonia „ Rudimentary 0 10 ♂, ♀ Scattered 4 „ „ „
spines
Ammotheidae Mobile, „ 4–9 10 (or Few, 4 Condensed, „ „
deflexed less) ♂, ♀ scattered, segmented
serrate or
smooth
? Large, 0 8 (5) 10 ♂, ♀ Toothed 4 „ 4 4
Rhynchothoracidae fixed, tubercles
aberrant
(Euchelata, Sars)
—
Nymphonidae Large, Large, scape 5 (7) 8–10 ♂, ♀ One row, 4–5 Well 2, 1,
fixed 1–jointed serrate segmented 3, 4 2,
(5) 3, 4
(5)
Pallenidae „ „ 0 or 10 ♂, ♀ „ 4 „ (1, „
rudimentary 2),
3, 4
Phoxichilidiidae „ „ 0 5–6 ♂ One row, 4 „ 1, „
simple 2,
3, 4
(Achelata, Sars)—
Phoxichilidae Large, 0 0 7♂ Scattered, 4 Well 2, 1,
fixed simple segmented 3, 4 2,
3, 4
Pycnogonidae „ 0 0 9♂ Small, 4 Segmented, 4 4
irregular condensed
CLASS PYCNOGONIDA.[429]
Marine Arthropoda, with typically seven (and very exceptionally eight)
pairs of appendages, of which none have their basal joints subservient to
mastication, the first three are subject to suppression, the first (when
present) are chelate, the second palpiform, the third ovigerous, and the rest
form ambulatory limbs, usually very slender and long; with a suctorial
legs. do. segments. Openings.
♂ ♀
(Cryptochelata,
Sars)—
Decolopodidae Fixed, Complete, 10 joints 10 joints Four 5 Condensed, 1, 1,
decurved small, scape ♂, ♀ rows, coalescent 2, 2,
2–jointed simple 3, 3,
4, 4, 5
5,
Colossendeidae Somewhat 0 10 10 ♂, ♀ Many 4 Coalescent 1, 1,
mobile, rows, 2, 2,
sometimes simple 3, 4 3, 4
decurved
Eurycididae Mobile, Scape 2– 10 10 ♂, ♀ More 4 Well 3, 4 1,
stalked, jointed, than one segmented 2,
deflexed chelae row, 3, 4
rudimentary serrate
Hannonia „ Rudimentary 0 10 ♂, ♀ Scattered 4 „ „ „
spines
Ammotheidae Mobile, „ 4–9 10 (or Few, 4 Condensed, „ „
deflexed less) ♂, ♀ scattered, segmented
serrate or
smooth
? Large, 0 8 (5) 10 ♂, ♀ Toothed 4 „ 4 4
Rhynchothoracidae fixed, tubercles
aberrant
(Euchelata, Sars)
—
Nymphonidae Large, Large, scape 5 (7) 8–10 ♂, ♀ One row, 4–5 Well 2, 1,
fixed 1–jointed serrate segmented 3, 4 2,
(5) 3, 4
(5)
Pallenidae „ „ 0 or 10 ♂, ♀ „ 4 „ (1, „
rudimentary 2),
3, 4
Phoxichilidiidae „ „ 0 5–6 ♂ One row, 4 „ 1, „
simple 2,
3, 4
(Achelata, Sars)—
Phoxichilidae Large, 0 0 7♂ Scattered, 4 Well 2, 1,
fixed simple segmented 3, 4 2,
3, 4
Pycnogonidae „ 0 0 9♂ Small, 4 Segmented, 4 4
irregular condensed
CLASS PYCNOGONIDA.[429]
Marine Arthropoda, with typically seven (and very exceptionally eight)
pairs of appendages, of which none have their basal joints subservient to
mastication, the first three are subject to suppression, the first (when
present) are chelate, the second palpiform, the third ovigerous, and the rest
form ambulatory limbs, usually very slender and long; with a suctorial
Page 582
proboscis, a limbless, unsegmented abdomen, and no manifest respiratory
organs.
Fig. 282.—Decolopoda australis, Eights. A, × 1: from a specimen obtained at
the South Shetlands by the Scotia Expedition. B, First appendage, or chelophore.
(A, original; B, after Hodgson.)
Fam. 1. Decolopodidae.—Appendage I. dwarfed, but complete and
chelate, scape with two joints; II. 9–10–jointed; III. well developed in both
sexes, 10–jointed, the terminal joints with about four rows of teeth; five
pairs of legs, destitute of accessory claws; genital apertures on all the legs
(Bouvier).
Decolopoda australis, Eights[430] (1834), a remarkable form from the
South Shetlands, recently re-discovered by the Scotia expedition. The
animal is large, seven inches or more in total span, in colour scarlet; it was
found in abundance in shallow water and cast upon the shore. The body is
greatly condensed, the proboscis is “clavate, arcuated downwards,” and
organs.
Fig. 282.—Decolopoda australis, Eights. A, × 1: from a specimen obtained at
the South Shetlands by the Scotia Expedition. B, First appendage, or chelophore.
(A, original; B, after Hodgson.)
Fam. 1. Decolopodidae.—Appendage I. dwarfed, but complete and
chelate, scape with two joints; II. 9–10–jointed; III. well developed in both
sexes, 10–jointed, the terminal joints with about four rows of teeth; five
pairs of legs, destitute of accessory claws; genital apertures on all the legs
(Bouvier).
Decolopoda australis, Eights[430] (1834), a remarkable form from the
South Shetlands, recently re-discovered by the Scotia expedition. The
animal is large, seven inches or more in total span, in colour scarlet; it was
found in abundance in shallow water and cast upon the shore. The body is
greatly condensed, the proboscis is “clavate, arcuated downwards,” and
Page 583
beset with small spines. A second Antarctic species, D. antarctica, has been
described by Bouvier. The presence of a fifth pair of legs distinguishes
Decolopoda from all known Pycnogons, except Pentanymphon. Stebbing
would ally Decolopoda with, or even include it in, the Nymphonidae; but
the presence of a second joint in the chelophoral scape, the number of joints
in, and the armature on, the ovigerous legs, and the deflexed proboscis, are
all characters either agreeing with or tending towards those of the
Eurycididae; while the Colossendeidae would be very like Decolopoda
were it not for the complete suppression of the chelophores. It seems
convenient to constitute a new family for this remarkable form.
Fam. 2. Colossendeidae (Pasithoidae, Sars).—Appendage I. absent in
adult; appendage II. very long, 10–jointed; appendage III. 10–jointed,
clawed, with many rows of teeth; auxiliary claws absent; segments of trunk
fused; proboscis very large, somewhat mobile; genital apertures, in at least
some cases, on all the legs.
Pasithoe, Goodsir (1842), which Sars assumes as the type of the family,
is here relegated to Ammothea.[431] Colossendeis, Jarszynsky (1870)
(Anomorhynchus, Miers (1881), Rhopalorhynchus, Wood-Mason (1873)),
remains as the only genus commonly accepted: large, more or less slender
short-necked forms; world-wide, principally Arctic, Antarctic, and deep-
sea; about twenty-five species.[432] The largest species, C. gigas, Hoek, from
great depths in the Southern Ocean, has a span of about two feet. The North
Atlantic C. proboscidea and Antarctic C. australis are very closely related
to one another. Carpenter would retain the genus Rhopalorhynchus for R.
kröyeri, W.-M. (Andamans), R. clavipes, Carp. (Torres Straits), and R.
tenuissimus, Haswell (Australia), all more or less shallow-water species,
excessively attenuated, with the second and third body-segments elongated,
the caudal segment excessively reduced, the club-shaped proboscis on a
slender stalk, and other common characters. Pipetta weberi, Loman (1904),
is a large and remarkable form from the Banda Sea, apparently referable, in
spite of certain abnormal features, to this family; the proboscis is
extraordinarily long and slender; the palps have eight joints, the ovigerous
legs eleven.
Fam. 3. Eurycididae (Ascorhynchidae, Meinert).—Appendage I. more
or less reduced; appendage II. 10–jointed (absent in Hannonia); appendage
III. 10–jointed, clawed, with more than one tow of serrated teeth; proboscis
described by Bouvier. The presence of a fifth pair of legs distinguishes
Decolopoda from all known Pycnogons, except Pentanymphon. Stebbing
would ally Decolopoda with, or even include it in, the Nymphonidae; but
the presence of a second joint in the chelophoral scape, the number of joints
in, and the armature on, the ovigerous legs, and the deflexed proboscis, are
all characters either agreeing with or tending towards those of the
Eurycididae; while the Colossendeidae would be very like Decolopoda
were it not for the complete suppression of the chelophores. It seems
convenient to constitute a new family for this remarkable form.
Fam. 2. Colossendeidae (Pasithoidae, Sars).—Appendage I. absent in
adult; appendage II. very long, 10–jointed; appendage III. 10–jointed,
clawed, with many rows of teeth; auxiliary claws absent; segments of trunk
fused; proboscis very large, somewhat mobile; genital apertures, in at least
some cases, on all the legs.
Pasithoe, Goodsir (1842), which Sars assumes as the type of the family,
is here relegated to Ammothea.[431] Colossendeis, Jarszynsky (1870)
(Anomorhynchus, Miers (1881), Rhopalorhynchus, Wood-Mason (1873)),
remains as the only genus commonly accepted: large, more or less slender
short-necked forms; world-wide, principally Arctic, Antarctic, and deep-
sea; about twenty-five species.[432] The largest species, C. gigas, Hoek, from
great depths in the Southern Ocean, has a span of about two feet. The North
Atlantic C. proboscidea and Antarctic C. australis are very closely related
to one another. Carpenter would retain the genus Rhopalorhynchus for R.
kröyeri, W.-M. (Andamans), R. clavipes, Carp. (Torres Straits), and R.
tenuissimus, Haswell (Australia), all more or less shallow-water species,
excessively attenuated, with the second and third body-segments elongated,
the caudal segment excessively reduced, the club-shaped proboscis on a
slender stalk, and other common characters. Pipetta weberi, Loman (1904),
is a large and remarkable form from the Banda Sea, apparently referable, in
spite of certain abnormal features, to this family; the proboscis is
extraordinarily long and slender; the palps have eight joints, the ovigerous
legs eleven.
Fam. 3. Eurycididae (Ascorhynchidae, Meinert).—Appendage I. more
or less reduced; appendage II. 10–jointed (absent in Hannonia); appendage
III. 10–jointed, clawed, with more than one tow of serrated teeth; proboscis
Page 584
movably articulated and more or less bent under the body; auxiliary claws
absent.
Eurycide, Schiödte (1857) (Zetes,
Kröyer, 1845): Appendage I. with
two-jointed scape, without chelae in
adult; one species (E. hispida, (Kr.)),
from the North Atlantic and Arctic,
and two others from the East Indies,
recently described by Loman.
Barana arenicola, Dohrn (1881), is
nearly allied. Ascorhynchus, G. O. Fig. 283.—Eurycide hispida, Kr.; side view.
Sars (1876) (Gnamptorhynchus,
Böhm, 1879; Scaeorhynchus, Wilson, 1881), very similar to Eurycide, with
which, according to Schimkewitsch, it should be merged, includes large,
smooth, elongated forms, with long neck and expanded frontal region, and a
long proboscis lacking the long scape that supports the proboscis in
Eurycide; about twelve species, world-wide, mostly deep-water. Barana
castelli, Dohrn, from Naples is akin to the foregoing genera, but seems to
deserve generic separation from B. arenicola. Ammothea longicollis,
Haswell, from Australia, is, as Schimkewitsch has already remarked, almost
certainly a Eurycide, as is also, probably, Parazetes auchenicus, Slater,
from Japan.
Hannonia typica, Hoek (1880), from Cape Town, is a remarkable form,
lately redescribed by Loman. The chelophores are much reduced, the palps
are absent; the ovigerous legs are 10–jointed, and clawed; the terminal
joints of the latter bear long straight spines, scattered over their whole
surface; the proboscis is borne on a narrow stalk, and sharply deflexed. The
eggs form a single flattened mass, as in Pycnogonum. While the lack of
palps would set this genus among the Pallenidae, the remarkable proboscis
seems to be better evidence of affinity with Ascorhynchus and Eurycide.[433]
Nymphopsis, Haswell (1881), is a genus of doubtful affinities, placed
here by Schimkewitsch. The first appendage is well-developed and chelate;
the palps are 9–jointed, the ovigerous legs are 7–jointed, none of the joints
being provided with the compound spines seen in Nymphon and Pallene. It
is perhaps an immature form. Schimkewitsch has described another species,
N. korotnevi, and Loman a third, N. muscosus, both from the East Indies.
absent.
Eurycide, Schiödte (1857) (Zetes,
Kröyer, 1845): Appendage I. with
two-jointed scape, without chelae in
adult; one species (E. hispida, (Kr.)),
from the North Atlantic and Arctic,
and two others from the East Indies,
recently described by Loman.
Barana arenicola, Dohrn (1881), is
nearly allied. Ascorhynchus, G. O. Fig. 283.—Eurycide hispida, Kr.; side view.
Sars (1876) (Gnamptorhynchus,
Böhm, 1879; Scaeorhynchus, Wilson, 1881), very similar to Eurycide, with
which, according to Schimkewitsch, it should be merged, includes large,
smooth, elongated forms, with long neck and expanded frontal region, and a
long proboscis lacking the long scape that supports the proboscis in
Eurycide; about twelve species, world-wide, mostly deep-water. Barana
castelli, Dohrn, from Naples is akin to the foregoing genera, but seems to
deserve generic separation from B. arenicola. Ammothea longicollis,
Haswell, from Australia, is, as Schimkewitsch has already remarked, almost
certainly a Eurycide, as is also, probably, Parazetes auchenicus, Slater,
from Japan.
Hannonia typica, Hoek (1880), from Cape Town, is a remarkable form,
lately redescribed by Loman. The chelophores are much reduced, the palps
are absent; the ovigerous legs are 10–jointed, and clawed; the terminal
joints of the latter bear long straight spines, scattered over their whole
surface; the proboscis is borne on a narrow stalk, and sharply deflexed. The
eggs form a single flattened mass, as in Pycnogonum. While the lack of
palps would set this genus among the Pallenidae, the remarkable proboscis
seems to be better evidence of affinity with Ascorhynchus and Eurycide.[433]
Nymphopsis, Haswell (1881), is a genus of doubtful affinities, placed
here by Schimkewitsch. The first appendage is well-developed and chelate;
the palps are 9–jointed, the ovigerous legs are 7–jointed, none of the joints
being provided with the compound spines seen in Nymphon and Pallene. It
is perhaps an immature form. Schimkewitsch has described another species,
N. korotnevi, and Loman a third, N. muscosus, both from the East Indies.
Page 585
Fam. 4. Ammotheidae.—Akin to Eurycididae in having the proboscis
more or less movably jointed to the cephalic segment, and appendage I.
reduced, non-chelate in the adult; the body is compact and more or less
imperfectly segmented; appendage II. 4–9–jointed; appendage III. clawless,
and the number of joints sometimes diminished, with a sparse row of
serrated spines; auxiliary claws usually present.
Ammothea, Leach (1815) (including Achelia, Hodge (1864) = the old
non-chelate individuals): appendage I. very small, 2–jointed; appendage II.
8–9–jointed; caudal segment fused with last body-segment; about eighteen
species, four from the South Seas, two or three from the East Indies, the rest
mostly Mediterranean and North Atlantic, in need of revision. Ammothea
longipes, Hodge, is the young of Achelia hispida, Hodge; and Ammothea
magnirostris, Dohrn, is apparently the same species. A. fibulifera, Dohrn,
seems identical with Achelia echinata, Hodge (of which A. brevipes,
Hodge, is the young), and so probably is A. achelioides, Wilson; Endeis
didactyla, Philippi (1843), is very probably the same species. A.
uniunguiculata, Dohrn (? Pariboea spinipalpis, Philippi (1843)), has no
auxiliary claws. Leionymphon, Möbius (1902), contains nine Antarctic
forms, allied to Ammothea (including A. grandis, Pfeffer, and Colossendeis
gibbosa, Möb., which two are probably identical), with characteristic
transverse ridges on the body, a large proboscis, a 9–jointed palp, and
somewhat peculiar ovigerous legs. Cilunculus, Fragilia, and Scipiolus are
new genera more or less allied to Leionymphon, described by Loman (1908)
from the Siboga Expedition.[434] Tanystylum, Miers (1879) (including
Clotenia, Dohrn (1881), and Discoarachne, Hoek (1880)), has appendage I.
reduced to a single joint or a small tubercle, and appendage II. 4–6–jointed;
world-wide; about eight species. Austrodecus glacialis and Austroraptus
polaris are two allied Antarctic species, described by Hodgson (1907), the
former a curious little form with a pointed, weevil-like proboscis, no
chelophores, and 6–jointed palp. Trygaeus communis, Dohrn (1881), from
Naples, has a 7–jointed, and Oorhynchus aucklandiae, Hoek (1881), a 9–
jointed palp; the former has only seven joints in the ovigerous leg.
Lecythorhynchus armatus, Böhm (1879), with rudimentary 2–jointed
chelophores, and L. (Corniger) hilgendorfi, Böhm, with small tubercles in
their place, both from Japan, have also 9–jointed palps: the former, at least,
is apparently an Ammothea. Several insufficiently described genera,
Phanodemus, Costa (1836), Platychelus, Costa (1861), Oiceobathes, Hesse
more or less movably jointed to the cephalic segment, and appendage I.
reduced, non-chelate in the adult; the body is compact and more or less
imperfectly segmented; appendage II. 4–9–jointed; appendage III. clawless,
and the number of joints sometimes diminished, with a sparse row of
serrated spines; auxiliary claws usually present.
Ammothea, Leach (1815) (including Achelia, Hodge (1864) = the old
non-chelate individuals): appendage I. very small, 2–jointed; appendage II.
8–9–jointed; caudal segment fused with last body-segment; about eighteen
species, four from the South Seas, two or three from the East Indies, the rest
mostly Mediterranean and North Atlantic, in need of revision. Ammothea
longipes, Hodge, is the young of Achelia hispida, Hodge; and Ammothea
magnirostris, Dohrn, is apparently the same species. A. fibulifera, Dohrn,
seems identical with Achelia echinata, Hodge (of which A. brevipes,
Hodge, is the young), and so probably is A. achelioides, Wilson; Endeis
didactyla, Philippi (1843), is very probably the same species. A.
uniunguiculata, Dohrn (? Pariboea spinipalpis, Philippi (1843)), has no
auxiliary claws. Leionymphon, Möbius (1902), contains nine Antarctic
forms, allied to Ammothea (including A. grandis, Pfeffer, and Colossendeis
gibbosa, Möb., which two are probably identical), with characteristic
transverse ridges on the body, a large proboscis, a 9–jointed palp, and
somewhat peculiar ovigerous legs. Cilunculus, Fragilia, and Scipiolus are
new genera more or less allied to Leionymphon, described by Loman (1908)
from the Siboga Expedition.[434] Tanystylum, Miers (1879) (including
Clotenia, Dohrn (1881), and Discoarachne, Hoek (1880)), has appendage I.
reduced to a single joint or a small tubercle, and appendage II. 4–6–jointed;
world-wide; about eight species. Austrodecus glacialis and Austroraptus
polaris are two allied Antarctic species, described by Hodgson (1907), the
former a curious little form with a pointed, weevil-like proboscis, no
chelophores, and 6–jointed palp. Trygaeus communis, Dohrn (1881), from
Naples, has a 7–jointed, and Oorhynchus aucklandiae, Hoek (1881), a 9–
jointed palp; the former has only seven joints in the ovigerous leg.
Lecythorhynchus armatus, Böhm (1879), with rudimentary 2–jointed
chelophores, and L. (Corniger) hilgendorfi, Böhm, with small tubercles in
their place, both from Japan, have also 9–jointed palps: the former, at least,
is apparently an Ammothea. Several insufficiently described genera,
Phanodemus, Costa (1836), Platychelus, Costa (1861), Oiceobathes, Hesse
Page 586
(1867), and Böhmia, Hoek (1880), seem to be referable to this group; all
have chelate mandibles, and may possibly be based on immature forms.
Goodsir’s Pasithoe vesiculosa[435] is, in my opinion, undoubtedly
Ammothea hispida, Hodge, and so also, I believe, is his Pephredo hirsuta;
P. umbonata, Gould[436] (Long Island Sound), is, with as little doubt,
Tanystylum orbiculare, Wilson.
Fam. 5. Rhynchothoracidae.—The animal identified by Dohrn as
Rhynchothorax mediterraneus, Costa (1861), is a minute and very
remarkable form, without chelophores, with large 8–jointed palps, reduced
by fusion to five joints, and 10–jointed, clawed ovigerous legs, which last
are provided on the last five joints with peculiar toothed tubercles. The
general aspect of the body is somewhat like that of an Ammothea, which
genus it resembles in the ventral insertion of the ovigerous legs and the
somewhat imperfect segmentation of the body. It differs from Ammotheidae
in the possession of a claw on appendage III. It is highly peculiar in the
structure of the mouth, in having a long forward extension of the
oculiferous tubercle jutting out over the proboscis, in the extreme shortness
of the intestinal caeca and ovaries which scarcely extend into the legs, and
in the absence of cement-glands from the fourth joint of the legs; these last
are present only in the third joint of the penultimate legs. A single pair of
generative orifices are found on the last legs. A second species, R. australis,
Hodgson, comes from the Antarctic.
have chelate mandibles, and may possibly be based on immature forms.
Goodsir’s Pasithoe vesiculosa[435] is, in my opinion, undoubtedly
Ammothea hispida, Hodge, and so also, I believe, is his Pephredo hirsuta;
P. umbonata, Gould[436] (Long Island Sound), is, with as little doubt,
Tanystylum orbiculare, Wilson.
Fam. 5. Rhynchothoracidae.—The animal identified by Dohrn as
Rhynchothorax mediterraneus, Costa (1861), is a minute and very
remarkable form, without chelophores, with large 8–jointed palps, reduced
by fusion to five joints, and 10–jointed, clawed ovigerous legs, which last
are provided on the last five joints with peculiar toothed tubercles. The
general aspect of the body is somewhat like that of an Ammothea, which
genus it resembles in the ventral insertion of the ovigerous legs and the
somewhat imperfect segmentation of the body. It differs from Ammotheidae
in the possession of a claw on appendage III. It is highly peculiar in the
structure of the mouth, in having a long forward extension of the
oculiferous tubercle jutting out over the proboscis, in the extreme shortness
of the intestinal caeca and ovaries which scarcely extend into the legs, and
in the absence of cement-glands from the fourth joint of the legs; these last
are present only in the third joint of the penultimate legs. A single pair of
generative orifices are found on the last legs. A second species, R. australis,
Hodgson, comes from the Antarctic.
Page 587
Fig. 284.—Rhynchothorax mediterraneus, Costa. A, Body and bases of legs; B,
terminal joints of palp. (After Dohrn.)
Fam. 6. Nymphonidae.—Appendage I. well-developed, chelate; II.
well-developed, usually 5–jointed; III. well-developed in both sexes,
usually 10–jointed, the terminal joints with one row of denticulated spines.
Nymphon, Fabr. (1794), about forty-five recognised species, of which
some are but narrowly defined. Closely allied are Chaetonymphon, G. O.
Sars (1888), including thick-set, hairy species, about eight in number, from
the North Atlantic, Arctic, and Antarctic; and Boreonymphon, G. O. Sars
(1888), with one species (B. robustum, Bell, Fig. 276), also northern, in
which the auxiliary claws are almost absent. Nymphon brevicaudatum,
Miers (= N. horridum, Böhm), an extraordinary hispid form from
Kerguelen,[437] is also peculiar. Pentanymphon, Hodgson (1904), from the
Antarctic (circumpolar), differs in no respect save in the presence of a fifth
pair of legs; one species.
The only other genus is Paranymphon, Caullery (1896) (one species,
Gulf of Gascony, West of Ireland, Greenland), in which the palp is (6–)7–
jointed, the ovigerous leg 8–jointed, and the auxiliary claws are absent.
terminal joints of palp. (After Dohrn.)
Fam. 6. Nymphonidae.—Appendage I. well-developed, chelate; II.
well-developed, usually 5–jointed; III. well-developed in both sexes,
usually 10–jointed, the terminal joints with one row of denticulated spines.
Nymphon, Fabr. (1794), about forty-five recognised species, of which
some are but narrowly defined. Closely allied are Chaetonymphon, G. O.
Sars (1888), including thick-set, hairy species, about eight in number, from
the North Atlantic, Arctic, and Antarctic; and Boreonymphon, G. O. Sars
(1888), with one species (B. robustum, Bell, Fig. 276), also northern, in
which the auxiliary claws are almost absent. Nymphon brevicaudatum,
Miers (= N. horridum, Böhm), an extraordinary hispid form from
Kerguelen,[437] is also peculiar. Pentanymphon, Hodgson (1904), from the
Antarctic (circumpolar), differs in no respect save in the presence of a fifth
pair of legs; one species.
The only other genus is Paranymphon, Caullery (1896) (one species,
Gulf of Gascony, West of Ireland, Greenland), in which the palp is (6–)7–
jointed, the ovigerous leg 8–jointed, and the auxiliary claws are absent.
Page 588
Fam. 7. Pallenidae.—As in Nymphon, but appendage II. absent or
rudimentary.
Pallene, Johnston (1837): about
ten species (Mediterranean, North
Atlantic, Arctic, Australia). P.
languida, Hoek, Australia, lacks
auxiliary claws, and is otherwise
distinct; but P. novaezealandiae, G.
M. Thomson, is typical.
Pseudopallene, Wilson (1878):[438]
appendage III. clawed; auxiliary
claws absent; four (or more) species
(North Atlantic, Arctic, Antarctic). P.
(Phoxichilus) pygmaea, Costa
(1836), and P. spinosa, Quatref.,
seem to belong to this genus or to
Pallene. Cordylochele, G. O. Sars
(1888): closely allied, but with front
of cephalic segment much expanded
and chelae remarkably swollen,
includes three very smooth,
elongated, northern species, to which
Bouvier has added one from the
Antarctic; Pallene laevis, Hoek, from
Bass’s Straits, is somewhat similar.
Neopallene, Dohrn (1881): as in
Pallene, but with a rudimentary Fig. 285.—Pallene brevirostris, Johnston, ♀ ,
Plymouth.
second appendage in the female, and
no generative aperture on the last leg
in the male (one species, Mediterranean). Parapallene, Carpenter (1892): as
in Pallene, but without auxiliary claws, and with the two last segments of
the trunk (which in Pallene are coalesced) independent (about ten species,
East Indies and Australia); Pallene grubii, Hoek (Phoxichilidium sp.,
Grube, 1869), is probably congeneric. Pallenopsis, Wilson (1881):
appendage I. 2–jointed; appendage II. rudimentary, 1–jointed; appendage
III. clawless; auxiliary claws present; slender forms, including some
formerly referred to Phoxichilidium; about fifteen species, world-wide.
rudimentary.
Pallene, Johnston (1837): about
ten species (Mediterranean, North
Atlantic, Arctic, Australia). P.
languida, Hoek, Australia, lacks
auxiliary claws, and is otherwise
distinct; but P. novaezealandiae, G.
M. Thomson, is typical.
Pseudopallene, Wilson (1878):[438]
appendage III. clawed; auxiliary
claws absent; four (or more) species
(North Atlantic, Arctic, Antarctic). P.
(Phoxichilus) pygmaea, Costa
(1836), and P. spinosa, Quatref.,
seem to belong to this genus or to
Pallene. Cordylochele, G. O. Sars
(1888): closely allied, but with front
of cephalic segment much expanded
and chelae remarkably swollen,
includes three very smooth,
elongated, northern species, to which
Bouvier has added one from the
Antarctic; Pallene laevis, Hoek, from
Bass’s Straits, is somewhat similar.
Neopallene, Dohrn (1881): as in
Pallene, but with a rudimentary Fig. 285.—Pallene brevirostris, Johnston, ♀ ,
Plymouth.
second appendage in the female, and
no generative aperture on the last leg
in the male (one species, Mediterranean). Parapallene, Carpenter (1892): as
in Pallene, but without auxiliary claws, and with the two last segments of
the trunk (which in Pallene are coalesced) independent (about ten species,
East Indies and Australia); Pallene grubii, Hoek (Phoxichilidium sp.,
Grube, 1869), is probably congeneric. Pallenopsis, Wilson (1881):
appendage I. 2–jointed; appendage II. rudimentary, 1–jointed; appendage
III. clawless; auxiliary claws present; slender forms, including some
formerly referred to Phoxichilidium; about fifteen species, world-wide.
Page 589
Pallene dimorpha, Hoek, from Kerguelen, with 4–jointed palps, deserves a
new generic appellation. P. longiceps, Böhm, from Japan, with rudimentary
2–jointed palps in the male, is also peculiar.
Fig. 286.—Phoxichilidium femoratum, Rathke, Britain. A, The animal with its
legs removed; B, leg and chela.
Fam. 8. Phoxichilidiidae.—Appendage I. well-developed; II. absent; III.
present only in the male, having a few simple spines in a single row. The
last character is conveniently diagnostic, but nevertheless the
Phoxichilidiidae come very near to the Pallenidae, with which, according to
Schimkewitsch and others, they should be merged; the two families
resemble one another in the single row of spines on the ovigerous legs and
in the extension of the cephalic segment over the base of the proboscis.
Phoxichilidium, M.-E. (1840): appendage III. 5–jointed; five or six
species (Mediterranean, North Atlantic, Arctic, Australia, Japan).
Anoplodactylus, Wilson (1878): appendage III. 6–jointed; auxiliary claws
absent or very rudimentary; about twelve species, cosmopolitan, of which
new generic appellation. P. longiceps, Böhm, from Japan, with rudimentary
2–jointed palps in the male, is also peculiar.
Fig. 286.—Phoxichilidium femoratum, Rathke, Britain. A, The animal with its
legs removed; B, leg and chela.
Fam. 8. Phoxichilidiidae.—Appendage I. well-developed; II. absent; III.
present only in the male, having a few simple spines in a single row. The
last character is conveniently diagnostic, but nevertheless the
Phoxichilidiidae come very near to the Pallenidae, with which, according to
Schimkewitsch and others, they should be merged; the two families
resemble one another in the single row of spines on the ovigerous legs and
in the extension of the cephalic segment over the base of the proboscis.
Phoxichilidium, M.-E. (1840): appendage III. 5–jointed; five or six
species (Mediterranean, North Atlantic, Arctic, Australia, Japan).
Anoplodactylus, Wilson (1878): appendage III. 6–jointed; auxiliary claws
absent or very rudimentary; about twelve species, cosmopolitan, of which
Page 590
many were first referred to Phoxichilidium. A. neglectus, Hoek, comes from
1600 fathoms off the Crozets. Oomerus stigmatophorus, Hesse (1874), from
Brest, seems to belong to one or other genus, but is unrecognisable.
Anaphia, Say (1821), is in all probability identical with Anoplodactylus, and
if so the name should have priority. Halosoma, Cole (1904), is an allied
genus from California.
Fig. 287.—Anoplodactylus petiolatus, Kr., Britain. A, Dorsal view; B, side view.
Fam. 9. Phoxichilidae.[439]—Appendage I. and II. absent; appendage III.
present only in the males, 7–jointed, with minute scattered spines; auxiliary
claws well-developed; body and legs slender. The only genus is Phoxichilus
(auctt., non Latreille, Chilophoxus, Stebbing, 1902); the type is P. spinosus,
Mont. (non Quatrefages), from the N. Atlantic, and P. vulgaris, Dohrn, P.
charybdaeus, Dohrn, and P. laevis, Grube, are all very similar. Endeis
gracilis, Philippi (1843), is probably identical with P. spinosus, or one of its
close allies. There are also known P. meridionalis, Böhm, P. mollis, Carp.,
and P. procerus, Loman, from the East Indies; P. australis, Hodgson, from
the Antarctic; P. böhmii, Schimk., of unknown locality; and forms ascribed
to P. charybdaeus by Haswell and by Schimkewitsch from Australia and
Brazil.
Fam. 10. Pycnogonidae.—Appendages I. and II. absent; appendage III.
present only in the male, 9–jointed, with small, simple spines; auxiliary
claws absent or rudimentary; body and legs short, thick-set.
1600 fathoms off the Crozets. Oomerus stigmatophorus, Hesse (1874), from
Brest, seems to belong to one or other genus, but is unrecognisable.
Anaphia, Say (1821), is in all probability identical with Anoplodactylus, and
if so the name should have priority. Halosoma, Cole (1904), is an allied
genus from California.
Fig. 287.—Anoplodactylus petiolatus, Kr., Britain. A, Dorsal view; B, side view.
Fam. 9. Phoxichilidae.[439]—Appendage I. and II. absent; appendage III.
present only in the males, 7–jointed, with minute scattered spines; auxiliary
claws well-developed; body and legs slender. The only genus is Phoxichilus
(auctt., non Latreille, Chilophoxus, Stebbing, 1902); the type is P. spinosus,
Mont. (non Quatrefages), from the N. Atlantic, and P. vulgaris, Dohrn, P.
charybdaeus, Dohrn, and P. laevis, Grube, are all very similar. Endeis
gracilis, Philippi (1843), is probably identical with P. spinosus, or one of its
close allies. There are also known P. meridionalis, Böhm, P. mollis, Carp.,
and P. procerus, Loman, from the East Indies; P. australis, Hodgson, from
the Antarctic; P. böhmii, Schimk., of unknown locality; and forms ascribed
to P. charybdaeus by Haswell and by Schimkewitsch from Australia and
Brazil.
Fam. 10. Pycnogonidae.—Appendages I. and II. absent; appendage III.
present only in the male, 9–jointed, with small, simple spines; auxiliary
claws absent or rudimentary; body and legs short, thick-set.
Page 591
The only genus is Pycnogonum, Brünnich (1764) (Polygonopus, Pallas,
1766); the type is P. littorale, Ström, of the N. Atlantic (0–430 fathoms), to
which species have also been ascribed forms from various remote localities,
e.g. Japan, Chile, and Kerguelen. P. crassirostre, G. O. Sars, a northern and
more or less deep-sea form, is distinct, and so also are P. nodulosum and P.
pusillum, Dohrn, from Naples. P. stearnsi, Ives, from California, is like P.
littorale, except for the rostrum, which resembles that of P. crassirostre. P.
magellanicum, Hoek, P. magnirostre, Möbius, both from the Southern
Ocean; P. microps, Loman, from Natal, and four others described by Loman
from the East Indies, are the other authenticated species. Of P.
philippinense, Semper, I know only the bare record; and P. australe, Grube,
is described only from a larval form with three pairs of legs. P. orientale,
Dana (first described as Astridium, n.g.), is also described from an
immature specimen, and more resembles a Phoxichilus.
The British Pycnogons.
Dr. George Johnston,[440] the naturalist-physician of Berwick-on-Tweed,
Harry Goodsir,[441] brother of the great anatomist, who perished with Sir
John Franklin, and George Hodge[442] of Seaham Harbour, a young naturalist
of singular promise, dead ere his prime, were in former days the chief
students of the British Pycnogons. Of late, Carpenter[443] has studied the
Irish species; and the cruises of the Porcupine, Triton, and Knight Errant
have given us a number of deep-water species from the verge of the British
area.
In compiling the following list, I have had the indispensable advantage of
access to Canon Norman’s collection, and the still greater benefit of his own
stores of endless information.[444]
Pseudopallene circularis, Goodsir: Firth of Forth.
Phoxichilidium femoratum, Rathke (P. globosum, Goodsir; Orithyia
coccinea, Johnston) (Figs. 270, B; 286): East and West coasts, Shetland,
Ireland.
Anoplodactylus virescens, Hodge (? Phoxichilidium olivaceum, Gosse):
South coast.
1766); the type is P. littorale, Ström, of the N. Atlantic (0–430 fathoms), to
which species have also been ascribed forms from various remote localities,
e.g. Japan, Chile, and Kerguelen. P. crassirostre, G. O. Sars, a northern and
more or less deep-sea form, is distinct, and so also are P. nodulosum and P.
pusillum, Dohrn, from Naples. P. stearnsi, Ives, from California, is like P.
littorale, except for the rostrum, which resembles that of P. crassirostre. P.
magellanicum, Hoek, P. magnirostre, Möbius, both from the Southern
Ocean; P. microps, Loman, from Natal, and four others described by Loman
from the East Indies, are the other authenticated species. Of P.
philippinense, Semper, I know only the bare record; and P. australe, Grube,
is described only from a larval form with three pairs of legs. P. orientale,
Dana (first described as Astridium, n.g.), is also described from an
immature specimen, and more resembles a Phoxichilus.
The British Pycnogons.
Dr. George Johnston,[440] the naturalist-physician of Berwick-on-Tweed,
Harry Goodsir,[441] brother of the great anatomist, who perished with Sir
John Franklin, and George Hodge[442] of Seaham Harbour, a young naturalist
of singular promise, dead ere his prime, were in former days the chief
students of the British Pycnogons. Of late, Carpenter[443] has studied the
Irish species; and the cruises of the Porcupine, Triton, and Knight Errant
have given us a number of deep-water species from the verge of the British
area.
In compiling the following list, I have had the indispensable advantage of
access to Canon Norman’s collection, and the still greater benefit of his own
stores of endless information.[444]
Pseudopallene circularis, Goodsir: Firth of Forth.
Phoxichilidium femoratum, Rathke (P. globosum, Goodsir; Orithyia
coccinea, Johnston) (Figs. 270, B; 286): East and West coasts, Shetland,
Ireland.
Anoplodactylus virescens, Hodge (? Phoxichilidium olivaceum, Gosse):
South coast.
Page 592
A. petiolatus, Kr. (Figs. 270, C; 275, B; 287) (Pallene attenuata and
pygmaea, Hodge; Phoxichilidium exiguum and longicolle, Dohrn):
Plymouth, Firth of Forth, Cumbrae, Irish coasts.
Ammothea (Achelia) echinata, Hodge (Fig. 265, B; 274, 4; 275, E):
Plymouth, Channel Islands, Isle of Man, Cumbrae, Durham (Hodge),
West of Ireland. We have not found it on the East of Scotland. A.
brevipes, Hodge, is presumed to be the young. Two of Dohrn’s
Neapolitan species, A. fibulifera and A. franciscana, are in my opinion
not to be distinguished from one another, nor from the present species.
A. hispida, Hodge (Fig. 266, C) (A. longipes, Hodge (juv); A.
magnirostris, Dohrn;? Pasithoe vesiculosa, Goodsir;? Pephredo
hirsuta, Goodsir): Cornwall and Devon (Hodge and Norman), Jersey.
The form common on the East of Scotland would seem to be this
species. The Mediterranean A. magnirostris, Dohrn, appears to be
identical.
A. laevis, Hodge: Cornwall (Hodge), Devon (Norman), Jersey (Sinel).
Tanystylum orbiculare, Wilson (Clotenia conirostre, Dohrn): Donegal
(Carpenter).
Phoxichilus spinosus, Mont. (Fig. 265, C; 270, A; 275, C): South Coast,
Moray Firth, Firth of Clyde, Ireland. A smaller and less spiny form
occurs, which Carpenter records as P. laevis, Grube, but Norman unites
the two under the name of Endeis spinosus (Mont.).
Pycnogonum littorale, Ström (Fig. 262): on all coasts, and to considerable
depths (150 fathoms, West of Ireland).
Nymphon brevirostre, Hodge (N. gracile, Sars) (Figs. 263, 264, 267, A;
272, 274, 3): common on the East Coast; Herm (Hodge), Dublin,
Queenstown (Carpenter). Our smallest species of Nymphon.
N. rubrum, Hodge (N. gracile, Johnston; N. rubrum, G. O. Sars):
common on the East Coast; Oban (Norman), Ireland (Carpenter).
N. grossipes, O. Fabr., Johnston (N. johnstoni, Goodsir): Northumberland,
East of Scotland, Orkney, etc., not uncommon.
N. gracile, Leach (N. gallicum, Hoek; ♂ N. femoratum, Leach): South of
England, West of Scotland, and Ireland.
pygmaea, Hodge; Phoxichilidium exiguum and longicolle, Dohrn):
Plymouth, Firth of Forth, Cumbrae, Irish coasts.
Ammothea (Achelia) echinata, Hodge (Fig. 265, B; 274, 4; 275, E):
Plymouth, Channel Islands, Isle of Man, Cumbrae, Durham (Hodge),
West of Ireland. We have not found it on the East of Scotland. A.
brevipes, Hodge, is presumed to be the young. Two of Dohrn’s
Neapolitan species, A. fibulifera and A. franciscana, are in my opinion
not to be distinguished from one another, nor from the present species.
A. hispida, Hodge (Fig. 266, C) (A. longipes, Hodge (juv); A.
magnirostris, Dohrn;? Pasithoe vesiculosa, Goodsir;? Pephredo
hirsuta, Goodsir): Cornwall and Devon (Hodge and Norman), Jersey.
The form common on the East of Scotland would seem to be this
species. The Mediterranean A. magnirostris, Dohrn, appears to be
identical.
A. laevis, Hodge: Cornwall (Hodge), Devon (Norman), Jersey (Sinel).
Tanystylum orbiculare, Wilson (Clotenia conirostre, Dohrn): Donegal
(Carpenter).
Phoxichilus spinosus, Mont. (Fig. 265, C; 270, A; 275, C): South Coast,
Moray Firth, Firth of Clyde, Ireland. A smaller and less spiny form
occurs, which Carpenter records as P. laevis, Grube, but Norman unites
the two under the name of Endeis spinosus (Mont.).
Pycnogonum littorale, Ström (Fig. 262): on all coasts, and to considerable
depths (150 fathoms, West of Ireland).
Nymphon brevirostre, Hodge (N. gracile, Sars) (Figs. 263, 264, 267, A;
272, 274, 3): common on the East Coast; Herm (Hodge), Dublin,
Queenstown (Carpenter). Our smallest species of Nymphon.
N. rubrum, Hodge (N. gracile, Johnston; N. rubrum, G. O. Sars):
common on the East Coast; Oban (Norman), Ireland (Carpenter).
N. grossipes, O. Fabr., Johnston (N. johnstoni, Goodsir): Northumberland,
East of Scotland, Orkney, etc., not uncommon.
N. gracile, Leach (N. gallicum, Hoek; ♂ N. femoratum, Leach): South of
England, West of Scotland, and Ireland.
Page 593
N. strömii, Kr. (N. giganteum, Goodsir) (Figs. 273, 274, 2): East Coast,
from Holy Island to Shetland.
Chaetonymphon hirtum, Fabr. (Fig. 274, 1): Northumberland (Hodge),
Margate (Hoek), East of Scotland, and Ireland, not uncommon. There
seems to be no doubt that British specimens agree with this species as
figured and identified by Sars. N. spinosum, Goodsir (East of Scotland,
Goodsir; Belfast, W. Thompson), is, according to Norman, the same
species. Sars’ Norwegian specimens figured under the latter name are
not identical, and have been renamed by Norman C. spinosissimum, but
are said by Meinert and Möbius to be identical with C. hirtipes, Bell.
Hodge (1864) records Nymphon mixtum, Kr., and N. longitarse, Kr., from
the Durham coast. His full list of the recorded species of other authors
also includes the following doubtful or unrecognised species: N.
pellucidum, N. simile, and N. minutum, all of Goodsir.
Pallene brevirostris, Johnston (P. empusa, Wilson;? P. emaciata, Dohrn)
(Figs. 275, A; 285): all coasts. Examples differ considerably in size and
proportions, as do Dohrn’s Neapolitan species one from another. We
have specimens from the Sound of Mull that come very near, and
perhaps agree with, Sars’ P. producta, a species that scarcely differs
from P. brevirostris, save in its greater attenuation; the same species has
also been recorded from Millport and from Port Erin.
P. spectrum, Dohrn: Plymouth (A. H. Norman).
Besides the above, all of which are littoral or more or less shallow-water
species, we have another series of forms, or, to speak more correctly, we
have two other series of forms, from the deep Atlantic waters within the
British area. In the cold area of the Faeroe Channel we have Boreonymphon
robustum, Bell; Nymphon elegans, Hansen; N. sluiteri, Hoek; N. stenocheir,
Norman; Colossendeis proboscidea, Sabine; C. angusta, Sars. In the warm
waters south and west of the Wyville-Thomson ridge we have
Chaetonymphon spinosissimum, Norman; Nymphon gracilipes, Heller (non
Fabr.); N. hirtipes, Bell; N. longitarse, Kr.; N. macrum, Wilson; Pallenopsis
tritonis, Hoek (= P. holti, Carpenter); Anoplodactylus oculatus, Carpenter,
and A. typhlops, G. O. Sars; and to the list under this section Canon Norman
has lately made the very interesting addition of Paranymphon spinosum,
from Holy Island to Shetland.
Chaetonymphon hirtum, Fabr. (Fig. 274, 1): Northumberland (Hodge),
Margate (Hoek), East of Scotland, and Ireland, not uncommon. There
seems to be no doubt that British specimens agree with this species as
figured and identified by Sars. N. spinosum, Goodsir (East of Scotland,
Goodsir; Belfast, W. Thompson), is, according to Norman, the same
species. Sars’ Norwegian specimens figured under the latter name are
not identical, and have been renamed by Norman C. spinosissimum, but
are said by Meinert and Möbius to be identical with C. hirtipes, Bell.
Hodge (1864) records Nymphon mixtum, Kr., and N. longitarse, Kr., from
the Durham coast. His full list of the recorded species of other authors
also includes the following doubtful or unrecognised species: N.
pellucidum, N. simile, and N. minutum, all of Goodsir.
Pallene brevirostris, Johnston (P. empusa, Wilson;? P. emaciata, Dohrn)
(Figs. 275, A; 285): all coasts. Examples differ considerably in size and
proportions, as do Dohrn’s Neapolitan species one from another. We
have specimens from the Sound of Mull that come very near, and
perhaps agree with, Sars’ P. producta, a species that scarcely differs
from P. brevirostris, save in its greater attenuation; the same species has
also been recorded from Millport and from Port Erin.
