Nit sieiegeie . ‘ ; ayetmt~eienh ee prey aren fe lecns mime et etry adel dek bento ek Sere epele eleimisie er ete tere minieletaiee/Pisininiel aie Aelia eiticie PIMIE He whe (etehete +19 = reretele See ei Oho where Sd Si Nl elma dieiere, 4>(e) wate Pe €19\ eee misieimiels aie + 0) erape Peel eierereieinisie “1m eel mini eee. H 18 8 laine meine tes al eleieleieieiaia(eie whole m\Simhstere S.91e) mej elelepetefaimie) ri. “ates Omi 1Fih (<1 elelaPe/ eth imis ie timrejaiateieieiieie bes evr ris + eheleimisi aera, HO Oh el Semin (= eh memie chet siateje/ apeiere:e\sieietepeie o/8e) Bl eterete eieheiere: rhevete niSie| Sia) elelejepat nieielmieieieteleimimiaiaie EF met) ia Lane | it o. ii ie ‘ wy rN) Aad My. ‘ 7 AL ol > i i A yi I ug | “4 i . Oh if * oN, Hh, oe he oie : pie Kea t ' ar) ¢ ee te y | 7 Wei fe \ wil Ni 1 sol 18 Deon i? A i i Vie ' j y : : ma 3 i cn 7" oF sh Nba Lv f if i t ' J { ~~ Ne ne a DEY, ry yi ¥ 7‘ oe i dA ig V4 : THE AMBRIDGE NATURAL HISTORY 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 Pee SHIP BY, M.A, Fellow and Tutor of Christs College, Cambridge ; Reader in Zoology in the University VOLUME IV 4 FEB 19 1987 LIBRARIES 75 ATHSON ARS. / 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 ansonian Ingti¢, is ON | SEP 20 1009 “N.4¥08 \ AS “onal Muse CRUSTACEA By Grorrrey Situ, M.A. (Oxon.), Fellow of New College, Oxford ; and the late W. F. R. WELpon, M.A. (D.Sc.,Oxon.), formerly Fellow of St. John’s College, Cambridge, and Linacre Professor of Human and Comparative Anatomy, Oxford MRILOBITES By Henry Woops, M.A., St. John’s College, Cambridge ; University Lecturer in Palaeozoology MITRODUCTION TO ARACHNIDA, AND KING-CRABS By A. E. Suiprey, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge ; Reader in Zoology EURYPTERIDA By Henry Woops, M.A., St. John’s College, Cambridge ; University Lecturer in Palaeozoology mem lONS, “SPIDERS, MITES? TICKS,. Erc: By Cecit Warsurton, M.A., Christ’s College, Cambridge ; Zoologist to the Royal Agricultural Society TARDIGRADA (WATER-BEARS) By A. E. Suiptey, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge ; Reader in Zoology PENTASTOMIDA By A. E. Surpiey, M.A., F.R.S., Fellow and Tutor of Christ’s College, Cambridge ; Reader in Zoology PYCNOGONIDA By D’Arcy W. Tuompson, C.B., M.A., Trinity College, Cambridge ; Professor of Natural History in University College, Dundee Rig AGVehiine AON UA NaC Or aie NEE ED Si MAREN’ S SRE ET -kON DON 1909 All the ingenious men, and all the scientific men, and all the fanciful men, in the world, with all the old German bogy- painters into the bargain, could never invent . . . anything so curious, and so ridiculous, as a lobster, CuHarLES KincsLey, 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, We work, as Nature taught, with ceaseless pains, Thy bowels thou dost spin, I spin my brains. SoutHry, 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. PREFACE Tue Editors feel that they owe an apology and some explanation to the readers of Zhe Cambridge Natural History tor the delay which has oceurred 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. R. 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. 7 hy aa eek Fite te MS ys a ae ne at Oe ML WED ah dia ‘ + aA ; iyi? 4 ., d ~ iy baie, ‘ . é “i oa he . } i" ; & % + ‘ § ’ P . Pe AS ; Us ee » i! ’ in Ts Ch? a | Ve ' et : Cane ie ? P71 T true t,) IPAs vio» ‘ CONTENTS 2 PAGE SCHEME OF THE CLASSIFICATION ADOPTED IN THIS VOLUME . : : : xi CRUSTACEKA (GISLALIPMMIO as II CRUSTACEA JENERAL ORGANISATION ; ; : d , : ; f 3 3 CERAVRAMEY Ry elo CRUSTACEA (continued) ENTOMOSTRACA —- BRANCHIOPODA — PHYLLOPODA — CLADOCERA — WATER- KEEAS. .. 5 e . : : : 3 é : ; - . 18 CHEAPER Re Wl CRUSTACEA ENTOMOSTRACA (continued) CoPpEPODA ; , : : ; : 5 : 3 : : ; ; 5 COUSLAUEMDNO IR IV CRUSTACEA ENTOMOSTRACA (continued) 79 CIRRIPEDIA— PHENOMENA OF GROWTH AND SEX—OSTRACODA Vil vill CONTENTS (ONELAIE MID ay \W CRUSTACEA (continued) PAGE MALACOSTRACA: LEPTOSTRACA—PHYLLOCARIDA: HEUMALACOSTRACA: SYN- CARIDA — ANASPIDACEA: PERACARIDA — MysIpDAcEA — CuMACEA — IsopopA—AMPHIPODA : HOPLOCARIDA—STOMATOPODA . é ¢ Re CHAPTER VI CRUSTACEA MALACOSTRACA (continued) - EUMALACOSTRACA (CONTINUED): EUCARIDA — EUPHAUSIACEA — COMPOUND EyvES—DECAPODA . : ; . s ; ; ; . : papell: CECATP IDE Re Vib CRUSTACEA (continued) REMARKS ON THE DISTRIBUTION OF MARINE AND FRESH-WATER CRUSTACEA. 197 CHAPTER VIII CRUSTACEA (continued) TRILOBITA . : 5 g : é : , ; : : : = 42211 ARACHNIDA CHARADE Ry ake ARACHNIDA—INTRODUCTION . 255 (COMSLIN TE MND ay ON ARACHNIDA (continued) DELOBRANCHIATA = MEROSTOMATA—XIPHOSURA . ‘ ; : : ». 259 CHAPTER XI ARACHNIDA DELOBRANCHIATA (continued) EuRYPTERIDA=GIGANTOSTRACA . ‘ ; ‘ ‘ : : 5 5 teks CONTENTS ix CHAPTER XII ARACHNIDA (continued) PAGE EMBOLOBRANCHIATA—SCORPIONIDEA—PEDIPALPI . : A E é 52 PAE (OUSUAIP MNT R Ie DUUL ARACHNIDA EMBOLOBRANCHIATA (continued) ARANEAE—EXTERNAL STRUCTURE—INTERNAL STRUCTURE . , : 5 Sule CEPAGE TB Rae xcs ARACHNIDA EMBOLOBRANCHIATA (continued) ARANEAE (CONTINUED) — HaApirs — Ecpysis— TREATMENT OF YOUNG — MIGRATION — WeEsBs — Nests — Eac-cocoons — Poison — FERTILITY — ENEMIES—PROTECTIVE COLORATION—MIMICRY—SENSES—INTELLIGENCE —Matine Hapirs—Fossin SPIDERS . , : ; ; : 5 ephe (CHETAN IP INI IR O\Y ARACHNIDA EMBOLOBRANCHIATA (continued) ARANEAE (CONTINUED)—CLASSIFICATION : ; : 2 : : 5 Biel! CHEAP UNIB IR, EWA ARACHNIDA EMBOLOBRANCHIATA (continued) PALPIGRADI—SOLIFUGAE = SOLPUGAE—CHERNETIDEA = PSEUDOSCORPIONES . 