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http://www.archive.org/details/cu31924024535472
THE
CAMBRIDGE NATURAL HISTORY
EDITED BY
S. F. HARMER, M.A., Fellow of King’s College, Cambridge ; Super- intendent of the University Museum of Zoology
AND
A. E. SHIPLEY, M.A., Fellow of Christ’s College, Cambridge ; University Lecturer on the Morphology of Invertebrates
VOLUME V
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“SNivdiddd JO NOILAGIHISIG IVOIHdVuOORD AHL JIVHLSNTI OL dvW SRS
PERIPATUS
By ADAm SEDGWICK, M.A., F.R.S., Fellow and Lecturer of Trinity College, Cambridge
MYRIAPODS
By F. G. Stncuatr, M.A., Trinity College, Cambridge
INSECTS
PART I. Introduction, Aptera, Orthoptera, Neuroptera, and a portion of Hymenoptera (Sessiliventres and Parasitica)
By Davip SHarp, M.A. (Cantab.), M.B. (Edinb.), F.R.S.
Lonvon MACMILLAN AND CO.
AND NEW YORK
1895 sw
All rights reserved
\ Beas
A.\S84S4 ‘Creavit in ccelo Angelos, in terra vermiculos: non superior in illis, non inferior in istis. Sicut enim nulla manus Angelum, ita nulla
posset creare vermiculum.”—SainT AUGUSTINE, Liber soltloquiorum animae ad Dewm, Caput TX.
CONTENTS
PAGE SCHEME OF THE CLASSIFICATION: ADOPTED IN THIS Book 3 : ix PERIPATUS CHAPTER I InTRODUCTION— EXTERNAL Fratures— Hasits —BreEepInc— ANATOMY— ALIMENTARY CANAL—NERVous SystEM—THE Bopy WALL—THE TRa- CHEAL SysTEM—TuHE MuscuLar SysrEM—THE VASCULAR SYSTEM—THE Bopy Caviry— NrpuripiaA — GENERATIVE ORGANS — DEVELOPMENT— SYNOPSIS OF THE SPEcIES—SUMMARY OF DISTRIBUTION . : j > By MYRIAPODA CHAPTER II INTRODUCTION — Habits — CLASSIFICATION — STRUCTURE — CHILOGNATHA— CHILOPODA — SCHIZOTARSIA — SYMPHYLA—PAUROPODA—EMBRYOLOGY— PALAEONTOLOGY F ; : : i ‘ . 29
INSECTA
CHAPTER III
CHARACTERISTIC FraTuRES OF INsEcT LIFE—SocraAL INsECTS—DEFINITION OF THE CLAss InsecrA—CoMPosITION oF INsECY SKELETYON—NUMBER OF SrcmMEeNTS—NATURE OF SCLERITES—HEAD—APPENDAGES OF THE MoutTu —Eyes—Tuorax—EnrToTHoraAx—Lecs— Wincs — ABDOMEN oR HIND Bopy—SprracLEs—SyYsTEMATIC ORIENTATION ‘ . 88
v1 CONTENTS
CHAPTER IV
ARRANGEMENT OF INTERNAL ORGANS—MuscLes—NERvoUS SYSTEM—GANG- LIONIC ~CHAIN—BraIN—SENSE - ORGANS—ALIMENTARY CANAL —MAL- PIGHIAN Tubes — ResrrraTION— TRACHEAL SysTEM— FUNCTION OF ReEsPIRATION—Bxioop or BLoop-cHyLtE—DorsaL VEsseL on HEart— Fat-BopY—OVARIES—TESTES— PARTHENOGENESIS—GLANDS A
CHAPTER V
DEVELOPMENT
EMBRYOLOGY — Ecos — MicropyLes — ForMATION OF EMBRYO — VENTRAL PLaTE—EcropERM AND ENDODERM—SEGMENTATION—LATER STAGES— Direct OBSERVATION oF EmMBRYO—METAMORPHOSIS—COMPLETE AND IxcoMPLeTE — InstArn — HYPERMETAMORPHOSIS — METAMORPHOSIS OF INTERNAL ORGANS—INTEGUMENT—METAMORPHOSIS OF BLOWFLY—HIs- ToLtysis—ImacinaL Discs—PuHyYsIoLocy oF METAMORPHOSIS—EcDYsIs .