P. spectrum, Dohrn: Plymouth (A. H. Norman).
Besides the above, all of which are littoral or more or less shallow-water
species, we have another series of forms, or, to speak more correctly, we
have two other series of forms, from the deep Atlantic waters within the
British area. In the cold area of the Faeroe Channel we have Boreonymphon
robustum, Bell; Nymphon elegans, Hansen; N. sluiteri, Hoek; N. stenocheir,
Norman; Colossendeis proboscidea, Sabine; C. angusta, Sars. In the warm
waters south and west of the Wyville-Thomson ridge we have
Chaetonymphon spinosissimum, Norman; Nymphon gracilipes, Heller (non
Fabr.); N. hirtipes, Bell; N. longitarse, Kr.; N. macrum, Wilson; Pallenopsis
tritonis, Hoek (= P. holti, Carpenter); Anoplodactylus oculatus, Carpenter,
and A. typhlops, G. O. Sars; and to the list under this section Canon Norman
has lately made the very interesting addition of Paranymphon spinosum,
Page 594
Caullery, from the Porcupine Station XVII., S.S.E. of Rockall, in 1230
fathoms. Lastly, and less clearly related to temperature, we have
Chaetonymphon tenellum, Sars; N. gracilipes, Fabr.; N. leptocheles, Sars;
N. macronyx, Sars; N. serratum, Sars; and Cordylochele malleolata, Sars.
Of the species recorded in the above list as a whole, Anoplodactylus
virescens, Nymphon gracile, and Pallene spectrum reach their northern
limit in the southern parts of our own area; Ammothea echinata,
Anoplodactylus petiolatus, Pallene brevirostris, and Phoxichilus spinosus
(or very closely related forms) range from the Mediterranean to Norway, the
last three also to the other side of the Atlantic; Nymphon brevirostre and N.
rubrum range from Britain, where they are in the main East Coast species,
to Norway. Of the Atlantic species, other than the Arctic ones, the majority
are known to extend to the New England coast.
fathoms. Lastly, and less clearly related to temperature, we have
Chaetonymphon tenellum, Sars; N. gracilipes, Fabr.; N. leptocheles, Sars;
N. macronyx, Sars; N. serratum, Sars; and Cordylochele malleolata, Sars.
Of the species recorded in the above list as a whole, Anoplodactylus
virescens, Nymphon gracile, and Pallene spectrum reach their northern
limit in the southern parts of our own area; Ammothea echinata,
Anoplodactylus petiolatus, Pallene brevirostris, and Phoxichilus spinosus
(or very closely related forms) range from the Mediterranean to Norway, the
last three also to the other side of the Atlantic; Nymphon brevirostre and N.
rubrum range from Britain, where they are in the main East Coast species,
to Norway. Of the Atlantic species, other than the Arctic ones, the majority
are known to extend to the New England coast.
Page 595
INDEX
Every reference is to the page: words in italics are names of genera or
species; figures in italics indicate that the reference relates to systematic
position; figures in thick type refer to an illustration; f. = and in
following page or pages; n. = note.
Abalius, 312
Abdomen, of Malacostraca, 110;
of Acantholithus, 178;
of Birgus, 176;
of Cenobita, 176;
of Dermaturus, 178;
of Hapalogaster, 178;
of Lithodes, 178;
of Pylopagurus, 178;
of Trilobites, 235;
of Scorpions, 297;
of Pedipalpi, 309;
of Spiders, 317;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 431;
of Podogona, 440;
of Phalangidea, 440, 443;
of Acarina, 457;
of Pentastomida, 489;
of Pycnogonida, 502
Every reference is to the page: words in italics are names of genera or
species; figures in italics indicate that the reference relates to systematic
position; figures in thick type refer to an illustration; f. = and in
following page or pages; n. = note.
Abalius, 312
Abdomen, of Malacostraca, 110;
of Acantholithus, 178;
of Birgus, 176;
of Cenobita, 176;
of Dermaturus, 178;
of Hapalogaster, 178;
of Lithodes, 178;
of Pylopagurus, 178;
of Trilobites, 235;
of Scorpions, 297;
of Pedipalpi, 309;
of Spiders, 317;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 431;
of Podogona, 440;
of Phalangidea, 440, 443;
of Acarina, 457;
of Pentastomida, 489;
of Pycnogonida, 502
Page 596
Abdominal glands, of Chernetidea, 432
Abyssal region (marine), 204;
(lacustrine), 209
Acantheis, 418
Acanthephyra, 163
Acanthephyridae, 163
Acanthoctenus, 415
Acanthodon, 388
Acanthogammarus, 138
Acantholeberis, 53
Acantholithus, 181;
A. hystrix, 178
Acanthophrynus, 313
Acari, 454 (= Acarina, q.v.)
Acaridea, 454 (= Acarina, q.v.)
Acarina, 258, 454 f.;
parasitic, 455;
external structure, 457;
spinning organs, 457;
internal structure, 459;
metamorphosis, 462;
classification, 464
Acaste, 249
Accola, 390
Acerocare, 247
Achelata, 529
Achelia, 534;
A. longipes, 506
Achtheres, 75;
Abyssal region (marine), 204;
(lacustrine), 209
Acantheis, 418
Acanthephyra, 163
Acanthephyridae, 163
Acanthoctenus, 415
Acanthodon, 388
Acanthogammarus, 138
Acantholeberis, 53
Acantholithus, 181;
A. hystrix, 178
Acanthophrynus, 313
Acari, 454 (= Acarina, q.v.)
Acaridea, 454 (= Acarina, q.v.)
Acarina, 258, 454 f.;
parasitic, 455;
external structure, 457;
spinning organs, 457;
internal structure, 459;
metamorphosis, 462;
classification, 464
Acaste, 249
Accola, 390
Acerocare, 247
Achelata, 529
Achelia, 534;
A. longipes, 506
Achtheres, 75;
Page 597
A. percarum, 75
Acidaspidae, 251
Acidaspis, 226, 227, 230, 231, 235, 241, 251;
A. dufrenoyi, 250;
A. tuberculata, larva, 240;
A. verneuili, 231;
A. vesiculosa, 231
Aciniform glands, 335, 349
Acoloides saitidis, 367
Acroperus, 53;
A. leucocephalus, 52
Acrosoma, 410
Acrothoracica, 92
Actaea, 191;
habitat, 198
Actinopodinae, 387
Actinopus, 387
Aculeus, of scorpion, 303
Admetus, 313
Aegidae, 126
Aegisthus, 61
Aeglea laevis, 169;
distribution, 212
Aegleidae, 169
Aeglina, 227, 249;
Ae. prisca, 248
Agelena, 416;
A. brunnea, 367;
A. labyrinthica, 352, 353, 378, 380, 381, 416;
Acidaspidae, 251
Acidaspis, 226, 227, 230, 231, 235, 241, 251;
A. dufrenoyi, 250;
A. tuberculata, larva, 240;
A. verneuili, 231;
A. vesiculosa, 231
Aciniform glands, 335, 349
Acoloides saitidis, 367
Acroperus, 53;
A. leucocephalus, 52
Acrosoma, 410
Acrothoracica, 92
Actaea, 191;
habitat, 198
Actinopodinae, 387
Actinopus, 387
Aculeus, of scorpion, 303
Admetus, 313
Aegidae, 126
Aegisthus, 61
Aeglea laevis, 169;
distribution, 212
Aegleidae, 169
Aeglina, 227, 249;
Ae. prisca, 248
Agelena, 416;
A. brunnea, 367;
A. labyrinthica, 352, 353, 378, 380, 381, 416;
Page 598
A. naevia, 339
Agelenidae, 325, 352, 353, 415
Ageleninae, 416
Aggregate glands, 335, 349
Aglaspis, 279
Agnathaner, 66
Agnathonia, 529
Agnostidae, 244
Agnostini, 243
Agnostus, 222, 223, 225, 231, 234, 245;
A. integer, 245
Agraulos, 247
Agroeca, 397;
A. brunnea, cocoon, 358
Albunea, 171;
respiration, 170;
distribution, 201
Albuneidae, 171
Alcippe, 92;
A. lampas, 92, 93
Alcock, on Oxyrhyncha, 192;
on phosphorescence, 151
Alepas, 89
Alima, larva of Squilla, 143
Alimentary canal, of Crustacea, 14;
of Phyllopoda, 28;
of Cladocera, 42;
of Squilla, 142;
of Malacostraca, 110;
Agelenidae, 325, 352, 353, 415
Ageleninae, 416
Aggregate glands, 335, 349
Aglaspis, 279
Agnathaner, 66
Agnathonia, 529
Agnostidae, 244
Agnostini, 243
Agnostus, 222, 223, 225, 231, 234, 245;
A. integer, 245
Agraulos, 247
Agroeca, 397;
A. brunnea, cocoon, 358
Albunea, 171;
respiration, 170;
distribution, 201
Albuneidae, 171
Alcippe, 92;
A. lampas, 92, 93
Alcock, on Oxyrhyncha, 192;
on phosphorescence, 151
Alepas, 89
Alima, larva of Squilla, 143
Alimentary canal, of Crustacea, 14;
of Phyllopoda, 28;
of Cladocera, 42;
of Squilla, 142;
of Malacostraca, 110;
Page 599
of
Trilobites, 222;
of Arachnida, 256;
of Limulus, 268;
of Scorpions, 304;
of Pedipalpi, 310;
of Spiders, 329;
of Solifugae, 427;
of Pseudoscorpions, 134;
of Phalangidea, 444;
of Acarina, 459;
of Tardigrada, 480;
of Pentastomida, 491;
of Pycnogous, 513
Alitropus (Aegidae), habitat, 211
Allman, on larvae of Pycnogons, 523
Alloptes, 466
Alona (including Leydigia, Alona, Harporhynchus, Graptoleberis), 53
Alonopsis, 53
Alpheidae, 163;
habitat, 198
Alpheus, 163;
reversal of regeneration, 156
Alveolus, of palpal organ of Spiders, 322
Amaurobius, 399;
A. fenestralis, 399;
A. ferox, 399;
A. similis, 399;
spinnerets, 326
Amblyocarenum, 388
Amblyomma, 470;
A. hebraeum, 456, 470
Trilobites, 222;
of Arachnida, 256;
of Limulus, 268;
of Scorpions, 304;
of Pedipalpi, 310;
of Spiders, 329;
of Solifugae, 427;
of Pseudoscorpions, 134;
of Phalangidea, 444;
of Acarina, 459;
of Tardigrada, 480;
of Pentastomida, 491;
of Pycnogous, 513
Alitropus (Aegidae), habitat, 211
Allman, on larvae of Pycnogons, 523
Alloptes, 466
Alona (including Leydigia, Alona, Harporhynchus, Graptoleberis), 53
Alonopsis, 53
Alpheidae, 163;
habitat, 198
Alpheus, 163;
reversal of regeneration, 156
Alveolus, of palpal organ of Spiders, 322
Amaurobius, 399;
A. fenestralis, 399;
A. ferox, 399;
A. similis, 399;
spinnerets, 326
Amblyocarenum, 388
Amblyomma, 470;
A. hebraeum, 456, 470
Page 600
Amblypygi, 312
Ammothea, 505, 534;
A. achelioides, 534;
A. brevipes, 541;
A. echinata, 505, 509, 510, 534, 541, 542;
A. fibulifera, 522, 534, 541;
A. franciscana, 541;
A. grandis, 534;
A. hispida, 534, 535, 541;
A. laevis, 541;
A. longicollis, 533;
A. longipes, 506, 534, 541;
A. magnirostris, 534, 541;
A. typhlops, 542;
A. uniunguiculata, 534
Ammotheidae, 534
Amopaum, 452
Ampharthrandria, 61
Amphascandria, 57
Amphion, 251
Amphipoda, 136 f.;
pelagic, 202;
fresh water, 211
Ampullaceal glands, 335, 349
Ampycini, 243
Ampyx, 231, 245;
A. roualti, 230
Anabiosis, in Tardigrada, 484
Analges, 455, 466
Analgesinae, 466
Ananteris, 306
Ammothea, 505, 534;
A. achelioides, 534;
A. brevipes, 541;
A. echinata, 505, 509, 510, 534, 541, 542;
A. fibulifera, 522, 534, 541;
A. franciscana, 541;
A. grandis, 534;
A. hispida, 534, 535, 541;
A. laevis, 541;
A. longicollis, 533;
A. longipes, 506, 534, 541;
A. magnirostris, 534, 541;
A. typhlops, 542;
A. uniunguiculata, 534
Ammotheidae, 534
Amopaum, 452
Ampharthrandria, 61
Amphascandria, 57
Amphion, 251
Amphipoda, 136 f.;
pelagic, 202;
fresh water, 211
Ampullaceal glands, 335, 349
Ampycini, 243
Ampyx, 231, 245;
A. roualti, 230
Anabiosis, in Tardigrada, 484
Analges, 455, 466
Analgesinae, 466
Ananteris, 306
Page 601
Anaphia, 539
Anaspidacea, 115;
distribution, 211, 217
Anaspidae, 89
Anaspides, 115, 117;
relation to Schizopoda, 112;
distribution, 211;
A. tasmaniae, 115, 116;
habitat, 211
Anaspididae, 115
Anelasma squalicola, 89
Anelasmocephalus, 452
Angelina, 247
Anisaspis bacillifera, 387
Anisopoda, 122
Anomalocera pattersoni, 60;
distribution, 202, 203
Anomopoda, 51
Anomorhynchus, 532
Anomura, 167;
relation to Thalassinidea, 167
Anoplodactylus, 511, 538;
A. lentus, 524;
A. neglectus, 539;
A. oculatus, 542;
A. petiolatus, 508, 510, 539, 541, 542;
A. virescens, 540, 542
Anopolenus, 247
Antarctic zone (marine), 200
Antarctica, evidence on, 200, 217
Anaspidacea, 115;
distribution, 211, 217
Anaspidae, 89
Anaspides, 115, 117;
relation to Schizopoda, 112;
distribution, 211;
A. tasmaniae, 115, 116;
habitat, 211
Anaspididae, 115
Anelasma squalicola, 89
Anelasmocephalus, 452
Angelina, 247
Anisaspis bacillifera, 387
Anisopoda, 122
Anomalocera pattersoni, 60;
distribution, 202, 203
Anomopoda, 51
Anomorhynchus, 532
Anomura, 167;
relation to Thalassinidea, 167
Anoplodactylus, 511, 538;
A. lentus, 524;
A. neglectus, 539;
A. oculatus, 542;
A. petiolatus, 508, 510, 539, 541, 542;
A. virescens, 540, 542
Anopolenus, 247
Antarctic zone (marine), 200
Antarctica, evidence on, 200, 217
Page 602
Antennae, of Crustacea, 5, 8;
of Phyllopoda, 24;
of Cladocera, 37;
of Copepoda, 55;
of Cirripedia, 81 f.;
of Ostracoda, 107;
of Malacostraca, 110;
of Anomura, 168;
of Corystes cassivelaunus, 170, 183, 189;
used in respiration, 170;
of Trilobites, 237
Antennary gland, 13 (= green gland, q.v.)
Anthrobia, 406;
A. mammouthia, 334, 366
Anthura, 124
Anthuridae, 124
Ants and spiders, 370
Anyphaena accentuata, 397
Aphantochilinae, 414
Aphantochilus, 414
Apoda, 94
Apodidae, 19, 21, 22, 23, 27, 28, 29, 31, 36, 241
Aponomma, 470
Appendages (incl. legs, limbs), of Crustacea, 7;
of Entomostraca, 18;
of Phyllopoda, 24;
of Cladocera, 40;
of Copepoda, 55;
of Cirripedia, 80 f.;
of Ostracoda, 107;
of Malacostraca, 110;
of Nebalia, 111;
of Phyllopoda, 24;
of Cladocera, 37;
of Copepoda, 55;
of Cirripedia, 81 f.;
of Ostracoda, 107;
of Malacostraca, 110;
of Anomura, 168;
of Corystes cassivelaunus, 170, 183, 189;
used in respiration, 170;
of Trilobites, 237
Antennary gland, 13 (= green gland, q.v.)
Anthrobia, 406;
A. mammouthia, 334, 366
Anthura, 124
Anthuridae, 124
Ants and spiders, 370
Anyphaena accentuata, 397
Aphantochilinae, 414
Aphantochilus, 414
Apoda, 94
Apodidae, 19, 21, 22, 23, 27, 28, 29, 31, 36, 241
Aponomma, 470
Appendages (incl. legs, limbs), of Crustacea, 7;
of Entomostraca, 18;
of Phyllopoda, 24;
of Cladocera, 40;
of Copepoda, 55;
of Cirripedia, 80 f.;
of Ostracoda, 107;
of Malacostraca, 110;
of Nebalia, 111;
Page 603
of Eumalacostraca, 113;
of Anaspides, 115;
of Mysidacea, 118 f.;
of Cumacea, 120;
of Isopoda, 121 f.;
of Amphipoda, 136 f.;
of Stomatopoda, 142;
of Euphausiacea, 144 f.;
of Decapoda, 152;
of Macrura, 153;
of their larvae, 159;
of Anomura, 167 f.;
of Birgus, 175;
of Brachyura, 181 f.;
alterations caused by parasites, 100 f.;
by hermaphroditism, 102 f.;
of Trilobita, 236, 237;
of Arachnida, 255 f.;
of Limulus, 262, 263;
of Eurypterus, 285 f.;
of Scorpions, 301, 303;
of Pedipalpi, 309;
of Spiders, 319;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 432;
of Podogona, 440;
of Phalangidea, 443;
of Acarina, 458;
of Tardigrada, 479;
of Pentastomida, 493;
of Pycnogons, 503 f.
Apseudes spinosus, 123
Apseudidae, 122
Apstein, 335
of Anaspides, 115;
of Mysidacea, 118 f.;
of Cumacea, 120;
of Isopoda, 121 f.;
of Amphipoda, 136 f.;
of Stomatopoda, 142;
of Euphausiacea, 144 f.;
of Decapoda, 152;
of Macrura, 153;
of their larvae, 159;
of Anomura, 167 f.;
of Birgus, 175;
of Brachyura, 181 f.;
alterations caused by parasites, 100 f.;
by hermaphroditism, 102 f.;
of Trilobita, 236, 237;
of Arachnida, 255 f.;
of Limulus, 262, 263;
of Eurypterus, 285 f.;
of Scorpions, 301, 303;
of Pedipalpi, 309;
of Spiders, 319;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 432;
of Podogona, 440;
of Phalangidea, 443;
of Acarina, 458;
of Tardigrada, 479;
of Pentastomida, 493;
of Pycnogons, 503 f.
Apseudes spinosus, 123
Apseudidae, 122
Apstein, 335
Page 604
Apus, 21, 23, 25, 28, 30, 32, 34, 36, 221, 242, 243;
segmentation, 6;
A. australiensis, 36;
A. cancriformis, 36;
habitat, 34
Arachnida, introduction to, 255;
segmentation of body, 255–6;
primitive, 256–7;
coxal glands, 257;
endosternite, 257;
sense-organs, 257;
classification, 258
Araneae, 258, 314 f.
Araneida, 314
Araneina, 314
Araneus, 408 n.
Aratus pisonii, 195
Arbanitis, 388
Archaeolepas, 84;
A. redtenbacheri, 84
Archea, 411;
A. paradoxa, 383;
A. workmani, 411
Archeidae, 321, 411
Archisometrus, 306
Arctic zone, 199
Arcturidae, 127
Arcturus, 127
Arcyinae, 410
Arcys, 410
segmentation, 6;
A. australiensis, 36;
A. cancriformis, 36;
habitat, 34
Arachnida, introduction to, 255;
segmentation of body, 255–6;
primitive, 256–7;
coxal glands, 257;
endosternite, 257;
sense-organs, 257;
classification, 258
Araneae, 258, 314 f.
Araneida, 314
Araneina, 314
Araneus, 408 n.
Aratus pisonii, 195
Arbanitis, 388
Archaeolepas, 84;
A. redtenbacheri, 84
Archea, 411;
A. paradoxa, 383;
A. workmani, 411
Archeidae, 321, 411
Archisometrus, 306
Arctic zone, 199
Arcturidae, 127
Arcturus, 127
Arcyinae, 410
Arcys, 410
Page 605
Arethusina, 223, 230, 251;
A. konincki, 250
Argas, 457, 469;
A. persicus, 469;
A. reflexus, 469
Argasidae, 469
Arges, 252
Argiope, 408;
A. aurelia, 340, 379;
A. bruennichi, 408;
A. cophinaria, 349, 365;
A. trifasciata, 408
Argiopidae, 406 n.
Argiopinae, 408
Argulidae, 76
Argulus foliaceus, 77
Argyrodes, 402;
A. piraticum, 367;
A. trigonum, 367
Argyrodinae, 402
Argyroneta, 336, 415;
A. aquatica, 357, 415
Ariadna, 395
Ariamnes, 402;
A. flagellum, 318
Arionellus, 247
Aristaeus, 162;
A. crassipes, 159;
A. coruscans, phosphorescence, 151
Armadillidium, 129
A. konincki, 250
Argas, 457, 469;
A. persicus, 469;
A. reflexus, 469
Argasidae, 469
Arges, 252
Argiope, 408;
A. aurelia, 340, 379;
A. bruennichi, 408;
A. cophinaria, 349, 365;
A. trifasciata, 408
Argiopidae, 406 n.
Argiopinae, 408
Argulidae, 76
Argulus foliaceus, 77
Argyrodes, 402;
A. piraticum, 367;
A. trigonum, 367
Argyrodinae, 402
Argyroneta, 336, 415;
A. aquatica, 357, 415
Ariadna, 395
Ariamnes, 402;
A. flagellum, 318
Arionellus, 247
Aristaeus, 162;
A. crassipes, 159;
A. coruscans, phosphorescence, 151
Armadillidium, 129
Page 606
Artema, 401
Artemia, 23, 24, 35;
A. fertilis, anal region, 23;
head, 26;
limb, 27;
A. salina, 23, 33, 36;
A. urmiana, 23
Arthrolycosa antiqua, 383
Arthropoda, 4;
segmentation, 7;
a natural group, 17
Arthrostraca, 121
Asagena, 404
Asaphellus, 249
Asaphidae, 249
Asaphini, 243
Asaphus, 222, 225, 227, 229, 235, 236, 249;
A. cornigerus, 227;
A. fallax, eye, 228;
A. kowalewskii, 227;
A. megistos, 236;
A. platycephalus, 236
Ascidicola rosea, 66
Ascidicolidae, 66
Asconiscidae, 130
Ascorhynchus, 505, 533;
A. abyssi, 506, 509, 519;
A. cryptopygius, 513 n.;
A. minutus, 517;
A. ramipes, 513 n.
Ascothoracica, 93
Artemia, 23, 24, 35;
A. fertilis, anal region, 23;
head, 26;
limb, 27;
A. salina, 23, 33, 36;
A. urmiana, 23
Arthrolycosa antiqua, 383
Arthropoda, 4;
segmentation, 7;
a natural group, 17
Arthrostraca, 121
Asagena, 404
Asaphellus, 249
Asaphidae, 249
Asaphini, 243
Asaphus, 222, 225, 227, 229, 235, 236, 249;
A. cornigerus, 227;
A. fallax, eye, 228;
A. kowalewskii, 227;
A. megistos, 236;
A. platycephalus, 236
Ascidicola rosea, 66
Ascidicolidae, 66
Asconiscidae, 130
Ascorhynchus, 505, 533;
A. abyssi, 506, 509, 519;
A. cryptopygius, 513 n.;
A. minutus, 517;
A. ramipes, 513 n.
Ascothoracica, 93
Page 607
Asellidae, 128
Asellota, 127
Asellus, 127;
habitat, 209, 211;
A. aquaticus, 127, 209;
A. cavaticus, 209, 210;
A. forelii, 209
Aspidoecia, 76
Astacidae, 157;
distribution, 213, 216
Astacoides, 157;
distribution, 213
Astacopsis, 157;
distribution, 213;
A. franklinii, 214
Astacus, 104, 157;
appendages, 10;
distribution, 213;
hermaphroditism, 104
Astacus gammarus (= Homarus vulgaris), 154
Asterocheres violaceus, 67
Asterocheridae, 67
Asterope oblonga, 108
Astia, 421;
A. vittata, 381
Astigmata, 465
Astridium, 540
Atax, 462, 472;
A. alticola, 472;
A. bonzi, 472
Asellota, 127
Asellus, 127;
habitat, 209, 211;
A. aquaticus, 127, 209;
A. cavaticus, 209, 210;
A. forelii, 209
Aspidoecia, 76
Astacidae, 157;
distribution, 213, 216
Astacoides, 157;
distribution, 213
Astacopsis, 157;
distribution, 213;
A. franklinii, 214
Astacus, 104, 157;
appendages, 10;
distribution, 213;
hermaphroditism, 104
Astacus gammarus (= Homarus vulgaris), 154
Asterocheres violaceus, 67
Asterocheridae, 67
Asterope oblonga, 108
Astia, 421;
A. vittata, 381
Astigmata, 465
Astridium, 540
Atax, 462, 472;
A. alticola, 472;
A. bonzi, 472
Page 608
Atelecyclidae, 190
Atelecyclus, 191;
respiration, 189
Atops, 247
Attidae, 376, 381, 419
Attus, 421;
A. pubescens, 372, 421;
A. saltator, 372, 421
Atya, 163
Atyephyra, 163;
habitat, 210
Atyidae, 159, 163;
distribution, 212
Atypidae, 390
Atypoides, 391
Atypus, 391;
A. abboti, 356;
A. affinis, 356, 391;
A. beckii, 391
Auditory organ, of Anaspides, 116;
of Decapoda, 153;
of Mysidae, 119
Augaptilus filigerus, 59
Austrodecus glacialis, 535
Austroraptus polaris, 535
Autotomy, 155
Avicularia, 389
Aviculariidae, 316, 327, 386;
bite of, 365;
poisonous hairs of, 365
Atelecyclus, 191;
respiration, 189
Atops, 247
Attidae, 376, 381, 419
Attus, 421;
A. pubescens, 372, 421;
A. saltator, 372, 421
Atya, 163
Atyephyra, 163;
habitat, 210
Atyidae, 159, 163;
distribution, 212
Atypidae, 390
Atypoides, 391
Atypus, 391;
A. abboti, 356;
A. affinis, 356, 391;
A. beckii, 391
Auditory organ, of Anaspides, 116;
of Decapoda, 153;
of Mysidae, 119
Augaptilus filigerus, 59
Austrodecus glacialis, 535
Austroraptus polaris, 535
Autotomy, 155
Avicularia, 389
Aviculariidae, 316, 327, 386;
bite of, 365;
poisonous hairs of, 365
Page 609
Aviculariinae, 389
Axial furrows, 223
Baglivi, 361
Baikal, Lake, Crustacea of, 212
Balanus, 91;
B. porcatus, shell, 90;
B. tintinnabulum, 91;
anatomy, 90
Ballus variegatus, 420
Barana, 506, 513, 533;
B. arenicola, 512, 513, 533;
B. castelli, 512, 513 n., 533
Barnacles, origin of term, 79
Barrande, J., on development of Trilobites, 238;
on their classification, 243
Barrandia, 249
Barrois, 435 n.
Barrus, 429
Barychelinae, 389
Basse, on Tardigrada, 481
Baster, Job, 503
Bates, 373
Bathynomus giganteus, 126;
habitat, 205
Bathynotus, 247
Bathyphantes, 406
Bdella lignicola, 471
Axial furrows, 223
Baglivi, 361
Baikal, Lake, Crustacea of, 212
Balanus, 91;
B. porcatus, shell, 90;
B. tintinnabulum, 91;
anatomy, 90
Ballus variegatus, 420
Barana, 506, 513, 533;
B. arenicola, 512, 513, 533;
B. castelli, 512, 513 n., 533
Barnacles, origin of term, 79
Barrande, J., on development of Trilobites, 238;
on their classification, 243
Barrandia, 249
Barrois, 435 n.
Barrus, 429
Barychelinae, 389
Basse, on Tardigrada, 481
Baster, Job, 503
Bates, 373
Bathynomus giganteus, 126;
habitat, 205
Bathynotus, 247
Bathyphantes, 406
Bdella lignicola, 471
Page 610
Bdellidae, 458, 471
Beecher, C. E., on facial sutures of Agnostus and Olenellus, 225;
on development of Trilobites, 238;
on their classification, 243
Beetle-mites, 467
Beetle-parasites, 470
Belinurus, 275, 279;
B. reginae, 278
Belisarius, 308
Belt, 368, 371
Beltina, 283 n.
Bernard, 311, 424, 426, 433 n., 434 n.
Bertkau, 323, 365, 395 n.
Beyrich, E., on facial suture of Trinucleus, 226
Billings, E., on appendages of Trilobites, 236
Bipolarity, 200
Birds and Spiders, 370
Birds’ feather Mites, 466
Birgus, 181;
B. latro, habits, 174;
structure, 175, 176
Black Corals, Cirripedia parasitic on, 93, 94
Blackwall, 348, 359 n., 365, 368, 385
Blindness, in Crustacea, 149, 209, 210;
in Spiders, 334
Blood, haemoglobin supposed in, 30, 68
Boas, on classification of Malacostraca, 113
Boeckella, distribution, 216
Beecher, C. E., on facial sutures of Agnostus and Olenellus, 225;
on development of Trilobites, 238;
on their classification, 243
Beetle-mites, 467
Beetle-parasites, 470
Belinurus, 275, 279;
B. reginae, 278
Belisarius, 308
Belt, 368, 371
Beltina, 283 n.
Bernard, 311, 424, 426, 433 n., 434 n.
Bertkau, 323, 365, 395 n.
Beyrich, E., on facial suture of Trinucleus, 226
Billings, E., on appendages of Trilobites, 236
Bipolarity, 200
Birds and Spiders, 370
Birds’ feather Mites, 466
Birgus, 181;
B. latro, habits, 174;
structure, 175, 176
Black Corals, Cirripedia parasitic on, 93, 94
Blackwall, 348, 359 n., 365, 368, 385
Blindness, in Crustacea, 149, 209, 210;
in Spiders, 334
Blood, haemoglobin supposed in, 30, 68
Boas, on classification of Malacostraca, 113
Boeckella, distribution, 216
Page 611
Boeckia, 138
Böhmia, 535
Bolocera, Pycnogonum with, 524
Bolyphantes, 406
Bomolochidae, 71
Bomolochus, 71, 72
Bon, 360
Bont-tick, 456
Boophilus, 456, 469;
B. australis, capitulum of, 468
Bopyridae, 130, 133
Bopyrina, 129, 130, 132
Bopyrus fougerouxi, 133;
male, 133;
adult female, 134
Bopyrus larva, of Bopyrina, 129, 133
Boreomysis, 120;
B. scyphops, distribution, 201
Boreonymphon, 536;
B. robustum, 506, 507, 511, 512, 542
Bosmina, 52, 53;
occurrence in Southern hemisphere, 216;
B. longirostris, habitat, 206
Bosminidae, 53;
appendages, 41;
alimentary canal, 42
Bothriuridae, 306, 308
Bothriurus, 308
Bouvier, 528 n.
Böhmia, 535
Bolocera, Pycnogonum with, 524
Bolyphantes, 406
Bomolochidae, 71
Bomolochus, 71, 72
Bon, 360
Bont-tick, 456
Boophilus, 456, 469;
B. australis, capitulum of, 468
Bopyridae, 130, 133
Bopyrina, 129, 130, 132
Bopyrus fougerouxi, 133;
male, 133;
adult female, 134
Bopyrus larva, of Bopyrina, 129, 133
Boreomysis, 120;
B. scyphops, distribution, 201
Boreonymphon, 536;
B. robustum, 506, 507, 511, 512, 542
Bosmina, 52, 53;
occurrence in Southern hemisphere, 216;
B. longirostris, habitat, 206
Bosminidae, 53;
appendages, 41;
alimentary canal, 42
Bothriuridae, 306, 308
Bothriurus, 308
Bouvier, 528 n.
Page 612
Boys, 348, 360, 376
Brachybothrium, 391
Brachymetopus, 251
Brachythele, 390
Brachyura, 181;
eyes, 150
Branchiae (= gills) of Crustacea, 16;
of Decapoda, 152;
of Limulus, 269;
of Eurypterids, 288
Branchinecta, 25, 35;
B. paludosa, 35;
range, 34
Branchiopoda, 18 f.
Branchiopodopsis, 35;
B. hodgsoni, 35
Branchiostegite, 152
Branchipodidae, 19, 22, 35, 241
Branchipus, 25, 35, 233, 242, 511 n.;
thoracic limb, 10;
nervous system, 30;
B. spinosus, habitat, 33;
B. stagnalis, 35;
eggs, 32
Branchiura, 76
Brauer, on development of Scorpions, 263, 301 n., 305
Breeding (see Reproduction)
British forms, of Cladocera, 51;
of Pycnogons, 540
Bronteidae, 249
Brachybothrium, 391
Brachymetopus, 251
Brachythele, 390
Brachyura, 181;
eyes, 150
Branchiae (= gills) of Crustacea, 16;
of Decapoda, 152;
of Limulus, 269;
of Eurypterids, 288
Branchinecta, 25, 35;
B. paludosa, 35;
range, 34
Branchiopoda, 18 f.
Branchiopodopsis, 35;
B. hodgsoni, 35
Branchiostegite, 152
Branchipodidae, 19, 22, 35, 241
Branchipus, 25, 35, 233, 242, 511 n.;
thoracic limb, 10;
nervous system, 30;
B. spinosus, habitat, 33;
B. stagnalis, 35;
eggs, 32
Branchiura, 76
Brauer, on development of Scorpions, 263, 301 n., 305
Breeding (see Reproduction)
British forms, of Cladocera, 51;
of Pycnogons, 540
Bronteidae, 249
Page 613
Bronteus, 228, 235, 249;
B. brongniarti, eye, 229;
B. palifer, eye, 229;
B. polyactin, hypostome, 233;
B. irradians, macula, 233
Brood-pouch, of Cladocera, 46, 47;
of Peracarida, 118
Broteas, 308
Broteochactas, 308
Brünnich, 502
Buckler, 330
Bucranium, 414
Bulb, of palpal organ of Spiders, 322
Bumastus, 235, 236, 249
Bunodella, 279
Bunodes, 279
Buthidae, 306
Buthinae, 306
Buthus, 306;
B. occitanus, 299, 300, 302
Bythotrephes, 38, 54;
reproduction, 47;
B. cederströmii, 42
Cabiropsidae, 130
Caecidotea nickajackensis, habitat, 210;
C. stygia, habitat, 210
Caeculinae, 472
Caeculus, 472
B. brongniarti, eye, 229;
B. palifer, eye, 229;
B. polyactin, hypostome, 233;
B. irradians, macula, 233
Brood-pouch, of Cladocera, 46, 47;
of Peracarida, 118
Broteas, 308
Broteochactas, 308
Brünnich, 502
Buckler, 330
Bucranium, 414
Bulb, of palpal organ of Spiders, 322
Bumastus, 235, 236, 249
Bunodella, 279
Bunodes, 279
Buthidae, 306
Buthinae, 306
Buthus, 306;
B. occitanus, 299, 300, 302
Bythotrephes, 38, 54;
reproduction, 47;
B. cederströmii, 42
Cabiropsidae, 130
Caecidotea nickajackensis, habitat, 210;
C. stygia, habitat, 210
Caeculinae, 472
Caeculus, 472
Page 614
Calamistrum, 326, 354, 385, 392, 399, 410
Calanidae, 57
Calanus, 57;
C. finmarchicus, distribution, 203, 204;
C. hyperboreus, 55, 56, 58
Calappa, 187;
respiration, 186;
habitat, 198;
distribution, 201;
C. granulata, 186
Calappidae, 187
Calathocratus, 452
Calathura brachiata (Anthuridae), Duplorbis parasitic on, 95
Calicurgus annulatus, 369
Caligidae, 73
Caligus nanus, 74;
C. rapax, 74;
C. lacustris, 74
Callianassa, 167;
habitat, 198;
C. subterranea, 167;
gut, 14
Callianassidae, 167
Callinectes, 191;
C. sapidus, 191
Calman, on classification of Crustacea, 112, 113
Calocalanus plumulosus, 58
Caloctenus, 418
Calommata, 391
Calymene, 225, 230, 235, 249;
Calanidae, 57
Calanus, 57;
C. finmarchicus, distribution, 203, 204;
C. hyperboreus, 55, 56, 58
Calappa, 187;
respiration, 186;
habitat, 198;
distribution, 201;
C. granulata, 186
Calappidae, 187
Calathocratus, 452
Calathura brachiata (Anthuridae), Duplorbis parasitic on, 95
Calicurgus annulatus, 369
Caligidae, 73
Caligus nanus, 74;
C. rapax, 74;
C. lacustris, 74
Callianassa, 167;
habitat, 198;
C. subterranea, 167;
gut, 14
Callianassidae, 167
Callinectes, 191;
C. sapidus, 191
Calman, on classification of Crustacea, 112, 113
Calocalanus plumulosus, 58
Caloctenus, 418
Calommata, 391
Calymene, 225, 230, 235, 249;
Page 615
C. senaria, 236;
C. tuberculata, 224
Calymenidae, 247
Calyptomera, 38, 51
Calyptopis, larva of Euphausia pellucida, 144
Cambaroides, distribution, 213
Cambarus, 157;
hermaphroditism, 103;
distribution, 213;
C. stygius, distribution, 213
Camerostome, 452
Campbell, 327
Camptocercus, 53;
C. macrurus, 48
Cancer, 191;
C. pagurus, 191
Cancerilla, 68;
C. tubulata, 68
Cancridae, 191
Candace, 60;
C. pectinata, 60
Candacidae, 60
Candona, 107;
C. reptans, 107
Canestrini, 464
Canthocamptus, 62;
habitat, 206
Capitulum, of Cirripedia, 81;
of Acarina, 457, 468, 471
C. tuberculata, 224
Calymenidae, 247
Calyptomera, 38, 51
Calyptopis, larva of Euphausia pellucida, 144
Cambaroides, distribution, 213
Cambarus, 157;
hermaphroditism, 103;
distribution, 213;
C. stygius, distribution, 213
Camerostome, 452
Campbell, 327
Camptocercus, 53;
C. macrurus, 48
Cancer, 191;
C. pagurus, 191
Cancerilla, 68;
C. tubulata, 68
Cancridae, 191
Candace, 60;
C. pectinata, 60
Candacidae, 60
Candona, 107;
C. reptans, 107
Canestrini, 464
Canthocamptus, 62;
habitat, 206
Capitulum, of Cirripedia, 81;
of Acarina, 457, 468, 471
Page 616
Caponia natalensis, 395
Caponiidae, 395
Caponina, 395
Caprella acutifrons, 140;
C. grandimana, 139
Caprellidae, 139
Carapace, of Phyllopoda, 19 f.;
of Cladocera, 38;
absence of, in Copepoda, 55;
of Malacostraca, 114
Carcinoplacidae, 195
Carrinoscorpius, 277;
C. rotundicauda, 277
Carcinus, 191;
C. maenas, 188, 191;
gut, 14;
respiration, 189, 190;
distribution, 198;
Portunion parasitic in, 135;
Sacculina parasitic on, 96
Cardisoma, 196;
distribution, 201
Caridea, 158, 163;
metamorphosis, 161
Caridina, 163;
C. nilotica, distribution, 212
Carniola, caves of, 34
Carpenter, on segmentation of Arthropods, 6, 263;
on affinities of Trilobites, 242;
on Irish Pycnogons, 540
Caruncle, 470
Caponiidae, 395
Caponina, 395
Caprella acutifrons, 140;
C. grandimana, 139
Caprellidae, 139
Carapace, of Phyllopoda, 19 f.;
of Cladocera, 38;
absence of, in Copepoda, 55;
of Malacostraca, 114
Carcinoplacidae, 195
Carrinoscorpius, 277;
C. rotundicauda, 277
Carcinus, 191;
C. maenas, 188, 191;
gut, 14;
respiration, 189, 190;
distribution, 198;
Portunion parasitic in, 135;
Sacculina parasitic on, 96
Cardisoma, 196;
distribution, 201
Caridea, 158, 163;
metamorphosis, 161
Caridina, 163;
C. nilotica, distribution, 212
Carniola, caves of, 34
Carpenter, on segmentation of Arthropods, 6, 263;
on affinities of Trilobites, 242;
on Irish Pycnogons, 540
Caruncle, 470
Page 617
Caspian Sea, Crustacea of, 215
Caspiocuma, 121
Catometopa, 193 f.;
habits, 194, 195
Catophragmus, 91
Caudal organs, 311
Caullery, on Liriopsidae, 132 n.
Causard, 332
Cavanna, 520
Cecrops, 74
Cenobita, 181;
relation to Birgus, 176
Cenobitidae, 181
Centropages hamatus, 203;
C. typicus, distribution, 203
Centropagidae, 58
Centropelma, 416
Centropleura, 247
Centrurinae, 306
Centrurus, 306
Cephalic shield, 223
Cepheus ocellatus, 467
Cerataspis, 162
Ceratolichas, 252
Ceratopyge, 247
Cercophonius, 308
Ceriodaphnia, 37, 39, 51
Caspiocuma, 121
Catometopa, 193 f.;
habits, 194, 195
Catophragmus, 91
Caudal organs, 311
Caullery, on Liriopsidae, 132 n.
Causard, 332
Cavanna, 520
Cecrops, 74
Cenobita, 181;
relation to Birgus, 176
Cenobitidae, 181
Centropages hamatus, 203;
C. typicus, distribution, 203
Centropagidae, 58
Centropelma, 416
Centropleura, 247
Centrurinae, 306
Centrurus, 306
Cephalic shield, 223
Cepheus ocellatus, 467
Cerataspis, 162
Ceratolichas, 252
Ceratopyge, 247
Cercophonius, 308
Ceriodaphnia, 37, 39, 51
Page 618
Ceroma, 429
Chactas, 308
Chactidae, 306, 307
Chaerilidae, 306, 307
Chaerilus, 307
Chaetolepas, 89
Chaetonymphon, 536;
C. hirtipes, 541;
C. hirtum, 509, 541;
C. macronyx, 506;
C. spinosissimum, 541, 542;
C. tenellum, 542
Chaetopelma, 389
Charontinae, 313
Chasmops, 249
Cheeks, of Trilobites, 223, 225
Cheese-mites, 466
Cheiracanthium, 397
Cheiruridae, 250
Cheirurus, 235, 251;
C. insignia, 250;
C. pleurexacanthus, 236
Chelicerae, of Xiphosura, 263 f.;
of Eurypterida, 285;
of Scorpions, 303;
of Pedipalpi, 309;
of Spiders, 319;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 432;
of Podogona, 439;
Chactas, 308
Chactidae, 306, 307
Chaerilidae, 306, 307
Chaerilus, 307
Chaetolepas, 89
Chaetonymphon, 536;
C. hirtipes, 541;
C. hirtum, 509, 541;
C. macronyx, 506;
C. spinosissimum, 541, 542;
C. tenellum, 542
Chaetopelma, 389
Charontinae, 313
Chasmops, 249
Cheeks, of Trilobites, 223, 225
Cheese-mites, 466
Cheiracanthium, 397
Cheiruridae, 250
Cheirurus, 235, 251;
C. insignia, 250;
C. pleurexacanthus, 236
Chelicerae, of Xiphosura, 263 f.;
of Eurypterida, 285;
of Scorpions, 303;
of Pedipalpi, 309;
of Spiders, 319;
of Palpigradi, 422;
of Solifugae, 426;
of Pseudoscorpions, 432;
of Podogona, 439;
Page 619
of Phalangids, 443;
of Acarina, 458
Chelifer, 436, 437;
development, 435;
C. cancroides, 437;
C. cyrneus, 437;
C. ferum 437
Chelifera, 122
Cheliferidae, 436
Chelophores, of Pycnogons, 505
Chernes, 432, 436, 437, 438
Chernetes, 430
Chernetidea, 258, 430 f.
Cheyletinae, 473
Cheyletus, 458, 473
Chilaria, 260, 271, 287, 292
Chilobrachys, 390;
C. stridulans, 328, 329
Chilophoxus, 539
Chiltonia, 139;
distribution, 217
Chiridium, 432, 436, 437;
C. museorum, 437
Chirocephalus, 35;
C. diaphanus, 20, 24, 25, 27, 29, 32, 33, 35
Chlorodinus, habitat, 198
Chlorodius, 191
Chondracanthidae, 72
Chondracanthus zei, 72
of Acarina, 458
Chelifer, 436, 437;
development, 435;
C. cancroides, 437;
C. cyrneus, 437;
C. ferum 437
Chelifera, 122
Cheliferidae, 436
Chelophores, of Pycnogons, 505
Chernes, 432, 436, 437, 438
Chernetes, 430
Chernetidea, 258, 430 f.
Cheyletinae, 473
Cheyletus, 458, 473
Chilaria, 260, 271, 287, 292
Chilobrachys, 390;
C. stridulans, 328, 329
Chilophoxus, 539
Chiltonia, 139;
distribution, 217
Chiridium, 432, 436, 437;
C. museorum, 437
Chirocephalus, 35;
C. diaphanus, 20, 24, 25, 27, 29, 32, 33, 35
Chlorodinus, habitat, 198
Chlorodius, 191
Chondracanthidae, 72
Chondracanthus zei, 72
Page 620
Choniostoma, 76
Choniostomatidae, 76
Chthonius, 436, 438
Chun, on phosphorescence and eyes, 150
Chydorus, 54
Cilunculus, 535
Circulatory (= vascular) system, of Crustacea, 11;
of Arachnids, 256;
of Limulus, 268 f.;
of Tardigrada, 482;
of Pentastomida, 491;
of Pycnogons, 516
Cirolana, 126
Cirripedia, 79 f.;
metamorphosis, 80;
anatomy, 83;
sex, 87, 105
Cladocera, 19, 37 f.;
carapace, 38;
dorsal organ, 39;
appendages, 40 f.;
alimentary canal, 42;
heart, 43;
reproduction, 43–50;
British genera, 51–54;
extra-European, 54;
pelagic, 207, 208
Claparède, 331, 462 n.
Clarke, J. M., on the eye of Calymene senaria, 229;
of Harpes, 231
Claus, on Copepoda, 55;
on Nebalia, 111;
Choniostomatidae, 76
Chthonius, 436, 438
Chun, on phosphorescence and eyes, 150
Chydorus, 54
Cilunculus, 535
Circulatory (= vascular) system, of Crustacea, 11;
of Arachnids, 256;
of Limulus, 268 f.;
of Tardigrada, 482;
of Pentastomida, 491;
of Pycnogons, 516
Cirolana, 126
Cirripedia, 79 f.;
metamorphosis, 80;
anatomy, 83;
sex, 87, 105
Cladocera, 19, 37 f.;
carapace, 38;
dorsal organ, 39;
appendages, 40 f.;
alimentary canal, 42;
heart, 43;
reproduction, 43–50;
British genera, 51–54;
extra-European, 54;
pelagic, 207, 208
Claparède, 331, 462 n.