422 (CIEUAAIE DIB IR, OSV IUL ARACHNIDA EMBOLOBRANCHIATA (continued) PopoGona = RICINULEI—PHALANGIDEA = OPILIONES—H ABITS—STRUCTURE— CLASSIFICATION f ; F 3 3 ; : : : ’ 4.3 9 CHABRLER XVEHI ARACHNIDA EMBOLOBRANCHIATA (continued) ACARINA— HARVEST-BUGS— Parasitic Mirrs—Ticks—SPpINNING MITEsS— STRUCTURE—METAMORPHOSIS—CLASSIFICATION : ; ; ». 454 x CONTENTS CHAPTER XIX ARACHNIDA (APPENDIX I) PAGE TARDIGRADA — OccURRENCE — EcpysIs — STRUCTURE DEVELOPMENT — AFFINITIES— BIOLOGY—DESICCATION—PARASITES—SYSTEMATIC . ee yi (C1ELAIP AIR, NOX ARACHNIDA (APPENDIX IT) PENTASTOMIDA — OccCURRENCE — Economic IMPORTANCE — STRUCTURE — DEVELOPMENT AND LIFE-HISTORY—SYSTEMATIC . : P ; . 488 PYCNOGONIDA CUEI/NIE MND RE, SOI PYCNOGONIDA : ; F : , . F 3 3 j 22 DOr INDEX 4 : : : - ; 3 : : : d 5 . 543 SCHEME OF THE CLASSIFIC IN THIS VOLUME The names of extinct groups are printed in italics. Divisions. Orders. Branchio- poda (p. 18) = Ye) = Copepoda =} (p. 55) Bo, a ° o =! Ay L (Continued on the next page. | CRUSTACEA (p. 3). ENTOMOSTRACA (p. 18). Sub-Orders. Tribes. Phyllopoda (pp. 19, 35) Ctenopoda { (p. 51) Caly ae e (pp. 38, Anomo- ease ee (p. 37) (p. 51) | Canes | i (pp. 38, 54) | ia Rita le (p. 57) rile eae (p. 57) ey ae (p. 58) | Peano i 61) x1 | | ATION ADOPTED Families. Branchipodidae (pp. 19, 35). A podidae (pp. 19, 36). Limnadidae (pp. 20, 36). Stitdaetp-ol). ae sdiidae (p. 51). aoe (p. 51). Bosminidae (p. 58). ee aphniidae (p. 53). Ly Paes = Chydoridae (p. 53). Pea ee (p. 54). Beas p. 54). Oat nil ae (p. 57). Centropagidae (p. 58). Candacidae (p. 60). Pontellidae (p. 60). Cyclopidae (pp. 61, 62). Harpacticidae (pp. 61, 62). Peltiidae (p. 63). Monstrillidae (p. 63). Ascidicolidae (p. 66). Asterocheridae (p. 67). Dichelestiidae (p. 68). xi SCHEME OF CLASSIFICATION Divisions. Orders. Sub-Orders, Tribes. Families. ( ( ( ( Oncaeidae (p. 69). Corycaeidae (p. 69). Lichomolgidae (p. 70). Ergasilidae (p. 71). Bomolochidae (pa): Chondracanthidae (p. 72). Eucopepoda’; Podoplea | Isokerandria 4 Philichthyidae Copepoda} (contd.) + (contd.) 1 (p. 69) (p. 73). (contd.) Nereicolidae (p. 73). Hersiliidae (p. 73). Caligidae (p. 73). Lernaeidae (p. 74). Lernaeopodidae (p27): Choniostomatidae L “(pi-76); | Argulidae (p. 76). ( ( Polyaspidae (p. 84). Pentaspidae (p. 87). Pedunculata.
Thelphusidae = Potamon-
idae (p. 191).
Renee (p. 193).
Oxyrhyncha Parthenopidae (p. 193).
(p. 191) (ee
(p. 193
\Carcinoplacidae (p. 195).
Gonoplacidae (p. 195).
Catometopa | Pinnotheridae (p. 195).
(p. 193) Grapsidae (p. 196).
| Gecarcinidae (p. 196).
L ( Ocypodidae (p. 196).
(Continued on the next page.)
SCHEME OF CLASSIFICATION XV
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).
Proétidae (p. 251).
Enerinuridae (p. 251).
Acidaspidae (p. 251).
Lichadidue (p. 252).
ARACHNIDA (p. 255).
DELOBRANCHIATA=MEROSTOMATA (pp. 258, 259).
Orders. Families. Sub-Families.
f Xiphosurinae (p. 276).
\ Tachypleinae (p. 276).
Xiphosura
(pp. 258, 259, 276)
Eurypterida=Gigantostraca
(pp. 258, 283)
| Xiphosuridae (p. 276)
\ ELurypteridue (p. 290).
EMBOLOBRANCHIATA (pp. 258, 297).
f Buthinae (p. 306).
\ Centrurinae (p. 306).
(faces (p. 307).
Buthidae (p. 306)
Urodacinae (p. 307).
Scorpionidae (p. 306) Scorpioninae (p. 307).
| Hemiscorpioninas (p. 307).
Sunnis Ischnurinae (p. 307).
(pp. 258, 297) 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).
Tarantulidae = Phrynidae {
(p. 312)
| Liphistiidae (p. 386).
Pedipalpi (pp. 258, 308 Tarantulinae (p. 313).
Phrynichinae (p. 313).
Charontinae (p. 313).
( Paratropidinae (p. 387).
Actinopodinae (p. 387).
: ve ; iginae (p. 387).
ee ees 4 eee Al (p. Oe
(1p Bie 3) Barychelinae (p. 389).
| Aviculariinae (p. 389).
\ Diplurinae (p. 390).
Araneae (pp. 258, 314)
(Continued on the next page.)
XVI
SCHEME OF CLASSIFICATION
Orders.
(
Araneae (contd.) 4
(Continued on the next page.)
ee
Families.
Atypidae (p. 390).
Vilistatidae (p. 391).
Oecobiidae = Urocteidae
(p. 392).
Sicariidae =Scytodidae
(p. 893).
Hypochilidae (p. 393).
Leptonetidae (p. 393).
Oonopidae (p. 393).
Hadrotarsidae (p. 394).
Dysderidae (p. 394)
Caponiidae (p. 395).
Prodidomidae (p. 395).
Drassidae (p. 396)
Palpimanidae (p. 398).
Eresidae (p. 398).
Dictynidae (p. 398).
Psechridae (p. 399).
Zodariidae = Enyoidae
(p. 399).
Hersiliidae (p. 400).
Pholeidae (p. 401).
Theridiidae (p. 401)
Epeiridae (p. 406)
Uloboridae (p. 410)
Archeidae (411).
Mimetidae (p. 411).
Thomisidae (p. 412)
Zoropsidae (p. 415).
Platoridae (p. 415).
Agelenidae (p. 415)
Sub-Families.
{ Dysderinae (p. 394).
\ Segestriinae (p. 395).
Wehr (p. 396).
Clubioninae (p. 397).
eae (p. 397).
Micariinae (p. 397).
( Argyrodinae (p. 402).
Episininae (p. 402).
Theridioninae (p. 403).
4 Phoroncidiinae (p. 404).
Erigoninae (p. 404).
Formicinae (p. 405).
( Linyphiinae (p. 405).
Theridiosomatinae (p. 407)-
Tetragnathinae (p. 407).
Argiopinae (p. 408).
Nephilinae (p. 408).
Epeirinae (p. 408).
Gasteracanthinae (p. 409).
Poltyinae (p. 410).
Arcyinae (p. 410).
Dinopinae (p. 410).
Uloborinae (p. 410).
Miagrammopinae (p. 411).
( Thomisinae = Misumeninae
| (p. 412).
Philodrominae (p. 413).
4 Sparassinae (p. 414).
Aphantochilinae (p. 414).
| Stephanopsinae (p. 414).
(Selenopinae (p. 414).
Cybaeinae (p. 415).
Ageleninae (p. 416).
Hahniinae (p. 416).
Nicodaminae (p. 416).
i
XVil
SCHEME OF CLASSIFICATION
Orders. Sub-Orders. Families.
; - Pisauridae (p.416).
| Lycosidae (p. 417).
Ctenidae (p. 418).
oe. . + Senoculidae (p. 418).
Reantd. ) Oxyopidae (p. 419).
Attidae =Salticidae
(p. 419).
Palpigradi
(pp. 258, 422).
‘ Galeodidae (p. 428).
Solifugae
=Solpugae Solpugidae (p. 429)
(pp. 258, 423) |
~ Hexisopodidae (p. 429).
Chernetidea |
=Chernetes
= Pseudoscor- Cheliferidae (p. 436)
piones
(pp. 258, 430)
Podogona PA
Becaate® | i Bi
(pp. 258, 439) i 1dae (p. ).
ies } Sironidae (p. 448).
Mecostethi | Phalangodidae (p. 448).