Clarke, J. M., on the eye of Calymene senaria, 229;
of Harpes, 231
Claus, on Copepoda, 55;
on Nebalia, 111;
Page 621
on discovery of metamorphosis of Decapods, 153 n.;
on Pycnogonida, 527
Claw-tufts, 389
Clerck, 384, 408 n.
Clibanarius, 181
Clotenia conirostre, 541
Clubiona, 337, 368, 397;
C. compta, 397;
C. corticalis, 396, 397
Clubioninae, 397
Clypeus, 316
Clytemnestra, 61
Coelotes atropos, 416
Cole, 520, 524, 525, 528 n.
Colossendeis, 505, 532;
C. angusta, 542;
C. australis, 533;
C. gibbosa, 534;
C. gigas, 532;
C. gracilis, 505 n.;
C. proboscidea, 505, 508, 510, 533, 542
Colour, adaptation in, of Crustacea, 159
Colulus, 317, 319
Commensalism, of Hermit-crabs, 172;
of Pinnotheres, 195
Complemental males, of Cirripedes, 83, 86, 99, 106
Conchoderma, 88;
C. virgata, 88
Conocephalidae, 247
on Pycnogonida, 527
Claw-tufts, 389
Clerck, 384, 408 n.
Clibanarius, 181
Clotenia conirostre, 541
Clubiona, 337, 368, 397;
C. compta, 397;
C. corticalis, 396, 397
Clubioninae, 397
Clypeus, 316
Clytemnestra, 61
Coelotes atropos, 416
Cole, 520, 524, 525, 528 n.
Colossendeis, 505, 532;
C. angusta, 542;
C. australis, 533;
C. gibbosa, 534;
C. gigas, 532;
C. gracilis, 505 n.;
C. proboscidea, 505, 508, 510, 533, 542
Colour, adaptation in, of Crustacea, 159
Colulus, 317, 319
Commensalism, of Hermit-crabs, 172;
of Pinnotheres, 195
Complemental males, of Cirripedes, 83, 86, 99, 106
Conchoderma, 88;
C. virgata, 88
Conocephalidae, 247
Page 622
Conocoryphe, 231, 247;
C. sulzeri, 248
Conocoryphidae, 247
Conolichas, 252
Conothele, 388
Constantia (Macrohectopus), 138;
occurrence, 212
Cook, 425 n.
Copepoda, 55 f.;
fresh-water, 59, 62;
pelagic, 202;
life-cycle of fresh-water, 209
Copilia vitrea, 69, 70
Cordylochele, 506, 537;
C. longicollis, 507;
C. malleolata, 542
Corniger hilgendorfi, 535
Coronula diadema, 91
Corophiidae, 139
Corophium, 139
Corycaeidae, 69
Corystes, 188, 190;
habitat, 198;
C. cassivelaunus, respiration, 170, 189;
metamorphosis, 182, 183
Corystidae, 190
Cosmetidae, 449
Costa, da, 221
Coxal glands, 257;
C. sulzeri, 248
Conocoryphidae, 247
Conolichas, 252
Conothele, 388
Constantia (Macrohectopus), 138;
occurrence, 212
Cook, 425 n.
Copepoda, 55 f.;
fresh-water, 59, 62;
pelagic, 202;
life-cycle of fresh-water, 209
Copilia vitrea, 69, 70
Cordylochele, 506, 537;
C. longicollis, 507;
C. malleolata, 542
Corniger hilgendorfi, 535
Coronula diadema, 91
Corophiidae, 139
Corophium, 139
Corycaeidae, 69
Corystes, 188, 190;
habitat, 198;
C. cassivelaunus, respiration, 170, 189;
metamorphosis, 182, 183
Corystidae, 190
Cosmetidae, 449
Costa, da, 221
Coxal glands, 257;
Page 623
of Limulus, 270;
of Scorpions, 306;
of Pedipalpi, 311;
of Spiders, 337
Coxopodite, of Trilobites, 237
Crab, Hermit-, 171–173;
River-, 214;
Robber-, 174;
Shore-, 188, 189, 198;
Edible, 188;
Spider-, 191;
Land-, 195;
enemies of, 192
Crab-spiders, 412 (= Thomisidae, q.v.)
Crangon, 164;
C. antarcticus, distribution, 200;
C. franciscorum, distribution, 200;
C. vulgaris, 158, 164;
distribution, 199
Crangonidae, 164;
distribution, 199
Crangonyx, 138
Crayfish, 154, 157;
distribution, 213, 215
Crevettina, 137
Cribellatae, 324, 385, 386 n.
Cribellum, 326, 354, 385, 386, 392, 398, 410
Croneberg, 460
Cruregens, 124;
C. fontanus, habitat, 210
Crustacea, organisation, 1 f.;
of Scorpions, 306;
of Pedipalpi, 311;
of Spiders, 337
Coxopodite, of Trilobites, 237
Crab, Hermit-, 171–173;
River-, 214;
Robber-, 174;
Shore-, 188, 189, 198;
Edible, 188;
Spider-, 191;
Land-, 195;
enemies of, 192
Crab-spiders, 412 (= Thomisidae, q.v.)
Crangon, 164;
C. antarcticus, distribution, 200;
C. franciscorum, distribution, 200;
C. vulgaris, 158, 164;
distribution, 199
Crangonidae, 164;
distribution, 199
Crangonyx, 138
Crayfish, 154, 157;
distribution, 213, 215
Crevettina, 137
Cribellatae, 324, 385, 386 n.
Cribellum, 326, 354, 385, 386, 392, 398, 410
Croneberg, 460
Cruregens, 124;
C. fontanus, habitat, 210
Crustacea, organisation, 1 f.;
Page 624
segmentation, 5;
appendages, 8 f.;
body-cavity and coelom, 11;
kidneys, 13;
alimentary canal, 14;
reproductive organs, 15;
respiratory organs, 16;
compound eyes, 146;
growth and sex in, 100;
metabolism, 104;
distribution, 197;
pelagic, 202, 207;
littoral, 197, 206;
abyssal, 204, 209;
fresh-water, 205;
subterranean and cave, 209
Crustacés aranéiformes, 501 n.
Cryphaeus, 249
Cryphoeca, 416
Cryptocellus, 439;
C. simonis, 439
Cryptocerus, 414
Cryptoniscidae, 130
Cryptoniscina, 129, 130
Cryptoniscus, larva of Epicarida, 129, 131, 132
Cryptophialus, 92;
C. minutus, 92, 93;
C. striatus, 93
Cryptostemma westermannii, 439
Cryptostemmatidae, 440
Cryptothele, 400
appendages, 8 f.;
body-cavity and coelom, 11;
kidneys, 13;
alimentary canal, 14;
reproductive organs, 15;
respiratory organs, 16;
compound eyes, 146;
growth and sex in, 100;
metabolism, 104;
distribution, 197;
pelagic, 202, 207;
littoral, 197, 206;
abyssal, 204, 209;
fresh-water, 205;
subterranean and cave, 209
Crustacés aranéiformes, 501 n.
Cryphaeus, 249
Cryphoeca, 416
Cryptocellus, 439;
C. simonis, 439
Cryptocerus, 414
Cryptoniscidae, 130
Cryptoniscina, 129, 130
Cryptoniscus, larva of Epicarida, 129, 131, 132
Cryptophialus, 92;
C. minutus, 92, 93;
C. striatus, 93
Cryptostemma westermannii, 439
Cryptostemmatidae, 440
Cryptothele, 400
Page 625
Ctenidae, 418
Cteninae, 418
Cteniza, 388;
C. ariana, 355
Ctenizinae, 388
Ctenocephalus, 247
Ctenophora, 412
Ctenopoda, 51
Ctenopyge, 232, 247
Ctenus, 418
Cucullus, 440
Cuma, 121
Cumacea, 114, 120;
of the Caspian, 215
Cumidae, 121
Cyamidae, 140
Cyamus ceti, 140
Cybaeinae, 415
Cybele, 251
Cyclaspis, 121
Cyclestheria, 37;
C. hislopi, 37
Cyclodorippe dromioides, eyes, 149
Cyclograpsus, 196;
distribution, 200
Cyclometopa, 188 f.;
respiration, 189, 190
Cyclopidae, 61, 62;
Cteninae, 418
Cteniza, 388;
C. ariana, 355
Ctenizinae, 388
Ctenocephalus, 247
Ctenophora, 412
Ctenopoda, 51
Ctenopyge, 232, 247
Ctenus, 418
Cucullus, 440
Cuma, 121
Cumacea, 114, 120;
of the Caspian, 215
Cumidae, 121
Cyamidae, 140
Cyamus ceti, 140
Cybaeinae, 415
Cybele, 251
Cyclaspis, 121
Cyclestheria, 37;
C. hislopi, 37
Cyclodorippe dromioides, eyes, 149
Cyclograpsus, 196;
distribution, 200
Cyclometopa, 188 f.;
respiration, 189, 190
Cyclopidae, 61, 62;
Page 626
subterranean, 209
Cyclops, 62;
C. fuscus, habitat, 207;
C. strenuus, habitat, 207, 208;
C. stygius, habitat, 210
Cyclosa conica, 409
Cyclosternum, 389
Cydrela, 399
Cymodoce, 126
Cymonomus, 188;
C. granulatus, 185;
eyes, 149, 186;
C. normani, 186;
C. quadratus, 186
Cymothoa, 126;
habitat, 211
Cymothoidae, 126
Cyphaspis, 251
Cyphophthalmi, 443, 444, 447
Cypridae, 107;
subterranean, 209
Cypridinidae, 108
Cypris, 107;
C. reptans, parthenogenesis, 108
Cypris larva, of Cirripedia, 80, 82;
of Sacculina, 97, 99
Cyrtauchenius, 388;
C. elongatus, funnel of, 356
Cythere dictyon, 108
Cytherellidae, 109
Cyclops, 62;
C. fuscus, habitat, 207;
C. strenuus, habitat, 207, 208;
C. stygius, habitat, 210
Cyclosa conica, 409
Cyclosternum, 389
Cydrela, 399
Cymodoce, 126
Cymonomus, 188;
C. granulatus, 185;
eyes, 149, 186;
C. normani, 186;
C. quadratus, 186
Cymothoa, 126;
habitat, 211
Cymothoidae, 126
Cyphaspis, 251
Cyphophthalmi, 443, 444, 447
Cypridae, 107;
subterranean, 209
Cypridinidae, 108
Cypris, 107;
C. reptans, parthenogenesis, 108
Cypris larva, of Cirripedia, 80, 82;
of Sacculina, 97, 99
Cyrtauchenius, 388;
C. elongatus, funnel of, 356
Cythere dictyon, 108
Cytherellidae, 109
Page 627
Cytheridae, 107
Dactylopisthes digiticeps, 405
Dactylopus tisboides, 62
Daesia, 429
Daesiinae, 429
Dajidae, 130
Dalmanites, 249;
D. imbricatulus, eye, 228;
D. limulurus, 250;
D. socialis, larvae, 240
Danalia curvata, 130, 131, 132
Daphnella, 51;
testes, 44
Daphnia, 37, 38, 39, 51;
ovary, 45, 48;
D. magna, 50;
D. obtusa, 51
Daphniidae, 51;
appendages, 40;
alimentary canal, 42;
reproduction, 48;
reactions, 50
Darwin, on Cirripedia, 80, 85, 86, 92, 94
Dasylobus, 450
Decapoda, 152 f.;
systematic position, 114;
alimentary canal, 14;
pelagic, 202;
subterranean, 210;
Rhizocephala parasitic on, 95, 101;
Dactylopisthes digiticeps, 405
Dactylopus tisboides, 62
Daesia, 429
Daesiinae, 429
Dajidae, 130
Dalmanites, 249;
D. imbricatulus, eye, 228;
D. limulurus, 250;
D. socialis, larvae, 240
Danalia curvata, 130, 131, 132
Daphnella, 51;
testes, 44
Daphnia, 37, 38, 39, 51;
ovary, 45, 48;
D. magna, 50;
D. obtusa, 51
Daphniidae, 51;
appendages, 40;
alimentary canal, 42;
reproduction, 48;
reactions, 50
Darwin, on Cirripedia, 80, 85, 86, 92, 94
Dasylobus, 450
Decapoda, 152 f.;
systematic position, 114;
alimentary canal, 14;
pelagic, 202;
subterranean, 210;
Rhizocephala parasitic on, 95, 101;
Page 628
Bopyridae parasitic on, 133
Dechenella, 251
Decolopoda, 504, 529, 532;
D. antarctica, 532;
D. australis, 531, 532
Decolopodidae, 531
Defective orb-webs, 349
Deiphon, 235, 251;
D. forbesi, 250
Delena, 414
Delobranchiata, 258, 259 f.
Demodex, 465;
D. folliculorum, 465
Demodicidae, 455, 465
Dendrogaster astericola, 94
Dermacentor, 469
Dermanyssinae, 471
Dermanyssus avium, 471
Dermaturus, 181;
D. hispidus, 178
Desis, 415
Deutovum, 462
Development, of Monstrillidae, 64;
of Cirripedia, 80;
of Rhizocephala, 96;
of Epicarida, 130;
of Stomatopoda, 142;
of Shrimps and Prawns, 159;
of Loricata, 165;
of Hermit-Crabs, 179;
Dechenella, 251
Decolopoda, 504, 529, 532;
D. antarctica, 532;
D. australis, 531, 532
Decolopodidae, 531
Defective orb-webs, 349
Deiphon, 235, 251;
D. forbesi, 250
Delena, 414
Delobranchiata, 258, 259 f.
Demodex, 465;
D. folliculorum, 465
Demodicidae, 455, 465
Dendrogaster astericola, 94
Dermacentor, 469
Dermanyssinae, 471
Dermanyssus avium, 471
Dermaturus, 181;
D. hispidus, 178
Desis, 415
Deutovum, 462
Development, of Monstrillidae, 64;
of Cirripedia, 80;
of Rhizocephala, 96;
of Epicarida, 130;
of Stomatopoda, 142;
of Shrimps and Prawns, 159;
of Loricata, 165;
of Hermit-Crabs, 179;
Page 629
of Brachyura, 181;
of Trilobites, 238 f.;
of Limulus, 275;
of Scorpio, 305;
of Pseudoscorpions, 434;
of Mites, 462;
of Tardigrada, 483;
of Pentastomida, 493;
of Pycnogons, 520
Diaea, 412;
D. dorsata, 413
Diaphragm, of Solifugae, 427
Diaptomus, 59;
distribution, 208, 216;
D. caeruleus, habitat, 208;
D. castor, habitat, 206;
D. gracilis, habitat, 206
Diastylidae, 121
Diastylis, 121;
D. goodsiri, 121;
D. stygia, 120
Dichelaspis, 88
Dichelestiidae, 68;
classification, 63
Dichelestium, 68
Dick, 363
Dicranogmus, 252
Dicranolasma, 452
Dictyna, 398;
D. arundinacea, 399;
D. uncinata, 399
of Trilobites, 238 f.;
of Limulus, 275;
of Scorpio, 305;
of Pseudoscorpions, 434;
of Mites, 462;
of Tardigrada, 483;
of Pentastomida, 493;
of Pycnogons, 520
Diaea, 412;
D. dorsata, 413
Diaphragm, of Solifugae, 427
Diaptomus, 59;
distribution, 208, 216;
D. caeruleus, habitat, 208;
D. castor, habitat, 206;
D. gracilis, habitat, 206
Diastylidae, 121
Diastylis, 121;
D. goodsiri, 121;
D. stygia, 120
Dichelaspis, 88
Dichelestiidae, 68;
classification, 63
Dichelestium, 68
Dick, 363
Dicranogmus, 252
Dicranolasma, 452
Dictyna, 398;
D. arundinacea, 399;
D. uncinata, 399
Page 630
Dictynidae, 352, 353, 398
Digestive system, = alimentary canal, q.v.
Dikelocephalus, 247
Dimorphism, high and low;
in Decapoda, 103;
in Tanaids, 123
Dindymene, 251
Dinopinae, 410
Dinopis, 410
Dinorhax, 429
Diogenes, 181
Dionide, 245
Diphascon, 485;
D. alpinum, 487;
D. angustatum, 487;
D. bullatum, 487;
D. chilenense, 486, 487;
D. oculatum, 487;
D. scoticum, 487;
D. spitzbergense, 487
Diplocentrinae, 306, 307
Diplocentrus, 307
Diplocephalus bicephalus, 405
Diplostichous eyes, 301
Diplura, 390
Diplurinae, 390
Dipoena, 403
Discoarachne, 512, 535
Distribution, of Crustacea, 197 f.;
Digestive system, = alimentary canal, q.v.
Dikelocephalus, 247
Dimorphism, high and low;
in Decapoda, 103;
in Tanaids, 123
Dindymene, 251
Dinopinae, 410
Dinopis, 410
Dinorhax, 429
Diogenes, 181
Dionide, 245
Diphascon, 485;
D. alpinum, 487;
D. angustatum, 487;
D. bullatum, 487;
D. chilenense, 486, 487;
D. oculatum, 487;
D. scoticum, 487;
D. spitzbergense, 487
Diplocentrinae, 306, 307
Diplocentrus, 307
Diplocephalus bicephalus, 405
Diplostichous eyes, 301
Diplura, 390
Diplurinae, 390
Dipoena, 403
Discoarachne, 512, 535
Distribution, of Crustacea, 197 f.;
Page 631
(stratigraphical) of Trilobites, 222
Doflein, on eyes of deep-sea Crustacea, 148, 150
Dohrn, 504, 513, 519
Doleschall, 365
Dolichopterus, 283, 291
Doliomelus, 415
Dolomedes fimbriatus, 416
Dolops, 78
Domed webs, 350
Donachochara, 406
Donnadieu, 457
Dorippe, 185, 188
Dorippidae, 188
Doropygus, 66;
D. pulex, 66
Dorsal organ, of Phyllopoda, 22;
of Cladocera, 39
Doublure, 232
Doyère, on Tardigrada, 481;
on their systematic position, 483
Doyeria, 485;
D. simplex, 480, 487
Drassidae, 324, 396
Drassinae, 396
Drassus, 397;
D. lapidosus, 396, 397
Drepanothrix, 53
Dromia, 184;
Doflein, on eyes of deep-sea Crustacea, 148, 150
Dohrn, 504, 513, 519
Doleschall, 365
Dolichopterus, 283, 291
Doliomelus, 415
Dolomedes fimbriatus, 416
Dolops, 78
Domed webs, 350
Donachochara, 406
Donnadieu, 457
Dorippe, 185, 188
Dorippidae, 188
Doropygus, 66;
D. pulex, 66
Dorsal organ, of Phyllopoda, 22;
of Cladocera, 39
Doublure, 232
Doyère, on Tardigrada, 481;
on their systematic position, 483
Doyeria, 485;
D. simplex, 480, 487
Drassidae, 324, 396
Drassinae, 396
Drassus, 397;
D. lapidosus, 396, 397
Drepanothrix, 53
Dromia, 184;
Page 632
D. vulgaris, 184
Dromiacea, 183;
metamorphosis, 182;
relation to Macrura, 184;
habitat, 198
Dromidia, distribution, 200
Dromiidae, 184
Drymusa, 393
Dufour, 385
Dujardin, 464 n.;
on systematic position of Tardigrada, 483
Duplorbis, 95;
D. calathurae, 99
Dynomene, 184
Dynomenidae, 184
Dysdera, 394;
D. cambridgii, 394;
D. crocota, 395
Dysderidae, 317, 319, 336, 394
Dysderina, 394
Dysderinae, 394
Ebalia, 188
Echiniscoides, 485;
E. sigismundi, 477, 486
Echiniscus, 480, 485;
E. arctomys, 486;
E. gladiator, 486;
E. granulatus, 486;
E. islandicus, 486;
Dromiacea, 183;
metamorphosis, 182;
relation to Macrura, 184;
habitat, 198
Dromidia, distribution, 200
Dromiidae, 184
Drymusa, 393
Dufour, 385
Dujardin, 464 n.;
on systematic position of Tardigrada, 483
Duplorbis, 95;
D. calathurae, 99
Dynomene, 184
Dynomenidae, 184
Dysdera, 394;
D. cambridgii, 394;
D. crocota, 395
Dysderidae, 317, 319, 336, 394
Dysderina, 394
Dysderinae, 394
Ebalia, 188
Echiniscoides, 485;
E. sigismundi, 477, 486
Echiniscus, 480, 485;
E. arctomys, 486;
E. gladiator, 486;
E. granulatus, 486;
E. islandicus, 486;
Page 633
E. muscicola, 486;
E. mutabilis, 486;
E. oihonnae, 486;
E. quadrispinosus, 486;
E. reticulatus, 486;
E. spinulosus, 479;
E. spitzbergensis, 486;
E. testudo, 478;
E. wendti, 486
Echinoderms, Dendrogaster parasitic on, 94
Echinognathus, 283
Ecribellatae, 385
Ectatosticta davidi, 393
Ectinosoma, 62
Edriophthalmata, 112, 121
Eggs, of Phyllopoda, 32;
of Cladocera, 44;
of Copepoda, 59, 62, 66, 67, 71, 74;
of Branchiura, 77;
of Syncarida, 114;
of Peracarida, 123;
of Hoplocarida, 141;
of Eucarida, 144;
of Trilobites, 238;
of Limulus, 275;
of Pedipalpi, 309;
of Spiders, 358;
of Solifugae, 424;
of Pseudoscorpions, 434;
of Phalangidea, 442;
of Acarina, 456;
of Tardigrada, 478;
of Pentastomida, 493;
of Pycnogons, 520
E. mutabilis, 486;
E. oihonnae, 486;
E. quadrispinosus, 486;
E. reticulatus, 486;
E. spinulosus, 479;
E. spitzbergensis, 486;
E. testudo, 478;
E. wendti, 486
Echinoderms, Dendrogaster parasitic on, 94
Echinognathus, 283
Ecribellatae, 385
Ectatosticta davidi, 393
Ectinosoma, 62
Edriophthalmata, 112, 121
Eggs, of Phyllopoda, 32;
of Cladocera, 44;
of Copepoda, 59, 62, 66, 67, 71, 74;
of Branchiura, 77;
of Syncarida, 114;
of Peracarida, 123;
of Hoplocarida, 141;
of Eucarida, 144;
of Trilobites, 238;
of Limulus, 275;
of Pedipalpi, 309;
of Spiders, 358;
of Solifugae, 424;
of Pseudoscorpions, 434;
of Phalangidea, 442;
of Acarina, 456;
of Tardigrada, 478;
of Pentastomida, 493;
of Pycnogons, 520
Page 634
Ehrenberg, on systematic position of Tardigrada, 483
Eleleis crinita, 396
Ellipsocephalus, 224, 235, 247;
E. hoffi, 248
Embolobranchiata, 258, 259, 297 f.
Emmerich, on facial suture of Trinucleus, 226
Encephaloides, 193;
E. armstrongi, 192, 193;
habitat, 205
Encrinuridae, 251
Encrinurus, 227, 235, 251
Endeis didactyla, 534;
E. gracilis, 539;
E. spinosus, 541
Endite, 9, 10
Endopodite, 9, 10;
of Trilobites, 237
Endosternite, 257, 305, 330
Endostoma, of Eurypterus, 287
Engaeus, 157;
E. fossor, distribution, 213
Enoplectenus, 418
Enterocola, 67;
E. fulgens, 67
Entomostraca, defined, 6;
diagnosis, 18;
of littoral zone, 197;
fresh-water, of southern hemisphere, 216
Entoniscidae, 130, 134
Eleleis crinita, 396
Ellipsocephalus, 224, 235, 247;
E. hoffi, 248
Embolobranchiata, 258, 259, 297 f.
Emmerich, on facial suture of Trinucleus, 226
Encephaloides, 193;
E. armstrongi, 192, 193;
habitat, 205
Encrinuridae, 251
Encrinurus, 227, 235, 251
Endeis didactyla, 534;
E. gracilis, 539;
E. spinosus, 541
Endite, 9, 10
Endopodite, 9, 10;
of Trilobites, 237
Endosternite, 257, 305, 330
Endostoma, of Eurypterus, 287
Engaeus, 157;
E. fossor, distribution, 213
Enoplectenus, 418
Enterocola, 67;
E. fulgens, 67
Entomostraca, defined, 6;
diagnosis, 18;
of littoral zone, 197;
fresh-water, of southern hemisphere, 216
Entoniscidae, 130, 134
Page 635
Enyo, 400
Enyoidae, 399
Eoscorpius, 298
Epeira, 409;
E. angulata, 315, 409;
E. basilica, 350, 351;
web of, 351;
E. bifurcata, 359;
E. caudata, 359;
E. cornuta, 409;
E. cucurbitina, 372, 409;
E. diademata, 335, 340, 343, 345, 359, 366, 380, 409;
anatomy, 332;
cocoon, 358;
silk, 360;
spinnerets, 325;
E. labyrinthea, 350;
E. madagascarensis, 360;
E. mauritia, 349;
E. pyramidata, 409;
E. quadrata, 366, 409;
E. triaranea, 350;
E. umbratica, 409
Epeiridae, 376, 377, 406
Epeirinae, 408
Ephippium, 48
Epiblemum, 420
Epicarida, 129;
sex in, 105
Epicaridian, larva of Epicarida, 130
Epicoxite, of Eurypterus, 287
Epidanus, 449
Enyoidae, 399
Eoscorpius, 298
Epeira, 409;
E. angulata, 315, 409;
E. basilica, 350, 351;
web of, 351;
E. bifurcata, 359;
E. caudata, 359;
E. cornuta, 409;
E. cucurbitina, 372, 409;
E. diademata, 335, 340, 343, 345, 359, 366, 380, 409;
anatomy, 332;
cocoon, 358;
silk, 360;
spinnerets, 325;
E. labyrinthea, 350;
E. madagascarensis, 360;
E. mauritia, 349;
E. pyramidata, 409;
E. quadrata, 366, 409;
E. triaranea, 350;
E. umbratica, 409
Epeiridae, 376, 377, 406
Epeirinae, 408
Ephippium, 48
Epiblemum, 420
Epicarida, 129;
sex in, 105
Epicaridian, larva of Epicarida, 130
Epicoxite, of Eurypterus, 287
Epidanus, 449
Page 636
Epigyne, 319, 333, 378
Epipharynx, 459
Epipodite, 9, 10
Episininae, 402
Episinus truncatus, 403
Epistome, of Eurypterida, 291;
of Pseudoscorpions, 431, 436;
of Phalangidea, 443
Erber, 355, 356
Eremobates, 429
Eremobatinae, 429
Eresidae, 398
Eresus cinnaberinus, 398
Eriauchenus, 411
Erichthoidina, larva of Stomatopod, 143
Ericthus, larva of Stomatopod, 143
Erigone, 405
Erigoninae, 404
Eriophyes, 465;
E. ribis, 455, 465;
E. tiliae, 465
Eriophyidae, 464
Eriphia, 191;
E. spinifrons, 191
Erlanger, von, on development and position of Tardigrada, 483
Ero, 411;
E. furcata, 366, 411;
cocoon, 358;
Epipharynx, 459
Epipodite, 9, 10
Episininae, 402
Episinus truncatus, 403
Epistome, of Eurypterida, 291;
of Pseudoscorpions, 431, 436;
of Phalangidea, 443
Erber, 355, 356
Eremobates, 429
Eremobatinae, 429
Eresidae, 398
Eresus cinnaberinus, 398
Eriauchenus, 411
Erichthoidina, larva of Stomatopod, 143
Ericthus, larva of Stomatopod, 143
Erigone, 405
Erigoninae, 404
Eriophyes, 465;
E. ribis, 455, 465;
E. tiliae, 465
Eriophyidae, 464
Eriphia, 191;
E. spinifrons, 191
Erlanger, von, on development and position of Tardigrada, 483
Ero, 411;
E. furcata, 366, 411;
cocoon, 358;
Page 637
E. tuberculata, 412
Eryonidae, 158;
habitat, 204
Eryonidea, 157
Erythraeinae, 473
Estheria, 21, 22, 23, 36;
E. gubernator and E. macgillivrayi, habitat, 33;
E. tetraceros, 36
Eucarida, 114, 144 f.
Euchaeta norwegica, 58
Eucopepoda, 57 f.
Eucopia australis, 119
Eucopiidae, 113, 114, 118
Eudendrium, Pycnogons on, 520
Eudorella, 121
Eukoenenia, 423;
E. augusta, 423;
E. florenciae, 423;
E. grassii, 423
Eulimnadia, 36;
E. mauritani, 36;
E. texana, 36
Euloma, 230
Eumalacostraca, 112 f.
Eupagurinae, 180
Eupagurus, 180;
E. bernhardus, commensalism, 172;
distribution, 199;
E. excavatus, parasitic castration of, 101;
E. longicarpus, metamorphosis, 179;
Eryonidae, 158;
habitat, 204
Eryonidea, 157
Erythraeinae, 473
Estheria, 21, 22, 23, 36;
E. gubernator and E. macgillivrayi, habitat, 33;
E. tetraceros, 36
Eucarida, 114, 144 f.
Euchaeta norwegica, 58
Eucopepoda, 57 f.
Eucopia australis, 119
Eucopiidae, 113, 114, 118
Eudendrium, Pycnogons on, 520
Eudorella, 121
Eukoenenia, 423;
E. augusta, 423;
E. florenciae, 423;
E. grassii, 423
Eulimnadia, 36;
E. mauritani, 36;
E. texana, 36
Euloma, 230
Eumalacostraca, 112 f.
Eupagurinae, 180
Eupagurus, 180;
E. bernhardus, commensalism, 172;
distribution, 199;
E. excavatus, parasitic castration of, 101;
E. longicarpus, metamorphosis, 179;
Page 638
E. prideauxii, commensalism, 172;
E. pubescens, distribution, 199
Euphausia pellucida, 145, 146
Euphausiacea, 144
Euphausiidae, 113, 114, 144;
larval history, 145;
eyes, 150
Eupodes, 471
Euproöps, 278
Eurycare, 232, 247
Eurycercus, 53;
alimentary canal, 42;
E. lamellatus, habitat, 207
Eurycide, 505, 533;
E. hispida, 506, 507, 533
Eurycididae, 533
Eurydium, 485
Euryopis, 404
Eurypelma, 389;
E. hentzii, 361, 370
Euryplax, 195
Eurypterida, 258, 278, 283 f.
Eurypteridae, 290 f.
Eurypterus, 283 f., 290, 291, 292;
E. fischeri, 284, 286, 289
Eurytemora, 59;
E. affinis, habitat, 206
Eusarcus, 283, 291
Euscorpiinae, 308
E. pubescens, distribution, 199
Euphausia pellucida, 145, 146
Euphausiacea, 144
Euphausiidae, 113, 114, 144;
larval history, 145;
eyes, 150
Eupodes, 471
Euproöps, 278
Eurycare, 232, 247
Eurycercus, 53;
alimentary canal, 42;
E. lamellatus, habitat, 207
Eurycide, 505, 533;
E. hispida, 506, 507, 533
Eurycididae, 533
Eurydium, 485
Euryopis, 404
Eurypelma, 389;
E. hentzii, 361, 370
Euryplax, 195
Eurypterida, 258, 278, 283 f.
Eurypteridae, 290 f.
Eurypterus, 283 f., 290, 291, 292;
E. fischeri, 284, 286, 289
Eurytemora, 59;
E. affinis, habitat, 206
Eusarcus, 283, 291
Euscorpiinae, 308
Page 639
Euscorpius, 298, 308;
E. carpathicus, 299
Eusimonia, 429
Euterpe acutifrons, 61, 61;
distribution, 203
Euthycoelus, 389
Evadne, 54;
young, 47
Excretory system (including Renal organs), in Crustacea, 12;
in Arachnids, 257;
in Limulus, 270;
in Tardigrada, 481;
in Pentastomida, 491
Exner, on mosaic vision, 148
Exopodite, 9, 10;
of Trilobites, 237
Eyes, compound, of Crustacea, 146, 147;
physiology of, 148;
of deep-sea Crustacea, 149;
connexion with phosphorescent organs, 151;
regeneration of, 6;
of Trilobites, 227 f., 228;
of Limulus, 271;
of Eurypterida, 285;
of Scorpions, 301;
of Pedipalpi, 309;
of Spiders, 315, 334; of Solifugae, 426;
of Pseudoscorpions, 431;
of Phalangidea, 442;
of Acarina, 458;
of Pycnogons, 517
Fabre, on habits of Spiders, 298 f.;
E. carpathicus, 299
Eusimonia, 429
Euterpe acutifrons, 61, 61;
distribution, 203
Euthycoelus, 389
Evadne, 54;
young, 47
Excretory system (including Renal organs), in Crustacea, 12;
in Arachnids, 257;
in Limulus, 270;
in Tardigrada, 481;
in Pentastomida, 491
Exner, on mosaic vision, 148
Exopodite, 9, 10;
of Trilobites, 237
Eyes, compound, of Crustacea, 146, 147;
physiology of, 148;
of deep-sea Crustacea, 149;
connexion with phosphorescent organs, 151;
regeneration of, 6;
of Trilobites, 227 f., 228;
of Limulus, 271;
of Eurypterida, 285;
of Scorpions, 301;
of Pedipalpi, 309;
of Spiders, 315, 334; of Solifugae, 426;
of Pseudoscorpions, 431;
of Phalangidea, 442;
of Acarina, 458;
of Pycnogons, 517
Fabre, on habits of Spiders, 298 f.;
Page 640
of Tarantula, 361 f.;
on Wasp v. Spider, 368 f.
Facet, of Trilobites, 235
Facial suture, 225 f., 232
Falanga, 424
False articulations, 444
False-scorpions, 430
Fecenia, 399
Filistata, 391;
F. capitata, 392;
F. testacea, 392
Filistatidae, 319, 336, 391
Finger-keel, 303
Fixed cheek, 225, 226, 227
Flabellifera, 124 f.
Flabellum, 270
Flacourt, 363
Flagellum, in Solifugae, 426, 428;
in Pseudoscorpions, 433
Forbes, 374
Ford, S. W., on development of Trilobites, 238
Forel, on Lake of Geneva, 206
Formicina, 405
Formicinae, 405
Formicinoides brasiliana, 318
Fragilia, 535
Free cheek, 225, 226, 227
on Wasp v. Spider, 368 f.
Facet, of Trilobites, 235
Facial suture, 225 f., 232
Falanga, 424
False articulations, 444
False-scorpions, 430
Fecenia, 399
Filistata, 391;
F. capitata, 392;
F. testacea, 392
Filistatidae, 319, 336, 391
Finger-keel, 303
Fixed cheek, 225, 226, 227
Flabellifera, 124 f.
Flabellum, 270
Flacourt, 363
Flagellum, in Solifugae, 426, 428;
in Pseudoscorpions, 433
Forbes, 374
Ford, S. W., on development of Trilobites, 238
Forel, on Lake of Geneva, 206
Formicina, 405
Formicinae, 405
Formicinoides brasiliana, 318
Fragilia, 535
Free cheek, 225, 226, 227
Page 641
Fresh-water, Crustacea, 205 f.;
Spiders, 357
Furcilia (Metazoaea), larva of Euphausia, 145
Fusulae, 325, 335
Galathea, 169, 170;
G. intermedia, Pleurocrypta parasitic on, 133;
G. strigosa, 170;
gut of, 15
Galatheidae, 169
Galatheidea, 169
Galea, 433, 436
Galena, 412
Galeodes, 429, 527;
nervous system, 428;
chelicera, 429;
G. arabs, 425;
G. araneoides, 425
Galeodidae, 428
Gall-mites, 455, 464
Gamasidae, 470
Gamasinae, 470
Gamasus, 460, 461, 463, 470;
G. coleoptratorum, 470;
G. crassipes, 470;
G. terribilis, 461
Gammaridae, 138
Gammarus, 137, 138;
of Lake Baikal, 212;
of Australia, 216;
Spiders, 357
Furcilia (Metazoaea), larva of Euphausia, 145
Fusulae, 325, 335
Galathea, 169, 170;
G. intermedia, Pleurocrypta parasitic on, 133;
G. strigosa, 170;
gut of, 15
Galatheidae, 169
Galatheidea, 169
Galea, 433, 436
Galena, 412
Galeodes, 429, 527;
nervous system, 428;
chelicera, 429;
G. arabs, 425;
G. araneoides, 425
Galeodidae, 428
Gall-mites, 455, 464
Gamasidae, 470
Gamasinae, 470
Gamasus, 460, 461, 463, 470;
G. coleoptratorum, 470;
G. crassipes, 470;
G. terribilis, 461
Gammaridae, 138
Gammarus, 137, 138;
of Lake Baikal, 212;
of Australia, 216;
Page 642
G. locusta, 138, 138;
G. pulex, 138
Gampsonyx, 115, 118
Garstang, on respiration of crabs, 186 n.
Garypinae, 436, 437
Garypus, 431, 436, 437, 438;
chelicera, 432;
G. littoralis, 430
Gaskell, 270, 277, 334
Gasteracantha, 410;
G. minax, 410
Gasteracanthinae, 317, 409
Gastrodelphys, 73
Gastrolith, of Lobster, 155
Gaubert, 525 n.
Gebia littoralis, 167
Gecarcinidae, 196
Gecarcinus, 194, 195, 196
Gegenbaur, 523
Gelanor, 411, 412
Gelasimus, 194, 196;
habitat, 198;
distribution, 210;
G. annulipes, 194
Genal angle, 225
Gené, 461
Genital operculum, of Eurypterida, 288, 289, 291
Genysa, 388
G. pulex, 138
Gampsonyx, 115, 118
Garstang, on respiration of crabs, 186 n.
Garypinae, 436, 437
Garypus, 431, 436, 437, 438;
chelicera, 432;
G. littoralis, 430
Gaskell, 270, 277, 334
Gasteracantha, 410;
G. minax, 410
Gasteracanthinae, 317, 409
Gastrodelphys, 73
Gastrolith, of Lobster, 155
Gaubert, 525 n.
Gebia littoralis, 167
Gecarcinidae, 196
Gecarcinus, 194, 195, 196
Gegenbaur, 523
Gelanor, 411, 412
Gelasimus, 194, 196;
habitat, 198;
distribution, 210;
G. annulipes, 194
Genal angle, 225
Gené, 461
Genital operculum, of Eurypterida, 288, 289, 291
Genysa, 388
Page 643
Gerardia, Laura parasitic on, 93
Geryon, 195
Giardella callianassae, 73
Gibocellidae, 448
Gibocellum sudeticum, 447
Giesbrecht, on Copepoda, 57;
on phosphorescence, 59
Gigantostraca, 258, 283 f.
Gill-book, 270
Glabella, 223
Glabella-furrows, 223
Glands, of Tardigrada, 481;
of Pentastomida, 490, 491;
of Pycnogons, 511;
coxal, of Arachnids, 257, 270, 337;
green, of Malacostraca, 110;
poison-, of Arachnids, 337, 360;
spinning, of Spiders, 335;
of Pseudoscorpions, 434
Glaucothoe, larva of Eupagurus, 179, 180
Gluvia, 429
Glycyphagus, 466;
G. palmifer, 466;
G. plumiger, 466
Glyphocrangon, 164;
G. spinulosa, 158, 164
Glyphocrangonidae, 164
Glyptoscorpius, 283, 291, 294
Gmelina, 138
Geryon, 195
Giardella callianassae, 73
Gibocellidae, 448
Gibocellum sudeticum, 447
Giesbrecht, on Copepoda, 57;
on phosphorescence, 59
Gigantostraca, 258, 283 f.
Gill-book, 270
Glabella, 223
Glabella-furrows, 223
Glands, of Tardigrada, 481;
of Pentastomida, 490, 491;
of Pycnogons, 511;
coxal, of Arachnids, 257, 270, 337;
green, of Malacostraca, 110;
poison-, of Arachnids, 337, 360;
spinning, of Spiders, 335;
of Pseudoscorpions, 434
Glaucothoe, larva of Eupagurus, 179, 180
Gluvia, 429
Glycyphagus, 466;
G. palmifer, 466;
G. plumiger, 466
Glyphocrangon, 164;
G. spinulosa, 158, 164
Glyphocrangonidae, 164
Glyptoscorpius, 283, 291, 294
Gmelina, 138
Page 644
Gmogala scarabaeus, 394
Gnamptorhynchus, 533
Gnaphosa, 397
Gnathia maxillaris, 124;
life-history of 125
Gnathiidae, 124
Gnathobase, 10, 264
Gnathophausia, 119, 256 n.;
maxillipede of, 10
Gnathostomata, 56
Gnosippus, 429
Goldsmith, 362
Gonads, = reproductive organs, q.v.
Gonodactylus, 143;
G. chiragra, 143
Gonoplacidae, 195
Gonoplax, 195;
G. rhomboides, 195
Gonyleptidae, 442, 448, 449
Goodsir, Harry, 535, 540
Gordius, parasitic in Spiders, 368
Gossamer, 342
Graells, 364
Graeophonus, 309
Graff, von, on position of Tardigrada, 483
Grapsidae, 193, 195;
habitat, 198, 201
Graptoleberis, 53
Gnamptorhynchus, 533
Gnaphosa, 397
Gnathia maxillaris, 124;
life-history of 125
Gnathiidae, 124
Gnathobase, 10, 264
Gnathophausia, 119, 256 n.;
maxillipede of, 10
Gnathostomata, 56
Gnosippus, 429
Goldsmith, 362
Gonads, = reproductive organs, q.v.
Gonodactylus, 143;
G. chiragra, 143
Gonoplacidae, 195
Gonoplax, 195;
G. rhomboides, 195
Gonyleptidae, 442, 448, 449
Goodsir, Harry, 535, 540
Gordius, parasitic in Spiders, 368
Gossamer, 342
Graells, 364
Graeophonus, 309
Graff, von, on position of Tardigrada, 483
Grapsidae, 193, 195;
habitat, 198, 201
Graptoleberis, 53
Page 645
Grassi, 422
Green gland, 110 (= antennary gland, q.v.)
Gregarious Spiders, 340
Grenacher, 517
Griffithides, 251
Gruvel, on Cirripedia, 80, 86
Guérin-Méneville, 439
Gurney, on Copepoda, 62;
on Brachyuran metamorphosis, 181 n.
Gyas, 450
Gylippus, 429
Gymnolepas, 89
Gymnomera, 38, 54
Gymnoplea, 57
Hadrotarsidae, 394
Hadrotarsus babirusa, 394
Haeckel, on plankton, 203
Haemaphysalis, 469
Haematodocha, 322
Haemocera, 64;
H. danae, life-history, 64, 65
Haemocoel, 5, 11
Hahnia, 325, 416
Hahniinae, 416
Halacaridae, 472
Halocypridae, 108
Green gland, 110 (= antennary gland, q.v.)
Gregarious Spiders, 340
Grenacher, 517
Griffithides, 251
Gruvel, on Cirripedia, 80, 86
Guérin-Méneville, 439
Gurney, on Copepoda, 62;
on Brachyuran metamorphosis, 181 n.
Gyas, 450
Gylippus, 429
Gymnolepas, 89
Gymnomera, 38, 54
Gymnoplea, 57
Hadrotarsidae, 394
Hadrotarsus babirusa, 394
Haeckel, on plankton, 203
Haemaphysalis, 469
Haematodocha, 322
Haemocera, 64;
H. danae, life-history, 64, 65
Haemocoel, 5, 11
Hahnia, 325, 416
Hahniinae, 416
Halacaridae, 472
Halocypridae, 108
Page 646
Halosoma, 539
Hannonia typica, 533
Hansen, on Choniostomatidae, 76;
on Cirripede Nauplii, 94;
on classification of Malacostraca, 113
Hansen and Sörensen, 422, 439, 443, 448
Hapalogaster, 181;
H. cavicauda, 178
Hapalogasterinae, 181
Harpactes hombergii, 395
Harpacticidae, 61, 62;
habitat, 206
Harpedidae, 245
Harpes, 225, 226, 230, 231, 234, 246;
H. ungula, 248;
H. vittatus, eyes, 228
Harporhynchus, 53
Harvest-bugs, 454, 473
Harvestmen, 440, = Phalangidea, q.v.
Harvest-spiders, 440, = Phalangidea, q.v.
Harvesters, 440, = Phalangidea, q.v.
Hasarius falcatus, 421
Haustellata, 501 n.
Haustoriidae, 137
Haustorius arenarius, 137
Hay, on name Lydella, 486 n.
Heart, of Phyllopoda, 29;
of Cladocera, 43;
Hannonia typica, 533
Hansen, on Choniostomatidae, 76;
on Cirripede Nauplii, 94;
on classification of Malacostraca, 113
Hansen and Sörensen, 422, 439, 443, 448
Hapalogaster, 181;
H. cavicauda, 178
Hapalogasterinae, 181
Harpactes hombergii, 395
Harpacticidae, 61, 62;
habitat, 206
Harpedidae, 245
Harpes, 225, 226, 230, 231, 234, 246;
H. ungula, 248;
H. vittatus, eyes, 228
Harporhynchus, 53
Harvest-bugs, 454, 473
Harvestmen, 440, = Phalangidea, q.v.
Harvest-spiders, 440, = Phalangidea, q.v.
Harvesters, 440, = Phalangidea, q.v.
Hasarius falcatus, 421
Haustellata, 501 n.
Haustoriidae, 137
Haustorius arenarius, 137
Hay, on name Lydella, 486 n.
Heart, of Phyllopoda, 29;
of Cladocera, 43;
Page 647
of Nebalia, 112;
of Syncarida, 115;
of Peracarida, 118;
of Isopoda, 122;
of Danalia, 132;
of Amphipoda, 136;
of Squilla, 142;
of Eucarida, 144;
of Limulus, 268;
of Scorpions, 305;
of Pedipalpi, 311;
of Spiders, 331;
of Solifugae, 427;
of Pseudoscorpions, 434;
of Phalangidea, 445;
of Acarina, 460;
of Pycnogons, 516
Heart-water, 470
Hedley, on home of cocoa-nut, 174
Heligmonerus, 388
Heller, 455
Hemeteles fasciatus, 367;
H. formosus, 367
Hemiaspis, 278;
H. limuloides, 278
Hemioniscidae, 130
Hemiscorpion lepturus, 307
Hemiscorpioninae, 306, 307
Henking, 447, 460
Hentz, 367
Herbst, on regeneration of eye, 6 n.
of Syncarida, 115;
of Peracarida, 118;
of Isopoda, 122;
of Danalia, 132;
of Amphipoda, 136;
of Squilla, 142;
of Eucarida, 144;
of Limulus, 268;
of Scorpions, 305;
of Pedipalpi, 311;
of Spiders, 331;
of Solifugae, 427;
of Pseudoscorpions, 434;
of Phalangidea, 445;
of Acarina, 460;
of Pycnogons, 516
Heart-water, 470
Hedley, on home of cocoa-nut, 174
Heligmonerus, 388
Heller, 455
Hemeteles fasciatus, 367;
H. formosus, 367
Hemiaspis, 278;
H. limuloides, 278
Hemioniscidae, 130
Hemiscorpion lepturus, 307
Hemiscorpioninae, 306, 307
Henking, 447, 460
Hentz, 367
Herbst, on regeneration of eye, 6 n.