. =Laniatores - Cosmetidae (p. 449).
eaanicics j (p. 448) | Gonyleptidae (p. 449).
pp. 258, 440) 3 5 | Phalangiidae (p. 449)
PI Plagiostethi | = I
=Palpatores { Ischyropsalidae (p. 451).
(p. 449) | Nem ep tid ; 451)
p. 449 emastomatidae (p. 451).
( Trogulidae (p. 452).
c : 3 Eriophyidae
aS ie i = Phytoptidae (p.464).
Ie | Demodicidae (p. 465).
eee \ Sarcoptidae (p. 466)
(p. 465) ri
Oribatidae (p. 467).
. ‘aS | Argasidae (p.469).
Metastigmata 1g. “Ixodidae (p. 469).
(p. 467) oe |
Acarina ame
= Acari J Gamasidae (p. 470)
= Acaridea .
(pp. 258, 454) Zena Tarsonemidae (p. 471).
( Bdellidae (p. 471).
Halacaridae (p. 472).
Hydrachnidae (p. 472).
Prostigmata |
(p. 471) }
| Trombidiidae (p. 472)
; L
(hue eas } Opitioacaridte (p. 473).
Sub-Families.
( Rhagodinae (p. 429).
Solpuginae (p. 429).
+ Daesiinae (p. 429).
Eremobatinae (p. 429).
Karshiinae (p. 429).
| Cheliferinae (p. 436).
, Garypinae (pp. 436, 437).
| Obisiinae (pp. 436, 437).
f Sclerosomatinae (p. 449).
\ Phalangiinae (p. 450).
( Sarcoptinae (p. 466).
Analgesinae (p. 466).
| Tyroglyphinae (p. 466).
{ Gamasinae (p. 470).
\ Dermanyssinae (p. 471).
r
Limnocharinae (p. 472).
Caeculinae (p. 472).
Tetranychinae (p. 472).
Cheyletinae (p. 473).
Erythraeinae (p. 473).
_ Trombidiinae (p. 473).
XVlll SCHEME OF CLASSIFICATION
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).
Phoxichilididae (p. 538).
Phoxichilidae (p. 539).
Pycnogonidae (p. 539).
CRUSTACEA.
CHAPTERS I awn 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.)
emery Fellow of St. John’s College, Cambridge, and Linacre Professor of Human
and Comparative Anatomy, Oxford
ay
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 abundarfce 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
2
2]
A CRUSTACEA CHAP.
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 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
ut most two pairs of kidneys are present. 3
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
i SEGMENTATION 5
of the other internal organs.’ 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 apples to the body-cavity, the musculature,
the renal, and often the generative organs. 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. belong-
ing to two true segments, or whether they are structures sui
generis, not homologous to the other hmbs. With regard to the
first antennae we are probably safe in assigning them to a true
body-segment, since in some of the Entomostraca, eg. 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 inner-
vated from the brain, but the brain, or at least part of it, 1s very
1 The muscles are to a certain extent segmented in correspondence with the
limbs ; and the heart, in Phyllopeda and Stomatopoda, may have segmentally
arranged ostia.
6 CRUSTACEA CHAP.
probably formed of paired trunk-ganglia which have fused into
a common cerebral mass ; and the fact that under certain cireum-
stances the stalked eye of Decapods when excised with its
peripheral ganglion’ 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 segmen-
tation of head and thorax agrees exactly with that of the
Malacostraca, but in the abdomen there are two additional
segments.
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” 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
1 Herbst, Arch. Entwick. Mech. ii., 1905, p. 544.
2 Quart. J. Micr. Sci. xlix., 1906, p. 469.
f. p. 263),
2
)
OF ARTHROPODS
SEGMENTATION
The following table shows the segmentation of the body in
the Malacostraca, as compared with that of Limulus (¢
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
Insecta, the primitive Myriapod Scolopendrella, and Peripatus.
species.
few segments which increase as we pass from Cambrian to
Carboniferous genera.
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xhibit a wonderful variety
The appendages of the Crustacea e
8 CRUSTACEA CHAP.
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 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-hke 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 wniramous.
I APPENDAGES 9
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 hfe is the first pair of antennae.
We are reduced, therefore, to two types—the foliaceous and
biramous. Sir E. Ray Lankester,’ 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
linb 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
lmb 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.
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
1 Quart. J. Micr. Sci. xxi., 1881, p. 343.
IO CRUSTACEA CHAP.
maxillipedes of masticatory functions. Thus in the Decapoda
the first maxillipede is decidedly foliaceous owing to the expanded
Fic. 1.—Appendages of Crustacea (A-G) and Trilobita (H). A, First maxillipede of
Astacus; B, second maxilla of Astacus; ©, second walking-leg of Astacus ; D,
thoracie 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 ; ca.s, coxopoditic
setae ; dp, dactylopodite ; end, endopodite ; ep, epipodite ; ex, exopodite ; 7p,
ischiopodite ; mp, meropodite ; pp, propodite ; 1-6, the six endites.
“onathobases” (Fig. 1, A, bp, cap), and the second maxilli-
pedes are flattened, with their basal joints somewhat expanded
and furnished with biting hairs; but in the “ Schizopoda”
I BODY-CAVITY II
(e.g. Mysis) the first maxillipede is a typical biramous limb,
though the expanded gnathobases in some forms are beginning
to project (Fig. 1, EK), 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 segmenta-
tion 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 seementation 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
TZ CRUSTACEA CHAP.
blood to the pericardium, and so to the heart again through the
apertures or ostia which pierce its walls.
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 1s 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 Reichen-
bach? 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
2 Abhandl. Senckenberg. Nat. Gesellsch. xiv., 1886.
I : KIDNEYS Tes
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 J/ysis; the antennary glands are characteristic of
adult Malacostraca' and the larvae of the Entomostraca, while the
maxillary glands (“shell-glands”) are present in adult Entomo-
straca 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 glaud of the Malacostraca is usually more
complicated: these complications have been studied especially by
Weldon,” Allen, and Marchal* 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 expand-
ing 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 Vejdovsky, 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 ecto-
dermal inpushings, but the more recent observations of Waite *
on Homarus americanus indicate that the antennary gland at
' The Cumacea, Anaspidacea, and certain Isopods possess a maxillary gland
only.
2 Quart. J. Micr. Sci. xxxii., 1891, p. 279.
® Arch. Zool. Exp. (2) x., 1892, p. 57.
* Bull. Mus. Comp. Zool. Harvard, xxxv., 1899, p. 152.
14 CRUSTACEA _ CHAP-
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 dJ/ysis and
Nebalia on carmine, excretory glands of a simple character were
observed by Metschnikoff situated at the bases of the thoracic
limbs.
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 bemg 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 hepato-
pancreas, 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 un-
published drawings of Mr. E. H. Schuster, which he kindly lent
me, it appears that in certain Decapods, eg. Callianassa sub-
terranea, the length of the mid-gut between the anterior and
posterior caeca is very long; in Carcinus maenas it is consider-
I REPRODUCTIVE ORGANS 15
able; 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 un-
known.
The reproductive organs usually make their appearance as
a small paired group of mesodermal cells in the thorax compara-
tively late in hfe; and neither in their early development nor
in the adult condition do they show any clear signs of segmenta-
tion or any connexion with a coelomic cavity. The sexes are
usually separate, but hermaphroditism occurs 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
egos 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 sperma-
tophores are hollow chitinous structures in which the sperma-
tozoa are packed; they are often very large and assume charac-
teristic 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 Koltzofft has observed that when the spermatozoon has
1 Arch. f. mikr. Anat. \xvii., 1906, p. 364.
16 . CRUSTACEA CHAP.
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
eges 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, ae. 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 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, ze.
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 hmbs (“ podobranchiae ”), to the body-
wall at the bases of these limbs, often in two series (“arthro-
branchiae ”), 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
I THE ARTHROPODS A NATURAL GROUP I
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’ 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 beheve that its actual formation in the
embryo as a distinct structure might have been secondarily
suppressed in Crustacea.
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.
PViol.e Boi pp. o/s 264.
VOL. IV C
CHAPTER, a
CRUSTACEA (CONTINUED) : ENTOMOSTRACA——BRANCHIOPODA—
PHY LLOPODA——CLADOCERA——WATER-FLEAS
SUB-CLASS I.—ENTOMOSTRACA.
THE Entomostraca are mostly small Crustacea in which the
seginentation of the body behind the head is very variable, both
in regard to the number of segments and the kind of differentia-
tion 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 Clado-
cera and Ostracoda the young hatch out in the Nauplius state.
Order I. Branchiopoda.'
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
' For this use of the term Branchiopoda, ef. Boas, Morph. Jahrb. viii., 1883, p. 519.
18
CHAP. II ENTOMOSTRACA—BRANCHIOPODA 19
smallest pools to the largest lakes, often swarm with them, as do
those streams which flow so slowly that the creatures can obtain
oceasional shelter among vegetation along the sides and bottom
without being swept away, while even rivers of considerable swift-
ness 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 down-
wards, 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 hmbs.
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 AropmpAx! the head is broad and depressed, the ventral
1 Bernard, ‘‘ The Apodidae,” Nature Series, 1892.
20 CRUSTACEA—-BRANCHIOPODA CHAP.
side being nearly flat, the dorsal stirface 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 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 enter-
ing the head to open at the base of the second maxilla. In ali
ES
Fia. 2.—Chirocephalus diaphanus, female, x 5, Sussex. D.O, Dorsal organ ; /, heart ;
Ov, ovary; U, uterus; V, external generative opening.
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.”
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 embryonie 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 LimnapipaE 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
Il STRUCTURE OF LIMNADIIDAE 21
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 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
: Fig. 3.—Limnetis brachyura, x 15.
of the thoracic feet, loco- (After G. 0. Sars.)
motion 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 carapace, and in
the form of the 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 Hstheria 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 con-
centrically 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
i)
i)
CRUSTACEA—BRANCHIOPODA CHAP.
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 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,’ 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 erystallina, for example,
will remain for hours attached by its dorsal organ to a water-
weed 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* the anus opens directly backwards; and
1 Arb. zool. Inst. Wien, vi., 1886, p. 267.
* I do not understand Packard’s account of the telson in Thamnocephalus.
II TELSON ‘OF PHYLEORODA 24723
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 Sranchipus, and never have their margins
completely fringed with setae; in A. salina from Western
Hurope, 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 4A. wrmiana from Persia the
anal lobes are well developed in the male, each lobe bearing a
Fic. 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 Hstheria (sp. 2).
single terminal hair, but they are altogether absent in the female.
Schmankewitch and Bateson have 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.
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 Limnadidae (Fig. 4, C) the telson is laterally com-
24 CRUSTACEA—-BRANCHIOPODA CHAP.
pressed 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 approxi-
mate 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
Fia. 5.—Chirocephalus diaphanus, male. Side view of head, showing the large second
antenna, A, with its appendage Ap, above which is seen the filiform first antenna ;
D.O, dorsal organ ; /), median eye.
character, except those affected by the sexual dimorphism, which
is usually great.
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 Hstheria 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
ote
II APPENDAGES OF PHYLLOPODA 25
plates as in Chirocephalus (Fig. 2), or minute vestigial fila-
ments 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 Lranchipus
the base is much thickened,
and bears on its inner side
a large filament (perhaps
represented by the proxi-
mal tubercle of Lranchinecta
and Artemia), which looks
hike an extra antenna. In
Streptocephalus the terminal
joint of the antenna is bifid,
and there is a basal filament
hike that of Sranchipus ,
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, ae ; ; ’
‘ ‘ oe Fic. 6.—Chirocephalus diaphanus. Second
while the proximal joint antenna of male, uncoiled.
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 stem and its appendages being beset 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
20 CRUSTACEA—BRANCHIOPODA CHAP.
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 pre-
senting a certain
remote resemblance to
Fic. 7.—Artemia fertilis, Front view of the head of a branchinecta. In the
ores he large second antennae, A.2; males of Polyartemia
A.1, first antennae.
the second antennae
have a remarkable branched form not easily comparable with
that found in other Branchipodidae.
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 the labrum, and is a simple oval plate, with or
without a special 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,
II APPENDAGES OF PHYLLOPODA 277,
excluding the gnathobase) being very mobile and attached to the
main stem by a definite joint. On the outer side are two pro-
cesses ; 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
A B
Fic. 8.—A, Thoracie limb of Ch irocephalus diaphanus ; B, prehensile thoracic limb
of male Estheria. gn, Gnathobase ; 1-6, the more distal endites.
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 ”)." In the two last-named families the basal exite
or bract of the Branchipodidae does not appear to be represented.
The limbs of the Apodidae are remarkable in two ways:
those in front of thé genital opening (very constantly ten pairs)
' The nomenclature here adopted is not that of Lankester.
28 CRUSTACEA—-BRANCHIOPODA CHAP.
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 caneriformis 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.
Tu 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.
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 (Hstheria, Limnadia), or at its posterior end
(Limnetis). In female LZimnetis 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 (Zimnadia, 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 per-
formed ; 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
II ALIMENTARY CANAL AND HEART 29
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 ned 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 ean 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 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 1s 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 Zimnetis 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
30 CRUSTACEA—BRANCHIOPODA CHAP.
Artemia has rather more, and the blood of Apus is very red.
The only other Crustacea in which the blood contains haemo-
globin are the Copepods of the genus Lernanthropus,’ 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 gangha, 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” has lately described
several terminal cells, containing peculiar chitinous bodies, in
the adult. The homologous sense-organs of Limnetis are appar-
ently 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 con-
nective just behind the brain. The post-oral nerve-cords are
widely separate, each of 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 ganghon is a re-
markable 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,”
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
‘(The red pigment in Lernanthropus, see p. 68, has been shown to be not
haemoglobin, so that the presence of this substance in Phylopod blood becomes
doubtful.—G.8. ] 2 Zeitschr. wiss. Zool. \xxi., 1902, p. 508.
3 Cf. Gaskell, Journ. Anat. Physiol. x., 1876, p. 153,
II REPRODUCTIVE ORGANS
ios)
=
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 dApus, 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
seoment 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 contaimed 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 egg-
shells. 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 hke 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.
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,’ and many are partheno-
genetic. Among Branchipodidae Artemia is the only genus
known to be parthenogenetic, but parthenogenesis is common in
1 Bernard’s statement that Apus is hermaphrodite seems based on insufficient
evidence.
32 CRUSTACEA—BRANCHIOPODA CHAP.
all Apodidae, while the’ males of several species of Zimnadia 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 (eg. of Chirocephalus diaphanus
and Branchipus stagnalis) float when placed in water after desic-
cation, 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
reinain quiescent until a fresh rainy season. The mud from the
beds of such temporary pools often contains large numbers of
egos, 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 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 con-
siderable increase in the salinity of the surrounding waters during
II HABITAT OF PHYLLOPODA
ios)
ios)
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 evapora-
tion went on, but that chlorides would probably remain in solu-
tion; 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 equiva-
lent to 0°025 orm. 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 germ. 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 pre-
cipitated as a visible film.
Some species of Branchipus (e.g. B. spinosus, M. Edw.) and
of Estheria (EF. macgillivrayi, Baird, F. gubernator, Klutzinger)
occur in salt pools, but Artemia flourishes in waters beside
whose salinity that endured by any other Branchiopod is in-
significant. 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, but the Apodidae occasionally
wriggle along the bottom on their ventral surface, and Zstheria
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
VOL. IV D
34 CRUSTACEA—BRANCHIOPODA CHAP.
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, represen-
tatives of every family and of some genera (e.g. Streptocephalus,
Lepidurus, Estheria) being found in every one of the great zoo-
logical regions, though a few aberrant genera are of limited range,
thus Polyartemia is known only from the northern Palaearctic
and Nearctic regions, Zamnocephalus only from the Central
United States. The genus Artemia is not at present known in
Australia.’ The only recorded British species are Chirocephalus
diaphanus, Artemia salina, and Apus cancriformis, but other
continental islands, for example the West Indian group, are
better supplied. The distribution of the species is very im-
perfectly 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 Euro-
pean 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 ;* an Apus, closely related to the modern A. cancriformis,
has been found in the Trias, but the most numerous remains have
been left, as might be expected, by the hard-shelled Limnadidae ;
1 Sayce has since described it, Proc. Roy. Soc. Victoria, xv., 1903, p. 229.
2 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, Vature,
Ixxvi., 1907, p. 589.
5 Branchipodides has been described by H. Woodward, from Tertiary strata.
HI GENERA OF PHYLLOPODA 35
earapaces, closely resembling those of the modern Hstheria, 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.