Page 648
Hermacha, 388
Hermaphroditism, 15;
caused by parasite, 101, 102;
partial and temporary, 102;
normal, 105;
in Cymothoidae, 126;
in Isopoda Epicarida, 129;
in Entoniscidae, 135;
in Caprella, 140
Hermippus, 317, 399;
H. loricatus, 400
Hermit-crab, 167, 171;
commensalism, 172;
reacquisition of symmetry, 173;
regeneration of limbs, 156
Hermit-lobster, 167
Herrick, on the Lobster, 154
Hersilia (Araneae), 401;
H. caudata, 400
Hersiliidae (Araneae), 326, 400
Hersiliidae (Copepoda), 73
Hersiliola, 401
Heterarthrandria, 58
Heterocarpus alphonsi (Pandalidae), phosphorescence, 151
Heterochaeta papilligera, 60
Heterocope, 59
Heterogammarus, 138
Heterometrus, 307
Heterophrynus, 313
Heteropoda venatoria, 414
Hermaphroditism, 15;
caused by parasite, 101, 102;
partial and temporary, 102;
normal, 105;
in Cymothoidae, 126;
in Isopoda Epicarida, 129;
in Entoniscidae, 135;
in Caprella, 140
Hermippus, 317, 399;
H. loricatus, 400
Hermit-crab, 167, 171;
commensalism, 172;
reacquisition of symmetry, 173;
regeneration of limbs, 156
Hermit-lobster, 167
Herrick, on the Lobster, 154
Hersilia (Araneae), 401;
H. caudata, 400
Hersiliidae (Araneae), 326, 400
Hersiliidae (Copepoda), 73
Hersiliola, 401
Heterarthrandria, 58
Heterocarpus alphonsi (Pandalidae), phosphorescence, 151
Heterochaeta papilligera, 60
Heterocope, 59
Heterogammarus, 138
Heterometrus, 307
Heterophrynus, 313
Heteropoda venatoria, 414
Page 649
Heterostigmata, 471
Heterotanais, 123
Hexameridae, 91
Hexathele, 390
Hexisopodidae, 429
Hexisopus, 429, 429
Hexura, 391
Hippa, 171;
H. emerita, distribution, 202
Hippidae, 171
Hippidea, 170;
habitat, 198
Hippolyte, 164;
distribution, 200;
H. varians, 164
Hippolytidae, 164;
distribution, 199
Hodge, George, 523, 540
Hodgson, 508
Hoek, on Cirripedia, 80;
on Pycnogons, 505, 512, 513
Holm, G., on Agnostus, 225;
on Eurypterus, 285 n.
Holmia, 236, 242, 247;
H. kjerulfi, 242, 246
Holochroal eye, 228
Holopediidae, 51
Holopedium, 38, 51
Heterotanais, 123
Hexameridae, 91
Hexathele, 390
Hexisopodidae, 429
Hexisopus, 429, 429
Hexura, 391
Hippa, 171;
H. emerita, distribution, 202
Hippidae, 171
Hippidea, 170;
habitat, 198
Hippolyte, 164;
distribution, 200;
H. varians, 164
Hippolytidae, 164;
distribution, 199
Hodge, George, 523, 540
Hodgson, 508
Hoek, on Cirripedia, 80;
on Pycnogons, 505, 512, 513
Holm, G., on Agnostus, 225;
on Eurypterus, 285 n.
Holmia, 236, 242, 247;
H. kjerulfi, 242, 246
Holochroal eye, 228
Holopediidae, 51
Holopedium, 38, 51
Page 650
Homalonotus, 222, 249;
H. delphinocephalus, 223
Homarus, 154;
habitat, 200;
excretory
glands, 13;
H. americanus, 154;
H. vulgaris, 154
Homoeoscelis, 76
Homola, 184;
distribution, 205
Homolidae, 184
Homolodromia, 184;
H. paradoxa, resemblance to Nephropsidae, 184
Hood, of Phalangidea, 442, 452
Hoplocarida, 114, 141
Hoploderma, 468;
H. magnum, 467
Hoplophora, 468
Horse-foot crab, = Limulus, q.v.
Hoyle, on classification of Pentastomids, 495
Hughmilleria, 283, 290, 292
Humboldt, on Porocephalus, 488 n.
Hutton, 424
Huttonia, 398
Hyale, 139
Hyalella, 137, 139;
distribution, 211, 217
Hyalomma, 469
H. delphinocephalus, 223
Homarus, 154;
habitat, 200;
excretory
glands, 13;
H. americanus, 154;
H. vulgaris, 154
Homoeoscelis, 76
Homola, 184;
distribution, 205
Homolidae, 184
Homolodromia, 184;
H. paradoxa, resemblance to Nephropsidae, 184
Hood, of Phalangidea, 442, 452
Hoplocarida, 114, 141
Hoploderma, 468;
H. magnum, 467
Hoplophora, 468
Horse-foot crab, = Limulus, q.v.
Hoyle, on classification of Pentastomids, 495
Hughmilleria, 283, 290, 292
Humboldt, on Porocephalus, 488 n.
Hutton, 424
Huttonia, 398
Hyale, 139
Hyalella, 137, 139;
distribution, 211, 217
Hyalomma, 469
Page 651
Hyas, 192, 193;
distribution, 200
Hyctia nivoyi, 421
Hydrachnidae, 472
Hydractinia, Pycnogons on, 523
Hydrallmania, Pycnogons on, 524
Hymenocaris, 112
Hymenodora, 163
Hymenosoma, 193;
distribution, 200
Hymenosomatidae, 193
Hyperina, 140
Hypochilidae, 393
Hypochilus, 336, 393;
H. thorelli, 393
Hypoctonus, 312
Hypoparia, 243
Hypopus, 463
Hypostome, of Trilobites, 233, 237;
of Bronteus, 233;
of Acarina, 469
Hyptiotes, 349, 411;
H. cavatus, snare, 350;
H. paradoxus, 350, 411
Iasus, 165, 167;
distribution, 200
Ibacus, 167
Ibla, 88;
distribution, 200
Hyctia nivoyi, 421
Hydrachnidae, 472
Hydractinia, Pycnogons on, 523
Hydrallmania, Pycnogons on, 524
Hymenocaris, 112
Hymenodora, 163
Hymenosoma, 193;
distribution, 200
Hymenosomatidae, 193
Hyperina, 140
Hypochilidae, 393
Hypochilus, 336, 393;
H. thorelli, 393
Hypoctonus, 312
Hypoparia, 243
Hypopus, 463
Hypostome, of Trilobites, 233, 237;
of Bronteus, 233;
of Acarina, 469
Hyptiotes, 349, 411;
H. cavatus, snare, 350;
H. paradoxus, 350, 411
Iasus, 165, 167;
distribution, 200
Ibacus, 167
Ibla, 88;
Page 652
I. cumingii, 88;
I. quadrivalvis, 88, 89
Ichneumon flies, and Spiders, 367
Icius, 421;
I. mitratus, 382
Idiops, 388
Idothea, habitat, 211
Idotheidae, 127
Ihle, J. E. W., 526 n.
Ilia, 188;
I. nucleus, 188;
respiration, 187
Illaenus, 229, 231, 235, 249;
I. dalmanni, 248
Ilyocryptus, 40, 53
Inachus, 192, 193;
I. mauritanicus, Sacculina parasitic on, 97 f.;
parasitic castration in, 101;
temporary hermaphroditism of, 103;
Danalia and Sacculina parasitic on, 131
Integument, of Pycnogons, 518
Irregular Spider-snares, 351
Ischnocolus, 389
Ischnothele dumicola, 390
Ischnurinae, 306, 307
Ischnurus ochropus, 307
Ischnyothyreus, 394
Ischyropsalidae, 451
Ischyropsalis, 444, 451
I. quadrivalvis, 88, 89
Ichneumon flies, and Spiders, 367
Icius, 421;
I. mitratus, 382
Idiops, 388
Idothea, habitat, 211
Idotheidae, 127
Ihle, J. E. W., 526 n.
Ilia, 188;
I. nucleus, 188;
respiration, 187
Illaenus, 229, 231, 235, 249;
I. dalmanni, 248
Ilyocryptus, 40, 53
Inachus, 192, 193;
I. mauritanicus, Sacculina parasitic on, 97 f.;
parasitic castration in, 101;
temporary hermaphroditism of, 103;
Danalia and Sacculina parasitic on, 131
Integument, of Pycnogons, 518
Irregular Spider-snares, 351
Ischnocolus, 389
Ischnothele dumicola, 390
Ischnurinae, 306, 307
Ischnurus ochropus, 307
Ischnyothyreus, 394
Ischyropsalidae, 451
Ischyropsalis, 444, 451
Page 653
Isokerandria, 69 f.
Isometrus europaeus, 306
Isopoda, 121 f., 242
Ixodes, 469;
I. ricinus, 469
Ixodidae, 469
Ixodoidea, 455, 462, 468
Janulus, 403
Jaworowski, on vestigial antennae in a Spider, 263
Johnston, George, 540
Jumping-Spiders, 419
Karshia, 429
Karshiinae, 429
Katipo, 363, 403
King-crab, =Limulus, q.v.
Kingsley, on Trilobites, 239, 243 n.;
on breeding habits of Limulus, 271
Kishinouye, on Limulus, 274, 275
Klebs, on the frequency of human Pentastomids, 494
Knight Errant, 540
Koch, C., 397 n.
Koch, L., 397 n.
Kochlorine, 92;
K. hamata, 93
Koenenia, 422, 527, 528;
Isometrus europaeus, 306
Isopoda, 121 f., 242
Ixodes, 469;
I. ricinus, 469
Ixodidae, 469
Ixodoidea, 455, 462, 468
Janulus, 403
Jaworowski, on vestigial antennae in a Spider, 263
Johnston, George, 540
Jumping-Spiders, 419
Karshia, 429
Karshiinae, 429
Katipo, 363, 403
King-crab, =Limulus, q.v.
Kingsley, on Trilobites, 239, 243 n.;
on breeding habits of Limulus, 271
Kishinouye, on Limulus, 274, 275
Klebs, on the frequency of human Pentastomids, 494
Knight Errant, 540
Koch, C., 397 n.
Koch, L., 397 n.
Kochlorine, 92;
K. hamata, 93
Koenenia, 422, 527, 528;
Page 654
K. mirabilis, 423
Koltzoff, 15
König, 524
Koonunga cursor, 117;
distribution, 211
Koonungidae, 117
Korschelt and Heider, on neuromeres in Arachnids, 263
Kowalevsky, 513
Kraepelin, 303, 306, 312 n., 428
Kramer, 460
Kröyer, 504, 526
Labdacus, 418
Labochirus, 312
Labrum, of Trilobites, 233
Labulla, 406
Laches, 399
Lachesis, 399
Lacinia mobilis, 114
Laemodipoda, 139
Laenger, on the frequency of human Pentastomids, 494
Lakes, characters of fauna of, 206;
English, 207, 208;
Baikal, 212;
Great Tasmanian, 216
Lambrus, 192, 193;
L. miersi, 193
Lamproglena, 68
Koltzoff, 15
König, 524
Koonunga cursor, 117;
distribution, 211
Koonungidae, 117
Korschelt and Heider, on neuromeres in Arachnids, 263
Kowalevsky, 513
Kraepelin, 303, 306, 312 n., 428
Kramer, 460
Kröyer, 504, 526
Labdacus, 418
Labochirus, 312
Labrum, of Trilobites, 233
Labulla, 406
Laches, 399
Lachesis, 399
Lacinia mobilis, 114
Laemodipoda, 139
Laenger, on the frequency of human Pentastomids, 494
Lakes, characters of fauna of, 206;
English, 207, 208;
Baikal, 212;
Great Tasmanian, 216
Lambrus, 192, 193;
L. miersi, 193
Lamproglena, 68
Page 655
Lampropidae, 121
Lamprops, 121
Langouste, 165
Laniatores, 448
Lankester, on Crustacean limb, 9;
on classification of Arachnids, 258, 277;
on Limulus, 274, 305
Laophonte littorale, 62;
L. mohammed, 62
Laseola, 404
Lathonura, 53
Latona, 51
Latreille, 385, 408 n., 412, 504, 526
Latreillia, 185;
distribution, 205
Latreillopsis, 185;
L. petterdi, 185
Latreutes ensiferus, habitat, 202
Latrodectus, 362, 403;
L. 13–guttatus, 364, 403;
L. mactans, 362, 363, 403;
L. scelio, 403
Laura, 93;
L. gerardiae, 93
Laurie, 309 n., 310, 311
Leach, 526
Lecythorhynchus armatus, 535
Leeuwenhoek, on desiccation in Tardigrada, 484
Leionymphon, 534
Lamprops, 121
Langouste, 165
Laniatores, 448
Lankester, on Crustacean limb, 9;
on classification of Arachnids, 258, 277;
on Limulus, 274, 305
Laophonte littorale, 62;
L. mohammed, 62
Laseola, 404
Lathonura, 53
Latona, 51
Latreille, 385, 408 n., 412, 504, 526
Latreillia, 185;
distribution, 205
Latreillopsis, 185;
L. petterdi, 185
Latreutes ensiferus, habitat, 202
Latrodectus, 362, 403;
L. 13–guttatus, 364, 403;
L. mactans, 362, 363, 403;
L. scelio, 403
Laura, 93;
L. gerardiae, 93
Laurie, 309 n., 310, 311
Leach, 526
Lecythorhynchus armatus, 535
Leeuwenhoek, on desiccation in Tardigrada, 484
Leionymphon, 534
Page 656
Lendenfeld, von, 512, 523
Lepas, 87;
metamorphosis, 80;
anatomy, 82;
L. australis, Cypris, 82;
L. fascicularis, Nauplius, 81;
L. pectinata, pupa, 82
Lephthyphantes, 327, 406
Lepidurus, 23, 24, 36;
heart, 29;
L. glacialis, range, 34;
L. patagonicus, 36;
L. productus, 36;
carapace, 20;
telson, 23;
L. viridis, 36
Leptestheria, 36;
L. siliqua, 37
Leptochela, 163
Leptochelia, 122;
L. dubia, dimorphism, 123
Leptoctenus, 418
Leptodora, 54;
appendages, 42;
alimentary canal, 43;
ovary, 44, 45;
L. hyalina, 54
Leptodoridae, 54
Leptoneta, 393
Leptonetidae, 393
Leptopelma, 389
Lepas, 87;
metamorphosis, 80;
anatomy, 82;
L. australis, Cypris, 82;
L. fascicularis, Nauplius, 81;
L. pectinata, pupa, 82
Lephthyphantes, 327, 406
Lepidurus, 23, 24, 36;
heart, 29;
L. glacialis, range, 34;
L. patagonicus, 36;
L. productus, 36;
carapace, 20;
telson, 23;
L. viridis, 36
Leptestheria, 36;
L. siliqua, 37
Leptochela, 163
Leptochelia, 122;
L. dubia, dimorphism, 123
Leptoctenus, 418
Leptodora, 54;
appendages, 42;
alimentary canal, 43;
ovary, 44, 45;
L. hyalina, 54
Leptodoridae, 54
Leptoneta, 393
Leptonetidae, 393
Leptopelma, 389
Page 657
Leptoplastus, 247
Leptostraca, 111, 242;
defined, 6;
segmentation, 7
Lernaea, 74;
L. branchialis, 74, 75
Lernaeascus, 73
Lernaeidae, 74
Lernaeodiscus, 95
Lernaeopoda salmonea, 76
Lernaeopodidae, 75
Lernanthropus, 68;
blood, 30, 68
Lernentoma cornuta, 72
Leuckart, on Pentastomida, 490, 492;
on development of, 494;
on sub-genera of, 495
Leuckartia flavicornis, 59
Leucon, 121
Leuconidae, 121
Leucosia, 188
Leucosiidae, 188;
respiration, 187;
habitat, 199
Leydigia, 53
Lhwyd, Edward, on Trilobites, 221
Lichadidae, 252
Lichas, 222, 252
Leptostraca, 111, 242;
defined, 6;
segmentation, 7
Lernaea, 74;
L. branchialis, 74, 75
Lernaeascus, 73
Lernaeidae, 74
Lernaeodiscus, 95
Lernaeopoda salmonea, 76
Lernaeopodidae, 75
Lernanthropus, 68;
blood, 30, 68
Lernentoma cornuta, 72
Leuckart, on Pentastomida, 490, 492;
on development of, 494;
on sub-genera of, 495
Leuckartia flavicornis, 59
Leucon, 121
Leuconidae, 121
Leucosia, 188
Leucosiidae, 188;
respiration, 187;
habitat, 199
Leydigia, 53
Lhwyd, Edward, on Trilobites, 221
Lichadidae, 252
Lichas, 222, 252
Page 658
Lichomolgidae, 70
Lichomolgus, 71;
L. agilis, 71;
L. albeus, 71
Ligia oceanica, 128
Ligidium, 129
Lilljeborg, on Cladocera, 51 n.
Limnadia, 21, 22, 36;
L. lenticularis, 22, 36
Limnadiidae, 20, 23, 28, 29, 36
Limnetis, 20, 21, 22, 36;
L. brachyura, 21, 24, 36
Limnocharinae, 472
Limnocharis aquaticus, 472
Limulus, 256, 292;
nervous system, 257;
classification, 260, 276;
segmentation, 260, 261, 262, 266, 270, 272;
appendages, 263;
habits, 265, 271;
food, 267;
digestive system, 268;
circulatory system, 268;
respiratory system, 269;
excretory system, 270;
nervous system, 270, 272;
eggs and larvae, 274, 275;
ecdysis, 274;
used as food, 275–6;
affinities, 277;
fossil, 277;
L. gigas, 276;
L. hoeveni, 277;
Lichomolgus, 71;
L. agilis, 71;
L. albeus, 71
Ligia oceanica, 128
Ligidium, 129
Lilljeborg, on Cladocera, 51 n.
Limnadia, 21, 22, 36;
L. lenticularis, 22, 36
Limnadiidae, 20, 23, 28, 29, 36
Limnetis, 20, 21, 22, 36;
L. brachyura, 21, 24, 36
Limnocharinae, 472
Limnocharis aquaticus, 472
Limulus, 256, 292;
nervous system, 257;
classification, 260, 276;
segmentation, 260, 261, 262, 266, 270, 272;
appendages, 263;
habits, 265, 271;
food, 267;
digestive system, 268;
circulatory system, 268;
respiratory system, 269;
excretory system, 270;
nervous system, 270, 272;
eggs and larvae, 274, 275;
ecdysis, 274;
used as food, 275–6;
affinities, 277;
fossil, 277;
L. gigas, 276;
L. hoeveni, 277;
Page 659
L. longispina, 264, 274;
L. moluccanus, 264, 274, 276, 277;
L. polyphemus, 261, 262, 264, 271;
L. rotundicauda, 275, 277;
L. tridentatus, 276
Lindström, on facial suture of Agnostus and Olenellus, 225;
on eyes of Trilobites, 228 f.;
on blind Trilobites, 231 f.;
on maculae of Trilobites, 233
Lingua, 459
Linguatula, 488 n., 495;
L. pusilla, 496;
L. recurvata, 496;
L. subtriquetra, 496;
L. taenioides, 489, 492, 493, 494, 496;
frequency of, 489;
larvae of, 489, 494;
hosts of, 496
Linnaeus, 408 n., 502
Linyphia, 406;
L. clathrata, 406;
L. marginata, 406;
L. montana, 406;
L. triangularis, 406
Linyphiinae, 405
Liobunum, 447, 450
Liocraninae, 397
Liocranum, 397
Liphistiidae, 386
Liphistioidae, 383
Liphistius, 317, 383, 385, 386;
L. desultor, 386
L. moluccanus, 264, 274, 276, 277;
L. polyphemus, 261, 262, 264, 271;
L. rotundicauda, 275, 277;
L. tridentatus, 276
Lindström, on facial suture of Agnostus and Olenellus, 225;
on eyes of Trilobites, 228 f.;
on blind Trilobites, 231 f.;
on maculae of Trilobites, 233
Lingua, 459
Linguatula, 488 n., 495;
L. pusilla, 496;
L. recurvata, 496;
L. subtriquetra, 496;
L. taenioides, 489, 492, 493, 494, 496;
frequency of, 489;
larvae of, 489, 494;
hosts of, 496
Linnaeus, 408 n., 502
Linyphia, 406;
L. clathrata, 406;
L. marginata, 406;
L. montana, 406;
L. triangularis, 406
Linyphiinae, 405
Liobunum, 447, 450
Liocraninae, 397
Liocranum, 397
Liphistiidae, 386
Liphistioidae, 383
Liphistius, 317, 383, 385, 386;
L. desultor, 386
Page 660
Liriopsidae, 130
Lispognathus thompsoni, eyes, 149
Lister, M., 341, 342
Lithodes, 181;
L. maia, 176, 177, 178
Lithodidae, 181;
evolution of, 176 f.
Lithodinae, 181;
distribution, 199, 201
Lithoglyptes, 92;
L. varians, 93
Lithotrya, 87;
L. dorsalis, 87
Lithyphantes, 404
Littoral region, of sea, 197;
of lakes, 206
Liver (gastric glands), of Crustacea, 14;
of Branchiopods, 29;
of Limulus, 268;
of Arachnids, 304 f., 331
Lobster, distribution, 199;
Mysis stage, 153;
natural history, 154 f.
Lockwood, on habits of Limulus, 265, 271
Loeb, 525 n.
Loman, 331, 514, 525
Lönnberg, 425
Lophocarenum insanum, 405
Lophogaster, 119
Lispognathus thompsoni, eyes, 149
Lister, M., 341, 342
Lithodes, 181;
L. maia, 176, 177, 178
Lithodidae, 181;
evolution of, 176 f.
Lithodinae, 181;
distribution, 199, 201
Lithoglyptes, 92;
L. varians, 93
Lithotrya, 87;
L. dorsalis, 87
Lithyphantes, 404
Littoral region, of sea, 197;
of lakes, 206
Liver (gastric glands), of Crustacea, 14;
of Branchiopods, 29;
of Limulus, 268;
of Arachnids, 304 f., 331
Lobster, distribution, 199;
Mysis stage, 153;
natural history, 154 f.
Lockwood, on habits of Limulus, 265, 271
Loeb, 525 n.
Loman, 331, 514, 525
Lönnberg, 425
Lophocarenum insanum, 405
Lophogaster, 119
Page 661
Lophogastridae, 113, 114, 119
Loricata, 165
Lounsbury, 456, 461
Love-dances, among spiders, 381
Lovén, on Trilobites, 226
Loxosceles, 393
Lubbock, 375
Lucas, 364
Lucifer, 162
Lung-books, 297, 308, 336;
origin of, 305
Lupa, 191;
L. hastata, 191;
resemblance to Matuta, 187, 189
Lycosa, 417;
L. arenicola, 357;
L. carolinensis, turret of, 357;
L. fabrilis, 417;
L. ingens, 418;
L. narbonensis, 361, 366;
L. picta, 357, 372, 417;
L. tigrina, 357, 369
Lycosidae, 359, 375, 381, 417
Lydella, 479, 485;
L. dujardini, 477, 486
Lynceidae, 53;
alimentary canal, 43;
winter-eggs, 48;
reproduction, 49
Lyncodaphniidae, 53
Loricata, 165
Lounsbury, 456, 461
Love-dances, among spiders, 381
Lovén, on Trilobites, 226
Loxosceles, 393
Lubbock, 375
Lucas, 364
Lucifer, 162
Lung-books, 297, 308, 336;
origin of, 305
Lupa, 191;
L. hastata, 191;
resemblance to Matuta, 187, 189
Lycosa, 417;
L. arenicola, 357;
L. carolinensis, turret of, 357;
L. fabrilis, 417;
L. ingens, 418;
L. narbonensis, 361, 366;
L. picta, 357, 372, 417;
L. tigrina, 357, 369
Lycosidae, 359, 375, 381, 417
Lydella, 479, 485;
L. dujardini, 477, 486
Lynceidae, 53;
alimentary canal, 43;
winter-eggs, 48;
reproduction, 49
Lyncodaphniidae, 53
Page 662
Lyonnet, 319, 320
Lyra, 328
Lyriform organs, 325, 422
Lysianassa, 137
Lysianassidae, 137
Lysianax punctatus, commensal with hermit-crab, 172
M‘Cook, 334, 339, 340, 346, 350, 352 n., 365 n., 366, 367 n., 369 n.
M‘Coy, F., on facial suture of Trinucleus, 226;
on free cheek of Trilobites, 227
M‘Leod, 336 n.
Macrobiotus, 480, 485;
M. ambiguus, 487;
M. angusti, 486;
M. annulatus, 486;
M. coronifer, 487;
M. crenulatus, 487;
M. dispar, 487;
M. dubius, 487;
M. echinogenitus, 487;
M. harmsworthi, 487;
M. hastatus, 487;
M. hufelandi, 480, 482, 483, 486;
M. intermedius, 486;
M. islandicus, 487;
M. macronyx, 477, 483, 487;
M. oberhäuseri, 486;
M. orcadensis, 487;
M. ornatus, 487;
M. papillifer, 487;
M. pullari, 487;
M. sattleri, 487;
M. schultzei, 480;
Lyra, 328
Lyriform organs, 325, 422
Lysianassa, 137
Lysianassidae, 137
Lysianax punctatus, commensal with hermit-crab, 172
M‘Cook, 334, 339, 340, 346, 350, 352 n., 365 n., 366, 367 n., 369 n.
M‘Coy, F., on facial suture of Trinucleus, 226;
on free cheek of Trilobites, 227
M‘Leod, 336 n.
Macrobiotus, 480, 485;
M. ambiguus, 487;
M. angusti, 486;
M. annulatus, 486;
M. coronifer, 487;
M. crenulatus, 487;
M. dispar, 487;
M. dubius, 487;
M. echinogenitus, 487;
M. harmsworthi, 487;
M. hastatus, 487;
M. hufelandi, 480, 482, 483, 486;
M. intermedius, 486;
M. islandicus, 487;
M. macronyx, 477, 483, 487;
M. oberhäuseri, 486;
M. orcadensis, 487;
M. ornatus, 487;
M. papillifer, 487;
M. pullari, 487;
M. sattleri, 487;
M. schultzei, 480;
Page 663
M. tetradactylus, 478;
M. tuberculatus, 487;
M. zetlandicus, 486
Macrocheira kämpferi, 192
Macrohectopus (= Constantia), 138, 212
Macrophthalmus, 196
Macrothele, 390
Macrothrix, 37, 53
Macrura, 153 f.
Macula, 233
Maia, 193;
distribution, 205;
M. squinado, 192;
alimentary canal, 15
Maiidae, 193
Malacostraca, 110 f.;
defined, 6;
classification, 113, 114;
fresh-water, 210 f.
Malaquin, on Monstrilla, 63 n.
Male Spider, devoured by female, 380
Malmignatte, 364, 403
Malpighian tubes or tubules, 12, 257, 311, 331, 427, 434, 460
Mandibles, of Crustacea, 8;
of Arachnida, 319
Mange, 465
Maracaudus, 449
Margaropus, 469
Marine Spiders, 415
M. tuberculatus, 487;
M. zetlandicus, 486
Macrocheira kämpferi, 192
Macrohectopus (= Constantia), 138, 212
Macrophthalmus, 196
Macrothele, 390
Macrothrix, 37, 53
Macrura, 153 f.
Macula, 233
Maia, 193;
distribution, 205;
M. squinado, 192;
alimentary canal, 15
Maiidae, 193
Malacostraca, 110 f.;
defined, 6;
classification, 113, 114;
fresh-water, 210 f.
Malaquin, on Monstrilla, 63 n.
Male Spider, devoured by female, 380
Malmignatte, 364, 403
Malpighian tubes or tubules, 12, 257, 311, 331, 427, 434, 460
Mandibles, of Crustacea, 8;
of Arachnida, 319
Mange, 465
Maracaudus, 449
Margaropus, 469
Marine Spiders, 415
Page 664
Marpissa, 421;
M. muscosa, 420;
M. pomatia, 421
Martins, Fr., 502
Marx, 350
Masteria, 390
Mastigoproctus, 312
Mastobunus, 449
Matthew, G. F., on development of Trilobites, 238
Matuta, 188;
habitat, 198;
M. banksii, 187
Maxilla, 8;
of Decapoda, 152;
of Spiders, 321
Maxillary gland, 13
Maxillipede, 8;
of Copepoda, 55, 78;
of Malacostraca, 113;
of Zoaea, 180, 181, 182
Mecicobothrium, 391
Mecostethi, 443, 447, 448
Mecysmauchenius segmentatus, 411
Meek, 363
Megabunus, 450, 451
Megacorminae, 308
Megacormus granosus, 308
Megalaspis, 222, 249
Megalopa, compared to Glaucothoe, 180;
M. muscosa, 420;
M. pomatia, 421
Martins, Fr., 502
Marx, 350
Masteria, 390
Mastigoproctus, 312
Mastobunus, 449
Matthew, G. F., on development of Trilobites, 238
Matuta, 188;
habitat, 198;
M. banksii, 187
Maxilla, 8;
of Decapoda, 152;
of Spiders, 321
Maxillary gland, 13
Maxillipede, 8;
of Copepoda, 55, 78;
of Malacostraca, 113;
of Zoaea, 180, 181, 182
Mecicobothrium, 391
Mecostethi, 443, 447, 448
Mecysmauchenius segmentatus, 411
Meek, 363
Megabunus, 450, 451
Megacorminae, 308
Megacormus granosus, 308
Megalaspis, 222, 249
Megalopa, compared to Glaucothoe, 180;
Page 665
of Corystes cassivelaunus, 183
Mégnin, 455, 457
Megninia, 466
Meinert, 522 n.
Meisenheimer, 511 n.
Melanophora, 397
Mena-vodi, 362
Menge, 319, 368, 385
Menneus, 410
Mermerus, 449
Merostomata, 258, 259 f.
Mertens, Hugo, 524 n.
Mesochra lilljeborgi, 62
Mesonacis, 247;
M. asaphoides, larva, 240
Mesosoma, of Arachnida, 256;
of Limulus, 260, 263;
of Eurypterus, 288;
of Scorpion, 302
Mesothelae, 386
Meta segmentata, 408
Metamorphosis, of Cirripedia, 80;
of Sacculina, 97;
of Epicarida, 130, 133, 135;
of Squilla, 142, 143;
of Euphausia, 144;
discovery of, in Decapoda, 153;
of Lobster, 156;
of Crayfish, 157;
of Peneus, 159;
Mégnin, 455, 457
Megninia, 466
Meinert, 522 n.
Meisenheimer, 511 n.
Melanophora, 397
Mena-vodi, 362
Menge, 319, 368, 385
Menneus, 410
Mermerus, 449
Merostomata, 258, 259 f.
Mertens, Hugo, 524 n.
Mesochra lilljeborgi, 62
Mesonacis, 247;
M. asaphoides, larva, 240
Mesosoma, of Arachnida, 256;
of Limulus, 260, 263;
of Eurypterus, 288;
of Scorpion, 302
Mesothelae, 386
Meta segmentata, 408
Metamorphosis, of Cirripedia, 80;
of Sacculina, 97;
of Epicarida, 130, 133, 135;
of Squilla, 142, 143;
of Euphausia, 144;
discovery of, in Decapoda, 153;
of Lobster, 156;
of Crayfish, 157;
of Peneus, 159;
Page 666
primitive nature of, in Macrura, 161;
of Loricata, 165, 166;
of Hermit-crab, 179;
of Brachyura, 181, 182;
of Dromiacea, 182;
of Trilobites, 239;
of Limulus, 275;
of Pseudoscorpions, 435;
of Acarina, 462;
of Pentastomida, 493 f.;
of Pycnogons, 521 f.
Metasoma, of Arachnida, 256;
of Limulus, 260, 263;
of Eurypterus, 289;
of Scorpion, 303
Metastigmata, 467
Metastoma, of Trilobites, 234;
of Eurypterida, 287, 292
Metazoaea, 182
Metopobractus rayi, 405
Metopoctea, 452
Metridia, 59;
M. lucens, distribution, 203
Metronax, 398
Metschnikoff, 435 n.
Miagrammopes, 411
Miagrammopinae, 411
Micaria, 397;
M. pulicaria, 396, 397;
M. scintillans, 372
Micariinae, 397
of Loricata, 165, 166;
of Hermit-crab, 179;
of Brachyura, 181, 182;
of Dromiacea, 182;
of Trilobites, 239;
of Limulus, 275;
of Pseudoscorpions, 435;
of Acarina, 462;
of Pentastomida, 493 f.;
of Pycnogons, 521 f.
Metasoma, of Arachnida, 256;
of Limulus, 260, 263;
of Eurypterus, 289;
of Scorpion, 303
Metastigmata, 467
Metastoma, of Trilobites, 234;
of Eurypterida, 287, 292
Metazoaea, 182
Metopobractus rayi, 405
Metopoctea, 452
Metridia, 59;
M. lucens, distribution, 203
Metronax, 398
Metschnikoff, 435 n.
Miagrammopes, 411
Miagrammopinae, 411
Micaria, 397;
M. pulicaria, 396, 397;
M. scintillans, 372
Micariinae, 397
Page 667
Micariosoma, 397
Michael, 460, 461, 462, 466 n.
Micrathena, 410
Microdiscus, 225, 231, 245
Microlyda, 486 n.
Micrommata, 414;
M. virescens, 413, 414
Microneta, 406
Microniscidae, 130
Migas, 387
Miginae, 387
Milne-Edwards, 504
Milnesium, 480, 485;
M. alpigenum, 487;
M. tardigradum, 487
Miltia, 396
Mimetidae, 411
Mimetus, 411;
M. interfector, 368
Mimicry, in Spiders, 372
Mimoscorpius, 312
Miopsalis, 448
Misumena, 412;
M. vatia, 371, 373, 412
Mites, = Acarina, q.v.
Moggridge, 354, 355 n.
Moggridgea, 387
Moina, 37, 52;
Michael, 460, 461, 462, 466 n.
Micrathena, 410
Microdiscus, 225, 231, 245
Microlyda, 486 n.
Micrommata, 414;
M. virescens, 413, 414
Microneta, 406
Microniscidae, 130
Migas, 387
Miginae, 387
Milne-Edwards, 504
Milnesium, 480, 485;
M. alpigenum, 487;
M. tardigradum, 487
Miltia, 396
Mimetidae, 411
Mimetus, 411;
M. interfector, 368
Mimicry, in Spiders, 372
Mimoscorpius, 312
Miopsalis, 448
Misumena, 412;
M. vatia, 371, 373, 412
Mites, = Acarina, q.v.
Moggridge, 354, 355 n.
Moggridgea, 387
Moina, 37, 52;
Page 668
reproduction, 46, 47, 48, 49;
M. rectirostris, 46, 47, 52
Mole-crab, 170
Monochetus, 465
Monolistra (Sphaeromidae), habitat, 211
Monopsilus, 54
Monostichous eyes, 301
Monstrilla, 64
Moustrillidae, 63
Morgan, 517, 518, 521
Mortimer, Cromwell, on Trilobites, 221
Mosaic vision, 147
Moseley, 523
Moulting (Ecdysis), 154, 155, 225, 338
Mouth, of Trilobites, 234
Mud-mites, 472
Müller, F., on Tanaids, 123
Müller, O. F., on position of Tardigrada, 483
Munidopsis, 170;
eyes, 149;
M. hamata, 168
Munnopsidae, 128
Munnopsis typica, 127
Murray, 455
Murray, J., on British Tardigrada, 485
Muscular system, in Tardigrada, 481;
in Pentastomida, 490
M. rectirostris, 46, 47, 52
Mole-crab, 170
Monochetus, 465
Monolistra (Sphaeromidae), habitat, 211
Monopsilus, 54
Monostichous eyes, 301
Monstrilla, 64
Moustrillidae, 63
Morgan, 517, 518, 521
Mortimer, Cromwell, on Trilobites, 221
Mosaic vision, 147
Moseley, 523
Moulting (Ecdysis), 154, 155, 225, 338
Mouth, of Trilobites, 234
Mud-mites, 472
Müller, F., on Tanaids, 123
Müller, O. F., on position of Tardigrada, 483
Munidopsis, 170;
eyes, 149;
M. hamata, 168
Munnopsidae, 128
Munnopsis typica, 127
Murray, 455
Murray, J., on British Tardigrada, 485
Muscular system, in Tardigrada, 481;
in Pentastomida, 490
Page 669
Mygale, 337, 386 n., 389
Mygalidae, = Aviculariidae, q.v.
Myrmarachne formicaria, 421
Myrmecium, 397
Myrtale perroti, 387
Mysidacea, 118
Mysidae, 113, 114, 119;
habitat, 201;
relation to Nebalia, 112
Mysis, 120;
maxillipede, 10, 11;
resemblance to Paranaspides, 117;
M. oculata, var. relicta, 120, 210;
M. vulgaris, 118
Mysis-larva, of Lobster, 156;
of Peneus, 161
Mytilicola, 68
Nanodamon, 313
Nauplius, of Haemocera danae, 64;
of Lepas fascicularis, 81;
of Sacculina, 97;
of Euphausia, 144;
an ancestral larval form, 145;
of Peneus, 159;
compared with Protaspis, 239
Nebalia, 111, 112, 114;
segmentation, 6, 7;
limbs, 10, 11;
relation to Cumacea, 120;
compared with Trilobita, 242;
N. geoffroyi, 111
Mygalidae, = Aviculariidae, q.v.
Myrmarachne formicaria, 421
Myrmecium, 397
Myrtale perroti, 387
Mysidacea, 118
Mysidae, 113, 114, 119;
habitat, 201;
relation to Nebalia, 112
Mysis, 120;
maxillipede, 10, 11;
resemblance to Paranaspides, 117;
M. oculata, var. relicta, 120, 210;
M. vulgaris, 118
Mysis-larva, of Lobster, 156;
of Peneus, 161
Mytilicola, 68
Nanodamon, 313
Nauplius, of Haemocera danae, 64;
of Lepas fascicularis, 81;
of Sacculina, 97;
of Euphausia, 144;
an ancestral larval form, 145;
of Peneus, 159;
compared with Protaspis, 239
Nebalia, 111, 112, 114;
segmentation, 6, 7;
limbs, 10, 11;
relation to Cumacea, 120;
compared with Trilobita, 242;
N. geoffroyi, 111
Page 670
Nebo, 307
Neck-furrow, 224
Nemastoma, 443, 451;
N. chrysomelas, 452;
N. lugubre, 452
Nemastomatidae, 451
Nematocarcinus, 163
Nemesia, 388;
N. congena, 355, 357
Neolimulus, 278, 279
Neoniphargus, distribution, 216
Neopallene, 537
Nephila, 408;
N. chrysogaster, 380;
N. plumipes, 366
Nephilinae, 408
Nephrops, 154;
N. andamanica, distribution, 205;
N. norwegica, 205
Nephropsidae, 154;
resemblance to Dromiacea, 184
Neptunus, 191;
N. sayi, habitat, 202
Nereicolidae, 73
Nervous system, of Crustacea, 5;
of Branchiopoda, 30;
of Squilla, 142;
of Arachnida, 257;
of Limulus, 270;
of Scorpions, 305;
of Pedipalpi, 311;
Neck-furrow, 224
Nemastoma, 443, 451;
N. chrysomelas, 452;
N. lugubre, 452
Nemastomatidae, 451
Nematocarcinus, 163
Nemesia, 388;
N. congena, 355, 357
Neolimulus, 278, 279
Neoniphargus, distribution, 216
Neopallene, 537
Nephila, 408;
N. chrysogaster, 380;
N. plumipes, 366
Nephilinae, 408
Nephrops, 154;
N. andamanica, distribution, 205;
N. norwegica, 205
Nephropsidae, 154;
resemblance to Dromiacea, 184
Neptunus, 191;
N. sayi, habitat, 202
Nereicolidae, 73
Nervous system, of Crustacea, 5;
of Branchiopoda, 30;
of Squilla, 142;
of Arachnida, 257;
of Limulus, 270;
of Scorpions, 305;
of Pedipalpi, 311;
Page 671
of Spiders, 332, 333;
of Solifugae, 428;
of Pseudoscorpions, 434;
of Phalangidea, 445, 446;
of Acarina, 460;
of Tardigrada, 482;
of Pentastomida, 491;
of Pycnogons, 516
Neumann, 470
Nicodaminae, 416
Nicodamus, 416
Nicothoe astaci, 68
Nileus, 229, 249;
N. armadillo, eye, 228
Niobe, 249
Niphargoides, 138
Niphargus, 137, 138;
distribution, 216;
N. forelii, 138;
N. puteanus, habitat, 209, 210
Nogagus, 73
Nops, 315, 336, 395
Norman, A. M., 540
Notaspis, 467
Nothrus, 468
Notodelphys, 66
Notostigmata, 473
Nyctalops, 312
Nycteribia (Diptera), 526
of Solifugae, 428;
of Pseudoscorpions, 434;
of Phalangidea, 445, 446;
of Acarina, 460;
of Tardigrada, 482;
of Pentastomida, 491;
of Pycnogons, 516
Neumann, 470
Nicodaminae, 416
Nicodamus, 416
Nicothoe astaci, 68
Nileus, 229, 249;
N. armadillo, eye, 228
Niobe, 249
Niphargoides, 138
Niphargus, 137, 138;
distribution, 216;
N. forelii, 138;
N. puteanus, habitat, 209, 210
Nogagus, 73
Nops, 315, 336, 395
Norman, A. M., 540
Notaspis, 467
Nothrus, 468
Notodelphys, 66
Notostigmata, 473
Nyctalops, 312
Nycteribia (Diptera), 526
Page 672
Nymph, 463
Nymphon, 503, 536;
N. brevicaudatum, 507, 536;
N. brevicollum, 511, 521;
N. brevirostre, 503, 504, 506, 508, 509, 541, 542;
N. elegans, 506, 542;
N. femoratum, 541;
N. gallicum, 541;
N. gracile, 511, 541, 542;
N. gracilipes, 542;
N. grossipes, 541;
N. hamatum, 512;
N. hirtipes, 542;
N. horridum, 537;
N. johnstoni, 541;
N. leptocheles, 542;
N. longitarse, 541, 542;
N. macronyx, 542;
N. macrum, 542;
N. minutum, 541;
N. mixtum, 541;
N. pellucidum, 541;
N. rubrum, 541, 542;
N. serratum, 542;
N. simile, 541;
N. sluiteri, 542;
N. spinosum, 541;
N. stenocheir, 542;
N. strömii, 509, 541
Nymphonidae, 536
Nymphopsinae, 535 n.
Nymphopsis, 534, 535 n.;
N. korotnevi, 534;
N. muscosus, 534
Nymphon, 503, 536;
N. brevicaudatum, 507, 536;
N. brevicollum, 511, 521;
N. brevirostre, 503, 504, 506, 508, 509, 541, 542;
N. elegans, 506, 542;
N. femoratum, 541;
N. gallicum, 541;
N. gracile, 511, 541, 542;
N. gracilipes, 542;
N. grossipes, 541;
N. hamatum, 512;
N. hirtipes, 542;
N. horridum, 537;
N. johnstoni, 541;
N. leptocheles, 542;
N. longitarse, 541, 542;
N. macronyx, 542;
N. macrum, 542;
N. minutum, 541;
N. mixtum, 541;
N. pellucidum, 541;
N. rubrum, 541, 542;
N. serratum, 542;
N. simile, 541;
N. sluiteri, 542;
N. spinosum, 541;
N. stenocheir, 542;
N. strömii, 509, 541
Nymphonidae, 536
Nymphopsinae, 535 n.
Nymphopsis, 534, 535 n.;
N. korotnevi, 534;
N. muscosus, 534
Page 673
Obisiinae, 436, 437
Obisium, 436, 438
Ochyrocera, 393
Octomeridae, 91
Octomeris, 91
Ocyale mirabilis, 416
Ocypoda, 194, 196;
habitat, 198;
distribution, 201
Ocypodidae, 196
Oecobiidae, 386 n., 392
Oecobius, 392;
Oe. maculatus, 392
Oehlert, on facial suture of Trinucleus, 226
Ogovia, 448
Ogygia, 249
Oiceobathes, 535
Oithona, 61;
O. nana, 203;
O. plumifera, 203
Olenelloides, 247;
O. armatus, 247
Olenellus, 225, 227, 232, 236, 247
Olenidae, 247
Olenus, 232, 247;
O. truncatus, 248
Oligolophus, 450;
O. agrestis, 450;
O. spinosus, 441, 450, 451
Obisium, 436, 438
Ochyrocera, 393
Octomeridae, 91
Octomeris, 91
Ocyale mirabilis, 416
Ocypoda, 194, 196;
habitat, 198;
distribution, 201
Ocypodidae, 196
Oecobiidae, 386 n., 392
Oecobius, 392;
Oe. maculatus, 392
Oehlert, on facial suture of Trinucleus, 226
Ogovia, 448
Ogygia, 249
Oiceobathes, 535
Oithona, 61;
O. nana, 203;
O. plumifera, 203
Olenelloides, 247;
O. armatus, 247
Olenellus, 225, 227, 232, 236, 247
Olenidae, 247
Olenus, 232, 247;
O. truncatus, 248
Oligolophus, 450;
O. agrestis, 450;
O. spinosus, 441, 450, 451
Page 674
Olpium, 436, 437;
O. pallipes, 437
Ommatoids, 310, 311, 312
Oncaea, 69;
O. conifera, phosphorescence, 60
Oncaeidae, 69
Oniscoida, 128
Oniscus, 129
Ononis hispanica, Spiders on, 419
Onychium, 324
Oomerus stigmatophorus, 539
Oonopidae, 336, 393
Oonops, 394;
O. pulcher, 366, 394
Oorhynchus, 507, 535;
O. aucklandiae, 535
Oostegites, of Malacostraca, 114
Operculata, 89, 91
Ophiocamptus (Moraria), 62;
O. brevipes, 62
Opilioacarus, 454, 473;
O. arabicus, 473;
O. italicus, 473;
O. platensis, 473;
O. segmentatus, 473
Opiliones (= Phalangidea, q.v.), 440
Opisthacanthus, 307
Opisthoparia, 244
Opisthophthalmus, 307
O. pallipes, 437
Ommatoids, 310, 311, 312
Oncaea, 69;
O. conifera, phosphorescence, 60
Oncaeidae, 69
Oniscoida, 128
Oniscus, 129
Ononis hispanica, Spiders on, 419
Onychium, 324
Oomerus stigmatophorus, 539
Oonopidae, 336, 393
Oonops, 394;
O. pulcher, 366, 394
Oorhynchus, 507, 535;
O. aucklandiae, 535
Oostegites, of Malacostraca, 114
Operculata, 89, 91
Ophiocamptus (Moraria), 62;
O. brevipes, 62
Opilioacarus, 454, 473;
O. arabicus, 473;
O. italicus, 473;
O. platensis, 473;
O. segmentatus, 473
Opiliones (= Phalangidea, q.v.), 440
Opisthacanthus, 307
Opisthoparia, 244
Opisthophthalmus, 307
Page 675
Opisthothelae, 386
Opopaea, 394
Orchestia, 139;
hermaphroditism, 104;
O. gammarellus, 137, 139;
habitat, 211
Orchestina, 394
Oribata, 467
Oribatidae, 457, 458, 459, 460, 462, 467;
anatomy, 459
Orithyia coccinea, 524, 540
Ornithodoros, 469;
O. megnini, 469;
O. moubata, 469;
O. talaje, 469;
O. turicata, 469
Ornithoscatoides, 374
Orometopus, 226, 245;
O. elatifrons, 230
Ortmann, on Brachyura, 181 n.;
on bipolarity, 200;
on crayfishes, 213;
on Pycnogons, 513 n.