Sus-ORDER PHyLLorpopsa.—BPranchiopoda with an elongated body, pro-
vided 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.'—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 9 elongated. B. paludosa, O. F.
Miull.— Circumpolar.
Branchiopodopsis, G. O. Sars?—Second antennae of ¢ as in
Branchinecta ; ovisac of Q short. B. hodgsoni, G. O. Sars
—Cape of Good Hope.
Branchipus, Schaeffer—Second antennae of ¢ with simple
internal filamentous appendage. JB. stagnalis, Linn. —
Central Europe.
Streptocephalus, Baird—Second antennae of ¢ 3-jointed, the
last joint bifid; an external filamentous appendage. ¥.
torvicornis, Wagn., Poland.
Chirocephalus, Prévost—Second antennae of ¢ 3-jointed, witha
jointed internal appendage, which bears secondary processes,
four cylindrical and one lamellar. ©. 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 g without filamentous
/; Consult Baird, ‘‘ Monograph of the Branchiopodidae,” Proc. Zool. Soc. 1852,
p. 18. Packard, 12th Ann. Rep. U.S. Geol. Survey, part 1., 1879.
2 Arch. f. Math. og Naturvidensk. xx., 1898, Nos. 4 and 6. Thiele, Zool. Jahrb.
System. xiii., 1900, p. 568.
36 CRUSTACEA—BRANCHIOPODA CHAP,
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 pro-
cess of unknown nature. Only species 7. platywrus, Packard
—Kansas, U.S.A.
B. Nineteen pairs of praegenital ambulatory limbs.
Polyartemia, Fischer—Second antennae of ¢ forcipate ; ovisae
of @ very short Only species P. forcipata, Fisch.
Fam. 2. Apodidae.'—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—tTelson not produced backwards over the anus ;
endites of first thoracic limb very long.
= *
MPL
rie! ¢
rie Ps
ta *
y ;
+
CHAPTER XXI
PYCNOGONIDA !
REMOTE, so far as we at present see, from all other Arthropods,
while yet manifesting the most patent features of the Arthropod
type, the Pyenogons 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, ~ a
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 (Phalangiwm lit-
torale, Strom, 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,
1G. 262.—Pycnogonuim littorale, Strom, x 2.
' Pycnogonides, Latreille, 1804 ; Podosomata, Leach, 1815 ; Pychnogonides ow
Crustacés aranéiformes, Milne-Edwards, 1834; Crustacea Haustellata, Johnston,
1837 ; Pantopoda, Gerstaecker, 1863.
501
502 PYCNOGONIDA CHAP,
tubular proboscis, at the apex of which is the mouth, suctorial,
devoid of jaws; the body terminates in a narrow, lmbless,
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 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
aninal 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 sub-
stance of the above account, and the perplexity attending the
classification of the animal, are all included in Linnaeus’s short
description :' “Simillimus Onisco Ceti, sed pedes omnes pluribus
articulis, omnes perfecti, nec plures quam octo. Dorsum rubrum,
pluribus segmentis; singulis tribus mucronibus. Cauda cylin-
drica, brevissima, truncata. Rostrum membranaceum, sub-
subulatum, 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.” *
1 Syst. Nat. ed. xii. 1767, vol. ii. p. 1027.
* Briinnich’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[om.] Strom inter phalangiis
relatum, Sindm. Tom. i. p. 209, t. 1, f.17. Exemplar hujus
insecti, quod munificentia R. Autoris possideo, ita describo ;
Caput cum thorace unitum, tubo 6 excavato cylindrico, antice
angustiore, postice in thoracem recepto, prominens ; Oculiiv.
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.
xO GENERAL STRUCTURE 503
The common Pycnogonum is, by reason of the suppression of
certain limbs, rather an outlying member than a typical repre-
sentative 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 Cap- ae
rellae with skeleton SY,
limbs to the branches a,
of Zoophytes, where
their slender forms are
not easily seen. In
contrast to the stouter
body and hmbs 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
tween the oculiferous ‘
tubercle and the pro- see
bosecis; the legs are
produced to an amazing
length and an extreme fi)
degree of attenuation : i
“mirum tam parvum — ~
corpus regere tam a}
magnos pedes,” says Fic. 263.—Dorsal view of Nymphon brevirostre,
a, Hodge, x 6. Britain.
neck intervenes _ be-
I
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-lke
brevissimis compositi, ungue valido terminati. Ex descriptione patet insectum
hoe a generibus antea notis omnino differre, ideoque novum genus, quod e crebris
articulationibus Pyenogonum dico, constituit.” The confusion between Cyamus
and Pycnogonum seems to have arisen with Job Baster, 1765; cf. Stebbing, Anow-
ledge, February 1902, and Challenger Reports, ‘‘ Amphipods,” 1888, pp. 28, 30, ete.
504 PYCNOGONIDA CHAP.
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 genera-
tive 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 Pyenogon, save these, exhibits a greater number of
appendages than Nymphon nor a less number than Pyenogonum,
nor are any other conspicuous organs to be discovered in other
genera that are not represented in these two: within so narrow
limits he 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 the ease with
which terms seem 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 Kroyer and Milne - Edwards, to
the Crustacean analogy, mandibles and
maxillae. Dohrn eludes the difficulty
qe Fain he ee by denominating the appendages by
below, showing chelo- simple numbers, Le Lt eT ee Ava.
ae palps, and oviger- 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
XX1 BODY AND LIMBS 505
or “chelophores,”’ the second or “palps,” the 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 Pyenogonum, still more attenuated than
in Vymphon.
In a few forms (eg. Pallene, Ammothea, Tanystylum, Colos-
sendeis) the last two, or even more, segments of the trunk are
A
Fic. 265.—A, Colossendeis proboscidea, Sabine, Britain ; B, Aimmothea echinata, Hodge,
Britain ; ©, Phozxichilus spinosus, Mont., Arctic Ocean. (The legs omitted.)
more or less coalescent. In Rhynchothorax the cephalic segment
is produced into 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 some-
times densely hispid.
The proboscis varies much in shape and size. It may be
much longer or much shorter than tne body, cylindrical or
tumid, blunt or pointed, straight or (e.g. Decolopoda) decurved ;
usually firmly affixed to the head and pointing straight forwards ;
sometimes (Hurycide, 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, Rhyncho-
thorax, and Colossendeis.'
1 Hoek, Chall. Rep. p. 15, mentions a specimen of Colossendeis gracilis, Hoek,
506 PYCNOGONIDA CHAP,
In Ammothea and its allies they are extremely rudimentary
in the adult, being reduced to tiny knobs in Vanystylum and
Fic. 266.—A, B, Chelophores of Ascorhynchus abyssi, G.O.S. A, Young; B, adult.
(After Sars.) ©, Anterior portion of Ammothea hispida, Hodge, Jersey: late
larval stage (= Achelia longipes, Hodge), showing complete chelae. D, Chela of
Eurycide hispida, Kr.
Trygaeus, and present as small two-jointed appendages in Ammo-
thea. in this last, if not in the others also, they are present in
complete chelate form in the later larval stages.
In Burycide, Ascorhynchus, and Barana they are usually less
atrophied, but yet comparatively small and with imperfect chelae,
while in some Ascorhynchi (4A. minutus, Hoek) they are reduced
to stumps.
In Pallenopsis the scape of the chelophore consists of two
joints, as also in Decolopoda and some Ascorhynchus: in Nymphon,
Frc. 267.—Chelae of species of Nymphonidae: A, Mymphon brevirostre, Hodge; B,
Boreonymphon robustum, Bell; C, Chaetonymphon macronyx, G.O.S. ; D, Nymphon
elegans, Hansen.
Phoxichilidium, Pallene, and Cordylochele of one only; in all
‘furnished with a pair of distinctly three-jointed mandibles ; and the specimen
was the largest of the three obtained.”
XXI CHELOPHORES, PALPI, ETC, 507
ce
these the terminal portion or “hand” forms a forcipate “chela,”
of which the ultimate joint forms the “movable finger.” In
some species of Vymphon 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
ereatly curved, with a wide gape between.
In this last, and in Phowichilidium, the oppos-
ing edges are smooth and toothless. In Cordy- Pre, 268. — Proboscis
lochele the hand is almost globular, the movable ee
finger being shortened down, and half enclosed _ coilis,G.0.8. (After
by the other. Sars.)
Palpi.—tThe second pair of appendages, or palps, are absent,
_or all but absent, in the adult Pyenogonum, Phoxichilus, Phoai-
chilidium, Pallene, and their allies. In certain of these cases,
eg. 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
Fig. 269.—Kury- the number of joints ranges from five or six in
— ies Tanystylum to nine (as a rule) in Ammothea and
stalked pro. Oorhynchus, or ten, according to Dohrn, in certain
pe “IS- species of Ammothea. Colossendeis and the Eury-
cididae 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 which the name connotes.' They
! As a rare exception, Hoek has found the eggs carried on the ovigerous legs in
a single female of Nymphon brevicaudatum, Miers.
508 PYCNOGONIDA CHAP,
probably also take some part, as Hodgson suggests, in the act of
feeding.
In Pycnogonum, Phoxichilus, Phoxichilidium, and their im-
mediate allies they are absent in the female; in all the rest
wy
A B Cc D
Fic. 270.—Ovigerous legs of A, Phoxichilus spinosus, Mont. ; B, Phoxichilidium femor-
ee Rathke ; C, Anoplodactylus petiolatus, Kr.; D, Colossendeis proboscideus,
they are alike present in both sexes, though often somewhat
smaller in the female than in the male. They are always turned
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 Phowi-
chilidium five, Anoplodactylus six,
FiG, 271.— Terminal joints of oviger- Phoxichilus seven ; in Paranymphon
ous leg of Rhynchothorax medi- _.- : ‘ . .
ihe ys COR Oe eight; in Pyenogonum nine, with,
in addition, a terminal claw; in the
Amuiotheidae from seven (7rygaeus) to ten, without a claw;
in Pallenidae ten, with or without a claw ;
in Lhynchothorax, Colossendeis, Eurycide,
Ascorhynchus, Nymphon, ten and a claw.
The appendage, especially when long, is apt
to be wound towards its extremity into a
spiral, and its last four joints usually possess
a peculiar armature, In Rhynchothorax this pene
takes the form of a stout toothed tubercle Terminal joints of
on each joint; in Colossendeis of several — oviserdus oe ae
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.
Legs.—The four pairs of ambulatory legs are composed, in
all cases without exception, of eight joints if we exclude, or nine
XXI AMBULATORY LEGS 509
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
j \
| \
|
\ j
Fic. 273.—Nymphon strémii, Kr. Male carrying egg-masses on his ovigerous legs.
} t=} fo] Lo] fo)
Colossendeis, the fourth, fifth, and sixth joimts being those that
suffer the greatest elongation. The seventh joint, or tarsus, 1s
Fig. 274.—Terminal joints (tarsus and propodus) of legs. 1, Chaetonymphon hirtum,
Fabr. ; 2, V. strémii, Kr. ; 3, Nymphon brevirostre, Hodge ; 4, Ammothea echinata,
Hodge ; 5, Ascorhynchus abyssi, G.O.S. (All after Sars.)
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
510 PYCNOGONIDA
CHAP.
Fie. 275.—Legs of A, Pallene brevirostris, Johnston ;
B, Anoplodactylus petiolatus, Kr. ; ©, Phoxichilus
spinosus, Mont. ; D, Oolossendeis proboscidea,
Sabine ; E, Ammothea echinata, Hodge, 3.
auxiliary claws, sometimes large, sometimes small, lie at the base
of the terminal claw in Ammotheidae, Phoxichilidae, in Phoxi-
Oe GLANDS St
chilidium, in most Pallenidae, in nearly all Nymphonidae. Their
presence or absence is often used as a generic character, helping
to separate, eg., Pallene from Pseudopallene and Pallenopsis,
and Phowxichilidium 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.
aya ®
NI
meg
~
Fic. 276.—Boreonyinphon 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 ' 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
' Meisenheimer (Zeitsch. wiss. Zool. \xxii., 1902, p. 235) compares these with
certain glands described in Branchipus by Spangenberg and by Claus.
512 : PYCNOGONIDA CHAP.
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 Pyenogonum 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 rudi-
mentary. 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 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 ning
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 Pyenogonum,
but in Phoxichilus, Phoxichilidium and Pallene he discovered
the glands appertaining to the palps, though the palps them-
selves have disappeared in those genera; he has found the glands
also in Ammothea, in larvae that have not yet attained their fuil
complement of legs.
The males in nearly all cases are known to possess glands in
XXI GLANDS—ALIMENTARY SYSTEM legs
the fourth joints or thighs of all the ambulatory legs, and these
glands without doubt act as cement-glands, emitting, lke 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 Vymphon and otf 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.’
In Discoarachne (Loman) and Trygaeus they open into a wide
chitinised sac with tubular orifice. While the function of these
last glands and of the larval glands seems plain enough, that of
those which oceur 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, lke 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.”
Alimentary System.—The proboscis is a very complicated
organ, and has been elaborately described by Dohrn.’ It is a
prolongation of the oral cavity, containing a highly developed
stomodaeum, but showing no sign of being built up of limbs or
1 Ortmann, who would unite Barana with Ascorhynchus, observes: ‘‘ Bei dieser
Gattung [Ascorhynchus] konnte ich die Kittdriisen beobachten, die bei 4. ramipes
mit dem von Barana castelnaudi [castelli] Dohrn, bei A. eryptopygius mit Barana
arenicola iibereinstimmen und also die primitivsten Formen der Ausbildung zeigen.”
—Zool. Jahrb. Syst. v., 1891, p. 159.
2 Mém. Acad. Sci. St-Pétersb. (vii.), xxxviii., 1892.
® Fauna u. 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.
VOL. IV 2 L
PYCNOGONIDA CHAP,
514
gnathites. The mouth, situated at its apex, is a three-sided
orifice, formed by a dorsal’ 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 pro-
minent 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 com-
plicated in others. Transverse ridges run
across the angles where adjacent lips meet,
and the whole mechanism
Fic. 277.— Longitudinal constitutes an
section through one efficient valve, preventing the escape of
‘“‘antimere"” of the Nowedetood Tl ; ; uke f tl
proboscis in Phoxi- SWallowed 1ood. ye greater portion of the
chilus — charybdaeus.
G, g', Principal and
secondary ganglia; /,
sieve -hairs; JZ, lip;
mt, oral tooth ; WV, NV’,
proboscis is occupied by a masticating or
triturating apparatus, the oesophageal cavity
expanding somewhat and having its walls
inner and outer nerve- Gensely covered, in three bands correspond-
cords; #, proboscis: ing to the antimeres, with innumerable
teeth. (After Dohrn.) = ; ‘
minute spines (i) or needles, sometimes
supplemented by large teeth (/) that point forwards somewhat
obliquely to the axis of the proboscis.”
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.
' The dorsal lobe is absent in Rhynchothorax.
’ 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 (¢. cit. pp. 46-53).
XXI PROBOSCIS—-ALIMENTARY SYSTEM 515
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
or”
Fic. 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 (1). Coec, Intestinal caeca ; Dil. M, dilator muscles ; 1, inner nerve-ganglion,
= — rn ? C + . 7! y oh ta . . 1+] C 7 1 7
with circular commissure ; V’, outer nerve ; 07, chitinous lining of oral cavity ;
RM, Ret.M, retractor muscles. (After Dohrn.)
which succeeds the masticatory apparatus is lkewise provided
with extrinsic muscles.
The oesophagus is followed by a
long gastric cavity, which sends forth
eaecal diverticula into the chelo-
phores (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
ol connective tissue, and the whole 7.5) o79 — tsnevems — eection
gut, central and diverticular, is further through the basal joint of the
supported by a horizontal septal mem- M4 Teg im Phowichilus charyb-
[i daeus, 9. Cut, Cuticle; Hyp,
brane, running through body and legs, —_hypodermis ; nt, intestinal cae-
hich t hed leplaad 1 cum; JV, nerve-cord; Ov, ovary ;
which separates the dorsa 00d-Vesse Sept, septum. (After Dohrn.)
and sinus from the gut, the nervous
system and the ventral sinus, giving support also to the reproduc-
tive glands. A short and simple rectum follows the gastric cavity.
In Phowichilus, 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.).'
1 Dolign, ¢. cit. p. 55.
5 16 PYCNOGONIDA CHAP.
Circulatory System.—The heart has been especially studied
by Dohrn in Phovichilus. 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 per-
forated 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 hmbs and the contrac-
tions 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 gangha, 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 gangha 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 com-
XXI NERVOUS SYSTEM—EYES 517
plicated. Its upper antimere is supphed 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 ganghon 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 Jacking 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 cephalo-
thorax, or first, compound, segment of the body. The anterior
pair are frequently a httle 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.’