Ostracoda, 107;
pelagic, 202
Oudemans, 528 n.
Ovary, of Cladocera, 44, 45;
of Danalia, 132;
of Spiders, 332
Oxynaspis, 88
Oxyopes, 419;
Opopaea, 394
Orchestia, 139;
hermaphroditism, 104;
O. gammarellus, 137, 139;
habitat, 211
Orchestina, 394
Oribata, 467
Oribatidae, 457, 458, 459, 460, 462, 467;
anatomy, 459
Orithyia coccinea, 524, 540
Ornithodoros, 469;
O. megnini, 469;
O. moubata, 469;
O. talaje, 469;
O. turicata, 469
Ornithoscatoides, 374
Orometopus, 226, 245;
O. elatifrons, 230
Ortmann, on Brachyura, 181 n.;
on bipolarity, 200;
on crayfishes, 213;
on Pycnogons, 513 n.
Ostracoda, 107;
pelagic, 202
Oudemans, 528 n.
Ovary, of Cladocera, 44, 45;
of Danalia, 132;
of Spiders, 332
Oxynaspis, 88
Oxyopes, 419;
Page 676
O. lineata, 419
Oxyopidae, 419
Oxyptila, 412
Oxyrhyncha, 191 f.;
habits, 192;
enemies, 192;
habitat, 198
Oxystomata, 185 f.;
respiration, 186, 187
Pachycheles, 170;
P. panamensis, distribution, 202
Pachygnatha, 407;
P. clerckii, 407;
P. degeerii, 407;
P. listeri, 407
Pachygrapsus, 196;
P. marmoratus, 193, 194, 196
Pachylasma giganteum, 91
Pachylomerus, 388
Pachysoma, 69
Pagurian, 180;
eyes of deep-sea, 149, 150
Paguridea, 171
Pagurinae, 180
Palaemon, 164;
excretory glands, 13;
fresh-water, 212;
P. serratus, 158, 164;
Bopyrus parasitic on, 133
Oxyopidae, 419
Oxyptila, 412
Oxyrhyncha, 191 f.;
habits, 192;
enemies, 192;
habitat, 198
Oxystomata, 185 f.;
respiration, 186, 187
Pachycheles, 170;
P. panamensis, distribution, 202
Pachygnatha, 407;
P. clerckii, 407;
P. degeerii, 407;
P. listeri, 407
Pachygrapsus, 196;
P. marmoratus, 193, 194, 196
Pachylasma giganteum, 91
Pachylomerus, 388
Pachysoma, 69
Pagurian, 180;
eyes of deep-sea, 149, 150
Paguridea, 171
Pagurinae, 180
Palaemon, 164;
excretory glands, 13;
fresh-water, 212;
P. serratus, 158, 164;
Bopyrus parasitic on, 133
Page 677
Palaemonetes, 164;
P. antrorum, habitat, 210;
P. varians, 161;
distribution, 212
Palaemonidae, 159, 164
Palaeocaris, 115, 118
Palaeophonus, 294, 298
Palamnaeus, 307;
P. swammerdami, tarsus, 304
Palinuridae, 167
Palinurus, 165, 167;
habitat, 198, 202;
P. elephas, 167;
P. quadricornis, embryo, 165
Pallene, 505, 537;
P. attenuata, 541;
P. brevirostris, 510, 524, 537, 541, 542;
P. dimorpha, 538;
P. emaciata, 541;
P. empusa, 541;
P. grubii, 538;
P. languida, 537;
P. longiceps, 538;
P. novaezealandiae, 537;
P. producta, 542;
P. pygmaea, 537, 541;
P. spectrum, 542;
P. spinosa, 537
Pallenidae, 537
Pallenopsis, 506, 511;
P. holti, 542;
P. tritonis, 542
Palp, of Pycnogons, 507
P. antrorum, habitat, 210;
P. varians, 161;
distribution, 212
Palaemonidae, 159, 164
Palaeocaris, 115, 118
Palaeophonus, 294, 298
Palamnaeus, 307;
P. swammerdami, tarsus, 304
Palinuridae, 167
Palinurus, 165, 167;
habitat, 198, 202;
P. elephas, 167;
P. quadricornis, embryo, 165
Pallene, 505, 537;
P. attenuata, 541;
P. brevirostris, 510, 524, 537, 541, 542;
P. dimorpha, 538;
P. emaciata, 541;
P. empusa, 541;
P. grubii, 538;
P. languida, 537;
P. longiceps, 538;
P. novaezealandiae, 537;
P. producta, 542;
P. pygmaea, 537, 541;
P. spectrum, 542;
P. spinosa, 537
Pallenidae, 537
Pallenopsis, 506, 511;
P. holti, 542;
P. tritonis, 542
Palp, of Pycnogons, 507
Page 678
Palpal organ, 322, 378
Palpebral lobe, 227
Palpigradi, 258, 422
Palpimanidae, 323, 325, 398
Palpimanus, 398
Panamomops diceros, 405
Pandalidae, 164
Pandalus, 164;
P. annulicornis, 164
Pandinus, 307
Panoplax, 195
Pantopoda, 501 n. (= Pycnogonida, q.v.)
Panulirus, 165, 167
Parabolina, 232, 247
Parabolinella, 247
Parabuthus, 298;
P. capensis, 298, 299
Paradoxides, 222, 232, 236, 247;
P. bohemicus, 246
Paragaleodes, 429
Paralomis, 179, 181
Paranaspides, 117;
P. lacustris, 117;
distribution, 210;
habitat, 210
Paranebalia, 242
Paranephrops, 157;
distribution, 213
Palpebral lobe, 227
Palpigradi, 258, 422
Palpimanidae, 323, 325, 398
Palpimanus, 398
Panamomops diceros, 405
Pandalidae, 164
Pandalus, 164;
P. annulicornis, 164
Pandinus, 307
Panoplax, 195
Pantopoda, 501 n. (= Pycnogonida, q.v.)
Panulirus, 165, 167
Parabolina, 232, 247
Parabolinella, 247
Parabuthus, 298;
P. capensis, 298, 299
Paradoxides, 222, 232, 236, 247;
P. bohemicus, 246
Paragaleodes, 429
Paralomis, 179, 181
Paranaspides, 117;
P. lacustris, 117;
distribution, 210;
habitat, 210
Paranebalia, 242
Paranephrops, 157;
distribution, 213
Page 679
Paranthura, 124
Parantipathes, Synagoga parasitic on, 94
Paranymphon, 507;
P. spinosum, 542
Parapagurus, 180
Parapallene, 537
Parapeneus, 162;
P. rectacutus, 159
Parapylocheles scorpio, eyes, 149
Parasiro, 448;
P. corsicus, 448
Parasites, in Tardigrada, 484
Parasitic castration, 100, 136
Parastacidae, 157;
distribution, 213
Parastacus, 157;
distribution, 213
Paratropidinae, 387
Paratropis scrupea, 387
Parazetes auchenicus, 533
Pardosa, 417;
female carrying young, 341;
P. amentata, 417, 418;
P. lugubris, 418
Pariboea spinipalpis, 534
Parthenogenesis, in Phyllopoda, 32;
in Cladocera, 44, 46, 49;
in Ostracoda, 108
Parthenope, 193;
Parantipathes, Synagoga parasitic on, 94
Paranymphon, 507;
P. spinosum, 542
Parapagurus, 180
Parapallene, 537
Parapeneus, 162;
P. rectacutus, 159
Parapylocheles scorpio, eyes, 149
Parasiro, 448;
P. corsicus, 448
Parasites, in Tardigrada, 484
Parasitic castration, 100, 136
Parastacidae, 157;
distribution, 213
Parastacus, 157;
distribution, 213
Paratropidinae, 387
Paratropis scrupea, 387
Parazetes auchenicus, 533
Pardosa, 417;
female carrying young, 341;
P. amentata, 417, 418;
P. lugubris, 418
Pariboea spinipalpis, 534
Parthenogenesis, in Phyllopoda, 32;
in Cladocera, 44, 46, 49;
in Ostracoda, 108
Parthenope, 193;
Page 680
P. investigatoris, 192
Parthenopidae, 193
Pasiphaea, 163
Pasiphaeidae, 163
Pasithoe, 532;
P. umbonata, 535;
P. vesiculosa, 535, 541
Pasithoidae, 532
Patten, 270, 271, 277
Patten and Redenbaugh, on Limulus, 266, 270, 272
Paturon, 319, 320
Peckham, 376, 377, 378, 381, 382
Pecten, 328
Pectines, of Scorpions, 302, 302;
function of, 299;
of Glytoscorpius, 294
Pedicle, 317
Pedipalpi, 258, 308;
habits, 309;
external structure, 309;
legs, 309;
internal structure, 310;
alimentary canal, 310;
nervous system, 311;
classification, 312
Pedipalpi (appendages), 263, 303, 309, 321, 422, 426, 433, 440, 458
Pedunculata, 84
Pelagic Crustacea, marine, 202;
lacustrine, 207
Pelops, 467
Parthenopidae, 193
Pasiphaea, 163
Pasiphaeidae, 163
Pasithoe, 532;
P. umbonata, 535;
P. vesiculosa, 535, 541
Pasithoidae, 532
Patten, 270, 271, 277
Patten and Redenbaugh, on Limulus, 266, 270, 272
Paturon, 319, 320
Peckham, 376, 377, 378, 381, 382
Pecten, 328
Pectines, of Scorpions, 302, 302;
function of, 299;
of Glytoscorpius, 294
Pedicle, 317
Pedipalpi, 258, 308;
habits, 309;
external structure, 309;
legs, 309;
internal structure, 310;
alimentary canal, 310;
nervous system, 311;
classification, 312
Pedipalpi (appendages), 263, 303, 309, 321, 422, 426, 433, 440, 458
Pedunculata, 84
Pelagic Crustacea, marine, 202;
lacustrine, 207
Pelops, 467
Page 681
Peltiidae, 63
Peltogaster, 95;
structure, 95;
males, 99;
castration caused by, 100;
P. curvatus, castration caused by, 100;
P. sulcatus, 95
Peltura, 247
Peneidae, 162
Peneidea, 158, 162;
metamorphosis, 159
Penella sagitta, 74
Peneus, 158, 162;
metamorphosis, 159, 159, 160, 161
Pentanymphon, 504, 537
Pentaspidae, 87
Pentastoma, 488 n.;
P. denticulatum, 489, 494;
P. emarginatum, 489;
P. serratum, 489
Pentastomida, 258, 488 f.;
structure, 489;
habitat, 488;
life-history, 488, 493;
hosts of, 496, 497
Pephredo hirsuta, 535, 541
Peracantha, 43, 53;
alimentary canal, 43
Peracarida, 114, 118
Pereiopod, defined, 110;
reduced hind, in Galatheidea, 168;
Peltogaster, 95;
structure, 95;
males, 99;
castration caused by, 100;
P. curvatus, castration caused by, 100;
P. sulcatus, 95
Peltura, 247
Peneidae, 162
Peneidea, 158, 162;
metamorphosis, 159
Penella sagitta, 74
Peneus, 158, 162;
metamorphosis, 159, 159, 160, 161
Pentanymphon, 504, 537
Pentaspidae, 87
Pentastoma, 488 n.;
P. denticulatum, 489, 494;
P. emarginatum, 489;
P. serratum, 489
Pentastomida, 258, 488 f.;
structure, 489;
habitat, 488;
life-history, 488, 493;
hosts of, 496, 497
Pephredo hirsuta, 535, 541
Peracantha, 43, 53;
alimentary canal, 43
Peracarida, 114, 118
Pereiopod, defined, 110;
reduced hind, in Galatheidea, 168;
Page 682
in Hippidea, 170;
in Paguridea, 172;
in Dromiacea, 184;
in Oxystomata, 185
Periegops hirsutus, 393
Peroderma cylindricum, 75
Petrarca bathyactidis, 93
Pettalus, 448
Pezomachus gracilis, parasitic in cocoons of Spiders, 367
Phacopidae, 249
Phacopini, 243
Phacops, 223, 232, 235, 249;
P. latifrons, 227;
P. sternbergi, 248
Phaeocedus braccatus, 397
Phagocytes, in Danalia, 132
Phalangidea, 258, 440 f.;
habits, 441;
external structure, 442;
internal structure, 444;
nervous system, 446;
classification, 447;
British species, 453
Phalangiidae, 449
Phalangiinae, 450
Phalangium, 444, 450, 526;
mouth-parts, 443;
P. balaenarum, 502;
P. cornutum, 450;
P. littorale, 501;
P. opilio, 445, 446, 450, 526
in Paguridea, 172;
in Dromiacea, 184;
in Oxystomata, 185
Periegops hirsutus, 393
Peroderma cylindricum, 75
Petrarca bathyactidis, 93
Pettalus, 448
Pezomachus gracilis, parasitic in cocoons of Spiders, 367
Phacopidae, 249
Phacopini, 243
Phacops, 223, 232, 235, 249;
P. latifrons, 227;
P. sternbergi, 248
Phaeocedus braccatus, 397
Phagocytes, in Danalia, 132
Phalangidea, 258, 440 f.;
habits, 441;
external structure, 442;
internal structure, 444;
nervous system, 446;
classification, 447;
British species, 453
Phalangiidae, 449
Phalangiinae, 450
Phalangium, 444, 450, 526;
mouth-parts, 443;
P. balaenarum, 502;
P. cornutum, 450;
P. littorale, 501;
P. opilio, 445, 446, 450, 526
Page 683
Phalangodes, 449;
P. armata, 449;
P. terricola, 449
Phalangodidae, 448
Phanodemus, 535
Phidippus, 421;
P. morsitans, 365, 421
Philichthyidae, 73
Philichthys, 73;
P. xiphiae, 73 n.
Phillipsia, 251;
P. gemmulifera, 250
Philodrominae, 413
Philodromus, 413;
P. aureolus, 413;
P. margaritatus, 413
Philoscia muscorum, 129
Pholcidae, 336, 401
Pholcus, 320, 401;
P. phalangioides, 401
Phoroncidia, 404;
P. 7–aculeata, 318
Phoroncidiinae, 317, 404
Phosphorescence, of Copepoda, 59;
relation to eyes in deep-sea Crustacea, 150, 151
Phosphorescent organs, of Euphausiidae, 145;
of Stylocheiron mastigophorum, 151
Phoxichilidae, 539
Phoxichilidiidae, 538
P. armata, 449;
P. terricola, 449
Phalangodidae, 448
Phanodemus, 535
Phidippus, 421;
P. morsitans, 365, 421
Philichthyidae, 73
Philichthys, 73;
P. xiphiae, 73 n.
Phillipsia, 251;
P. gemmulifera, 250
Philodrominae, 413
Philodromus, 413;
P. aureolus, 413;
P. margaritatus, 413
Philoscia muscorum, 129
Pholcidae, 336, 401
Pholcus, 320, 401;
P. phalangioides, 401
Phoroncidia, 404;
P. 7–aculeata, 318
Phoroncidiinae, 317, 404
Phosphorescence, of Copepoda, 59;
relation to eyes in deep-sea Crustacea, 150, 151
Phosphorescent organs, of Euphausiidae, 145;
of Stylocheiron mastigophorum, 151
Phoxichilidae, 539
Phoxichilidiidae, 538
Page 684
Phoxichilidium, 506, 512, 520, 521 n., 523, 525, 538;
P. angulatum, 520;
P. exiguum, 541;
P. femoratum, 508, 524, 538, 540;
P. globosum, 540;
P. mollissimum, 517;
P. olivaceum, 540
Phoxichilus, 505, 512, 539;
P. australis, 539, 540;
P. böhmii, 539;
P. charybdaeus, 514, 515, 539;
P. laevis, 537, 539, 541;
P. meridionalis, 539;
P. mollis, 539;
P. proboscideus, 532;
P. procerus, 539;
P. spinosus, 505, 508, 510, 537, 539, 541, 542;
P. vulgaris, 539
Phreatoicidae, 136;
distribution, 211, 217
Phreatoicidea, 136
Phreatoicopsis, 136;
distribution, 211
Phreatoicus, 136;
distribution, 210, 211, 217;
P. assimilis, habitat, 210;
P. typicus, habitat, 210
Phronima, 140;
P. sedentaria, 140
Phrynarachne, 414;
P. decipiens, 374, 414
Phrynichinae, 313
Phrynichus, 313
P. angulatum, 520;
P. exiguum, 541;
P. femoratum, 508, 524, 538, 540;
P. globosum, 540;
P. mollissimum, 517;
P. olivaceum, 540
Phoxichilus, 505, 512, 539;
P. australis, 539, 540;
P. böhmii, 539;
P. charybdaeus, 514, 515, 539;
P. laevis, 537, 539, 541;
P. meridionalis, 539;
P. mollis, 539;
P. proboscideus, 532;
P. procerus, 539;
P. spinosus, 505, 508, 510, 537, 539, 541, 542;
P. vulgaris, 539
Phreatoicidae, 136;
distribution, 211, 217
Phreatoicidea, 136
Phreatoicopsis, 136;
distribution, 211
Phreatoicus, 136;
distribution, 210, 211, 217;
P. assimilis, habitat, 210;
P. typicus, habitat, 210
Phronima, 140;
P. sedentaria, 140
Phrynarachne, 414;
P. decipiens, 374, 414
Phrynichinae, 313
Phrynichus, 313
Page 685
Phrynidae, 309, 310, 312
Phrynopsis, 313
Phrynus, 312
Phryxidae, 130
Phyllocarida, 111, 242
Phyllocoptes, 465
Phyllopoda, 19 f.;
appendages, 24 f.;
alimentary canal, 29;
vascular system, 29;
nervous system, 30;
reproductive organs, 31;
habitat, 32;
genera, 35
Phyllosoma, larva of Palinurus, 166
Phytoptidae, 464
Phytoptus, 464 n., 495 (= Eriophyes, q.v.)
Pickard-Cambridge, F., 352
Pickard-Cambridge, O., 318, 321 n., 323 n., 359 n., 372, 374, 380, 385, 401
n., 436, 438, 450, 451, 452
Pillai, 375
Pilumnus, 191
Pinnotheres pisum, 195
Pinnotheridae, 195
Pipetta, 514, 533;
P. weberi, 533
Pirata, 417
Piriform glands, 335, 349
Pisa, 193
Phrynopsis, 313
Phrynus, 312
Phryxidae, 130
Phyllocarida, 111, 242
Phyllocoptes, 465
Phyllopoda, 19 f.;
appendages, 24 f.;
alimentary canal, 29;
vascular system, 29;
nervous system, 30;
reproductive organs, 31;
habitat, 32;
genera, 35
Phyllosoma, larva of Palinurus, 166
Phytoptidae, 464
Phytoptus, 464 n., 495 (= Eriophyes, q.v.)
Pickard-Cambridge, F., 352
Pickard-Cambridge, O., 318, 321 n., 323 n., 359 n., 372, 374, 380, 385, 401
n., 436, 438, 450, 451, 452
Pillai, 375
Pilumnus, 191
Pinnotheres pisum, 195
Pinnotheridae, 195
Pipetta, 514, 533;
P. weberi, 533
Pirata, 417
Piriform glands, 335, 349
Pisa, 193
Page 686
Pisaura mirabilis, 416
Pisauridae, 416
Placoparia, 251
Plagiostethi, 443, 447, 449, 452
Plagula, 317
Planes minutus, habitat, 202
Plankton, characters of, 203;
fresh-water, 207, 216;
Cladocera in, 50
Plastron, 316
Plate, on Tardigrada, 481, 482, 484
Plator insolens, 415
Platoridae, 415
Platyarthrus hoffmannseggii, 129
Platyaspis, 121
Platybunus, 450, 451
Platycheles, 535
Plectreurys, 393
Pleopod, defined, 110
Pleura, 234 f.
Pleurocrypta microbranchiata, 133
Pleuromma, 59;
P. abdominale, 59;
P. gracile, 59
Pliobothrus symmetricus, Pycnogon larvae in, 523
Pocock, 298, 308 n., 312, 328, 329, 425 n., 534 n.
Podasconidae, 130
Pisauridae, 416
Placoparia, 251
Plagiostethi, 443, 447, 449, 452
Plagula, 317
Planes minutus, habitat, 202
Plankton, characters of, 203;
fresh-water, 207, 216;
Cladocera in, 50
Plastron, 316
Plate, on Tardigrada, 481, 482, 484
Plator insolens, 415
Platoridae, 415
Platyarthrus hoffmannseggii, 129
Platyaspis, 121
Platybunus, 450, 451
Platycheles, 535
Plectreurys, 393
Pleopod, defined, 110
Pleura, 234 f.
Pleurocrypta microbranchiata, 133
Pleuromma, 59;
P. abdominale, 59;
P. gracile, 59
Pliobothrus symmetricus, Pycnogon larvae in, 523
Pocock, 298, 308 n., 312, 328, 329, 425 n., 534 n.
Podasconidae, 130
Page 687
Podogona, 258, 439
Podon, 54
Podophthalmata, 112
Podoplea, 61
Podosomata, 501 n. (= Pycnogonida, q.v.)
Poecilotheria, 390
Poisonous hairs, of Spiders, 365
Pollicipes, 84;
fertilisation, 86;
P. cornucopia, 85;
P. mitella, 85
Pollock, 340
Poltyinae, 410
Poltys, 410;
P. ideae, 318
Polyartemia, 36;
antennae, 26, 28;
range of, 34;
P. forcipata, 36
Polyaspidae, 84
Polycopidae, 109
Polygonopus, 539
Polyphemidae, 54;
appendages, 42;
ovary, 47;
reproduction, 49
Polyphemus, 47, 54;
P. pediculus, habitat, 206, 208
Polysphincta carbonaria, parasitic on Spiders, 368
Podon, 54
Podophthalmata, 112
Podoplea, 61
Podosomata, 501 n. (= Pycnogonida, q.v.)
Poecilotheria, 390
Poisonous hairs, of Spiders, 365
Pollicipes, 84;
fertilisation, 86;
P. cornucopia, 85;
P. mitella, 85
Pollock, 340
Poltyinae, 410
Poltys, 410;
P. ideae, 318
Polyartemia, 36;
antennae, 26, 28;
range of, 34;
P. forcipata, 36
Polyaspidae, 84
Polycopidae, 109
Polygonopus, 539
Polyphemidae, 54;
appendages, 42;
ovary, 47;
reproduction, 49
Polyphemus, 47, 54;
P. pediculus, habitat, 206, 208
Polysphincta carbonaria, parasitic on Spiders, 368
Page 688
Pompeckj, on Calymenidae, 244
Pompilus, 368
Pontellidae, 60
Pontoporeia, 137;
distribution, 212;
P. affinis, 138;
P. femorata, 138;
P. loyi, 138;
P. microphthalma, 138
Porcellana, 168, 170;
Zoaea, 168;
P. platycheles, 170
Porcellanidae, 170;
habitat, 198
Porcellio, 129
Porcupine, 540
Porhomma, 406
Porocephalus, 488 n., 495;
P. annulatus, 490, 496;
P. aonycis, 496;
P. armillatus, 496;
P. bifurcatus, 496;
P. clavatus, 496;
P. crocidura, 496;
P. crotali, 496;
P. geckonis, 496;
P. gracilis, 496;
P. heterodontis, 496;
P. indicus, 496;
P. lari, 496;
P. megacephalus, 497;
P. megastomus, 497;
P. moniliformis, 497;
Pompilus, 368
Pontellidae, 60
Pontoporeia, 137;
distribution, 212;
P. affinis, 138;
P. femorata, 138;
P. loyi, 138;
P. microphthalma, 138
Porcellana, 168, 170;
Zoaea, 168;
P. platycheles, 170
Porcellanidae, 170;
habitat, 198
Porcellio, 129
Porcupine, 540
Porhomma, 406
Porocephalus, 488 n., 495;
P. annulatus, 490, 496;
P. aonycis, 496;
P. armillatus, 496;
P. bifurcatus, 496;
P. clavatus, 496;
P. crocidura, 496;
P. crotali, 496;
P. geckonis, 496;
P. gracilis, 496;
P. heterodontis, 496;
P. indicus, 496;
P. lari, 496;
P. megacephalus, 497;
P. megastomus, 497;
P. moniliformis, 497;
Page 689
P. najae sputatricis, 497;
P. oxycephalus, 497;
P. platycephalus, 497;
P. proboscideus, 493, 494;
larvae of, 493, 494;
hosts of, 496;
P. protelis, larva, 495;
P. subuliferus, 497;
P. teretiusculus, 489, 491, 492, 492, 497;
P. tortus, 497
Portunidae, 191
Portunion, 134;
P. maenadis, 134;
life-history, 135, 136
Portunus, 191
Potamobius (= Astacus), 157;
distribution, 213
Potamocarcinus, 191;
distribution, 213
Potamon, 191
Potamonidae, 191
Praniza, larva of Gnathia, 125
Prawn, 151, 153, 158, 164, 198;
fresh-water, 212, 214
Pre-epistome, 443
Prestwichia (Euproöps), 275, 278, 279
Preyer, on anabiosis in Tardigrades, 484
Prionurus, 298, 299
Prismatic eye, of Trilobites, 229
Procurved eyes, 316
P. oxycephalus, 497;
P. platycephalus, 497;
P. proboscideus, 493, 494;
larvae of, 493, 494;
hosts of, 496;
P. protelis, larva, 495;
P. subuliferus, 497;
P. teretiusculus, 489, 491, 492, 492, 497;
P. tortus, 497
Portunidae, 191
Portunion, 134;
P. maenadis, 134;
life-history, 135, 136
Portunus, 191
Potamobius (= Astacus), 157;
distribution, 213
Potamocarcinus, 191;
distribution, 213
Potamon, 191
Potamonidae, 191
Praniza, larva of Gnathia, 125
Prawn, 151, 153, 158, 164, 198;
fresh-water, 212, 214
Pre-epistome, 443
Prestwichia (Euproöps), 275, 278, 279
Preyer, on anabiosis in Tardigrades, 484
Prionurus, 298, 299
Prismatic eye, of Trilobites, 229
Procurved eyes, 316
Page 690
Prodidomidae, 395
Prodidomus, 396
Proëtidae, 251
Proëtus, 251;
P. bohemicus, 248
Prokoenenia, 423;
P. chilensis, 423;
P. wheeleri, 423
Prolimulus, 279
Promesosternite, in Limulus, 264
Proparia, 244
Prosalpia, 450
Prosoma, of Arachnida, 260;
of Limulus, 260, 263;
of Eurypterida, 285;
of Scorpion, 301
Prosthesima, 397
Prostigmata, 471
Protaspis, 239, 239, 240
Proteolepas, 94;
P. bivincta, 94
Protocaris, 243
Protolenus, 247
Protolimulus, 279
Protolycosa anthrocophila, 383
Przibram, on regeneration in Crustacea, 156
Psalidopodidae, 164;
habitat, 204
Prodidomus, 396
Proëtidae, 251
Proëtus, 251;
P. bohemicus, 248
Prokoenenia, 423;
P. chilensis, 423;
P. wheeleri, 423
Prolimulus, 279
Promesosternite, in Limulus, 264
Proparia, 244
Prosalpia, 450
Prosoma, of Arachnida, 260;
of Limulus, 260, 263;
of Eurypterida, 285;
of Scorpion, 301
Prosthesima, 397
Prostigmata, 471
Protaspis, 239, 239, 240
Proteolepas, 94;
P. bivincta, 94
Protocaris, 243
Protolenus, 247
Protolimulus, 279
Protolycosa anthrocophila, 383
Przibram, on regeneration in Crustacea, 156
Psalidopodidae, 164;
habitat, 204
Page 691
Psalidopus, 164
Psalistops, 389
Psechridae, 399
Psechrus, 399
Pseudalibrotus, 137
Pseudidiops, 388
Pseudocuma, 121;
distribution, 215
Pseudocumidae, 121
Pseudoniscus, 279
Pseudopallene, 511, 537;
P. circularis, 540;
P. spinipes, 537 n.
Pseudoscorpiones, 258, 430 f.;
habits, 430;
external structure, 431, 432;
internal structure, 433;
development, 434, 435;
classification, 436;
British species, 438
Pseudo-stigmatic organs, 467
Pseudozoaea, larva of Stomatopod, 143
Pterocuma, 121
Pterolichus, 466
Pteronyssus, 466
Pterygometopus, 249
Pterygotus, 283, 291, 292;
P. osiliensis, 290
Ptychoparia, 247
Psalistops, 389
Psechridae, 399
Psechrus, 399
Pseudalibrotus, 137
Pseudidiops, 388
Pseudocuma, 121;
distribution, 215
Pseudocumidae, 121
Pseudoniscus, 279
Pseudopallene, 511, 537;
P. circularis, 540;
P. spinipes, 537 n.
Pseudoscorpiones, 258, 430 f.;
habits, 430;
external structure, 431, 432;
internal structure, 433;
development, 434, 435;
classification, 436;
British species, 438
Pseudo-stigmatic organs, 467
Pseudozoaea, larva of Stomatopod, 143
Pterocuma, 121
Pterolichus, 466
Pteronyssus, 466
Pterygometopus, 249
Pterygotus, 283, 291, 292;
P. osiliensis, 290
Ptychoparia, 247
Page 692
Pucetia viridis, 419
Pupa, of Cirripedia, 81, 82
Purcellia, 448
Pychnogonides, 501 n.
Pycnogonida, 501 f.;
body, 505;
chelophores, 505;
palpi, 507;
ovigerous legs, 507;
glands, 511;
alimentary system, 513;
circulatory system, 516;
nervous system, 516;
eyes, 517;
integument, 518;
reproductive organs, 519;
eggs, 520;
development, 520;
habits, 524;
systematic position, 525;
classification, 528 f.;
British species, 540 f.
Pycnogonidae, 539
Pycnogonum, 503, 539;
P. australe, 540;
P. crassirostre, 540;
P. littorale, 501, 540, 541;
P. magellanicum, 540;
P. magnirostre, 540;
P. microps, 540;
P. nodulosum, 540;
P. orientale, 540;
P. philippinense, 540;
P. pusillum, 540;
Pupa, of Cirripedia, 81, 82
Purcellia, 448
Pychnogonides, 501 n.
Pycnogonida, 501 f.;
body, 505;
chelophores, 505;
palpi, 507;
ovigerous legs, 507;
glands, 511;
alimentary system, 513;
circulatory system, 516;
nervous system, 516;
eyes, 517;
integument, 518;
reproductive organs, 519;
eggs, 520;
development, 520;
habits, 524;
systematic position, 525;
classification, 528 f.;
British species, 540 f.
Pycnogonidae, 539
Pycnogonum, 503, 539;
P. australe, 540;
P. crassirostre, 540;
P. littorale, 501, 540, 541;
P. magellanicum, 540;
P. magnirostre, 540;
P. microps, 540;
P. nodulosum, 540;
P. orientale, 540;
P. philippinense, 540;
P. pusillum, 540;
Page 693
P. stearnsi, 540
Pygidium, 235
Pylocheles, 180;
P. miersii, 173
Pylochelidae, 180;
habitat, 204
Pylopagurus, 180;
relation to Lithodidae, 177, 178
Pyrgoma, 92
Rachias, 388
Railliet, on classification of Pentastomids, 495
Ranina dentata, 188
Raninidae, 188
Rastellus, 320, 387
Ratania, 68;
mouth, 63
Réaumur, 360
Recurved eyes, 316
Red spider, 455, 472
Red-water, 456
Regeneration, of Crustacean limbs, 155, 156
Regillus, 414
Reichenbach, on embryology of Astacus, 12
Reighardia, 495, 497;
hosts of, 497
Remipes, 171;
R. scutellatus, 171
Pygidium, 235
Pylocheles, 180;
P. miersii, 173
Pylochelidae, 180;
habitat, 204
Pylopagurus, 180;
relation to Lithodidae, 177, 178
Pyrgoma, 92
Rachias, 388
Railliet, on classification of Pentastomids, 495
Ranina dentata, 188
Raninidae, 188
Rastellus, 320, 387
Ratania, 68;
mouth, 63
Réaumur, 360
Recurved eyes, 316
Red spider, 455, 472
Red-water, 456
Regeneration, of Crustacean limbs, 155, 156
Regillus, 414
Reichenbach, on embryology of Astacus, 12
Reighardia, 495, 497;
hosts of, 497
Remipes, 171;
R. scutellatus, 171
Page 694
Remopleurides, 232, 247;
R. radians, 229, 248
Reproduction (incl. Breeding), of Cladocera, 43 f.;
of Anaspides, 116;
of Lobster, 156;
of Limulus, 274;
of Spiders, 365; of Ticks, 461;
of Pycnogons, 520
Reproductive (generative) organs, of Crustacea, 15;
of Phyllopods, 31;
of Cladocera, 43;
of Arachnids, 257;
of Limulus, 271;
of Scorpions, 305;
of Spiders, 333;
of Solifugae, 428;
of Phalangidea, 446;
of Acarina, 461;
of Tardigrada, 482;
of Pentastomida, 492;
of Pycnogons, 519
Respiration, of Crustacea, 16;
of Anaspides, 115;
of Albunea, 170;
of Corystes, 170, 189
of Birgus, 174;
of Oxystomata, 186, 187;
of Catometopa, 194, 195;
of Arachnids, 256.
(See also Respiratory organs.)
Respiratory organs, of Arachnids, 256;
of Limulus, 269, 270;
of Eurypterids, 288;
of Scorpions, 305;
of Spiders, 336;
R. radians, 229, 248
Reproduction (incl. Breeding), of Cladocera, 43 f.;
of Anaspides, 116;
of Lobster, 156;
of Limulus, 274;
of Spiders, 365; of Ticks, 461;
of Pycnogons, 520
Reproductive (generative) organs, of Crustacea, 15;
of Phyllopods, 31;
of Cladocera, 43;
of Arachnids, 257;
of Limulus, 271;
of Scorpions, 305;
of Spiders, 333;
of Solifugae, 428;
of Phalangidea, 446;
of Acarina, 461;
of Tardigrada, 482;
of Pentastomida, 492;
of Pycnogons, 519
Respiration, of Crustacea, 16;
of Anaspides, 115;
of Albunea, 170;
of Corystes, 170, 189
of Birgus, 174;
of Oxystomata, 186, 187;
of Catometopa, 194, 195;
of Arachnids, 256.
(See also Respiratory organs.)
Respiratory organs, of Arachnids, 256;
of Limulus, 269, 270;
of Eurypterids, 288;
of Scorpions, 305;
of Spiders, 336;
Page 695
of Tardigrada, 482;
of Pentastomida, 491.
(See also Respiration.)
Rhagodes, 425, 429
Rhagodinae, 429
Rhax, 429
Rhipicentor, 469
Rhipicephalus, 469;
R. sanguineus, 470
Rhizocephala, 95 f.;
compared with Monstrilla, 66;
with Anelasma, 89;
castration caused by, 100;
males, 106;
association with Entoniscidae, 136
Rhomphaea, 402
Rhopalorhynchus, 532;
R. clavipes, 533;
R. kröyeri, 533;
R. tenuissimus, 533
Rhynchothoracidae, 535
Rhynchothorax, 505, 535;
R. australis, 536;
R. mediterraneus, 508, 535, 536
Ricinulei, 439
Robber-crab, 173
Roncus, 436, 438
Rucker, 423
Rudolphi, on Pentastoma, 488 n.
of Pentastomida, 491.
(See also Respiration.)
Rhagodes, 425, 429
Rhagodinae, 429
Rhax, 429
Rhipicentor, 469
Rhipicephalus, 469;
R. sanguineus, 470
Rhizocephala, 95 f.;
compared with Monstrilla, 66;
with Anelasma, 89;
castration caused by, 100;
males, 106;
association with Entoniscidae, 136
Rhomphaea, 402
Rhopalorhynchus, 532;
R. clavipes, 533;
R. kröyeri, 533;
R. tenuissimus, 533
Rhynchothoracidae, 535
Rhynchothorax, 505, 535;
R. australis, 536;
R. mediterraneus, 508, 535, 536
Ricinulei, 439
Robber-crab, 173
Roncus, 436, 438
Rucker, 423
Rudolphi, on Pentastoma, 488 n.
Page 696
Sabacon, 451
Sabelliphilus, 71
Sacculina, 95;
life-history, 96 f.;
males, 99;
castration caused by, 100 f.;
S. carcini, 96;
S. neglecta, Nauplius, 97;
Cypris, 97;
internal stages, 98;
with parasitic Danalia, 130, 131
Saitis, 421;
S. pulex, 382, 421
Salter, on facial suture of Trinucleus, 226;
on classification of Trilobites, 243
Salticidae, 419
Salticus, 420;
S. scenicus, 372, 376, 420
Sao, 235, 247;
S. hirsuta, development, 239
Sapphirina, 69;
colour, 60;
S. opalina, 69
Sarcoptes, 466;
S. mutans, 466
Sarcoptidae, 455, 466
Sarcoptinae, 466
Sars, G. O., on Calanidae, 58;
on Isopoda, 122;
on Crustacea of the Caspian, 215;
on Pycnogons, 504
Sabelliphilus, 71
Sacculina, 95;
life-history, 96 f.;
males, 99;
castration caused by, 100 f.;
S. carcini, 96;
S. neglecta, Nauplius, 97;
Cypris, 97;
internal stages, 98;
with parasitic Danalia, 130, 131
Saitis, 421;
S. pulex, 382, 421
Salter, on facial suture of Trinucleus, 226;
on classification of Trilobites, 243
Salticidae, 419
Salticus, 420;
S. scenicus, 372, 376, 420
Sao, 235, 247;
S. hirsuta, development, 239
Sapphirina, 69;
colour, 60;
S. opalina, 69
Sarcoptes, 466;
S. mutans, 466
Sarcoptidae, 455, 466
Sarcoptinae, 466
Sars, G. O., on Calanidae, 58;
on Isopoda, 122;
on Crustacea of the Caspian, 215;
on Pycnogons, 504
Page 697
Savigny, 526
Scaeorhynchus, 533
Scalidognathus, 388
Scalpellum, 84, 85;
complemental male, 86;
sex, 86, 105 f.;
S. balanoides, sex, 86;
S. ornatum, sex, 87;
S. peronii, male, 86;
sex, 87, 105;
S. velutinum, sex, 87;
S. vulgare, 85, 86;
male, 83;
sex, 86, 87
Scaphognathite, 152
Scapholeberis, 39, 52;
S. mucronata, 52
Schimkewitsch, 527, 534
Schizochroal eye, 228, 229
Schizonotidae, 310, 312
Schizonotus, 312
Schizopoda, 112;
re-classification, 113;
relation to Macrura, 162
Schizorhynchus, 121
Schmeil, on fresh-water Copepoda, 59, 62
Schultze, on position of Tardigrada, 483
Scipiolus, 535
Sclerocrangon, distribution, 200
Sclerosoma, 450;
Scaeorhynchus, 533
Scalidognathus, 388
Scalpellum, 84, 85;
complemental male, 86;
sex, 86, 105 f.;
S. balanoides, sex, 86;
S. ornatum, sex, 87;
S. peronii, male, 86;
sex, 87, 105;
S. velutinum, sex, 87;
S. vulgare, 85, 86;
male, 83;
sex, 86, 87
Scaphognathite, 152
Scapholeberis, 39, 52;
S. mucronata, 52
Schimkewitsch, 527, 534
Schizochroal eye, 228, 229
Schizonotidae, 310, 312
Schizonotus, 312
Schizopoda, 112;
re-classification, 113;
relation to Macrura, 162
Schizorhynchus, 121
Schmeil, on fresh-water Copepoda, 59, 62
Schultze, on position of Tardigrada, 483
Scipiolus, 535
Sclerocrangon, distribution, 200
Sclerosoma, 450;
Page 698
S. quadridentatum, 450
Sclerosomatinae, 449
Scodra, 390
Scopula, 324, 324, 389 n.
Scorpio, 305, 307;
S. boehmi, 307;
S. maurus, 307
Scorpion, 297 f.
Scorpionidae, 306
Scorpionidea, 258, 297 f.;
habits, 298;
senses, 299;
poison, 299, 301;
mating habits, 300;
external structure, 301;
prosoma, 301;
pre-cheliceral segment, 301;
development of eyes, 301;
mesosoma, 302;
metasoma, 303;
appendages, 303;
pedal spurs, 304, 306, 307, 308;
tibial spurs, 304, 306, 307, 308;
internal anatomy, 304;
alimentary canal, 304;
vascular system, 305;
nervous system, 305;
endosternite, 305;
generative organ, 305;
development of, 305;
classification, 306;
fossil, 298;
resemblance to Eurypterids, 292
Scorpioninae, 306, 307
Sclerosomatinae, 449
Scodra, 390
Scopula, 324, 324, 389 n.
Scorpio, 305, 307;
S. boehmi, 307;
S. maurus, 307
Scorpion, 297 f.
Scorpionidae, 306
Scorpionidea, 258, 297 f.;
habits, 298;
senses, 299;
poison, 299, 301;
mating habits, 300;
external structure, 301;
prosoma, 301;
pre-cheliceral segment, 301;
development of eyes, 301;
mesosoma, 302;
metasoma, 303;
appendages, 303;
pedal spurs, 304, 306, 307, 308;
tibial spurs, 304, 306, 307, 308;
internal anatomy, 304;
alimentary canal, 304;
vascular system, 305;
nervous system, 305;
endosternite, 305;
generative organ, 305;
development of, 305;
classification, 306;
fossil, 298;
resemblance to Eurypterids, 292
Scorpioninae, 306, 307
Page 699
Scorpiops, 308
Scotinoecus, 390
Scott, on fish-parasites, 69 n.
Scourfield, on Cladocera, 51 n.
Scutum, of Spiders, 317, 394;
of Ticks, 469
Scyllarus, 167;
S. arctus, 165, 167
Scytodes thoracica, 393
Scytodidae, 393
Segestria, 395;
S. perfida, 369;
S. senoculata, 395
Segestriinae, 395
Segmentation, of Crustacea, 5 f.;
of Trilobites, 223 f.;
of Arachnida, 256;
of Limulus, 263;
of Pycnogons, 501 f.
Selenopinae, 414
Selenops, 414
Semper, 521 n.
Senoculidae, 418
Senoculus, 418
Sense-organs, of Arachnids, 257;
of Limulus, 271, 272;
of Tardigrada, 482;
of Pentastomida, 491 (see also Auditory organ, Eyes)
Sergestes, 162
Scotinoecus, 390
Scott, on fish-parasites, 69 n.
Scourfield, on Cladocera, 51 n.
Scutum, of Spiders, 317, 394;
of Ticks, 469
Scyllarus, 167;
S. arctus, 165, 167
Scytodes thoracica, 393
Scytodidae, 393
Segestria, 395;
S. perfida, 369;
S. senoculata, 395
Segestriinae, 395
Segmentation, of Crustacea, 5 f.;
of Trilobites, 223 f.;
of Arachnida, 256;
of Limulus, 263;
of Pycnogons, 501 f.
Selenopinae, 414
Selenops, 414
Semper, 521 n.
Senoculidae, 418
Senoculus, 418
Sense-organs, of Arachnids, 257;
of Limulus, 271, 272;
of Tardigrada, 482;
of Pentastomida, 491 (see also Auditory organ, Eyes)
Sergestes, 162
Page 700
Sergestidae, 162;
Zoaea, 161;
distribution, 204
Serolidae, 126
Serolis, 126;
distribution, 200;
S. antarctica, S. bronleyana, S. schytei—eyes, 149
Serrula, 322, 433
Sesarma, 196;
distribution, 213
Setella, 61
Sex, in Crustacea, 100;
in Trilobites, 235
Sexual dimorphism, of Copepoda, 57, 67, 75;
of Inachus, 103;
of Tanaidae, 123;
of Gnathia, 125;
of Prawns, 159;
of Gelasimus, 194;
of Spiders, 379
Sheet-webs, 352
Shell-gland, 13
Shipley, A. E., introduction to Arachnida, 253 f.;
on Xiphosura, 259 f.;
on Tardigrada, 475 f.;
on Pentastomida, 488 f.
Shrimp, 153, 158, 164, 198, 199
Shumardia, 245
Shumardiidae, 245
Sicariidae, 327, 393
Sicarius, 393
Zoaea, 161;
distribution, 204
Serolidae, 126
Serolis, 126;
distribution, 200;
S. antarctica, S. bronleyana, S. schytei—eyes, 149
Serrula, 322, 433
Sesarma, 196;
distribution, 213
Setella, 61
Sex, in Crustacea, 100;
in Trilobites, 235
Sexual dimorphism, of Copepoda, 57, 67, 75;
of Inachus, 103;
of Tanaidae, 123;
of Gnathia, 125;
of Prawns, 159;
of Gelasimus, 194;
of Spiders, 379
Sheet-webs, 352
Shell-gland, 13
Shipley, A. E., introduction to Arachnida, 253 f.;
on Xiphosura, 259 f.;
on Tardigrada, 475 f.;
on Pentastomida, 488 f.