The eye of a Pyenogon (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
1 Biol. Stud. Johns Hopkins Univ. v., 1891, p. 49.
pt 8 PYCNOGONIDA CHAP.
interwoven in a protoplasmic syncytium, whose middle parts are
occupied by the nuclei and whose inwardly-directed ends form
the retinal 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 ap-
proximate 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 Jegs are
present, Morgan shows us the pigment-layer apparently con-
tinuous 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 invagina-
tion, 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.'
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
1 Vergl. Entwickl. d. wirbellosen Tiere, Jena, 1893, p. 664.
XXI INTEGUMENT—REPRODUCTIVE ORGANS 519
many little cavities, some of them conical and tapering to a
minute external pore, the others more regularly tubular. Some-
times, 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 more, sometimes in rosettes of eight or nine. These
setae are small or rudimentary in Ascorhynchus and_ totally
wanting in Oolossendeis; 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 imtegumentary
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 imdeed, 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 Phowichilidium, 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,’ which, in many forms, are
ereatly 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 Phowichilus ;
1 Tn the second joint in Ascorhynchus abyssi, Sars, and A. tridens, Meinert.
520 PYCNOGONIDA CHAP,
in most genera on the last two; in Pycnogonum and Rhynchothoraxz
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’ in
Anoplodactylus. The animal reproduces towards the end of
August. Consorting on their Hudendrium (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 1s 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 Phowichilidium 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 Phowxichilidium 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 Phowichilus, 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;?
1 Biol. Bulletin Woods Holl, vol. ii., Feb. 1901, p. 196.
2 Studi e ricerche sui Picnogonidi, Firenze, 1876.
LO DEVELOPMENT 521
before, and by some even after lis time, the two sexes were
constantly confused.'
Segmentation is complete, symmetrical in the forms with
smaller eggs, unequal in those burdened with a preponderance
of yolk (Morgan). In Padlene, 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 con-
centrated at the germinal pole of the egg. ‘MONT (ssey 10) OT 6-F 2 “OTIQOW * WVCIAHLOWNY
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XXI CLASSIFICATION —DECOLOPODIDAE IS seyal
CLASS PYCNOGONIDA|!
Marine Arthropoda, with typically seven (and very exception-
ally 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 proboscis, a
limbless, unsegmented abdomen, and no manifest respiratory organs.
Fam. 1. Decolopodidae.— Appendage I. dwarfed, but com-
Fic. 282.—Decolopoda australis, Bights. A, x 1: from a specimen obtained at the
South Shetlands by the Scotia Expedition. B, First appendage, or chelophore.
(A, original ; B, after Hodgson.)
plete and chelate, scape with two joints; II. 9-10-jointed; III.
well developed in both sexes, 10-jointed, the terminal joints with
1 See (inter alia) Dohrn, 7.c. ; E. B. Wilson, Rep. U.S. Fish. Comm. (1878), 1880 ;
Hoek, Chall. Report, 1881-; G. O. Sars, Norw. N. Atl. Exp. 1891; Meinert, Lngol/
532 PYCNOGONIDA CHAP.
about four rows of teeth; five pairs of legs, destitute of accessory
claws; genital apertures on all the legs (Bouvier).
Decolopoda australis, Eights ' (1834), a remarkable form from
the South Shetlands, recently re-discovered by the Scotia expedi-
tion. 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 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 KEurycididae ; 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 IL. 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.’ 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.» The largest species, C. gigas, Hoek, from great depths
Exped. 1899; Mobius, Fawna Arctica, 1901, Valdivia Exped. 1902; Cole, Harri-
man Alaska Exped. 1904; Hodgson, Discovery Exped. 1907 ; Bouvier, Exp.
Antarct. Fr. 1907.
1 Boston Journ. Nat. Hist. i., 1834, p. 203; Cf. Hodgson, Pr. R. Phys. Soc.
Edinburgh, xvi., 1905, p. 85; Zool. Anz. xxv., 1905, p. 254; Discovery Exp.,
‘*Pyenogonida,” 1907 ; Bouvier, Hxp. Antarct. Fr. 1907.
2 See pp. 535, 541. Cf. Dohrn (é. cit.), p. 228.
3 The first known species was described as Phowichilus proboscideus, Sabine,
from the shores of the North Georgian Islands (1821).
3
XXI COLOSSENDEIDAE—EURYCIDIDAE 533
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 tor Rh. kréyeri, W.-M. (Andamans), 2. clavipes,
Carp. (Torres Straits), and &. tenwissimus, 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. Burycididae (Ascorhynchidae, Meinert).— Appen-
dage I. more or less reduced; appendage II. 10-jointed (absent
in Hannonia); appendage III. 10-jointed, clawed, with more
than one row of serrated teeth; proboscis movably articulated
and more or less bent under the body ; auxiliary claws absent.
Hurycide, Schiddte (1857) (Zetes, Kroyer, 1845): Appendage
I. with two-jointed scape, without chelae in adult ; one species (£.
hispida, (Ky.)), from the North Atlantic and
Arctic, and two others from the East Indies,
recently described by Loman. Sarana
arenicola, Dohrn (1881), is nearly allied.
Ascorhynchus, G. O. Sars (1876) (Gnampto-
rhynchus, Bohm, 1879; Scaeorhynchus,
Wilson, 1881), very similar to Hurycide,
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 Lurycide; 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 Hurycide, as 1s also, probably,
Parazetes auchenicus, Slater, from Japan.
Hannonia typica, Hoek (1880), from Cape Town, is a
remarkable form, lately redeseribed by Loman. The chelophores
are much reduced, the palps are absent; the ovigerous legs are
Fic. 283.— Hurycide his-
pida, Kr. ; side view.
534 PYCNOGONIDA CHAP.
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
egos 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.'
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 Vymphon and pre It is perhaps
an immature form. Schimkewitsch has described another species,
N. korotnevi, and Loman a third, WV. muscosus, both from the
East Indies.
Fam. 4. Ammotheidae.—Akin to Enurycididae 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 inperfectly segmented ;
appendage IT. 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) (meluding Achelia, Hodge (1864) =
the old non-chelate individuals): appendage I. very all 2-jointed;
appendage I]. 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 dAchelia hispida, Hodge ; and Ammothea
magnirostris, Dohrn, is apparently the same species. A. fibuli-
fera, Dohrn, seems identical with Achelia echinata, Hodge (of
which A. brevipes, Hodge, is the young), and so probably is 4.
achelioides, Wilson; Hndeis didactyla, Philippi (1843), is very
probably the same species. 4. wniunguiculata, Dohrn (? Pariboea
spinipalpis, Philippi (1848)), has no auxiliary claws, Leionym-
phon, Mobius (1902), contains nine Antarctic forms, allied to
Ammothea (including A. grandis, Pfeffer, and Colossendeis gibbosa,
Mob., which two are probably identical), with characteristic
1 Pocock (Encycl. Brit., 10th ed., Art. ‘‘ Arachnida’’) makes Hannonia the
solitary type of a family. Cf. Loman, Zool. Jahrb., Syst., xx., 1904, p. 385.
XXI AMMOTHEIDAE—-RHYNCHOTHORACIDAE 535
transverse ridges on the body, a large proboscis, a 9-jointed
palp, and somewhat peculiar ovigerous legs. Ciluneulus,
Fragilia, and Scipiolus are new genera more or less allied to
Leionymphon, described by Loman (1908) from the Siboga
Expedition." Tanystylum, Miers (1879) (including Clotenia,
Dohrn (1881), and Discoarachne, Hoek (1880)), has append-
age 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. Zrygaeus communis, Dohrn
(1881), from Naples, has a 7-jointed, and Oorhynchus auck-
landiae, Hoek (1881), a 9-jointed palp; the former has only
seven joints in the ovigerous leg. Lecythorhynchus armatus,
Bohm (1879), with rudimentary 2-jointed chelophores, and J.
(Corniger) hilgendorfi, Bohm, 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 (1867), and Béhmia, 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” is, in my opinion, undoubtedly
Ammothea hispida, Hodge, and so also, I believe, is his Pephredo
hirsuta; P. umbonata, Gould? (Long Island Sound), is, with as
little doubt, Zanystylum 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-joited, clawed ovigerous legs, which last are provided on
the last five jomts with peculiar toothed tubercles. The general
aspect of the body is somewhat lke 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
1 Loman conjoins all these genera, and also Lecythorhynchus, with Nymphopsis,
as a sub-family Nymphopsinae of Ammotheidae.
2 Edinb. New Phil. Journal, Oct. 1842, p. 367 (P. capillata on Plate).
3 Proc. Boston Nat. Hist. Society, vol. i., 1841-44, p. 92.
536 PYCNOGONIDA CHAP,
differs from Ammotheidae in the possession of a claw on appen-
dage 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 pen-
ultimate legs. A single pair of generative orifices are found on
A B
Fic. 284.—Rhynchothorax mediterraneus, Costa. A, Body and bases of legs ;
B, terminal joints of palp. (After Dohrn.)
the last legs. A second species, F. australis, Hodgson, comes
from the Antarctic.
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,
XI NYMPHONIDAE
PALLENIDAE 537
Miers (=. horridum, Bohm), an extraordinary hispid form
from Kerguelen,’ is also peculiar. Pentanymphon, Hodgson
(1904), from the Antarctic (cireumpolar), 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.
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):° appendage ITI.
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 SS tee)
three very smooth, elongated, northern species, to — brevirostris, John-
which Bouvier has added one from the Antarctic; PEN
Pallene laevis, Hoek, from Bass’s Straits, is
somewhat similar. Neopallene, Dohrn (1881): as in Pallene,
but with a rudimentary 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
1 Found by Sir John Ross’s expedition in 1840, and subsequently by the
Challenger expedition and other visitors.
° Stebbing has recently shown (Knowledge, Aug. 1902, p. 157) that the genus
Phoxichilus was instituted by Latreille (Nowy. Dict. d’hist. nat. 1804) for the
Pycnogonum spinipes of Fabricius, now Pseudopallene spinipes, auctt. Hence he
changes Pseudopallene to Phowxichilus, Latr., and Phoxichilidae and Phowxichilus,
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).
538 PYCNOGONIDA CHAP.
ten species, East Indies and Australia); Pallene grubw, Hoek
(Phouichilidium 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. Pallene
dimorpha, Hoek, from Kerguelen, with 4-jointed palps, deserves
a new generic appellation. P. Jongiceps, Bohm, from Japan, with
rudimentary 2-jointed palps in the male, is also peculiar.
Fam. 8. Phoxichilidiidae——Appendage I. well-developed ;
II. absent; III. present only in the male, having a few simple
A B
Fic. 286.—Phoxichilidium femoratum, Rathke, Britain. A, The animal with its legs
removed ; B, leg and chela.
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 ITI. 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 many were first
XXI PHOXICHILIDIIDAE—PYCNOGONIDAE 539
referred to Phowichilidium. 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.
A
Fie. 287.—A noplodactylus petiolatus, Kr., Britain. A, Dorsal view; B, side view.
Fam. 9. Phoxichilidae.'— 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 Phowxichilus (auctt., non Latreille,
Chilophozus, 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, Bohm, P. mollis, Carp., and P. procerus, Loman,
from the East Indies; P. australis, Hodgson, from the Antarctic ;
P. béhmii, 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.
The only genus is Pycnogonum, Briinnich (1764) (Polygonopus,
1 Vide note 2, p. 537.
540 PYCNOGONIDA CHAP,
Pallas, 1766); the type is P. littorale, Strom, of the N. Atlantic
()-450 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, Mobius,
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 de-
scribed only from a larval form with three pairs of legs.
P. orientale, Dana (first described as Astridiwm, n.g.), 1s also
described from an immature specimen, and more resembles a
Phoxichilus.
The British Pycnogons.
Dr. George Johnston,’ the naturalist-physician of Berwick-on-
Tweed, Harry Goodsir,? brother of the great anatomist, who
perished with Sir John Franklin, and George Hodge® 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 * 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 mdispensable
advantage of access to Canon Norman’s collection, and the still
greater benefit of his own stores of endless information.’
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.
1 Mag. Nat. Hist. vi., 1838, p. 42; Mag. Zool. and Bot. i:, 1837, p. 368.
2 Edinb. New Phil. Journ. xxxii., 1842, p. 136 ; xxxiii., 1842, p. 867 ; Ann. Mag.
Nat. Hist. (1), xiv., 1844, p. 4.
3 Ann. Mag. Nat. Hist. (3), xiii., 1864, p. 113.
* Proc. R. Dublin Soc. (N.S.), viii., 1893, p. 195; Fisheries, Ireland, Sci. Invest.
1904, No. iv. (1905).
° Cf. A. M. Norman, J. Linn. Soc. xxx., 1908, pp. 198-238.
XXI THE BRITISH PYCNOGONS 541
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, 8):
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. franeiscana, 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): Corn-
wall 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 Jess spiny form occurs
which Carpenter records as P. laevis, Grube, but Norman unites the two
under the name of Hndeis spinosus (Mont.).
Pycnogonum littorale, Strom (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, Queens-
town (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): Northumber-
land, East of Scotland, Orkney, etc., not uncommon.
N. gracile, Leach (N. gallicum, Hoek; p N. femoratum, Leach): South
of England, West of Scotland, and Ireland.
N. strémit, Kr. (N. gigantewm, 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. spinoswm, 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 Mobius 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. minutwm, 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
542 PYCNOGONIDA CHAP. XXI
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.); NV. hirtipes, Bell; N. longitarse,
Kr.; V. 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, Caullery, from the Porcupine Station XVIL., 8.S.E. of
Rockall, in 1230 fathoms. Lastly, and less clearly related to
temperature, we have Chaetonymphon tenellum, Sars; N. gracilipes,
Fabr. ; WV. leptocheles, Sars; WN. macronyx, Sars; N. serratum, Sars ;
and Cordylochele malleolata, Sars.
Of the species recorded in the above list as a whole, Anoplo-
dactylus 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.
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 Acan-
tholithus, 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 Pyenogonida, 502
Abdominal glands, of Chernetidea, 432
Abyssal region (marine), 204 ; (lacustrine),
209
Acantheis, 418
Acanthephyra, 163
Acanthephyridae, 763
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; ex-
ternal structure, 457 ; spinning organs,
457; internal structure, 459; meta-
morphosis, 462 ; classification, 464
Acaste, 249
Accola, 390
Acerocare, 247
Achelata, 429
Achelia, 534; A. longipes, 506
Achtheres, 75; A. percarum, 75
Acidaspidae, 251
Acidaspis, 226, 227, 230, 231, 235, 241,
251; A. dufrenoyi, 250; A. tubercu-
lata, 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 ;
Aegleidae, 169
Aeglina, 227, 249; Ae. prisca, 248
Agelena, 416; A. brunnea, 367 ; A. laby-
rinthica, 352, 353, 378, 380, 381, 416 ;
A. naevia, 339
Agelenidae, 325, 352, 353, 415
Ageleninae, 4/6
Ageregate glands, 335, 349
Aglaspis, 279
Agnathaner, 66
Agnathonia, 529
Agnostidae, 244
Agnostini, 243
Agmnostus, 222, 223, 225, 231, 234, 245 ;
A. integer, 245
Agraulos, 247
Agroeca, 3897 ; A. brunnea, cocoon, 358
Albunea, 171 ; respiration, 170 ; distribu-
tion, 201
Albuneidae, 177
Alcippe, 92; A. lampas, 92, 93
Aleock, on Oxyrhyncha, 192; on phos-
phorescence, 151
Alepas, S9
Alima, larva of Squilla, 145
Alimentary canal, of Crustacea, 14; of
Phyllopoda, 28; of Cladocera, 42; of
Squilla, 142 ; of Malacostraca, 110 ; of
distribution, 212
543
544
INDEX
Trilobites, 222; of Arachnida, 256 ; of
Limulus, 268; of Scorpions, 304 ; of
Pedipalpi, 310; of Spiders, 329; of
Solifugae, 427; of Pseudoscorpions, 434 ;
of Phalangidea, 444 ; of Acarina, 459 ;
of Tardigrada, 480; of Pentastomida,
’ 491 ; of Pyenogons, 513
Alitropus (Aegidae), habitat, 211
Allman, on larvae of Pycnogons, 523
Alloptes, 466
Alona (including Leydigia, Alona, Harpo-
rhynchus, 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
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;