Shrimp, 153, 158, 164, 198, 199
Shumardia, 245
Shumardiidae, 245
Sicariidae, 327, 393
Sicarius, 393
Page 701
Sida, 51;
reproduction, 49;
S. crystallina, 22, 39, 40
Sididae, 51;
appendages, 40;
heart, 43
Siebold, von, 464 n.
Sigilla, 410
Silvestri, 473 n.
Simocephalus, 52;
S. vetulus, 38, 39;
appendages, 41
Simon, 303, 314 n., 326, 385, 386 n., 387, 391 n., 397 n., 400, 401 n., 406,
408 n., 414 n., 418, 431, 433, 449, 452
Singa, 409
Sintula, 406
Siphonostomata, 56
Siriella, 120
Siro, 448
Sironidae, 448
Sitalces, 449
Slimonia, 283, 290, 292;
S. acuminata, 291
Smith, F., 367
Smith, G. on Crustacea, 1 f.
Smith, H., 373
Smith and Kilborne, 456
Snouted Mites, 458, 471
reproduction, 49;
S. crystallina, 22, 39, 40
Sididae, 51;
appendages, 40;
heart, 43
Siebold, von, 464 n.
Sigilla, 410
Silvestri, 473 n.
Simocephalus, 52;
S. vetulus, 38, 39;
appendages, 41
Simon, 303, 314 n., 326, 385, 386 n., 387, 391 n., 397 n., 400, 401 n., 406,
408 n., 414 n., 418, 431, 433, 449, 452
Singa, 409
Sintula, 406
Siphonostomata, 56
Siriella, 120
Siro, 448
Sironidae, 448
Sitalces, 449
Slimonia, 283, 290, 292;
S. acuminata, 291
Smith, F., 367
Smith, G. on Crustacea, 1 f.
Smith, H., 373
Smith and Kilborne, 456
Snouted Mites, 458, 471
Page 702
Solenopleura, 247
Solenysa, 405
Solifugae, 258, 423 f.;
habits, 423;
climbing habits, 425;
doubtfully poisonous, 424;
external structure, 425;
internal structure, 427;
classification, 428
Solpuga, 429;
S. sericea, 425
Solpugae, 423
Solpugidae, 429
Solpuginae, 429
Spallanzani, on desiccation of Tardigrada, 484
Sparassinae, 323, 414
Sparassus, 414
Spencer, on Pentastomida, 489 n., 490
Spermatheca, 15
Spermatophore, 15
Spermatozoa, of Crustacea, 15;
of Malacostraca, 114
Spermophora, 401
Sphaerexochus, 251
Sphaeroma, habitat, 211
Sphaeromidae, 126
Sphaeronella, 76
Sphaerophthalmus, 232, 247;
S. alatus, eye, 228
Solenysa, 405
Solifugae, 258, 423 f.;
habits, 423;
climbing habits, 425;
doubtfully poisonous, 424;
external structure, 425;
internal structure, 427;
classification, 428
Solpuga, 429;
S. sericea, 425
Solpugae, 423
Solpugidae, 429
Solpuginae, 429
Spallanzani, on desiccation of Tardigrada, 484
Sparassinae, 323, 414
Sparassus, 414
Spencer, on Pentastomida, 489 n., 490
Spermatheca, 15
Spermatophore, 15
Spermatozoa, of Crustacea, 15;
of Malacostraca, 114
Spermophora, 401
Sphaerexochus, 251
Sphaeroma, habitat, 211
Sphaeromidae, 126
Sphaeronella, 76
Sphaerophthalmus, 232, 247;
S. alatus, eye, 228
Page 703
Spiders, 314 f.;
external structure, 314, 316, 317;
appendages, 319 f.;
rostrum, 320;
maxilla, 321;
palpal organs, 321;
tarsi, 324;
spinnerets, 325;
stridulating organs, 327, 404;
internal anatomy, 329, 330;
alimentary system, 329;
vascular system, 331;
generative system, 333;
nervous system, 333;
sense-organs, 333;
eyes, 315, 334, 375;
spinning glands, 335;
respiratory organs, 318, 336;
coxal glands, 337;
poison-glands, 337;
ecdysis, 338;
early life, 338;
ballooning habit, 341, 342;
webs, 343 f.;
nests, 354;
cocoons, 358, 358;
commercial use of silk, 359;
poison, 360;
fertility, 365;
cannibalism, 367;
enemies, 368;
protective coloration, 371;
senses, 375 f.;
sight, 375;
hearing, 376;
touch, 334;
intelligence, 377;
external structure, 314, 316, 317;
appendages, 319 f.;
rostrum, 320;
maxilla, 321;
palpal organs, 321;
tarsi, 324;
spinnerets, 325;
stridulating organs, 327, 404;
internal anatomy, 329, 330;
alimentary system, 329;
vascular system, 331;
generative system, 333;
nervous system, 333;
sense-organs, 333;
eyes, 315, 334, 375;
spinning glands, 335;
respiratory organs, 318, 336;
coxal glands, 337;
poison-glands, 337;
ecdysis, 338;
early life, 338;
ballooning habit, 341, 342;
webs, 343 f.;
nests, 354;
cocoons, 358, 358;
commercial use of silk, 359;
poison, 360;
fertility, 365;
cannibalism, 367;
enemies, 368;
protective coloration, 371;
senses, 375 f.;
sight, 375;
hearing, 376;
touch, 334;
intelligence, 377;
Page 704
mating habits, 378;
fossil, 383;
classification, 384 f.
Spinning glands, 335
Spinning Mites, 472
Spiroctenus, 388
Spongicola, 162
Squilla, 141, 141, 142, 143;
S. desmaresti, 141;
S. mantis, 141
Squillidae, 114, 143;
compared with Loricata, 166
Stalita, 395
Stasinopus caffrus, 387
Staurocephalus, 251
Steatoda, 404;
S. bipunctata, 327, 404
Stebbing, on Amphipods, 137;
on Pycnogons, 503 n., 527 n.
Stecker, 447
Stegosoma testudo, 318
Stenochilus, 398
Stenochotheres, 76;
S. egregius, 76, 76
Stenocuma, 121
Stenopodidae, 162
Stenopus, 162
Stenorhynchus, 192, 193
fossil, 383;
classification, 384 f.
Spinning glands, 335
Spinning Mites, 472
Spiroctenus, 388
Spongicola, 162
Squilla, 141, 141, 142, 143;
S. desmaresti, 141;
S. mantis, 141
Squillidae, 114, 143;
compared with Loricata, 166
Stalita, 395
Stasinopus caffrus, 387
Staurocephalus, 251
Steatoda, 404;
S. bipunctata, 327, 404
Stebbing, on Amphipods, 137;
on Pycnogons, 503 n., 527 n.
Stecker, 447
Stegosoma testudo, 318
Stenochilus, 398
Stenochotheres, 76;
S. egregius, 76, 76
Stenocuma, 121
Stenopodidae, 162
Stenopus, 162
Stenorhynchus, 192, 193
Page 705
Stephanopsinae, 414
Stephanopsis, 414
Stiles, on larval Pentastomids, 493, 494
Stomatopoda, 114, 141 f.
Storena, 399
Strabops, 283;
eyes, 290
Strauss-Durckheim, on Limulus, 277
Streblocerus, 53
Streptocephalus, 25, 35;
range of, 34;
S. torvicornis, 35
Stridulating organs, in Arachnids, 257, 327, 327, 404
Stygina, 249
Style, of palpal organ of Spiders, 322
Stylocellus, 448
Stylonurus, 283, 291;
S. lacoanus, 293
Sunaristes paguri, 63
Sun-spiders, 423
Sybota, 410
Sylon, 95;
sex, 99
Symphysurus, 249
Synageles, 421;
S. picata, 366, 373
Synagoga mira, 94
Syncarida, 114
Stephanopsis, 414
Stiles, on larval Pentastomids, 493, 494
Stomatopoda, 114, 141 f.
Storena, 399
Strabops, 283;
eyes, 290
Strauss-Durckheim, on Limulus, 277
Streblocerus, 53
Streptocephalus, 25, 35;
range of, 34;
S. torvicornis, 35
Stridulating organs, in Arachnids, 257, 327, 327, 404
Stygina, 249
Style, of palpal organ of Spiders, 322
Stylocellus, 448
Stylonurus, 283, 291;
S. lacoanus, 293
Sunaristes paguri, 63
Sun-spiders, 423
Sybota, 410
Sylon, 95;
sex, 99
Symphysurus, 249
Synageles, 421;
S. picata, 366, 373
Synagoga mira, 94
Syncarida, 114
Page 706
Synemosyna, 420, 421;
S. formica, 373
Synhomalonotus, 249
Syringophilus, 455, 473
Tachidius brevicornis, 62;
T. littoralis, 62
Tachypleinae, 276
Tachypleus, 276;
T. gigas, 276;
T. hoeveni, 277;
T. tridentatus, 276
Talitridae, 139
Talitrus, 139;
T. sylvaticus, 139;
habitat, 211
Talorchestia, 139
Tanaidae, 122
Tanais, 122
Tanganyika, Lake, prawns of, 212
Tanystylum, 505, 535;
T. orbiculare, 524, 535, 541
Taracus, 451
Tarantella, 361
Tarantism, 361
Tarantula (Spider), 361
Tarantula, 313;
T. reniformis, 312
Tarantulidae, 310, 312
S. formica, 373
Synhomalonotus, 249
Syringophilus, 455, 473
Tachidius brevicornis, 62;
T. littoralis, 62
Tachypleinae, 276
Tachypleus, 276;
T. gigas, 276;
T. hoeveni, 277;
T. tridentatus, 276
Talitridae, 139
Talitrus, 139;
T. sylvaticus, 139;
habitat, 211
Talorchestia, 139
Tanaidae, 122
Tanais, 122
Tanganyika, Lake, prawns of, 212
Tanystylum, 505, 535;
T. orbiculare, 524, 535, 541
Taracus, 451
Tarantella, 361
Tarantism, 361
Tarantula (Spider), 361
Tarantula, 313;
T. reniformis, 312
Tarantulidae, 310, 312
Page 707
Tarantulinae, 313
Tardigrada, 258, 477 f.;
occurrence, 477;
how to capture, 477;
powers of resisting drying up, 484;
classification, 485;
British species, 486, 487
Tarentula, 417
Tarsonemidae, 471
Tartaridae, 312, 527
Tealia, Pycnogonum on, 524
Tegenaria, 416;
T. civilis, 352;
T. domestica, 416;
palp, 321;
T. parietina, 352, 416
Telema tenella, 393
Telson, 6, 7;
of Phyllopoda, 22
Temora longicornis, distribution, 203
Tethys (Mollusca), Pycnogon larva on, 524
Tetrabalius, 312
Tetrablemma, 315, 404;
T. medioculatum, 318
Tetraclita, 91, 92
Tetragnatha, 407;
T. extensa, 372
Tetragnathinae, 407
Tetrameridae, 92
Tetranychinae, 472
Tardigrada, 258, 477 f.;
occurrence, 477;
how to capture, 477;
powers of resisting drying up, 484;
classification, 485;
British species, 486, 487
Tarentula, 417
Tarsonemidae, 471
Tartaridae, 312, 527
Tealia, Pycnogonum on, 524
Tegenaria, 416;
T. civilis, 352;
T. domestica, 416;
palp, 321;
T. parietina, 352, 416
Telema tenella, 393
Telson, 6, 7;
of Phyllopoda, 22
Temora longicornis, distribution, 203
Tethys (Mollusca), Pycnogon larva on, 524
Tetrabalius, 312
Tetrablemma, 315, 404;
T. medioculatum, 318
Tetraclita, 91, 92
Tetragnatha, 407;
T. extensa, 372
Tetragnathinae, 407
Tetrameridae, 92
Tetranychinae, 472
Page 708
Tetranychus, 472;
T. gibbosus, 472;
T. telarius, 455, 472
Tetraspidae, 88
Teutana, 404
Teuthraustes, 308
Texas fever, 456, 470
Thalassinidea, 167
Thamnocephalus, 36;
range of, 34;
T. platyurus, 36
Thanatus, 414;
T. formicinus, 414;
T. hirsutus, 414;
T. striatus, 414
Thaumasia, 416
Thelphusa, 191;
T. fluviatilis, development, 190;
distribution, 213
Thelphusidae, 191
Thelyphonellus, 312
Thelyphonidae, 309, 312
Thelyphonus, 309, 310, 312;
resemblance to Eurypterids, 294
Theotina, 393
Theraphosa, 389;
T. leblondi, 366, 389
Theraphosae, 319
Theraphosidae, 391 n.
T. gibbosus, 472;
T. telarius, 455, 472
Tetraspidae, 88
Teutana, 404
Teuthraustes, 308
Texas fever, 456, 470
Thalassinidea, 167
Thamnocephalus, 36;
range of, 34;
T. platyurus, 36
Thanatus, 414;
T. formicinus, 414;
T. hirsutus, 414;
T. striatus, 414
Thaumasia, 416
Thelphusa, 191;
T. fluviatilis, development, 190;
distribution, 213
Thelphusidae, 191
Thelyphonellus, 312
Thelyphonidae, 309, 312
Thelyphonus, 309, 310, 312;
resemblance to Eurypterids, 294
Theotina, 393
Theraphosa, 389;
T. leblondi, 366, 389
Theraphosae, 319
Theraphosidae, 391 n.
Page 709
Theridiidae, 327, 351, 401
Theridion, 376, 403;
T. bimaculatum, 403;
T. formosum, 403;
T. pallens, cocoon, 358;
T. riparium, 403;
T. sisyphium, 340, 351, 359, 403;
T. tepidariorum, 352, 368, 403
Theridioninae, 403
Theridiosoma argenteolum, 407
Theridiosomatinae, 407
Thersites gasterostei, 71
Thomisidae, 323, 324, 369, 371, 381, 412
Thomisinae, 412
Thomisus, 412;
T. onustus, 413
Thompson, D’A. W., on Pycnogonida, 499 f.
Thoracica, 84
Thorax, of Trilobites, 234
Thorell, 383
Thyas petrophilus, 460
Tibellus, 414;
T. oblongus, 371, 413, 414
Tick fever, 469
Ticks, 468 f.;
habits, 455, 461;
synopsis of genera, 470
Titanodamon, 313
Tityus, 298, 306
Theridion, 376, 403;
T. bimaculatum, 403;
T. formosum, 403;
T. pallens, cocoon, 358;
T. riparium, 403;
T. sisyphium, 340, 351, 359, 403;
T. tepidariorum, 352, 368, 403
Theridioninae, 403
Theridiosoma argenteolum, 407
Theridiosomatinae, 407
Thersites gasterostei, 71
Thomisidae, 323, 324, 369, 371, 381, 412
Thomisinae, 412
Thomisus, 412;
T. onustus, 413
Thompson, D’A. W., on Pycnogonida, 499 f.
Thoracica, 84
Thorax, of Trilobites, 234
Thorell, 383
Thyas petrophilus, 460
Tibellus, 414;
T. oblongus, 371, 413, 414
Tick fever, 469
Ticks, 468 f.;
habits, 455, 461;
synopsis of genera, 470
Titanodamon, 313
Tityus, 298, 306
Page 710
Tmeticus, 406
Tomoxena, 403
Torania, 414
Tracheae, in Arachnida, 256;
in Peripatus, 256;
in Spiders, 336;
in Phalangids, 446;
in Acarina, 462
Trap-door Spiders, 354, 387, 388
Trechona venosa, 390
Triarthrus, 230, 234, 236, 247;
thoracic limb, 10;
T. becki, 237;
Protaspis, 240
Trichoniscus, 129
Trigonoplax, 193
Trilobita, 219 f.
Trilobite larva, of Limulus, 275, 276
Trimerocephalus, 249;
T. volborthi, 229
Trinucleidae, 230, 245
Trinucleus, 225, 226, 230, 231, 236, 238, 245;
T. bucklandi, 230, 231;
T. seticornis, 231
Tripeltis, 312
Trithena tricuspidata, 404
Trithyreus, 312
Triton, cruise of the, 540
Trochantin, 433, 436, 449, 451, 452
Tomoxena, 403
Torania, 414
Tracheae, in Arachnida, 256;
in Peripatus, 256;
in Spiders, 336;
in Phalangids, 446;
in Acarina, 462
Trap-door Spiders, 354, 387, 388
Trechona venosa, 390
Triarthrus, 230, 234, 236, 247;
thoracic limb, 10;
T. becki, 237;
Protaspis, 240
Trichoniscus, 129
Trigonoplax, 193
Trilobita, 219 f.
Trilobite larva, of Limulus, 275, 276
Trimerocephalus, 249;
T. volborthi, 229
Trinucleidae, 230, 245
Trinucleus, 225, 226, 230, 231, 236, 238, 245;
T. bucklandi, 230, 231;
T. seticornis, 231
Tripeltis, 312
Trithena tricuspidata, 404
Trithyreus, 312
Triton, cruise of the, 540
Trochantin, 433, 436, 449, 451, 452
Page 711
Trochosa, 417;
vestigial antennae in, 256, 263
Troglocaris, 163;
T. schmidtii, habitat, 210
Trogulidae, 439, 442, 444, 452
Trogulus, 452;
T. aquaticus, 452;
T. tricarinatus, 452, 453
Trombidiidae, 472
Trombidiinae, 473
Trombidium, 473;
T. gymnopterorum, 455;
T. holosericeum, 455, 473
Tropical zone (marine), 201
Trouessart, 455
Trygaeus, 506, 535;
T. communis, 535
Tubicinella trachealis, 91
Tubularia, Pycnogons on, 522, 525
Tubuliform glands, 335, 349
Tulk, 445, 446, 461 n.
Turret-spider, 357
Turrilepas, 84;
T. wrightianus, 84
Tylaspis, 179
Typhlocarcinus, 195
Typopeltis, 312
Tyroglyphidae, 466 n.
vestigial antennae in, 256, 263
Troglocaris, 163;
T. schmidtii, habitat, 210
Trogulidae, 439, 442, 444, 452
Trogulus, 452;
T. aquaticus, 452;
T. tricarinatus, 452, 453
Trombidiidae, 472
Trombidiinae, 473
Trombidium, 473;
T. gymnopterorum, 455;
T. holosericeum, 455, 473
Tropical zone (marine), 201
Trouessart, 455
Trygaeus, 506, 535;
T. communis, 535
Tubicinella trachealis, 91
Tubularia, Pycnogons on, 522, 525
Tubuliform glands, 335, 349
Tulk, 445, 446, 461 n.
Turret-spider, 357
Turrilepas, 84;
T. wrightianus, 84
Tylaspis, 179
Typhlocarcinus, 195
Typopeltis, 312
Tyroglyphidae, 466 n.
Page 712
Tyroglyphinae, 466
Tyroglyphus, 464, 466, 481;
T. longior, 466;
T. siro, 466
Uliodon, 418
Uloboridae, 350, 410
Uloborinae, 410
Uloborus, 352, 410;
snare of, 352;
U. republicanus, 411;
U. walckenaerius, 411
Unguis, 319, 320
Uroctea, 392;
U. durandi, 392
Urocteidae, 386, 392
Urodacinae, 306, 307
Urodacus, 307
Uroplectes, 306
Uropoda, 471
Uropodinae, 471
Uroproctus, 312
Uropygi, 312
Usofila, 393
Valvifera, 127
Vancoho, 362
Vectius, 415
Tyroglyphus, 464, 466, 481;
T. longior, 466;
T. siro, 466
Uliodon, 418
Uloboridae, 350, 410
Uloborinae, 410
Uloborus, 352, 410;
snare of, 352;
U. republicanus, 411;
U. walckenaerius, 411
Unguis, 319, 320
Uroctea, 392;
U. durandi, 392
Urocteidae, 386, 392
Urodacinae, 306, 307
Urodacus, 307
Uroplectes, 306
Uropoda, 471
Uropodinae, 471
Uroproctus, 312
Uropygi, 312
Usofila, 393
Valvifera, 127
Vancoho, 362
Vectius, 415
Page 713
Vejdovský, 435 n.
Vejovidae, 306, 308
Vejovis, 308
Vermiformia, 464
Verruca, 89, 91
Verrucidae, 91
Vesicle, of Scorpion, 303
Vinson, 349, 360, 362
Virbius, 164;
V. acuminatus, 164;
habitat, 202
Virchow, on human Pentastomids, 494
Viscid globules, on Spider web, 347
Waite, 13
Walckenaer, 365, 386 n., 408 n.
Walckenaera, 405;
W. acuminata, 405
Walcott, on appendages of Trilobites, 236;
on their development, 238;
on early forms of Eurypterids, 283 n.
Wallace, 381
Wall-spider, 369
Warburton, C., on Arachnida, 295 f., 344 n., 349 n., 378 n.
Ward, on Reighardia, 495
Wasps and Spiders, 368
Water-mites, 460, 471, 472
Water-spider, 357, 415
Vejovidae, 306, 308
Vejovis, 308
Vermiformia, 464
Verruca, 89, 91
Verrucidae, 91
Vesicle, of Scorpion, 303
Vinson, 349, 360, 362
Virbius, 164;
V. acuminatus, 164;
habitat, 202
Virchow, on human Pentastomids, 494
Viscid globules, on Spider web, 347
Waite, 13
Walckenaer, 365, 386 n., 408 n.
Walckenaera, 405;
W. acuminata, 405
Walcott, on appendages of Trilobites, 236;
on their development, 238;
on early forms of Eurypterids, 283 n.
Wallace, 381
Wall-spider, 369
Warburton, C., on Arachnida, 295 f., 344 n., 349 n., 378 n.
Ward, on Reighardia, 495
Wasps and Spiders, 368
Water-mites, 460, 471, 472
Water-spider, 357, 415
Page 714
Weismann, on Cladocera, 44, 49
Weldon, W. F. R., on excretory glands, 13;
on Branchiopoda, 18 f.;
on respiration in Carcinus, 189
Westring, 327, 384
Whale-louse, 502
Whip scorpions, 309
White, Gilbert, 342
Wilder, 366
Willemoesia, 157;
W. inornata, 158
Winkler, 463
With, 473 n.
Wolf-spiders, 341, 356, 359, 369, 375, 377, 381, 417
Wood-Mason, 328
Woods, H., on Trilobita, 219 f.;
on fossil Xiphosura, 277 f.;
on Eurypterida, 281 f.
Xanthidae, 191
Xantho, 191;
habitat, 198
Xenobalanus globicipitis, 92
Xiphocaris, 163;
distribution, 210
Xiphosura, 258, 259 f.;
classification, 260, 276;
fossil, 277 f.;
affinities with Eurypterida, 292
Weldon, W. F. R., on excretory glands, 13;
on Branchiopoda, 18 f.;
on respiration in Carcinus, 189
Westring, 327, 384
Whale-louse, 502
Whip scorpions, 309
White, Gilbert, 342
Wilder, 366
Willemoesia, 157;
W. inornata, 158
Winkler, 463
With, 473 n.
Wolf-spiders, 341, 356, 359, 369, 375, 377, 381, 417
Wood-Mason, 328
Woods, H., on Trilobita, 219 f.;
on fossil Xiphosura, 277 f.;
on Eurypterida, 281 f.
Xanthidae, 191
Xantho, 191;
habitat, 198
Xenobalanus globicipitis, 92
Xiphocaris, 163;
distribution, 210
Xiphosura, 258, 259 f.;
classification, 260, 276;
fossil, 277 f.;
affinities with Eurypterida, 292
Page 715
Xiphosura, 276;
X. polyphemus, 276
Xiphosuridae, 276
Xiphosurinae, 276
Xysticus, 412;
X. cristatus, 412;
X. pini, 413
Zacanthoides, 247
Zaeslin, on the frequency of human Pentastomids, 494
Zeriana, 429
Zilla, 409;
Z. x-notata, 359, 409
Zimris, 396
Zoaea, compared with Cumacea, 120;
with Erichthus, 143;
Calyptopis of Euphausia, 144;
of Peneus, 160;
of Sergestidae, 161;
of Porcellana, 169;
of Birgus, 174;
of Eupagurus, 179;
of Corystes cassivelaunus, 182
Zodariidae, 317, 399
Zodarion, 399
Zora, 397;
Z. spinimana, 396
Zoropsis, 415
Zoropsidae, 415
X. polyphemus, 276
Xiphosuridae, 276
Xiphosurinae, 276
Xysticus, 412;
X. cristatus, 412;
X. pini, 413
Zacanthoides, 247
Zaeslin, on the frequency of human Pentastomids, 494
Zeriana, 429
Zilla, 409;
Z. x-notata, 359, 409
Zimris, 396
Zoaea, compared with Cumacea, 120;
with Erichthus, 143;
Calyptopis of Euphausia, 144;
of Peneus, 160;
of Sergestidae, 161;
of Porcellana, 169;
of Birgus, 174;
of Eupagurus, 179;
of Corystes cassivelaunus, 182
Zodariidae, 317, 399
Zodarion, 399
Zora, 397;
Z. spinimana, 396
Zoropsis, 415
Zoropsidae, 415
Page 716
END OF VOL. IV
Printed by R. & R. Clark, Limited, Edinburgh.
1. The muscles are to a certain extent segmented in correspondence with the limbs; and the
heart, in Phyllopoda and Stomatopoda, may have segmentally arranged ostia.
2. Herbst, Arch. Entwick. Mech. ii., 1905, p. 544.
3. Quart. J. Micr. Sci. xlix., 1906, p. 469.
4. Present in Nebalia.
5. As many as 37 ambulatory appendages may be present.
6. Quart. J. Micr. Sci. xxi., 1881, p. 343.
7. Abhandl. Senckenberg. Nat. Gesellsch. xiv., 1886.
8. The Cumacea, Anaspidacea, and certain Isopods possess a maxillary gland only.
9. Quart. J. Micr. Sci. xxxii., 1891, p. 279.
10. Arch. Zool. Exp. (2) x., 1892, p. 57.
11. Bull. Mus. Comp. Zool. Harvard, xxxv., 1899, p. 152.
12. Arch. f. mikr. Anat. lxvii., 1906, p. 364.
13. Vol. x., 1897, pp. 97, 264.
14. For this use of the term Branchiopoda, cf. Boas, Morph. Jahrb. viii., 1883, p. 519.
15. Bernard, “The Apodidae,” Nature Series, 1892.
16. Arb. Zool. Inst. Wien, vi., 1886, p. 267.
17. I do not understand Packard’s account of the telson in Thamnocephalus.
18. The nomenclature here adopted is not that of Lankester.
19. [The red pigment in Lernanthropus, see p. 68, has been shown to be not haemoglobin, so
that the presence of this substance in Phyllopod blood becomes doubtful.—G.S.]
20. Zeitschr. wiss. Zool. lxxi., 1902, p. 508.
21. Cf. Gaskell, Journ. Anat. Physiol. x., 1876, p. 153.
Printed by R. & R. Clark, Limited, Edinburgh.
1. The muscles are to a certain extent segmented in correspondence with the limbs; and the
heart, in Phyllopoda and Stomatopoda, may have segmentally arranged ostia.
2. Herbst, Arch. Entwick. Mech. ii., 1905, p. 544.
3. Quart. J. Micr. Sci. xlix., 1906, p. 469.
4. Present in Nebalia.
5. As many as 37 ambulatory appendages may be present.
6. Quart. J. Micr. Sci. xxi., 1881, p. 343.
7. Abhandl. Senckenberg. Nat. Gesellsch. xiv., 1886.
8. The Cumacea, Anaspidacea, and certain Isopods possess a maxillary gland only.
9. Quart. J. Micr. Sci. xxxii., 1891, p. 279.
10. Arch. Zool. Exp. (2) x., 1892, p. 57.
11. Bull. Mus. Comp. Zool. Harvard, xxxv., 1899, p. 152.
12. Arch. f. mikr. Anat. lxvii., 1906, p. 364.
13. Vol. x., 1897, pp. 97, 264.
14. For this use of the term Branchiopoda, cf. Boas, Morph. Jahrb. viii., 1883, p. 519.
15. Bernard, “The Apodidae,” Nature Series, 1892.
16. Arb. Zool. Inst. Wien, vi., 1886, p. 267.
17. I do not understand Packard’s account of the telson in Thamnocephalus.
18. The nomenclature here adopted is not that of Lankester.
19. [The red pigment in Lernanthropus, see p. 68, has been shown to be not haemoglobin, so
that the presence of this substance in Phyllopod blood becomes doubtful.—G.S.]
20. Zeitschr. wiss. Zool. lxxi., 1902, p. 508.
21. Cf. Gaskell, Journ. Anat. Physiol. x., 1876, p. 153.
Page 717
22. Bernard’s statement that Apus is hermaphrodite seems based on insufficient evidence.
23. Sayce has since described it, Proc. Roy. Soc. Victoria, xv., 1903, p. 229.
24. A. cancriformis had been supposed to have disappeared from the British fauna for many
years, but it was found in Scotland in 1907. See R. Gurney, Nature, lxxvi., 1907, p. 589.
25. Branchipodides has been described by H. Woodward, from Tertiary strata.
26. Consult Baird, “Monograph of the Branchiopodidae,” Proc. Zool. Soc. 1852, p. 18. Packard,
12th Ann. Rep. U.S. Geol. Survey, part i., 1879.
27. Arch. f. Math. og Naturvidensk. xx., 1898, Nos. 4 and 6. Thiele, Zool. Jahrb. System. xiii.,
1900, p. 563.
28. Bernard, loc. cit. p. 19; Baird, Proc. Zool. Soc. 1852, p. 1; Sayce, Proc. Roy. Soc. Victoria,
xv., 1903, p. 224.
29. Sars, Arch. f. Math. og Naturvidensk. xx., 1898, Nos. 4 and 6.
30. Sars, Christiania Vidensk. Forhand. 1887. For Australian Phyllopods, see Sars, Arch. f.
Math. og Naturvid. xvii., 1895, No. 7, and Sayce, loc. cit. p. 36.
31. Simocephalus vetulus anchors itself to weeds, etc., by a modified seta on the exopodite of
the second antenna. It does not employ a dorsal organ for purposes of fixation. [G. S.]
32. Zeitschr. wiss. Zool. xxiv., 1874, p. 1.
33. Zeitschr. wiss. Zool. xxvii., xxxiii., 1876, 1879.
34. Consult Lilljeborg, Nov. Acta Reg. Soc. Upsalensis, 1901; Scourfield, J. Quekett Micr. Club,
1903–4.
35. More properly Chydoridae, but the universally known name Lynceidae is convenient.
36. Grundzüge der Zoologie, 4. Aufl. 1880, p. 543.
37. Fauna and Flora G. v. Neapel, Monograph 19, 1892.
38. Ibid. Monograph 25, 1899.
39. Norwegian North Polar Exp. Sci. Results, vol. i. part v., 1900.
40. They may assist the animal by retarding its sinking. Cf. Chun, “Aus den Tiefen des
Weltmeeres,” 1905.
41. Schmeil, Bibliotheca Zoologica, Hefte 11, 15, and 21.
42. Giesbrecht, Mitth. Zool. Stat. Neap. xi., 1895, p. 648.
43. Loc. cit. p. 59.
44. Claus, Copepodenstudien, 1. Heft, Vienna, 1889.
23. Sayce has since described it, Proc. Roy. Soc. Victoria, xv., 1903, p. 229.
24. A. cancriformis had been supposed to have disappeared from the British fauna for many
years, but it was found in Scotland in 1907. See R. Gurney, Nature, lxxvi., 1907, p. 589.
25. Branchipodides has been described by H. Woodward, from Tertiary strata.
26. Consult Baird, “Monograph of the Branchiopodidae,” Proc. Zool. Soc. 1852, p. 18. Packard,
12th Ann. Rep. U.S. Geol. Survey, part i., 1879.
27. Arch. f. Math. og Naturvidensk. xx., 1898, Nos. 4 and 6. Thiele, Zool. Jahrb. System. xiii.,
1900, p. 563.
28. Bernard, loc. cit. p. 19; Baird, Proc. Zool. Soc. 1852, p. 1; Sayce, Proc. Roy. Soc. Victoria,
xv., 1903, p. 224.
29. Sars, Arch. f. Math. og Naturvidensk. xx., 1898, Nos. 4 and 6.
30. Sars, Christiania Vidensk. Forhand. 1887. For Australian Phyllopods, see Sars, Arch. f.
Math. og Naturvid. xvii., 1895, No. 7, and Sayce, loc. cit. p. 36.
31. Simocephalus vetulus anchors itself to weeds, etc., by a modified seta on the exopodite of
the second antenna. It does not employ a dorsal organ for purposes of fixation. [G. S.]
32. Zeitschr. wiss. Zool. xxiv., 1874, p. 1.
33. Zeitschr. wiss. Zool. xxvii., xxxiii., 1876, 1879.
34. Consult Lilljeborg, Nov. Acta Reg. Soc. Upsalensis, 1901; Scourfield, J. Quekett Micr. Club,
1903–4.
35. More properly Chydoridae, but the universally known name Lynceidae is convenient.
36. Grundzüge der Zoologie, 4. Aufl. 1880, p. 543.
37. Fauna and Flora G. v. Neapel, Monograph 19, 1892.
38. Ibid. Monograph 25, 1899.
39. Norwegian North Polar Exp. Sci. Results, vol. i. part v., 1900.
40. They may assist the animal by retarding its sinking. Cf. Chun, “Aus den Tiefen des
Weltmeeres,” 1905.
41. Schmeil, Bibliotheca Zoologica, Hefte 11, 15, and 21.
42. Giesbrecht, Mitth. Zool. Stat. Neap. xi., 1895, p. 648.
43. Loc. cit. p. 59.
44. Claus, Copepodenstudien, 1. Heft, Vienna, 1889.
Page 718
45. Malaquin, Arch. Zool. Exp. (3), ix., 1901, p. 81.
46. Canu, Trav. Inst. Zool. Litte. vi., 1892.
47. Giesbrecht, Fauna and Flora G. v. Neapel, Monogr. 25, 1899.
48. Arb. Zool. Inst. Wien, ii. 1879, p. 268.
49. Ibid. xv., 1905, p. 1.
50. Heller, Reise der Novara, vol. iii., 1868.
51. For fish-parasites in British waters consult Scott, Fishery Board for Scotland, Scientific
Investigations, xix., 1900 et seq.
52. Canu, loc. cit. p. 66.
53. The Cambridge Museum possesses two specimens of Philichthys xiphiae, from the frontal
bones of a Swordfish (Xiphias gladius) taken off Lowestoft in 1892.
54. Claus, Arb. Zool. Inst. Wien, vii., 1888, p. 281.
55. Proc. Biol. Soc. Liverpool, i., 1887.
56. Zeitschr. wiss. Zool. xlix., 1890, p. 71.
57. The genus Pennella also includes parasites on the whales Hyperoodon and Balaenoptera.
58. Claus, Schriften d. Gesellsch. Marburg. Suppl. 1868.
59. Claus, Zeitschr. wiss. Zool. xi., 1861, p. 287.
60. Hansen, “The Choniostomatidae,” Copenhagen.
61. Claus, Zeitschr. wiss. Zool. xxv., 1875, p. 217.
62. C. B. Wilson, Proc. U.S. Nat. Museum, xxv., 1902, p. 635.
63. Max Müller (Science of Language, 2nd series, p. 534) gives references to a number of old
authors who vouch for the truth of this legend, going back as far as Giraldus Cambrensis in the
twelfth century. The legend appears to be of Scotch or Irish origin. Giraldus complains of the clergy
in Ireland eating Barnacle geese at the time of fasting under the pretext that they are not flesh, but
born of fish living in the sea. The form of the legend varies, certain authors alleging that the geese are
produced from the fruits of a tree which drop into the water, others that they grow in shells
(Barnacles) attached to floating logs. Aldrovandus (De Avibus, T. iii., 1603, p. 174) ingeniously
combines both versions in a woodcut representing undoubted Barnacles growing on a tree with
luxuriant foliage at the water’s edge, below which a number of liberated geese are swimming. Müller
ascribes an etymological origin to the legend, the Barnacle goose (deriv. Hibernicula, bernicula =
Irish goose) being confounded with pernacula, bernacula, a little shell.
64. “A Monograph of the Cirripedia,” vols. i. and ii., Ray Society, 1851, 1853.
65. “Rep. on the Cirripedia, H.M.S. ‘Challenger,’” vols. viii. and x., 1883.
46. Canu, Trav. Inst. Zool. Litte. vi., 1892.
47. Giesbrecht, Fauna and Flora G. v. Neapel, Monogr. 25, 1899.
48. Arb. Zool. Inst. Wien, ii. 1879, p. 268.
49. Ibid. xv., 1905, p. 1.
50. Heller, Reise der Novara, vol. iii., 1868.
51. For fish-parasites in British waters consult Scott, Fishery Board for Scotland, Scientific
Investigations, xix., 1900 et seq.
52. Canu, loc. cit. p. 66.
53. The Cambridge Museum possesses two specimens of Philichthys xiphiae, from the frontal
bones of a Swordfish (Xiphias gladius) taken off Lowestoft in 1892.
54. Claus, Arb. Zool. Inst. Wien, vii., 1888, p. 281.
55. Proc. Biol. Soc. Liverpool, i., 1887.
56. Zeitschr. wiss. Zool. xlix., 1890, p. 71.
57. The genus Pennella also includes parasites on the whales Hyperoodon and Balaenoptera.
58. Claus, Schriften d. Gesellsch. Marburg. Suppl. 1868.
59. Claus, Zeitschr. wiss. Zool. xi., 1861, p. 287.
60. Hansen, “The Choniostomatidae,” Copenhagen.
61. Claus, Zeitschr. wiss. Zool. xxv., 1875, p. 217.
62. C. B. Wilson, Proc. U.S. Nat. Museum, xxv., 1902, p. 635.
63. Max Müller (Science of Language, 2nd series, p. 534) gives references to a number of old
authors who vouch for the truth of this legend, going back as far as Giraldus Cambrensis in the
twelfth century. The legend appears to be of Scotch or Irish origin. Giraldus complains of the clergy
in Ireland eating Barnacle geese at the time of fasting under the pretext that they are not flesh, but
born of fish living in the sea. The form of the legend varies, certain authors alleging that the geese are
produced from the fruits of a tree which drop into the water, others that they grow in shells
(Barnacles) attached to floating logs. Aldrovandus (De Avibus, T. iii., 1603, p. 174) ingeniously
combines both versions in a woodcut representing undoubted Barnacles growing on a tree with
luxuriant foliage at the water’s edge, below which a number of liberated geese are swimming. Müller
ascribes an etymological origin to the legend, the Barnacle goose (deriv. Hibernicula, bernicula =
Irish goose) being confounded with pernacula, bernacula, a little shell.
64. “A Monograph of the Cirripedia,” vols. i. and ii., Ray Society, 1851, 1853.
65. “Rep. on the Cirripedia, H.M.S. ‘Challenger,’” vols. viii. and x., 1883.
Page 719
66. “Monographie des Cirrhipèdes,” Paris, 1905, in which will be found full references to
literature.
67. Arch. Biol. xvi., 1899, p 27.
68. Berndt, Sitzb. Ges. Naturfr. Berlin, 1903, p. 436.
69. Arch. Zool. Exp. viii., 1880, p. 537.
70. Quart. J. Micr. Sci. xxx., 1890, p. 107.
71. Plankton Expedition, ii. G. d. 1899.
72. Y. Delage, Arch. Zool. Exp. (2), ii., 1884, p. 417; G. Smith, Fauna u. Flora G. von Neapel,
Monogr. 29, 1906.
73. G. Smith, Fauna u. Flora d. Golfes v. Neapel, Monogr. xxix., 1906, pp. 60–64, 119–121.
74. Bull. Sc. Dép. Nord (2), 10 Ann. xviii., 1887, p. 1. Ibid. (3), i., 1888, p. 12; and other papers.
75. G. Smith, loc. cit. chap. v. I. scorpio should be I. mauritanicus throughout this Monograph.
76. F. A. Potts, Quart. J. Micr. Sci. l., 1906, p. 599.
77. Faxon, Ann. Mag. Nat. Hist. (5), xiii., 1884, p. 147.
78. G. Smith, Mitth. Zool. Stat. Neapel, xvii., 1905, p. 312.
79. C. L. Boulenger, Proc. Zool. Soc. 1908, p. 42.
80. Garnier, C. R. Soc. Biol. liii., 1901, p. 38.
81. Gruvel, Monographie des Cirrhipèdes, 1905, p. 152.
82. Claus, Untersuchungen zur Erforschung des Crustaceensystems, Wien, 1876. Brady and
Norman, “Monograph of the Marine and Fresh-Water Ostracoda of the N. Atlantic,” Trans. R. Dublin
Soc. (2) iv., 1889, p. 63. Müller, Fauna und Flora G. von Neapel, Monogr. xxi., 1894; “Deutschlands
Süsswasser-Ostracoden,” Chun’s Zoologica, xii., 1900.
83. “The Germ Plasm,” Contemp. Science Series, 1893, p. 345.
84. The term pereiopod is applied to those thoracic limbs which are used in locomotion, and are
not specially differentiated for any other purpose.
85. Claus, Arb. Inst. Wien, viii., 1889, p. 1.
86. Robinson, Quart. J. Micr. Sci. 1., 1906, p. 383.
87. Morphol. Jahrb. viii., 1883, p. 485.
88. Ann. Mag. Nat. Hist. (7), xiii., 1904, p. 144.
literature.
67. Arch. Biol. xvi., 1899, p 27.
68. Berndt, Sitzb. Ges. Naturfr. Berlin, 1903, p. 436.
69. Arch. Zool. Exp. viii., 1880, p. 537.
70. Quart. J. Micr. Sci. xxx., 1890, p. 107.
71. Plankton Expedition, ii. G. d. 1899.
72. Y. Delage, Arch. Zool. Exp. (2), ii., 1884, p. 417; G. Smith, Fauna u. Flora G. von Neapel,
Monogr. 29, 1906.
73. G. Smith, Fauna u. Flora d. Golfes v. Neapel, Monogr. xxix., 1906, pp. 60–64, 119–121.
74. Bull. Sc. Dép. Nord (2), 10 Ann. xviii., 1887, p. 1. Ibid. (3), i., 1888, p. 12; and other papers.
75. G. Smith, loc. cit. chap. v. I. scorpio should be I. mauritanicus throughout this Monograph.
76. F. A. Potts, Quart. J. Micr. Sci. l., 1906, p. 599.
77. Faxon, Ann. Mag. Nat. Hist. (5), xiii., 1884, p. 147.
78. G. Smith, Mitth. Zool. Stat. Neapel, xvii., 1905, p. 312.
79. C. L. Boulenger, Proc. Zool. Soc. 1908, p. 42.
80. Garnier, C. R. Soc. Biol. liii., 1901, p. 38.
81. Gruvel, Monographie des Cirrhipèdes, 1905, p. 152.
82. Claus, Untersuchungen zur Erforschung des Crustaceensystems, Wien, 1876. Brady and
Norman, “Monograph of the Marine and Fresh-Water Ostracoda of the N. Atlantic,” Trans. R. Dublin
Soc. (2) iv., 1889, p. 63. Müller, Fauna und Flora G. von Neapel, Monogr. xxi., 1894; “Deutschlands
Süsswasser-Ostracoden,” Chun’s Zoologica, xii., 1900.
83. “The Germ Plasm,” Contemp. Science Series, 1893, p. 345.
84. The term pereiopod is applied to those thoracic limbs which are used in locomotion, and are
not specially differentiated for any other purpose.
85. Claus, Arb. Inst. Wien, viii., 1889, p. 1.
86. Robinson, Quart. J. Micr. Sci. 1., 1906, p. 383.
87. Morphol. Jahrb. viii., 1883, p. 485.
88. Ann. Mag. Nat. Hist. (7), xiii., 1904, p. 144.
Page 720
89. The lacinia mobilis is a movable tooth-like structure jointed on to the biting face of the
mandible.
90. Trans. Linn. Soc. (2), vi., 1894–1897, p. 285.
91. Trans. Roy. Soc. Edinburgh, xxxviii., 1897, p. 787.
92. G. Smith, Proc. Roy. Soc. 1908.
93. This characteristic is found in the Crustacea elsewhere only in the Argulidae and certain
Euphausiidae.
94. The Victorian Naturalist, xxiv., 1907, p. 117.
95. Challenger Reports, vol. xiii., 1885, p. 55.
96. Sars, “Crustacea of Norway,” iii., 1900.
97. Sars, “Crustacea Caspia,” Bull. Acad. Imp. Sci. St. Pétersbourg, series 4, xxxvi., 1894, and
“Crustacea of Norway,” iii., 1900, p. 120.
98. “Crustacea of Norway,” vol. ii., Isopoda, 1899, in which many references to literature will
be found.
99. Smith, Mitth. Zool. Stat. Neapel, xvii., 1905, p. 312.
100. G. Smith, Mitth. Zool. Stat. Neapel, xvi., 1903, p. 469.
101. Mayer, Mitth. Zool. Stat. Neapel, i., 1879, p. 165.
102. Beddard, Challenger Reports, vol. xi., 1884.
103. Hansen, Quart. J. Micr. Sci. xlix., 1906, p. 69.
104. A useful little book on British Woodlice by Webb and Sillem (1906) may be profitably
consulted. Budde Lund’s Isopoda Terrestria, 1900, is useful to the specialist.
105. The pleopods are traversed by a system of minute tubes called pseudotracheae, somewhat
resembling the tracheae of Insects.
106. Bonnier, Trans. Inst. Zool. Lille, viii., 1900.
107. G. Smith, Fauna and Flora Neapel, Monograph 29, chap. vi.; M. Caullery, Mitth. Zool.
Stat. Neapel, xviii., 1908, p. 583.
108. M. Caullery (loc. cit. p. 130) questions the truth of this observation, but I am convinced of
its accuracy.
109. Trav. Inst. Lille, v., 1887.
110. Chilton, Trans. Linn. Soc. vi., 1894, p. 185.
111. Spenser and Hall, Proc. Roy. Soc. Victoria, ix. p. 12.
mandible.
90. Trans. Linn. Soc. (2), vi., 1894–1897, p. 285.
91. Trans. Roy. Soc. Edinburgh, xxxviii., 1897, p. 787.
92. G. Smith, Proc. Roy. Soc. 1908.
93. This characteristic is found in the Crustacea elsewhere only in the Argulidae and certain
Euphausiidae.
94. The Victorian Naturalist, xxiv., 1907, p. 117.
95. Challenger Reports, vol. xiii., 1885, p. 55.
96. Sars, “Crustacea of Norway,” iii., 1900.
97. Sars, “Crustacea Caspia,” Bull. Acad. Imp. Sci. St. Pétersbourg, series 4, xxxvi., 1894, and
“Crustacea of Norway,” iii., 1900, p. 120.
98. “Crustacea of Norway,” vol. ii., Isopoda, 1899, in which many references to literature will
be found.
99. Smith, Mitth. Zool. Stat. Neapel, xvii., 1905, p. 312.
100. G. Smith, Mitth. Zool. Stat. Neapel, xvi., 1903, p. 469.
101. Mayer, Mitth. Zool. Stat. Neapel, i., 1879, p. 165.
102. Beddard, Challenger Reports, vol. xi., 1884.
103. Hansen, Quart. J. Micr. Sci. xlix., 1906, p. 69.
104. A useful little book on British Woodlice by Webb and Sillem (1906) may be profitably
consulted. Budde Lund’s Isopoda Terrestria, 1900, is useful to the specialist.
105. The pleopods are traversed by a system of minute tubes called pseudotracheae, somewhat
resembling the tracheae of Insects.
106. Bonnier, Trans. Inst. Zool. Lille, viii., 1900.
107. G. Smith, Fauna and Flora Neapel, Monograph 29, chap. vi.; M. Caullery, Mitth. Zool.
Stat. Neapel, xviii., 1908, p. 583.
108. M. Caullery (loc. cit. p. 130) questions the truth of this observation, but I am convinced of
its accuracy.
109. Trav. Inst. Lille, v., 1887.
110. Chilton, Trans. Linn. Soc. vi., 1894, p. 185.
111. Spenser and Hall, Proc. Roy. Soc. Victoria, ix. p. 12.
Page 721
112. “Das Tierreich,” 21, Amphipoda Gammaridea, 1906.
113. Cf. P. Mayer, Fauna u. Flora G. von Neapel, Monogr. vi., 1882; xvii., 1890.
114. Abhandl. königl. Gesellsch. Göttingen, xvi., 1871.
115. Mem. Nat. Acad. Sci. v., 1891.
116. Sars, Challenger Reports, xiii., 1885; Chun, Bibliotheca Zoologica, xix., 1896, p. 139.
117. Die Physiologie der facettierten Augen von Krebsen und Insecten. Leipzig, Wien, 1891.
118. Valdivia Expedition, vol. vi., 1904.
119. Ann. Sci. Nat. (Zool.) (7), xiii., 1892, p. 185.
120. A Naturalist in Indian Seas, 1902.
121. “Atlantis,” Bibliotheca Zoologica, Heft 19, 1896, p. 193.
122. Loc. cit. p. 150.
123. Bell, A History of the British Stalk-eyed Crustacea, 1853; Heller, Die Crustaceen des
Südlichen Europa, 1863.
124. Cf. Claus, Würzburger Naturwiss. Zeitschr. ii., 1861, p. 23.
125. Arch. f. Naturg. vi., 1840, p. 241.
126. Spence Bate’s Challenger Reports.
127. Some of the pereiopods remain biramous in certain Peneidea and Caridea (see p. 163).
128. Bull. U.S. Fish Commission, xv., 1895.
129. Zool. Bulletin, i., 1898, p. 287.
130. Archiv für Entw. Mech. xi., 1901, p. 321.
131. Challenger Reports, xxiv., 1888.
132. Loc. cit. p. 150.
133. Keeble and Gamble, Phil. Trans., Ser. B, cxcvi., 1904, p. 295. The chromatophores are also
directly responsive to light, but the lasting adaptations to colour-backgrounds are brought about
indirectly, the stimulus being transmitted through the eyes and nervous system. The influence of light
may also affect the metabolism of the animal, the chromatophores being accompanied by a ramifying
fatty tissue, which disappears if the animal is kept in the dark.
134. Challenger Reports, xxiv., 1881.
135. Borradaile’s useful paper on the classification of the Decapoda (Ann. Mag. Nat. Hist. (7),
xix., 1907, p. 457) should be consulted for this and other Decapod groups. Also Alcock’s Cat. of the
113. Cf. P. Mayer, Fauna u. Flora G. von Neapel, Monogr. vi., 1882; xvii., 1890.
114. Abhandl. königl. Gesellsch. Göttingen, xvi., 1871.
115. Mem. Nat. Acad. Sci. v., 1891.
116. Sars, Challenger Reports, xiii., 1885; Chun, Bibliotheca Zoologica, xix., 1896, p. 139.
117. Die Physiologie der facettierten Augen von Krebsen und Insecten. Leipzig, Wien, 1891.
118. Valdivia Expedition, vol. vi., 1904.
119. Ann. Sci. Nat. (Zool.) (7), xiii., 1892, p. 185.
120. A Naturalist in Indian Seas, 1902.
121. “Atlantis,” Bibliotheca Zoologica, Heft 19, 1896, p. 193.
122. Loc. cit. p. 150.
123. Bell, A History of the British Stalk-eyed Crustacea, 1853; Heller, Die Crustaceen des
Südlichen Europa, 1863.
124. Cf. Claus, Würzburger Naturwiss. Zeitschr. ii., 1861, p. 23.
125. Arch. f. Naturg. vi., 1840, p. 241.
126. Spence Bate’s Challenger Reports.
127. Some of the pereiopods remain biramous in certain Peneidea and Caridea (see p. 163).
128. Bull. U.S. Fish Commission, xv., 1895.
129. Zool. Bulletin, i., 1898, p. 287.
130. Archiv für Entw. Mech. xi., 1901, p. 321.
131. Challenger Reports, xxiv., 1888.
132. Loc. cit. p. 150.
133. Keeble and Gamble, Phil. Trans., Ser. B, cxcvi., 1904, p. 295. The chromatophores are also
directly responsive to light, but the lasting adaptations to colour-backgrounds are brought about
indirectly, the stimulus being transmitted through the eyes and nervous system. The influence of light
may also affect the metabolism of the animal, the chromatophores being accompanied by a ramifying
fatty tissue, which disappears if the animal is kept in the dark.
134. Challenger Reports, xxiv., 1881.
135. Borradaile’s useful paper on the classification of the Decapoda (Ann. Mag. Nat. Hist. (7),
xix., 1907, p. 457) should be consulted for this and other Decapod groups. Also Alcock’s Cat. of the
Page 722
Indian Mus., “Decapod Crustacea.”
136. Giard and Bonnier, Compt. Rend. Soc. Biol. 1892.
137. Coutière, Fauna and Geogr. Maldive and Laccadive Archipelagos, ii., 1905, p. 852.
138. Keeble and Gamble, Phil. Trans. Ser. B., cxcvi., 1904, p. 295. In the young a constant and
very simple chromatophore-system is present, but in the adult a barred, lined, or monochrome colour-
pattern may be present, which is ultimately induced by the nature of the environment, and does not
subsequently change. In other species of Hippolyte, and in Palaemon and Crangon, only one adult
colour-pattern occurs. Thus H. varians, besides reacting to light by its chromatophores, possesses a
permanent colour-pattern, which is also determined by environment.
139. Claus, Unt. z. Erforschung d. genealog. Grundlage d. Crustaceensystems. Vienna, 1876.
140. Milne Edwards and Bouvier, Ann. Sci. Nat. (7), xvi., 1894, p. 91.
141. Garstang, Quart. J. Micr. Sci. xl., 1897, p. 211.
142. Milne Edwards and Bouvier, Bull. Soc. Philomath. Paris (8), ii., 1889; and Expédition du
Talisman, “Crustacés Décapodes,” 1900.
143. Alcock, loc. cit.; Borradaile, op. cit. p. 162; i. p. 64.
144. Brandt, Bull. Phys. Math. Acad. St. Pétersbourg, i. p. 171, and viii. p. 54; Boas, K. Dansk.
Vidensk. Selskab. Skrift. Naturvid. og Math. Afd. 6, Bd. 2, 1880; Bouvier, Ann. Sci. Nat. (Zool.) (7)
xviii. p. 157.
145. Vol. xxvii. p. 81.
146. Proc. Boston Soc. Nat. Hist., xxxi., 1904, p. 147.
147. For general literature consult Ortmann in Bronn’s Tier-Reich, v. 2, 1901, p. 778. See also
Reports of Challenger, Valdivia, and Talisman Expeditions, etc.
148. Gurney, Quart. J. Micr. Sci. xlvi., 1902, p. 461.
149. Bouvier, Bull. Soc. Philomath. Paris, (8) viii., 1896.
150. Loc. cit. p. 183.
151. M‘Culloch, Rec. Australian Mus. vi. part 5, 1907, p. 353.
152. Lankester, Quart. J. Micr. Sci. xlvii., 1903, p. 439.
153. Garstang, Quart. J. Micr. Sci. xl., 1897, p. 211, and Journ. Mar. Biol. Ass. iv., 1895–97, p.
396.
154. Loc. cit. p. 181.
155. Rep. Brit. Ass. for 1898, p. 887.
156. Naturalist in Indian Seas, 1902.
136. Giard and Bonnier, Compt. Rend. Soc. Biol. 1892.
137. Coutière, Fauna and Geogr. Maldive and Laccadive Archipelagos, ii., 1905, p. 852.
138. Keeble and Gamble, Phil. Trans. Ser. B., cxcvi., 1904, p. 295. In the young a constant and
very simple chromatophore-system is present, but in the adult a barred, lined, or monochrome colour-
pattern may be present, which is ultimately induced by the nature of the environment, and does not
subsequently change. In other species of Hippolyte, and in Palaemon and Crangon, only one adult
colour-pattern occurs. Thus H. varians, besides reacting to light by its chromatophores, possesses a
permanent colour-pattern, which is also determined by environment.
139. Claus, Unt. z. Erforschung d. genealog. Grundlage d. Crustaceensystems. Vienna, 1876.
140. Milne Edwards and Bouvier, Ann. Sci. Nat. (7), xvi., 1894, p. 91.
141. Garstang, Quart. J. Micr. Sci. xl., 1897, p. 211.
142. Milne Edwards and Bouvier, Bull. Soc. Philomath. Paris (8), ii., 1889; and Expédition du
Talisman, “Crustacés Décapodes,” 1900.
143. Alcock, loc. cit.; Borradaile, op. cit. p. 162; i. p. 64.
144. Brandt, Bull. Phys. Math. Acad. St. Pétersbourg, i. p. 171, and viii. p. 54; Boas, K. Dansk.
Vidensk. Selskab. Skrift. Naturvid. og Math. Afd. 6, Bd. 2, 1880; Bouvier, Ann. Sci. Nat. (Zool.) (7)
xviii. p. 157.
145. Vol. xxvii. p. 81.
146. Proc. Boston Soc. Nat. Hist., xxxi., 1904, p. 147.
147. For general literature consult Ortmann in Bronn’s Tier-Reich, v. 2, 1901, p. 778. See also
Reports of Challenger, Valdivia, and Talisman Expeditions, etc.
148. Gurney, Quart. J. Micr. Sci. xlvi., 1902, p. 461.
149. Bouvier, Bull. Soc. Philomath. Paris, (8) viii., 1896.
150. Loc. cit. p. 183.
151. M‘Culloch, Rec. Australian Mus. vi. part 5, 1907, p. 353.
152. Lankester, Quart. J. Micr. Sci. xlvii., 1903, p. 439.
153. Garstang, Quart. J. Micr. Sci. xl., 1897, p. 211, and Journ. Mar. Biol. Ass. iv., 1895–97, p.
396.
154. Loc. cit. p. 181.
155. Rep. Brit. Ass. for 1898, p. 887.
156. Naturalist in Indian Seas, 1902.
Page 723
157. There appears to be some doubt on this point, as Westwood (see p. 153) described direct
development in a Gecarcinus. Possibly different species behave variously.
158. Kingsley, Proc. Acad. Nat. Sci. Philadelphia, 1880, p. 187.
159. American Naturalist, xxxiii., 1899, p. 583.
160. Planktonstudien, Jena, 1890.
161. “Report on the Plankton,” Internat. Inst. Marine Biol. 1903.
162. Internat. Inst. Mar. Biol. 1903.
163. A Naturalist in Indian Seas.
164. Scourfield, J. Quekett Micr. Club, 1903–4, gives a useful list of British Fresh-water
Entomostraca. For the identification of fresh-water Cladocera, Lilljeborg’s “Cladocera Sueciae,” Nov.
Act. Reg. Soc. Upsalensis, 1901; for Copepoda, Schmeil’s “Süsswasser Copepoden,” in Bibliotheca
Zoologica, iv., v., and viii., 1892, 1893, and 1895 are recommended.
165. Trans. Norfolk and Norwich Nat. Soc. vii.
166. Le Lac Leman, 3 vols., Lausanne, 1892.
167. Consult Apstein, “Das Süsswasserplankton,” Kiel and Leipzig, 1896; and Arch. f.
Hydrobiologie u. Planktonkunde, numerous papers.
168. Mr. C. H. Martin points out to me that in the Scottish lochs, which from their geological
nature are evidently not connected with subterranean waters, none of them nor similar forms occur;
nor do they in the Tasmanian lakes which are on igneous diabase, so that Forel’s conclusion would
seem to be of wide application.
169. See Chilton, Trans. Linn. Soc. (2) vi., 1894, p. 163, with review of literature.
170. S. F. Harmer, Trans. Norfolk and Norwich Nat. Soc. ii., 1899, p. 489.
171. Mem. Nat. Acad. Washington, iii., 1886, p. 1.
172. Arch. Zool. Exp. (4), ii., 1904, p. 1.
173. See Calman, Proc. Zool. Soc. 1906, p. 187.
174. The Crayfish, Internat. Scient. Series.
175. Mem. Harvard. Mus. x., 1885.
176. Proc. Amer. Phil. Soc. xli., 1902, p. 267, and xliv., 1905, p. 91.
177. G. O. Sars, “Crustacea Caspia,” Bull. Acad. Imp. Sc. St. Pétersbourg (4), xxxvi., 1893–4,
pp. 51 and 297; (5) i., 1894, pp. 179 and 243; also Crustacea of Norway, vol. ii. Isopoda, 1900, p. 73.
178. Daday, Termés Füzetek, xxv., 1902, pp. 101 and 436.
development in a Gecarcinus. Possibly different species behave variously.
158. Kingsley, Proc. Acad. Nat. Sci. Philadelphia, 1880, p. 187.
159. American Naturalist, xxxiii., 1899, p. 583.
160. Planktonstudien, Jena, 1890.
161. “Report on the Plankton,” Internat. Inst. Marine Biol. 1903.
162. Internat. Inst. Mar. Biol. 1903.
163. A Naturalist in Indian Seas.
164. Scourfield, J. Quekett Micr. Club, 1903–4, gives a useful list of British Fresh-water
Entomostraca. For the identification of fresh-water Cladocera, Lilljeborg’s “Cladocera Sueciae,” Nov.
Act. Reg. Soc. Upsalensis, 1901; for Copepoda, Schmeil’s “Süsswasser Copepoden,” in Bibliotheca
Zoologica, iv., v., and viii., 1892, 1893, and 1895 are recommended.
165. Trans. Norfolk and Norwich Nat. Soc. vii.
166. Le Lac Leman, 3 vols., Lausanne, 1892.
167. Consult Apstein, “Das Süsswasserplankton,” Kiel and Leipzig, 1896; and Arch. f.
Hydrobiologie u. Planktonkunde, numerous papers.
168. Mr. C. H. Martin points out to me that in the Scottish lochs, which from their geological
nature are evidently not connected with subterranean waters, none of them nor similar forms occur;
nor do they in the Tasmanian lakes which are on igneous diabase, so that Forel’s conclusion would
seem to be of wide application.
169. See Chilton, Trans. Linn. Soc. (2) vi., 1894, p. 163, with review of literature.
170. S. F. Harmer, Trans. Norfolk and Norwich Nat. Soc. ii., 1899, p. 489.
171. Mem. Nat. Acad. Washington, iii., 1886, p. 1.
172. Arch. Zool. Exp. (4), ii., 1904, p. 1.
173. See Calman, Proc. Zool. Soc. 1906, p. 187.
174. The Crayfish, Internat. Scient. Series.
175. Mem. Harvard. Mus. x., 1885.
176. Proc. Amer. Phil. Soc. xli., 1902, p. 267, and xliv., 1905, p. 91.
177. G. O. Sars, “Crustacea Caspia,” Bull. Acad. Imp. Sc. St. Pétersbourg (4), xxxvi., 1893–4,
pp. 51 and 297; (5) i., 1894, pp. 179 and 243; also Crustacea of Norway, vol. ii. Isopoda, 1900, p. 73.
178. Daday, Termés Füzetek, xxv., 1902, pp. 101 and 436.
Page 724
179. Daday, Bibliotheca Zoologica, Heft 44, 1905.
180. On the cheek the furrow represents a pleural groove, and does not form the limit of the
posterior cephalic segment.
181. M‘Coy, Synop. Sil. Foss. Ireland, 1846, p. 56, and Brit. Pal. Foss., 1851, p. 146, pl. 1 E,
fig. 16; Salter, Quart. Journ. Geol. Soc. iii., 1847, p. 251.
182. Figures showing this suture are given by Oehlert, Bull. Soc. géol. de France (3), xxiii.,
1895, pl. 1, figs. 9, 12, 15.
183. Ann. Mag. Nat. Hist. (2) iv., 1849, p. 396.
184. Lindström, “Visual Organs of Trilobites,” Svenska Vet. Akad. Handl. xxxiv., 1903. Exner,
Physiol. d. facett. Augen v. Krebsen u. Insecten, 1891, p. 34, pl. ii. figs. 18, 19.
185. Journ. Morphol. ii., 1889, p. 253, pl. 21.
186. Watase, Johns Hopkins Univ. Studies, Biol. Lab. iv., 1890, p. 290. Lindström, op. cit. p. 27.
187. A suture is said to be present at the external margin of the flattened cephalic border.
188. Goldfuss, “Beitr. zur Petrefaktenkunde,” 1839, p. 359, pl. 33, fig. 2d.
189. Spencer, Geol. Mag. 1903, p. 489.
190. For an example of this see Salter, Mon. Brit. Trilobites, 1864–83, pls. 15, 16.
191. Bull. Mus. Comp. Zool. Harvard, viii., 1881, p. 191.
192. Studies in Evolution, 1901, pp. 197–225; Geol. Mag. 1902, p. 152. Walcott, Proc. Biol. Soc.
Washington, ix., 1894, p. 89.
193. Syst. Sil. Bohême, i., 1852, pp. 257–276.
194. American Geologist, xx., 1897, p. 34.
195. Proc. R. Irish Acad. xxiv., 1903, p. 332, and Quart. Journ. Micr. Sci. xlix., 1906, p. 469.
196. This has received some support from H. Milne Edwards, Ann. Sci. Nat. Zool. (6), xii.,
1881, p. 33; H. Woodward, Quart. Journ. Geol. Soc. xxvi., 1870, p. 487, and vol. 1., 1894, p. 433;
Bernard, ibid. vol. 1. p. 432.
197. Kingsley does not admit this relationship, and regards the Trilobita as a group quite distinct
from all other Crustacea. See American Naturalist, xxviii., 1894, p. 118, and American Geologist,
xx., 1897, p. 33.
198. Zittel states that Apus appears first in the Trias.
199. Monogr. Brit. Trilobites, 1864, p. 2.
200. “A Natural Classification of Trilobites,” Amer. Jour. Sci. (4), iii., 1897, pp. 89–106, 181–
207. Reprinted in Beecher’s Studies in Evolution, 1901, p. 109. A classification based on the
180. On the cheek the furrow represents a pleural groove, and does not form the limit of the
posterior cephalic segment.
181. M‘Coy, Synop. Sil. Foss. Ireland, 1846, p. 56, and Brit. Pal. Foss., 1851, p. 146, pl. 1 E,
fig. 16; Salter, Quart. Journ. Geol. Soc. iii., 1847, p. 251.
182. Figures showing this suture are given by Oehlert, Bull. Soc. géol. de France (3), xxiii.,
1895, pl. 1, figs. 9, 12, 15.
183. Ann. Mag. Nat. Hist. (2) iv., 1849, p. 396.
184. Lindström, “Visual Organs of Trilobites,” Svenska Vet. Akad. Handl. xxxiv., 1903. Exner,
Physiol. d. facett. Augen v. Krebsen u. Insecten, 1891, p. 34, pl. ii. figs. 18, 19.
185. Journ. Morphol. ii., 1889, p. 253, pl. 21.
186. Watase, Johns Hopkins Univ. Studies, Biol. Lab. iv., 1890, p. 290. Lindström, op. cit. p. 27.
187. A suture is said to be present at the external margin of the flattened cephalic border.
188. Goldfuss, “Beitr. zur Petrefaktenkunde,” 1839, p. 359, pl. 33, fig. 2d.
189. Spencer, Geol. Mag. 1903, p. 489.
190. For an example of this see Salter, Mon. Brit. Trilobites, 1864–83, pls. 15, 16.
191. Bull. Mus. Comp. Zool. Harvard, viii., 1881, p. 191.
192. Studies in Evolution, 1901, pp. 197–225; Geol. Mag. 1902, p. 152. Walcott, Proc. Biol. Soc.
Washington, ix., 1894, p. 89.
193. Syst. Sil. Bohême, i., 1852, pp. 257–276.
194. American Geologist, xx., 1897, p. 34.
195. Proc. R. Irish Acad. xxiv., 1903, p. 332, and Quart. Journ. Micr. Sci. xlix., 1906, p. 469.
196. This has received some support from H. Milne Edwards, Ann. Sci. Nat. Zool. (6), xii.,
1881, p. 33; H. Woodward, Quart. Journ. Geol. Soc. xxvi., 1870, p. 487, and vol. 1., 1894, p. 433;
Bernard, ibid. vol. 1. p. 432.
197. Kingsley does not admit this relationship, and regards the Trilobita as a group quite distinct
from all other Crustacea. See American Naturalist, xxviii., 1894, p. 118, and American Geologist,
xx., 1897, p. 33.
198. Zittel states that Apus appears first in the Trias.
199. Monogr. Brit. Trilobites, 1864, p. 2.
200. “A Natural Classification of Trilobites,” Amer. Jour. Sci. (4), iii., 1897, pp. 89–106, 181–
207. Reprinted in Beecher’s Studies in Evolution, 1901, p. 109. A classification based on the
Page 725
character of the pygidium has been proposed by Gürich, Centralbl. für Min. Geol. u. Pal. 1907, p.
129. A classification based on the minute structure of the test has been given by Lorenz, Zeitschr. d.
deutsch. geol. Gesellsch. lviii., 1906, p. 56.
201. Neues Jahrb. für Min. Geol. u. Pal. 1898, i. p. 187.
202. Lake, Brit. Cambrian Tril. 1907, p. 45.
203. The British Carboniferous Proëtidae are described by H. Woodward, Monogr. Brit. Carb.
Trilobites, Palaeont. Soc. 1883–84.
204. This can be maintained in the Crustacea by counting the seventh abdominal segment,
which appears in Gnathophausia; but this is not universally regarded as a true segment. See also
Nebalia (p. 111).
205. This and the following Sub-class correspond with Lankester’s Sub-class Euarachnida. The
Delobranchiata have gills patent and exposed, and adapted for breathing oxygen dissolved in water.
The Embolobranchiata have either the gill-books (now termed lung-books) sunk into their body, or
the gill-books are wholly or partially replaced by tracheae. In either case the members of this Sub-
class breathe atmospheric oxygen.
206. Woodward, “On some Points in the Structure of the Xiphosura, having reference to their
relationship with the Eurypteridae,” Quart. J. Geol. Soc. xxiii., 1867, p. 28, and xxviii., 1871, p. 46.
Milne Edwards, A., “Recherches sur l’anat. des Limules,” Ann. Sci. Nat. (5), xvii., 1873, Art. 4.
Lankester, E. R., “Limulus an Arachnid,” Quart. J. Micr. Sci. xxi., 1881, p. 504. Kingsley, J. S., “The
Embryology of Limulus,” Journ. Morph. vii. p. 35, and viii. p. 195, 1892–3. Kishinouye, “On the
Development of Limulus longispina,” Journ. Coll. Sci. Japan, v., 1892, p. 53. Patten, W., and
Redenbaugh, W. A., “Studies on Limulus,” Journ. Morph. xvi., 1900, pp. 1, 91.
207. Quart. J. Micr. Sci. xlviii., 1905, p. 165.
208. μηρός = a thigh.
209. This segment, though present in embryo Scorpions, has disappeared in the adults of those
animals.
210. Quart. J. Micr. Sci. xlix., 1906, p. 469.
211. Zool. Anz. xiv., 1891, pp. 164, 173.
212. Zeitschr. wiss. Zool. lix., 1895, p. 351.
213. They are described in great detail in Lankester’s article, “Limulus an Arachnid,” Quart. J.
Micr. Sci. xxi., 1881, p. 504.
214. Tr. Linn. Soc. xxviii., 1872, p. 471.
215. Tr. Linn. Soc. xxviii., 1872, p. 472.
216. A rudimentary ninth pair of ostia are described anteriorly.
217. J. Morph. vii., 1892, p. 35.
129. A classification based on the minute structure of the test has been given by Lorenz, Zeitschr. d.
deutsch. geol. Gesellsch. lviii., 1906, p. 56.
201. Neues Jahrb. für Min. Geol. u. Pal. 1898, i. p. 187.
202. Lake, Brit. Cambrian Tril. 1907, p. 45.
203. The British Carboniferous Proëtidae are described by H. Woodward, Monogr. Brit. Carb.
Trilobites, Palaeont. Soc. 1883–84.
204. This can be maintained in the Crustacea by counting the seventh abdominal segment,
which appears in Gnathophausia; but this is not universally regarded as a true segment. See also
Nebalia (p. 111).
205. This and the following Sub-class correspond with Lankester’s Sub-class Euarachnida. The
Delobranchiata have gills patent and exposed, and adapted for breathing oxygen dissolved in water.
The Embolobranchiata have either the gill-books (now termed lung-books) sunk into their body, or
the gill-books are wholly or partially replaced by tracheae. In either case the members of this Sub-
class breathe atmospheric oxygen.
206. Woodward, “On some Points in the Structure of the Xiphosura, having reference to their
relationship with the Eurypteridae,” Quart. J. Geol. Soc. xxiii., 1867, p. 28, and xxviii., 1871, p. 46.
Milne Edwards, A., “Recherches sur l’anat. des Limules,” Ann. Sci. Nat. (5), xvii., 1873, Art. 4.
Lankester, E. R., “Limulus an Arachnid,” Quart. J. Micr. Sci. xxi., 1881, p. 504. Kingsley, J. S., “The
Embryology of Limulus,” Journ. Morph. vii. p. 35, and viii. p. 195, 1892–3. Kishinouye, “On the
Development of Limulus longispina,” Journ. Coll. Sci. Japan, v., 1892, p. 53. Patten, W., and
Redenbaugh, W. A., “Studies on Limulus,” Journ. Morph. xvi., 1900, pp. 1, 91.
207. Quart. J. Micr. Sci. xlviii., 1905, p. 165.
208. μηρός = a thigh.
209. This segment, though present in embryo Scorpions, has disappeared in the adults of those
animals.
210. Quart. J. Micr. Sci. xlix., 1906, p. 469.
211. Zool. Anz. xiv., 1891, pp. 164, 173.
212. Zeitschr. wiss. Zool. lix., 1895, p. 351.
213. They are described in great detail in Lankester’s article, “Limulus an Arachnid,” Quart. J.
Micr. Sci. xxi., 1881, p. 504.
214. Tr. Linn. Soc. xxviii., 1872, p. 471.
215. Tr. Linn. Soc. xxviii., 1872, p. 472.
216. A rudimentary ninth pair of ostia are described anteriorly.
217. J. Morph. vii., 1892, p. 35.
Page 726
218. Kingsley, loc. cit.
219. J. Coll. Tokyo, v., 1893, p. 53.
220. Lockwood, Amer. Nat. iv., 1870–71, p. 261.
221. For a diagnosis of the species and a list of synonyms, see Pocock, Ann. Mag. Nat. Hist. (7),
ix., 1902, p. 256.
222. Quart. J. Micr. Sci. xxxi., 1890, p. 379; Proc. Cambr. Phil. Soc. ix., 1895–1898, p. 19; J.
Anat. Physiol. xxxiii., 1899, p. 154.
223. Quart. J. Micr. Sci. xxxi., 1890, p. 317.
224. I am indebted to Mr. Henry Woods for these paragraphs on fossil Xiphosura.
225. The British fossil forms of this group are described and figured by H. Woodward,
“Monograph of the Merostomata,” Palaeontogr. Soc. 1866–78, and Geol. Mag. 1907, p. 539.
226. Packard, “Carb. Xiphos. N. America,” Mem. Nat. Acad. Sci. Washington, iii., 1885, p. 146,
pl. vi. fig. 1a, pl. v. fig. 3a (restoration). Williams, Amer. Journ. Sci. (3), xxx., 1885, p. 45. Fritsch,
Fauna d. Gaskohle, iv., 1901, p. 64, pl. 155, figs. 1–3, and text-figures, 369, 370.
227. Walcott has described, under the generic name Beltina, imperfect specimens from the
Algonkian (pre-Cambrian) of Montana, which he thinks may be the remains of Eurypterids (Bull.
Geol. Soc. America, x., 1899, p. 238).
228. Walcott, Amer. Jour. Sci. (3), xxiii., 1882, p. 213.
229. Descriptions and figures of British Eurypterids are given in the following works:—Huxley
and Salter, “Pterygotus,” Mem. Geol. Survey, Brit. Org. Remains, i., 1859; H. Woodward,
“Monograph of the Merostomata,” Palaeont. Soc. 1866–78, and Geol. Mag. 1879, p. 196; 1887, p.
481; 1888, p. 419; 1907, p. 277; Peach, Trans. Roy. Soc. Edinb. xxx., 1882, p. 511; Laurie, ibid.
xxxvii., 1892, p. 151; xxxvii., 1893, p. 509; and xxxix., 1899, p. 575.
230. A detailed account of Eurypterus fischeri has been given by G. Holm, Mém. Acad. Impér.
Sci. St. Pétersbourg (8), viii. 2, 1898. See also F. Schmidt, ibid. (7), xxxi. 5, 1883. Descriptions of
American forms of Eurypterus are given by Hall, “Nat. Hist. New York,” Palaeont. iii., 1859, p. 395;
ibid. vii., 1888, p, 156; and Second Geol. Survey Pennsylvania, “Report of Progress,” PPP., 1884;
Whiteaves, Geol. and Nat. Hist. Surv. Canada, “Palaeozoic Foss.,” iii., 1884, p. 42.
231. It was this ornamentation found on fragments of Pterygotus anglicus which led the Scotch
quarrymen to apply the name “Seraphim” to that Eurypterid. On this subject Hugh Miller writes:
“The workmen in the quarries in which they occur, finding form without body, and struck by the
resemblance which the delicately waved scales bear to the sculptured markings on the wings of
cherubs—of all subjects of the chisel the most common—fancifully termed them ‘Seraphim’” (The
Old Red Sandstone, ed. 6, 1855, p. 180).
232. The third leg in the male possesses on the fifth joint a curved appendage which extends
backwards to the proximal end of the second joint. This structure may have been a clasping organ.
219. J. Coll. Tokyo, v., 1893, p. 53.
220. Lockwood, Amer. Nat. iv., 1870–71, p. 261.
221. For a diagnosis of the species and a list of synonyms, see Pocock, Ann. Mag. Nat. Hist. (7),
ix., 1902, p. 256.
222. Quart. J. Micr. Sci. xxxi., 1890, p. 379; Proc. Cambr. Phil. Soc. ix., 1895–1898, p. 19; J.
Anat. Physiol. xxxiii., 1899, p. 154.
223. Quart. J. Micr. Sci. xxxi., 1890, p. 317.
224. I am indebted to Mr. Henry Woods for these paragraphs on fossil Xiphosura.
225. The British fossil forms of this group are described and figured by H. Woodward,
“Monograph of the Merostomata,” Palaeontogr. Soc. 1866–78, and Geol. Mag. 1907, p. 539.
226. Packard, “Carb. Xiphos. N. America,” Mem. Nat. Acad. Sci. Washington, iii., 1885, p. 146,
pl. vi. fig. 1a, pl. v. fig. 3a (restoration). Williams, Amer. Journ. Sci. (3), xxx., 1885, p. 45. Fritsch,
Fauna d. Gaskohle, iv., 1901, p. 64, pl. 155, figs. 1–3, and text-figures, 369, 370.
227. Walcott has described, under the generic name Beltina, imperfect specimens from the
Algonkian (pre-Cambrian) of Montana, which he thinks may be the remains of Eurypterids (Bull.
Geol. Soc. America, x., 1899, p. 238).
228. Walcott, Amer. Jour. Sci. (3), xxiii., 1882, p. 213.
229. Descriptions and figures of British Eurypterids are given in the following works:—Huxley
and Salter, “Pterygotus,” Mem. Geol. Survey, Brit. Org. Remains, i., 1859; H. Woodward,
“Monograph of the Merostomata,” Palaeont. Soc. 1866–78, and Geol. Mag. 1879, p. 196; 1887, p.
481; 1888, p. 419; 1907, p. 277; Peach, Trans. Roy. Soc. Edinb. xxx., 1882, p. 511; Laurie, ibid.
xxxvii., 1892, p. 151; xxxvii., 1893, p. 509; and xxxix., 1899, p. 575.
230. A detailed account of Eurypterus fischeri has been given by G. Holm, Mém. Acad. Impér.
Sci. St. Pétersbourg (8), viii. 2, 1898. See also F. Schmidt, ibid. (7), xxxi. 5, 1883. Descriptions of
American forms of Eurypterus are given by Hall, “Nat. Hist. New York,” Palaeont. iii., 1859, p. 395;
ibid. vii., 1888, p, 156; and Second Geol. Survey Pennsylvania, “Report of Progress,” PPP., 1884;
Whiteaves, Geol. and Nat. Hist. Surv. Canada, “Palaeozoic Foss.,” iii., 1884, p. 42.
231. It was this ornamentation found on fragments of Pterygotus anglicus which led the Scotch
quarrymen to apply the name “Seraphim” to that Eurypterid. On this subject Hugh Miller writes:
“The workmen in the quarries in which they occur, finding form without body, and struck by the
resemblance which the delicately waved scales bear to the sculptured markings on the wings of
cherubs—of all subjects of the chisel the most common—fancifully termed them ‘Seraphim’” (The
Old Red Sandstone, ed. 6, 1855, p. 180).
232. The third leg in the male possesses on the fifth joint a curved appendage which extends
backwards to the proximal end of the second joint. This structure may have been a clasping organ.
Page 727
233. It has been suggested that the metastoma really belongs to a pregenital segment of the
mesosoma which is absent in the adult, but has been found in the embryo of Scorpions.
234. Sarle, New York State Museum, Bulletin 69, Palaeont. 9, 1903, p. 1087.
235. Beecher, Geol. Mag. 1901, p. 561.
236. Peach, Nature, xxxi., 1885, p. 295; Pocock, Quart. Journ. Micr. Sci. xliv., 1901, p. 291;
Laurie, Trans. Roy. Soc. Edinb. xxxix., 1899, p. 575.
237. Peach, Trans. Roy. Soc. Edinb. xxx., 1882, p. 516.
238. Cf. p. 258.
239. Nature, xlviii., 1893, p. 104.
240. Souvenirs entomologiques, Sér. 9, 1907, p. 229.
241. Brauer, Zeitschr. wiss. Zool. lix., 1895, p. 355.
242. Das Tierreich, 8. Lief., 1899, p. 4.
243. Arachnides de France, vii., 1879, p. 84.
244. Fauna of British India, “Arachnida,” 1900, p. 8.
245. Tr. Zool. Soc. xi. part x., 1885, p. 373.
246. Zeitschr. wiss. Zool. lix., 1895, p. 351.
247. Das Tierreich, 8. Lief., 1899.
248. Pocock, Fauna of British India, “Arachnida.” London, 1900.
249. Laurie, J. Linn. Soc. Zool. xxv., 1894, p. 30.
250. See M. Laurie in J. Linn. Soc. Zool. xxv., 1894, p. 20.
251. Tr. Linn. Soc. (2) vi., 1896, p. 344.
252. Bernard, loc. cit. p. 366.
253. J. Linn. Soc. xxv., 1894, p. 29.
254. See Pocock, Ann. Nat. Hist. (6), xiv., 1894, p. 120.
255. Kraepelin, Das Tierreich, Berlin, 8. Lief., 1899, p. 234.
256. The term mostly in use is Araneida, which should mean Araneus-like animals. This is
clearly not allowable, unless there is a genus Araneus or Aranea. For many years there has been no
such genus recognised, but Simon now attempts to re-establish it, inadmissibly, as it appears to us.
(See note, p. 408).
mesosoma which is absent in the adult, but has been found in the embryo of Scorpions.
234. Sarle, New York State Museum, Bulletin 69, Palaeont. 9, 1903, p. 1087.
235. Beecher, Geol. Mag. 1901, p. 561.
236. Peach, Nature, xxxi., 1885, p. 295; Pocock, Quart. Journ. Micr. Sci. xliv., 1901, p. 291;
Laurie, Trans. Roy. Soc. Edinb. xxxix., 1899, p. 575.
237. Peach, Trans. Roy. Soc. Edinb. xxx., 1882, p. 516.
238. Cf. p. 258.
239. Nature, xlviii., 1893, p. 104.
240. Souvenirs entomologiques, Sér. 9, 1907, p. 229.
241. Brauer, Zeitschr. wiss. Zool. lix., 1895, p. 355.
242. Das Tierreich, 8. Lief., 1899, p. 4.
243. Arachnides de France, vii., 1879, p. 84.
244. Fauna of British India, “Arachnida,” 1900, p. 8.
245. Tr. Zool. Soc. xi. part x., 1885, p. 373.
246. Zeitschr. wiss. Zool. lix., 1895, p. 351.
247. Das Tierreich, 8. Lief., 1899.
248. Pocock, Fauna of British India, “Arachnida.” London, 1900.
249. Laurie, J. Linn. Soc. Zool. xxv., 1894, p. 30.
250. See M. Laurie in J. Linn. Soc. Zool. xxv., 1894, p. 20.
251. Tr. Linn. Soc. (2) vi., 1896, p. 344.
252. Bernard, loc. cit. p. 366.
253. J. Linn. Soc. xxv., 1894, p. 29.
254. See Pocock, Ann. Nat. Hist. (6), xiv., 1894, p. 120.
255. Kraepelin, Das Tierreich, Berlin, 8. Lief., 1899, p. 234.
256. The term mostly in use is Araneida, which should mean Araneus-like animals. This is
clearly not allowable, unless there is a genus Araneus or Aranea. For many years there has been no
such genus recognised, but Simon now attempts to re-establish it, inadmissibly, as it appears to us.
(See note, p. 408).
Page 728
257. Mém. Mus. d’Hist. Nat. xviii., 1829, p. 377.
258. Pickard-Cambridge (Spiders of Dorset, 1879–1881) omits the coxal joint, which, with its
lobe, he calls the maxilla, and therefore gives only five joints, which he names axillary, humeral,
cubital, radial, and digital.
259. Pickard-Cambridge, in his Spiders of Dorset, names them exinguinal, coxal, femoral,
genual, tibial, metatarsal, and tarsal.
260. Nat. Hist. Tidsskr. iv., 1843, p. 349.
261. J. Linn. Soc. xv., 1881, p. 155.
262. Proc. Asiat. Soc. Beng. 1875, p. 197.
263. Tijdschr. v. d. Nederl. Dierkundige Ver. (2), i., 1885–1887, p. 109.
264. Études sur la circulation du sang chez les Aranées du genre Lycose. Utrecht, 1862.
265. Recherches sur l’appareil circulatoire des Aranéides. Lille, 1896.
266. Arch. f. Naturg. 55 Jahrg., i., 1889, p. 29.
267. M‘Leod, Bull. Ac. Belg. (3), iii., 1882, p. 779.
268. American Spiders and their Spinning Work, ii., 1890, p. 208.
269. Ann. Nat. Hist. (3), xv., 1865, p. 459.
270. Voyage of the Beagle.
271. Correspondence of John Ray, p. 77.
272. Warburton, Q. J. Micr. Sci. xxi., 1890, p. 29.
273. Rep. Brit. Ass. 1844, p. 77.
274. Nature, xl., 1889, p. 250.
275. See Warburton, Quart. J. Micr. Sci. xxi., 1890, p. 29.
276. Aranéides de la Réunion, Maurice et Madagascar, Paris, 1863, p. 238.
277. M‘Cook, American Spiders and their Spinning Work, i., 1889, p. 351; F. O. Pickard-
Cambridge, J. Micr. and Nat. Sci. July 1890.
278. Moggridge, Harvesting Ants and Trap-door Spiders. London, 1873, p. 120.
279. Verh. Ges. Wien, xviii., 1868, p. 905 (Abstract in Zool. Rec. v., 1868, p. 175).
280. The figure of this cocoon has been accidentally inverted in the works of both Blackwall
and Pickard-Cambridge.
258. Pickard-Cambridge (Spiders of Dorset, 1879–1881) omits the coxal joint, which, with its
lobe, he calls the maxilla, and therefore gives only five joints, which he names axillary, humeral,
cubital, radial, and digital.
259. Pickard-Cambridge, in his Spiders of Dorset, names them exinguinal, coxal, femoral,
genual, tibial, metatarsal, and tarsal.
260. Nat. Hist. Tidsskr. iv., 1843, p. 349.
261. J. Linn. Soc. xv., 1881, p. 155.
262. Proc. Asiat. Soc. Beng. 1875, p. 197.
263. Tijdschr. v. d. Nederl. Dierkundige Ver. (2), i., 1885–1887, p. 109.
264. Études sur la circulation du sang chez les Aranées du genre Lycose. Utrecht, 1862.
265. Recherches sur l’appareil circulatoire des Aranéides. Lille, 1896.
266. Arch. f. Naturg. 55 Jahrg., i., 1889, p. 29.
267. M‘Leod, Bull. Ac. Belg. (3), iii., 1882, p. 779.
268. American Spiders and their Spinning Work, ii., 1890, p. 208.
269. Ann. Nat. Hist. (3), xv., 1865, p. 459.
270. Voyage of the Beagle.
271. Correspondence of John Ray, p. 77.
272. Warburton, Q. J. Micr. Sci. xxi., 1890, p. 29.
273. Rep. Brit. Ass. 1844, p. 77.
274. Nature, xl., 1889, p. 250.
275. See Warburton, Quart. J. Micr. Sci. xxi., 1890, p. 29.
276. Aranéides de la Réunion, Maurice et Madagascar, Paris, 1863, p. 238.
277. M‘Cook, American Spiders and their Spinning Work, i., 1889, p. 351; F. O. Pickard-
Cambridge, J. Micr. and Nat. Sci. July 1890.
278. Moggridge, Harvesting Ants and Trap-door Spiders. London, 1873, p. 120.
279. Verh. Ges. Wien, xviii., 1868, p. 905 (Abstract in Zool. Rec. v., 1868, p. 175).
280. The figure of this cocoon has been accidentally inverted in the works of both Blackwall
and Pickard-Cambridge.
Page 729
281. Fabre, Nouveaux souvenirs entomologiques, ch. xi.
282. Aranéides de la Réunior, Maurice et Madagascar, Paris, 1863, p. xlvi.
283. Hist. de la grande île de Madagascar, 1658, p. 156.
284. Science Gossip, 1877, p. 46.
285. Insect Life, i., 1889, p. 205.
286. Ann. Soc. ent. France, xi., 1842, p. 205. Translated from the Spanish by L. Fairmaire.
287. M‘Cook, American Spiders and their Spinning Work, ii., 1890, p. 188.
288. M‘Cook, t.c. p. 389.
289. British Spiders, 1861, p. 102.
290. Ann. Nat. Hist. (1), xi., 1843, p. 1.
291. Naturalist in Nicaragua, 2nd ed., 1888, p. 134.
292. Nouveaux souvenirs entomologiques, ch. xii.
293. M‘Cook, t.c. p. 384.
294. The Naturalist in Nicaragua, p. 19.
295. Spiders of Dorset, 1879–1881, p. 292.
296. Ibid. p. 360.
297. Naturalist on the Amazon, 1873, p. 54.
298. Protective Resemblances and Mimicry in Animals, 1873, p. 4.
299. Nature, lxviii., 1908, p. 631.
300. J. Morph. (Boston, U.S.A.) i., 1887, p. 403.
301. Nature, xxiii., 1880, p. 149.
302. Warburton, Ann. Nat. Hist. (6), viii., 1891, p. 113.
303. Spiders of Dorset, 1879–1881, p. xxvii.
304. Spiders, their Structure and Habits, 1883, p. 98.
305. Sexual Selection in Spiders, p. 37. (Occasional Papers of the Nat. Hist. Soc. of Wisconsin,
I., 1889.)
306. Arachnides de France (vol. i., published 1874). Histoire naturelle des araignées (2nd ed.
vol i., published 1892).
282. Aranéides de la Réunior, Maurice et Madagascar, Paris, 1863, p. xlvi.
283. Hist. de la grande île de Madagascar, 1658, p. 156.
284. Science Gossip, 1877, p. 46.
285. Insect Life, i., 1889, p. 205.
286. Ann. Soc. ent. France, xi., 1842, p. 205. Translated from the Spanish by L. Fairmaire.
287. M‘Cook, American Spiders and their Spinning Work, ii., 1890, p. 188.
288. M‘Cook, t.c. p. 389.
289. British Spiders, 1861, p. 102.
290. Ann. Nat. Hist. (1), xi., 1843, p. 1.
291. Naturalist in Nicaragua, 2nd ed., 1888, p. 134.
292. Nouveaux souvenirs entomologiques, ch. xii.
293. M‘Cook, t.c. p. 384.
294. The Naturalist in Nicaragua, p. 19.
295. Spiders of Dorset, 1879–1881, p. 292.
296. Ibid. p. 360.
297. Naturalist on the Amazon, 1873, p. 54.
298. Protective Resemblances and Mimicry in Animals, 1873, p. 4.
299. Nature, lxviii., 1908, p. 631.
300. J. Morph. (Boston, U.S.A.) i., 1887, p. 403.
301. Nature, xxiii., 1880, p. 149.
302. Warburton, Ann. Nat. Hist. (6), viii., 1891, p. 113.
303. Spiders of Dorset, 1879–1881, p. xxvii.
304. Spiders, their Structure and Habits, 1883, p. 98.
305. Sexual Selection in Spiders, p. 37. (Occasional Papers of the Nat. Hist. Soc. of Wisconsin,
I., 1889.)
306. Arachnides de France (vol. i., published 1874). Histoire naturelle des araignées (2nd ed.
vol i., published 1892).
Page 730
307. Simon’s Cribellatae comprise Hypochilidae, Uloboridae, Psechridae, Zoropsidae,
Dictynidae, Oecobiidae, Eresidae, Filistatidae.
308. The Spider genus Mygale was established by Walckenaer in 1802, but the name was
preoccupied, having been used by Cuvier (Mammalia) in 1800.
309. Hist. Nat. des Araignées (2nd ed.), i., 1892, p. 76.
310. The “scopula” is the pad of close-set thick hairs which covers the under surface of the
tarsus and often of the metatarsus. The “claw-tufts” are groups of longer hairs, often extending
beyond the claws, and giving the foot a bifid appearance.
311. The three families mentioned above constitute the “Araneae Theraphosae” of Simon, the
remaining families being distinguished as “Araneae Verae.” The Aviculariidae and the Atypidae are
united by some authors to form the Theraphosidae.
312. According to Bertkau (in a letter to Simon, cited in Hist. Nat. des Ar. i. p. 327), two pairs of
linear stigmata under the anterior part of the abdomen lead, to pulmonary sacs, but to tracheae.
313. L. Koch replaced Melanophora by Prosthesima, believing the former to be preoccupied,
but according to Simon (Hist. Nat. des Ar. i. p. 341) C. Koch’s use of Melanophora for an Arachnid
was antecedent (1833) to Meigen’s employment of it for Diptera, 1838.
314. Hist. Nat. des Ar. i. p. 416.
315. Pickard-Cambridge, Spiders of Dorset, p. 77.
316. Hist. Nat. des Ar. i. p. 594.
317. Hist. Nat. des Ar. i. p. 692.
318. The Erigoninae, Formicinae, and Linyphiinae, together with the Epeiridae, form Simon’s
family of Argiopidae.
319. I.e. as developed in the course of the work, not as set forth on p. 594 of vol. i., where five
sub-families are established (Theridiosomatinae, Arciinae, Eurycorminae, Amazulinae, Poltyinae),
which are afterwards merged in the Argiopinae.
320. Simon’s treatment of this group in his Hist. Nat. Ar. does not appear to us satisfactory. He
revives the name Araneus as a generic term, a proceeding to which there are very valid objections,
and merges in it, in whole or in part, about twenty-five generally received genera, including 800
species. He then proceeds to break up the genus Araneus into six entirely artificial “series,”
according to the eyes. However unsatisfactory the merged genera may be, nothing seems to be gained
by this proceeding. The facts about “Araneus” are these. Clerck and Linnaeus used the name
“Araneus” for every member of the order. Latreille, in subdividing the order, retained the name for A.
(Epeira) diademata (1804), but later (1827) transferred it to A. (Tegenaria) domestica. Walckenaer,
seeing the impropriety of using Araneus as a generic term, discarded it, establishing Epeira, which
has since obtained universal recognition.
321. Simon, in his Histoire naturelle des araignées, removes the Sparassinae and the
Selenopinae to the Clubionidae, considering that, notwithstanding the direction of their legs, they
have a greater affinity with that group than with the other Thomisidae.
Dictynidae, Oecobiidae, Eresidae, Filistatidae.
308. The Spider genus Mygale was established by Walckenaer in 1802, but the name was
preoccupied, having been used by Cuvier (Mammalia) in 1800.
309. Hist. Nat. des Araignées (2nd ed.), i., 1892, p. 76.
310. The “scopula” is the pad of close-set thick hairs which covers the under surface of the
tarsus and often of the metatarsus. The “claw-tufts” are groups of longer hairs, often extending
beyond the claws, and giving the foot a bifid appearance.
311. The three families mentioned above constitute the “Araneae Theraphosae” of Simon, the
remaining families being distinguished as “Araneae Verae.” The Aviculariidae and the Atypidae are
united by some authors to form the Theraphosidae.
312. According to Bertkau (in a letter to Simon, cited in Hist. Nat. des Ar. i. p. 327), two pairs of
linear stigmata under the anterior part of the abdomen lead, to pulmonary sacs, but to tracheae.
313. L. Koch replaced Melanophora by Prosthesima, believing the former to be preoccupied,
but according to Simon (Hist. Nat. des Ar. i. p. 341) C. Koch’s use of Melanophora for an Arachnid
was antecedent (1833) to Meigen’s employment of it for Diptera, 1838.
314. Hist. Nat. des Ar. i. p. 416.
315. Pickard-Cambridge, Spiders of Dorset, p. 77.
316. Hist. Nat. des Ar. i. p. 594.
317. Hist. Nat. des Ar. i. p. 692.
318. The Erigoninae, Formicinae, and Linyphiinae, together with the Epeiridae, form Simon’s
family of Argiopidae.
319. I.e. as developed in the course of the work, not as set forth on p. 594 of vol. i., where five
sub-families are established (Theridiosomatinae, Arciinae, Eurycorminae, Amazulinae, Poltyinae),
which are afterwards merged in the Argiopinae.
320. Simon’s treatment of this group in his Hist. Nat. Ar. does not appear to us satisfactory. He
revives the name Araneus as a generic term, a proceeding to which there are very valid objections,
and merges in it, in whole or in part, about twenty-five generally received genera, including 800
species. He then proceeds to break up the genus Araneus into six entirely artificial “series,”
according to the eyes. However unsatisfactory the merged genera may be, nothing seems to be gained
by this proceeding. The facts about “Araneus” are these. Clerck and Linnaeus used the name
“Araneus” for every member of the order. Latreille, in subdividing the order, retained the name for A.
(Epeira) diademata (1804), but later (1827) transferred it to A. (Tegenaria) domestica. Walckenaer,
seeing the impropriety of using Araneus as a generic term, discarded it, establishing Epeira, which
has since obtained universal recognition.
321. Simon, in his Histoire naturelle des araignées, removes the Sparassinae and the
Selenopinae to the Clubionidae, considering that, notwithstanding the direction of their legs, they
have a greater affinity with that group than with the other Thomisidae.
Page 731
322. Ent. Tidsskr. xviii., 1897, p. 223, pl. iv.
323. Zool. Anz. xxiv., 1901, p. 537.
324. Quart. J. Micr. Sci. xlvii., 1904, p. 215.
325. Trans. Linn. Soc. (2), vi., 1896, p. 323.
326. Nature, xlvi., 1892, p. 247.
327. Ann. Nat. Hist. (1), xii., 1843, p. 81.
328. Pocock, Nature, lvii., 1897, p. 618.
329. Cook, Nature, lviii., 1898, p. 247.
330. Öfv. Ak. Förh. lvi., 1899, p. 977.
331. Trans. Linn. Soc. (2), vi., 1896, p. 310.
332. Das Tierreich, Berlin, 12. Lief., Arachnoidea, 1901, p. 4.
333. Arachnides de France, vii., 1879, p. 2.
334. Arachnides de France, vii., 1879, p. 5.
335. See Bernard, J. Linn. Soc. xxiv. (Zool.), 1893, p. 410.
336. See Bernard, J. Linn. Soc. xxiv. (Zool.), 1893, p. 422.
337. For the embryology of Chernetidea, see J. Barrois, “Mém. sur le développement des
Chélifers,” Rev. Suisse de Zool. iii., 1896. Metschnikoff, Zeitschr. wiss. Zool. xxi., 1876, p. 514; and
Vejdovský, Congrès zool. international de Moscou, 1892, p. 120, may also be consulted.
338. Monograph of the British Species of Chernetidea, Dorchester, 1892.
339. Revue Zoologique par la Société Cuvierienne, p. 10.
340. Arachnides de France, vii., 1879, p. 122.
341. On two Orders of Arachnida, Cambridge University Press, 1904.
342. Mag. Nat. Hist. (i.), xii., 1843, p. 325.
343. Zool. Jahrb. iii., 1888, p. 319.
344. T. C. pp. 67–75.
345. Long sternum (μῆκος = length; στῆθος = breast).
346. Arachnides de France, vii., 1879.
347. Transverse sternum (πλάγιος = transverse).
323. Zool. Anz. xxiv., 1901, p. 537.
324. Quart. J. Micr. Sci. xlvii., 1904, p. 215.
325. Trans. Linn. Soc. (2), vi., 1896, p. 323.
326. Nature, xlvi., 1892, p. 247.
327. Ann. Nat. Hist. (1), xii., 1843, p. 81.
328. Pocock, Nature, lvii., 1897, p. 618.
329. Cook, Nature, lviii., 1898, p. 247.
330. Öfv. Ak. Förh. lvi., 1899, p. 977.
331. Trans. Linn. Soc. (2), vi., 1896, p. 310.
332. Das Tierreich, Berlin, 12. Lief., Arachnoidea, 1901, p. 4.
333. Arachnides de France, vii., 1879, p. 2.
334. Arachnides de France, vii., 1879, p. 5.
335. See Bernard, J. Linn. Soc. xxiv. (Zool.), 1893, p. 410.
336. See Bernard, J. Linn. Soc. xxiv. (Zool.), 1893, p. 422.
337. For the embryology of Chernetidea, see J. Barrois, “Mém. sur le développement des
Chélifers,” Rev. Suisse de Zool. iii., 1896. Metschnikoff, Zeitschr. wiss. Zool. xxi., 1876, p. 514; and
Vejdovský, Congrès zool. international de Moscou, 1892, p. 120, may also be consulted.
338. Monograph of the British Species of Chernetidea, Dorchester, 1892.
339. Revue Zoologique par la Société Cuvierienne, p. 10.
340. Arachnides de France, vii., 1879, p. 122.
341. On two Orders of Arachnida, Cambridge University Press, 1904.
342. Mag. Nat. Hist. (i.), xii., 1843, p. 325.
343. Zool. Jahrb. iii., 1888, p. 319.
344. T. C. pp. 67–75.
345. Long sternum (μῆκος = length; στῆθος = breast).
346. Arachnides de France, vii., 1879.
347. Transverse sternum (πλάγιος = transverse).
Page 732
348. Monograph of the British Phalangidea, Dorchester, 1890.
349. The single exception is Opilioacarus, see p. 473.
350. C. R. Ac. Sci. cxxv., 1897, p. 879.
351. “The Biology of the Cattle Tick,” Journ. Compar. Med. and Vet. Archives, 1891, p. 313.
352. Entomological News (Philadelphia), vol. xi., Jan. 1900.
353. For the Protozoa to which these and similar diseases are due, cf. vol. i. pp. 120 f.
354. C. R. Soc. Biol. Paris (7), iv., 1882, p. 305.
355. Ann. Soc. Linn. Lyon, xxii., 1876, p. 29.
356. Bull. Soc. Nat. de Moscou, liv. 1879, pt. i. p. 234.
357. Z. wiss. Zool. xxxvii., 1882, p. 553.
358. P. Z. S., 1895, p. 174.
359. Arch. f. Naturg. i., 1876, p. 65.
360. Tr. Linn. Soc. (2), v. Zool., 1890, p. 281.
361. See account given by Tulk in Mag. Nat. Hist. xviii., 1846, p. 160.
362. Entomological News (Philadelphia), vol. xi., Jan. 1900.
363. Michael, British Oribatidae (Ray Soc.), i., 1883, p. 176.
364. Loc. cit. p. 168.
365. Claparède, Z. wiss. Zool. xviii., 1868, p. 455. Michael, British Oribatidae, i., 1883, p. 73,
writes it “Deutovium.”
366. Atti Ist. Veneto, ii., 1891, p. 699.
367. Rev. Sci. Nat. Ouest, ii., 1892, p. 20.
368. Eriophyes, v. Siebold, Jahresber. Schles. Ges. xxviii., 1850, p. 89; Phytoptus, Dujardin,
Ann. Sci. Nat. (3), xv., 1851, p. 166.
369. See Michael, British Tyroglyphidae, published by the Ray Society, 1901–2.
370. The first paper appeared in Mém. Soc. Zool. ix., 1896, pp. 1–44.
371. “Ticks, a Monograph of the Ixodoidea.” Part I. Argasidae, 1908.
372. With, Vid. Medd. 1904, p. 137.
373. Silvestri, Redia, ii., 1904, fasc. 2, p. 257.
349. The single exception is Opilioacarus, see p. 473.
350. C. R. Ac. Sci. cxxv., 1897, p. 879.
351. “The Biology of the Cattle Tick,” Journ. Compar. Med. and Vet. Archives, 1891, p. 313.
352. Entomological News (Philadelphia), vol. xi., Jan. 1900.
353. For the Protozoa to which these and similar diseases are due, cf. vol. i. pp. 120 f.
354. C. R. Soc. Biol. Paris (7), iv., 1882, p. 305.
355. Ann. Soc. Linn. Lyon, xxii., 1876, p. 29.
356. Bull. Soc. Nat. de Moscou, liv. 1879, pt. i. p. 234.
357. Z. wiss. Zool. xxxvii., 1882, p. 553.
358. P. Z. S., 1895, p. 174.
359. Arch. f. Naturg. i., 1876, p. 65.
360. Tr. Linn. Soc. (2), v. Zool., 1890, p. 281.
361. See account given by Tulk in Mag. Nat. Hist. xviii., 1846, p. 160.
362. Entomological News (Philadelphia), vol. xi., Jan. 1900.
363. Michael, British Oribatidae (Ray Soc.), i., 1883, p. 176.
364. Loc. cit. p. 168.
365. Claparède, Z. wiss. Zool. xviii., 1868, p. 455. Michael, British Oribatidae, i., 1883, p. 73,
writes it “Deutovium.”
366. Atti Ist. Veneto, ii., 1891, p. 699.
367. Rev. Sci. Nat. Ouest, ii., 1892, p. 20.
368. Eriophyes, v. Siebold, Jahresber. Schles. Ges. xxviii., 1850, p. 89; Phytoptus, Dujardin,
Ann. Sci. Nat. (3), xv., 1851, p. 166.
369. See Michael, British Tyroglyphidae, published by the Ray Society, 1901–2.
370. The first paper appeared in Mém. Soc. Zool. ix., 1896, pp. 1–44.
371. “Ticks, a Monograph of the Ixodoidea.” Part I. Argasidae, 1908.
372. With, Vid. Medd. 1904, p. 137.
373. Silvestri, Redia, ii., 1904, fasc. 2, p. 257.
Page 733
374. Arch. mikr. Anat. Bd. i., 1865, p. 428.
375. A. Basse, Zeitschr. wiss. Zool. lxxx., 1906, p. 259.
376. Ann. Sci. nat. (2), xiv., 1840, p. 269, and xvii., 1842, p. 193.
377. Zool. Jahrb. Anat. iii., 1889. This paper contains a bibliography.
378. Morph. Jahrb. xxii., 1895, p. 491.
379. C. R. Ac. Sci. cxviii., 1894, p. 817.
380. Tr. R. Soc. Edinb. xlv., 1908, p. 641. This contains a Bibliography of recent literature. See
also Richters, Zool. Anz. xxx., 1906, p. 125, and Heinis, Zool. Anz. xxxiii., 1908, p. 69.
381. P. Zool. Soc. 1897, p. 790.
382. Hay, in P. Biol. Soc. Washington, xix., 1906, p. 46, states that the name Lydella, Dujardin,
is preoccupied, and suggests as a substitute Microlyda.
383. The animals included in this group are usually called Linguatulidae or Pentastomidae after
the two genera or sub-genera Linguatula and Pentastoma. But the animal which Rudolphi in 1819
(Synopsis Entozoorum) named Pentastoma had been described, figured, and named Porocephalus by
Humboldt (Recueil d’observations de zoologie et anatomie comparee, i. p. 298, pl. xxvi.) in 1811.
The familiar name Pentastoma may, however, be preserved by incorporating it in the designation of
the group.
384. This description is mainly based on the account of P. teretiusculus given by Spencer, Quart.
J. Micr. Sci. xxxiv., 1893, p. 1.
385. Zeitschr. wiss. Zool. lii., 1891, p. 85. This contains a very full bibliography, of 143 entries.
386. Centrbl. Bakter. xl., 1906, p. 368; v. also Thiroux, C. R. Soc. Biol. lix., 1905, p. 78.
387. Shipley, Arch. parasit. i., 1898, p. 52. This contains lists of synonyms and of memoirs
published since Stiles’ paper, etc.
388. H. B. Ward, P. Amer. Ass. 1899, p. 254.
389. Nouv. Dict. de méd., de chir. et d’hyg. vétérinaires, xii. 1883.
390. Tr. R. Soc. Edinb. xxxii., 1884, p. 165.
391. Lohrmann, Arch. Naturg. Jahrg. 55, i., 1889, p. 303.
392. Von Linstow, J. R. Asiat. Soc. Bengal, ii., 1906, p. 270.
393. Pycnogonides, Latreille, 1804; Podosomata, Leach, 1815; Pychnogonides ou Crustacés
aranéiformes, Milne-Edwards, 1834; Crustacea Haustellata, Johnston, 1837; Pantopoda,
Gerstaecker, 1863.
394. Syst. Nat. ed. xii. 1767, vol. ii. p. 1027.
375. A. Basse, Zeitschr. wiss. Zool. lxxx., 1906, p. 259.
376. Ann. Sci. nat. (2), xiv., 1840, p. 269, and xvii., 1842, p. 193.
377. Zool. Jahrb. Anat. iii., 1889. This paper contains a bibliography.
378. Morph. Jahrb. xxii., 1895, p. 491.
379. C. R. Ac. Sci. cxviii., 1894, p. 817.
380. Tr. R. Soc. Edinb. xlv., 1908, p. 641. This contains a Bibliography of recent literature. See
also Richters, Zool. Anz. xxx., 1906, p. 125, and Heinis, Zool. Anz. xxxiii., 1908, p. 69.
381. P. Zool. Soc. 1897, p. 790.
382. Hay, in P. Biol. Soc. Washington, xix., 1906, p. 46, states that the name Lydella, Dujardin,
is preoccupied, and suggests as a substitute Microlyda.
383. The animals included in this group are usually called Linguatulidae or Pentastomidae after
the two genera or sub-genera Linguatula and Pentastoma. But the animal which Rudolphi in 1819
(Synopsis Entozoorum) named Pentastoma had been described, figured, and named Porocephalus by
Humboldt (Recueil d’observations de zoologie et anatomie comparee, i. p. 298, pl. xxvi.) in 1811.
The familiar name Pentastoma may, however, be preserved by incorporating it in the designation of
the group.
384. This description is mainly based on the account of P. teretiusculus given by Spencer, Quart.
J. Micr. Sci. xxxiv., 1893, p. 1.
385. Zeitschr. wiss. Zool. lii., 1891, p. 85. This contains a very full bibliography, of 143 entries.
386. Centrbl. Bakter. xl., 1906, p. 368; v. also Thiroux, C. R. Soc. Biol. lix., 1905, p. 78.
387. Shipley, Arch. parasit. i., 1898, p. 52. This contains lists of synonyms and of memoirs
published since Stiles’ paper, etc.
388. H. B. Ward, P. Amer. Ass. 1899, p. 254.
389. Nouv. Dict. de méd., de chir. et d’hyg. vétérinaires, xii. 1883.
390. Tr. R. Soc. Edinb. xxxii., 1884, p. 165.
391. Lohrmann, Arch. Naturg. Jahrg. 55, i., 1889, p. 303.
392. Von Linstow, J. R. Asiat. Soc. Bengal, ii., 1906, p. 270.
393. Pycnogonides, Latreille, 1804; Podosomata, Leach, 1815; Pychnogonides ou Crustacés
aranéiformes, Milne-Edwards, 1834; Crustacea Haustellata, Johnston, 1837; Pantopoda,
Gerstaecker, 1863.
394. Syst. Nat. ed. xii. 1767, vol. ii. p. 1027.
Page 734
395.
Brünnich’s description (“Entomologia,”
1764), is still more accurate, and is worthy of
transcription as an excellent example of early
work. “Fig. iv. Novum genus, a R[ev.] D[on.]
Ström inter phalangiis relatum, Söndm. Tom. i. p.
209, t. 1, f. 17. Exemplar hujus insecti, quod
munificentia R. Autoris possideo, ita describo;
Caput cum thorace unitum, tubo b excavato
cylindrico, antice angustiore, postice in thoracem
recepto, prominens; Oculi iv. dorsales, a, in
gibbositate thoracis positi; c, Antennae 2 tubo
breviores moniliformes, subtus in segmento
thoracis, cui oculi insident, radicatae; segmenta
corporis, excepto tubo, iv., cum tuberculo e medio
singuli segmenti prominulo. Pedes viii., singuli ex
articulis vii. brevissimis compositi, ungue valido
terminati. Ex descriptione patet insectum hoc a
generibus antea notis omnino differre, ideoque
novum genus, quod e crebris articulationibus
Pycnogonum dico, constituit.” The confusion
between Cyamus and Pycnogonum seems to have arisen with Job Baster, 1765; cf. Stebbing,
Knowledge, February 1902, and Challenger Reports, “Amphipods,” 1888, pp. 28, 30, etc.
396. Hoek, Chall. Rep. p. 15, mentions a specimen of Colossendeis gracilis, Hoek, “furnished
with a pair of distinctly three-jointed mandibles; and the specimen was the largest of the three
obtained.”
397. As a rare exception, Hoek has found the eggs carried on the ovigerous legs in a single
female of Nymphon brevicaudatum, Miers.
398. Meisenheimer (Zeitsch. wiss. Zool. lxxii., 1902, p. 235) compares these with certain glands
described in Branchipus by Spangenberg and by Claus.
399. Ortmann, who would unite Barana with Ascorhynchus, observes: “Bei dieser Gattung
[Ascorhynchus] konnte ich die Kittdrüsen beobachten, die bei A. ramipes mit dem von Barana
castelnaudi [castelli] Dohrn, bei A. cryptopygius mit Barana arenicola übereinstimmen und also die
primitivsten Formen der Ausbildung zeigen.”—Zool. Jahrb. Syst. v., 1891, p. 159.
400. Mém. Acad. Sci. St-Pétersb. (vii.), xxxviii., 1892.
401. Fauna und Flora G. von Neapel, iii. Monogr. 1881, p. 46; see also Loman, J. C. C.,
Tijdschr. D. Ned. Dierk. Ver. (2), viii., 1907, p. 259.
402. The dorsal lobe is absent in Rhynchothorax.
403. For a very detailed account of this mechanism, here epitomised in the merest outline, and
for an account of its modifications in diverse forms, the student must consult Dohrn’s Monograph (t.
cit. pp. 46–53).
404. Dohrn, t. cit. p. 55.
Brünnich’s description (“Entomologia,”
1764), is still more accurate, and is worthy of
transcription as an excellent example of early
work. “Fig. iv. Novum genus, a R[ev.] D[on.]
Ström inter phalangiis relatum, Söndm. Tom. i. p.
209, t. 1, f. 17. Exemplar hujus insecti, quod
munificentia R. Autoris possideo, ita describo;
Caput cum thorace unitum, tubo b excavato
cylindrico, antice angustiore, postice in thoracem
recepto, prominens; Oculi iv. dorsales, a, in
gibbositate thoracis positi; c, Antennae 2 tubo
breviores moniliformes, subtus in segmento
thoracis, cui oculi insident, radicatae; segmenta
corporis, excepto tubo, iv., cum tuberculo e medio
singuli segmenti prominulo. Pedes viii., singuli ex
articulis vii. brevissimis compositi, ungue valido
terminati. Ex descriptione patet insectum hoc a
generibus antea notis omnino differre, ideoque
novum genus, quod e crebris articulationibus
Pycnogonum dico, constituit.” The confusion
between Cyamus and Pycnogonum seems to have arisen with Job Baster, 1765; cf. Stebbing,
Knowledge, February 1902, and Challenger Reports, “Amphipods,” 1888, pp. 28, 30, etc.
396. Hoek, Chall. Rep. p. 15, mentions a specimen of Colossendeis gracilis, Hoek, “furnished
with a pair of distinctly three-jointed mandibles; and the specimen was the largest of the three
obtained.”
397. As a rare exception, Hoek has found the eggs carried on the ovigerous legs in a single
female of Nymphon brevicaudatum, Miers.
398. Meisenheimer (Zeitsch. wiss. Zool. lxxii., 1902, p. 235) compares these with certain glands
described in Branchipus by Spangenberg and by Claus.
399. Ortmann, who would unite Barana with Ascorhynchus, observes: “Bei dieser Gattung
[Ascorhynchus] konnte ich die Kittdrüsen beobachten, die bei A. ramipes mit dem von Barana
castelnaudi [castelli] Dohrn, bei A. cryptopygius mit Barana arenicola übereinstimmen und also die
primitivsten Formen der Ausbildung zeigen.”—Zool. Jahrb. Syst. v., 1891, p. 159.
400. Mém. Acad. Sci. St-Pétersb. (vii.), xxxviii., 1892.
401. Fauna und Flora G. von Neapel, iii. Monogr. 1881, p. 46; see also Loman, J. C. C.,
Tijdschr. D. Ned. Dierk. Ver. (2), viii., 1907, p. 259.
402. The dorsal lobe is absent in Rhynchothorax.
403. For a very detailed account of this mechanism, here epitomised in the merest outline, and
for an account of its modifications in diverse forms, the student must consult Dohrn’s Monograph (t.
cit. pp. 46–53).
404. Dohrn, t. cit. p. 55.
Page 735
405. Biol. Stud. Johns Hopkins Univ. v., 1891, p. 49.
406. Vergl. Entwickl. d. wirbellosen Tiere, Jena, 1893, p. 664.
407. In the second joint in Ascorhynchus abyssi, Sars, and A. tridens, Meinert.
408. Biol. Bulletin Woods Holl, vol. ii., Feb. 1901, p. 196.
409. Studi e ricerche sui Picnogonidi, Firenze, 1876.
410. Semper came near to discovering the fact when he saw, at Heligoland, ripe eggs in a
Phoxichilidium that was, nevertheless, totally destitute of ovigerous legs. The animal, he says, was
adult and sexually mature: “Trotzdem fehlen dem Tiere die Eierträger vollständig; es muss sich also
das Tier noch mindestens ein Mal häuten vor der Eierablag, und dabei müssen die Eierträger gebildet
werden.” (Arb. Inst. Würzburg, 1874, p. 273).
411. The correspondence is not universally admitted. Meinert (Ingolf Expedition, 1899) believes
that the second and third appendages of the larva disappear, and that the palps and ovigerous legs are
new developments; so giving to the normal Pycnogon nine instead of seven appendages. See also
Carpenter “On the Relationship between the Classes of the Arthropoda,” Proc. R. Irish Acad. xxiv.,
1903, pp. 320–360. The latest observer (Loman) inclines to the older view.
412. A slightly different account is given of the Australian P. plumulariae by v. Lendenfeld
(Zeitschr. wiss. Zool. xxxviii., 1883, pp. 323–329).
413. Zur Lehre vom Generationswechsel und Fortpflanzung bei Medusen und Polypen, 1854.
414. Rep. Brit. Ass. 1859; cf. “Gymnoblastic Hydroids,” Ray Soc. pl. vi. fig. 6.
415. Trans. Tyneside Field Club, v. (1862–3), 1864, pp. 124–136, pls. vi., vii.; Ann. Mag. Nat.
Hist. (3), ix., 1862, p. 33.
416. See also Hallez, Arch. Zool. Exp. (4), v., 1905, p. 3; Loman, Tijdschr. Ned. Dierk. Ver. (2),
x., 1906, p. 271, etc.
417. “On Hydroid and other Corals,” 1881, p. 78.
418. Hugo Mertens, Mitth. Zool. Stat. Neapel, xviii., 1906, pp. 136–141.
419. One is tempted to explain such cases as the above of harmonious or identical coloration by
the simple passage of pigments unchanged from the food.
406. Vergl. Entwickl. d. wirbellosen Tiere, Jena, 1893, p. 664.
407. In the second joint in Ascorhynchus abyssi, Sars, and A. tridens, Meinert.
408. Biol. Bulletin Woods Holl, vol. ii., Feb. 1901, p. 196.
409. Studi e ricerche sui Picnogonidi, Firenze, 1876.
410. Semper came near to discovering the fact when he saw, at Heligoland, ripe eggs in a
Phoxichilidium that was, nevertheless, totally destitute of ovigerous legs. The animal, he says, was
adult and sexually mature: “Trotzdem fehlen dem Tiere die Eierträger vollständig; es muss sich also
das Tier noch mindestens ein Mal häuten vor der Eierablag, und dabei müssen die Eierträger gebildet
werden.” (Arb. Inst. Würzburg, 1874, p. 273).
411. The correspondence is not universally admitted. Meinert (Ingolf Expedition, 1899) believes
that the second and third appendages of the larva disappear, and that the palps and ovigerous legs are
new developments; so giving to the normal Pycnogon nine instead of seven appendages. See also
Carpenter “On the Relationship between the Classes of the Arthropoda,” Proc. R. Irish Acad. xxiv.,
1903, pp. 320–360. The latest observer (Loman) inclines to the older view.
412. A slightly different account is given of the Australian P. plumulariae by v. Lendenfeld
(Zeitschr. wiss. Zool. xxxviii., 1883, pp. 323–329).
413. Zur Lehre vom Generationswechsel und Fortpflanzung bei Medusen und Polypen, 1854.
414. Rep. Brit. Ass. 1859; cf. “Gymnoblastic Hydroids,” Ray Soc. pl. vi. fig. 6.
415. Trans. Tyneside Field Club, v. (1862–3), 1864, pp. 124–136, pls. vi., vii.; Ann. Mag. Nat.
Hist. (3), ix., 1862, p. 33.
416. See also Hallez, Arch. Zool. Exp. (4), v., 1905, p. 3; Loman, Tijdschr. Ned. Dierk. Ver. (2),
x., 1906, p. 271, etc.
417. “On Hydroid and other Corals,” 1881, p. 78.
418. Hugo Mertens, Mitth. Zool. Stat. Neapel, xviii., 1906, pp. 136–141.
419. One is tempted to explain such cases as the above of harmonious or identical coloration by
the simple passage of pigments unchanged from the food.
Page 736
420. Fabricius says of his Pycnogonum (Nymphon) grossipes, “Vescitur insectis et vermibus
marinis minutis; quod autem testas mytilorum exhauriat mihi ignotum est, dum nunquam intra testam
mytili illud inveni, licet sit verisimile satis,” Fauna Groenlandica, p. 231.
421. Loeb (Arch. Entw. Mech. v. 2, 1897, p. 250) also says that the Pycnogons are positively
heliotropic.
422. See also P. Gaubert, “Autotomie chez les Pycnogonides,” Bull. Soc. Zool. Fr. xvii., 1892, p.
224.
423. Cf. Carpenter, Proc. R. Irish Acad. xxiv., 1903, p. 320; Lankester, Quart. J. Micr. Sci.
xlviii., 1904, p. 223; Bouvier, Exp. Antarct. Fr., “Pycnogonides,” 1907, p. 7, etc.
424. “Nous ne les plaçons ici qu’avec doute,” Règne Anim. éd. 3, tom. vi. p. 298.
425. Cf. also J. E. W. Ihle, “Phylogenie und systematische Stellung der Pantopoden,” Biol.
Centralbl., Bd. xviii., 1898, pp. 603–609; Meisenheimer, Verh. zool.-bot. Ges. Wien, xii., 1902, pp.
57–64; also Stebbing, in Knowledge, 1902.
426. The chelate form of the foremost appendages is of little moment. A chela consists merely of
a more or less mobile terminal joint flexing on a more or less protuberant penultimate one, and in the
Scorpions, in Limulus, throughout the Crustacea, and even in Insects (cf. vol. vi. p. 554), we see such
a structure arising independently on very diverse appendages.
427. Cf. Oudemans, Tijdschr. d. Ned. Dierk. Ver. (2), i., 1886, p. 41: “Jedermann weiss nun, dass
diese Tiere eine ganz besondere Urgruppe bilden, ohne alle Verwandschaft mit irgend einer anderen
Arthropodengruppe.”
428. Cole (Ann. Mag. Nat. Hist. (7), xv., 1905, pp. 405–415) has attempted such a phylogenetic
classification, starting with Decolopoda, and leading in two divergent lines, through Nymphon and
Pallene to the Pycnogonidae, and through Eurycide and Ammothea to Colossendeis. This hint is in
part adopted in the subjoined classification. Bouvier, in his recent Report on the Pycnogons of the
French Antarctic Expedition (t. cit.), gives reasons for separating the Decolopodidae and
Colossendeidae from all the rest. Loman, in Die Pantopoden der Siboga Expedition, 1908, has
recently suggested another, and in many respects novel, classification of the whole group.
429. See (inter alia) Dohrn, l.c.; E. B. Wilson, Rep. U.S. Fish. Comm. (1878), 1880; Hoek,
Chall. Report, 1881; G. O. Sars, Norw. N. Atl. Exp. 1891; Meinert, Ingolf Exped. 1899; Möbius,
Fauna Arctica, 1901, Valdivia Exped. 1902; Cole, Harriman Alaska Exped. 1904; Hodgson,
Discovery Exped. 1907; Bouvier, Exp. Antarct. Fr. 1907.
430. Boston Journ. Nat. Hist. i., 1834, p. 203; Cf. Hodgson, Pr. R. Phys. Soc. Edinburgh, xvi.,
1905, p. 35; Zool. Anz. xxv., 1905, p. 254; Discovery Exp., “Pycnogonida,” 1907; Bouvier, Exp.
Antarct. Fr. 1907.
431. See pp. 535, 541. Cf. Dohrn (t. cit.), p. 228.
432. The first known species was described as Phoxichilus proboscideus, Sabine, from the
shores of the North Georgian Islands (1821).
marinis minutis; quod autem testas mytilorum exhauriat mihi ignotum est, dum nunquam intra testam
mytili illud inveni, licet sit verisimile satis,” Fauna Groenlandica, p. 231.
421. Loeb (Arch. Entw. Mech. v. 2, 1897, p. 250) also says that the Pycnogons are positively
heliotropic.
422. See also P. Gaubert, “Autotomie chez les Pycnogonides,” Bull. Soc. Zool. Fr. xvii., 1892, p.
224.
423. Cf. Carpenter, Proc. R. Irish Acad. xxiv., 1903, p. 320; Lankester, Quart. J. Micr. Sci.
xlviii., 1904, p. 223; Bouvier, Exp. Antarct. Fr., “Pycnogonides,” 1907, p. 7, etc.
424. “Nous ne les plaçons ici qu’avec doute,” Règne Anim. éd. 3, tom. vi. p. 298.
425. Cf. also J. E. W. Ihle, “Phylogenie und systematische Stellung der Pantopoden,” Biol.
Centralbl., Bd. xviii., 1898, pp. 603–609; Meisenheimer, Verh. zool.-bot. Ges. Wien, xii., 1902, pp.
57–64; also Stebbing, in Knowledge, 1902.
426. The chelate form of the foremost appendages is of little moment. A chela consists merely of
a more or less mobile terminal joint flexing on a more or less protuberant penultimate one, and in the
Scorpions, in Limulus, throughout the Crustacea, and even in Insects (cf. vol. vi. p. 554), we see such
a structure arising independently on very diverse appendages.
427. Cf. Oudemans, Tijdschr. d. Ned. Dierk. Ver. (2), i., 1886, p. 41: “Jedermann weiss nun, dass
diese Tiere eine ganz besondere Urgruppe bilden, ohne alle Verwandschaft mit irgend einer anderen
Arthropodengruppe.”
428. Cole (Ann. Mag. Nat. Hist. (7), xv., 1905, pp. 405–415) has attempted such a phylogenetic
classification, starting with Decolopoda, and leading in two divergent lines, through Nymphon and
Pallene to the Pycnogonidae, and through Eurycide and Ammothea to Colossendeis. This hint is in
part adopted in the subjoined classification. Bouvier, in his recent Report on the Pycnogons of the
French Antarctic Expedition (t. cit.), gives reasons for separating the Decolopodidae and
Colossendeidae from all the rest. Loman, in Die Pantopoden der Siboga Expedition, 1908, has
recently suggested another, and in many respects novel, classification of the whole group.
429. See (inter alia) Dohrn, l.c.; E. B. Wilson, Rep. U.S. Fish. Comm. (1878), 1880; Hoek,
Chall. Report, 1881; G. O. Sars, Norw. N. Atl. Exp. 1891; Meinert, Ingolf Exped. 1899; Möbius,
Fauna Arctica, 1901, Valdivia Exped. 1902; Cole, Harriman Alaska Exped. 1904; Hodgson,
Discovery Exped. 1907; Bouvier, Exp. Antarct. Fr. 1907.
430. Boston Journ. Nat. Hist. i., 1834, p. 203; Cf. Hodgson, Pr. R. Phys. Soc. Edinburgh, xvi.,
1905, p. 35; Zool. Anz. xxv., 1905, p. 254; Discovery Exp., “Pycnogonida,” 1907; Bouvier, Exp.
Antarct. Fr. 1907.
431. See pp. 535, 541. Cf. Dohrn (t. cit.), p. 228.
432. The first known species was described as Phoxichilus proboscideus, Sabine, from the
shores of the North Georgian Islands (1821).
Page 737
433. Pocock (Encycl. Brit., 10th ed., Art. “Arachnida”) makes Hannonia the solitary type of a
family. Cf. Loman, Zool. Jahrb., Syst., xx., 1904, p. 385.
434. Loman conjoins all these genera, and also Lecythorhynchus, with Nymphopsis, as a sub-
family Nymphopsinae of Ammotheidae.
435. Edinb. New Phil. Journal, Oct. 1842, p. 367 (P. capillata on Plate).
436. Proc. Boston Nat. Hist. Society, vol. i., 1841–44, p. 92.
437. Found by Sir John Ross’s expedition in 1840, and subsequently by the Challenger
expedition and other visitors.
438. Stebbing has recently shown (Knowledge, Aug. 1902, p. 157) that the genus Phoxichilus
was instituted by Latreille (Nouv. Dict. d’hist. nat. 1804) for the Pycnogonum spinipes of Fabricius,
now Pseudopallene spinipes, auctt. Hence he changes Pseudopallene to Phoxichilus, Latr., and
Phoxichilidae and Phoxichilus, auctt., to Chilophoxidae, etc.; it also follows that the family known to
all naturalists as Pallenidae should, according to the letter of the law of priority, be henceforth known
as the Phoxichilidae. In my opinion this is a case where strict adherence to priority would serve no
good end, but would only lead to great and lasting confusion (cf. Norman, J. Linn. Soc. xxx., 1908, p.
231).
439. Vide note 2, p. 537.
440. Mag. Nat. Hist. vi., 1838, p. 42; Mag. Zool. and Bot. i., 1837, p. 368.
441. Edinb. New Phil. Journ. xxxii., 1842, p. 136; xxxiii., 1842, p. 367; Ann. Mag. Nat. Hist.
(1), xiv., 1844, p. 4.
442. Ann. Mag. Nat. Hist. (3), xiii., 1864, p. 113.
443. Proc. R. Dublin Soc. (N.S.), viii., 1893, p. 195; Fisheries, Ireland, Sci. Invest. 1904, No. iv.
(1905).
444. Cf. A. M. Norman, J. Linn. Soc. xxx., 1908, pp. 198–238.
family. Cf. Loman, Zool. Jahrb., Syst., xx., 1904, p. 385.
434. Loman conjoins all these genera, and also Lecythorhynchus, with Nymphopsis, as a sub-
family Nymphopsinae of Ammotheidae.
435. Edinb. New Phil. Journal, Oct. 1842, p. 367 (P. capillata on Plate).
436. Proc. Boston Nat. Hist. Society, vol. i., 1841–44, p. 92.
437. Found by Sir John Ross’s expedition in 1840, and subsequently by the Challenger
expedition and other visitors.
438. Stebbing has recently shown (Knowledge, Aug. 1902, p. 157) that the genus Phoxichilus
was instituted by Latreille (Nouv. Dict. d’hist. nat. 1804) for the Pycnogonum spinipes of Fabricius,
now Pseudopallene spinipes, auctt. Hence he changes Pseudopallene to Phoxichilus, Latr., and
Phoxichilidae and Phoxichilus, auctt., to Chilophoxidae, etc.; it also follows that the family known to
all naturalists as Pallenidae should, according to the letter of the law of priority, be henceforth known
as the Phoxichilidae. In my opinion this is a case where strict adherence to priority would serve no
good end, but would only lead to great and lasting confusion (cf. Norman, J. Linn. Soc. xxx., 1908, p.
231).
439. Vide note 2, p. 537.
440. Mag. Nat. Hist. vi., 1838, p. 42; Mag. Zool. and Bot. i., 1837, p. 368.
441. Edinb. New Phil. Journ. xxxii., 1842, p. 136; xxxiii., 1842, p. 367; Ann. Mag. Nat. Hist.
(1), xiv., 1844, p. 4.
442. Ann. Mag. Nat. Hist. (3), xiii., 1864, p. 113.
443. Proc. R. Dublin Soc. (N.S.), viii., 1893, p. 195; Fisheries, Ireland, Sci. Invest. 1904, No. iv.
(1905).
444. Cf. A. M. Norman, J. Linn. Soc. xxx., 1908, pp. 198–238.
Page 738
THE CAMBRIDGE NATURAL HISTORY
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VOLUME I.
Protozoa, by Marcus Hartog, M.A., D.Sc.; Porifera (Sponges), by
Igerna B. J. Sollas, B.Sc.; Coelenterata and Ctenophora, by S. J.
Hickson, M.A., F.R.S.; Echinodermata, by E. W. MacBride, M.A.,
F.R.S.
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Flatworms and Mesozoa, by F. W. Gamble, D.Sc.; Nemertines, by Miss
L. Sheldon; Threadworms and Sagitta, by A. E. Shipley, M.A.,
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F. E. Beddard, M.A., F.R.S.; Gephyrea and Phoronis, by A. E.
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Page 739
with confidence that the same amount of information, within the same compass, is to be had in no
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TIMES.—“There are very many, not only among educated people who take an interest in science,
but even among specialists, who will welcome a work of reasonable compass and handy form
containing a trustworthy treatment of the various departments of Natural History by men who are
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prospectus holds out.”
VOLUME IV.
Crustacea, by Geoffrey W. Smith, M.A., and the late W. F. R. Weldon,
M.A.; Trilobites, by Henry Woods, M.A.; Introduction to Arachnida,
and King-Crabs, by A. E. Shipley, M.A., F.R.S.; Eurypterida, by
Henry Woods, M.A.; Scorpions, Spiders, Mites, Ticks, etc., by Cecil
Warburton, M.A.; Tardigrada (Water-Bears), by A. E. Shipley,
M.A., F.R.S.; Pentastomida, by A. E. Shipley, M.A., F.R.S.;
Pycnogonida, by D’Arcy W. Thompson, C.B., M.A.
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Prof. RAPHAEL MELDOLA, F.R.S., F.C.S., in his Presidential Address to the Entomological
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venture to express the hope that this will be at no very distant period, we shall be in possession of a
treatise on the natural history of insects which, from the point of view of the general reader, will
compare most favourably with any similar work that has been published in the English language.”
other zoological work.”
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Molluscs, by the Rev. A. H. Cooke, M.A.; Brachiopods (Recent), by A.
E. Shipley, M.A., F.R.S.; Brachiopods (Fossil), by F. R. C. Reed, M.A.
TIMES.—“There are very many, not only among educated people who take an interest in science,
but even among specialists, who will welcome a work of reasonable compass and handy form
containing a trustworthy treatment of the various departments of Natural History by men who are
familiar with, and competent to deal with, the latest results of scientific research. Altogether, to judge
from this first volume, the Cambridge Natural History promises to fulfil all the expectations that its
prospectus holds out.”
VOLUME IV.
Crustacea, by Geoffrey W. Smith, M.A., and the late W. F. R. Weldon,
M.A.; Trilobites, by Henry Woods, M.A.; Introduction to Arachnida,
and King-Crabs, by A. E. Shipley, M.A., F.R.S.; Eurypterida, by
Henry Woods, M.A.; Scorpions, Spiders, Mites, Ticks, etc., by Cecil
Warburton, M.A.; Tardigrada (Water-Bears), by A. E. Shipley,
M.A., F.R.S.; Pentastomida, by A. E. Shipley, M.A., F.R.S.;
Pycnogonida, by D’Arcy W. Thompson, C.B., M.A.
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Sinclair, M.A.; Insects, Part I., Introduction, Aptera, Orthoptera,
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Parasitica), by David Sharp, M.A., M.B., F.R.S.
Prof. RAPHAEL MELDOLA, F.R.S., F.C.S., in his Presidential Address to the Entomological
Society of London, said:—“The authors of this volume are certainly to be congratulated upon having
furnished such a valuable contribution to our literature. When its successor appears, and I will
venture to express the hope that this will be at no very distant period, we shall be in possession of a
treatise on the natural history of insects which, from the point of view of the general reader, will
compare most favourably with any similar work that has been published in the English language.”
Page 740
VOLUME VI.
Hymenoptera (continued) (Tubulifera and Aculeata), Coleoptera,
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Page 741
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Page 742
Page 743
TRANSCRIBER’S NOTES
1. Silently corrected obvious typographical errors and variations in
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2. Retained archaic, non-standard, and uncertain spellings as printed.
1. Silently corrected obvious typographical errors and variations in
spelling.
2. Retained archaic, non-standard, and uncertain spellings as printed.
Page 744
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Professor Michael S. Hart was the originator of the Project Gutenberg
concept of a library of electronic works that could be freely shared
with anyone. For forty years, he produced and distributed Project
Gutenberg eBooks with only a loose network of volunteer support.
Project Gutenberg eBooks are often created from several printed
editions, all of which are confirmed as not protected by copyright in
the U.S. unless a copyright notice is included. Thus, we do not
necessarily keep eBooks in compliance with any particular paper
edition.
Most people start at our website which has the main PG search facility:
www.gutenberg.org.
This website includes information about Project Gutenberg, including
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Foundation, how to help produce our new eBooks, and how to
subscribe to our email newsletter to hear about new eBooks.