CHAPTER VI
CLASSIFICATION — THE NINE OrpeERS oF INsects— THEIR CHARACTERS— PackARD’s ARRANGEMENT—BRAUER’S CLASSIFICATION—CLASSIFICATIONS BASED ON METAMORPHOSIS — SUPER-ORDERS— THE SUBDIVISIONS OF ORDERS
CHAPTER VII
Tue Orprr APTERA—DEFINITION—CHIEF CHARACTERISTICS—THYSANURA— CaMPpopEA—JAPYX — Macuitis — LerismA — Diversity oF INTERNAL STRUCTURE IN THYSANURA — EcTorROPHI AND ENTOTROPHI — COLLEM- BOLA—LIPURIDAE—PopunIDAE — SMYNTHURIDAE—THE Sprinc — THE VENTRAL TvUBE—ABDOMINAL APPENDAGES—PROSTEMMATIC ORGAN— TRACHEAL SystrEM— ANURIDA MARITIMA—COLLEMBOLA ON SNow— Lirr-Historirs OF CoLLEMBOLA—FossIL APTERA—APTERYGOGENEA— ANTIQUITY AND DISTRIBUTION OF CAMPODEA
CHAPTER VIII
ORTHOPTERA—FORFICULIDAE, EARWIGS—HEMIMERIDAE
PAGE
143
171
180
198
CONTENTS vil
CHAPTER IX
PAGE ORTHOPTERA CONTINUED—BLATIYIDAE, COCKROACHES é 220 CHAPTER X ORTHOPTERA CONTINUED—-MANTIDAE, SOOTHSAYERS - . 242 CHAPTER XI ORTHOPTERA CONTINUED—PHASMIDAE, WALKING-LEAVES, STICK-INSECTS 260 CHAPTER XII ORVHOPTERA CONTINVED—ACRIDIDAE, Locusts, GRASSHOPPERS . 2 279 CHAPTER XIII ORTHOPTERA CONTINUED—LOCUSTIDAE, GREEN GRASSHOPPERS, Katypips . 311 CHAPTER XIV ORTHOPTERA CONTINUED—GRYLLIDAE, CRICKETS . - 3 . 2830 CHAPTER XV NEvUROPTERA—MALLOPHAGA—EMBIIDAE g 341
CHAPTER XVI
NEUROPTERA CONTINUED—TERMITIDAE, TERMITES OR WHITE ANTS : . 856
vill CONTENTS
CHAPTER XVII
PAGE NEUROPTERA CONTINUED—PsocIDAE (Boox-Licr AND DEATH-WATCHES)—THE Firsr FAmity of AMPHIBIOUS NEUROPTERA (PERLIDAE, STONE-FLIES) 390 CHAPTER XVIII AMPHIBIOUS NEUROPTERA CONTINUED—ODONATA, DRAGON-FLIES é 409 CHAPTER XIX AMPHIBIOUS NEUROPTERA CONTINUED—EPHEMERIDAE, MAy-FLIEs i 429
CHAPTER XX NrEvnoprera PLANIPENNIA—SIALIDAE, ALDER-F Lies, SNAKE-FLIES—PANOR- PIDAE, SCORPION-FLIES—HEMEROBIIDAE, ANr-Lions, LAcEWINGS, ETc. 444 CHAPTER XXI NEUROPTERA CONTINUED — TRICHOPTERA, THE PHRYGANEIDAE OR CADDIS- Furs. . : ‘ 5 , 3 » 473 CHAPTER XXII HYMENOPTERA—HYMENOPTERA SESSILIVENTRES—CEPHIDAE—ORYSSIDAE— SIRICIDAE—TENTHREDINIDAE OR SAWFLIES . : 487 CHAPTER XNIII
HYMENOPTERA PETIOLATA—PARASITIC HYMENOPTERA—CYNIPIDAE OR GALL- Fiirs— Procrorrypmpan — CHALCIDIDAE — ICHNEUMONIDAE— BRracon- IDAE — STEPHANIDAE — MrcaLyrmar — EVANIIDAE — PELECINIDAE TRIGONALIDAE ‘ i . : : ; . 519
INDEX . 5 3 x 567
SCHEME OF THE CLASSIFICATION (RECENT FORMS) ADOPTED IN THIS BOOK
PROTOTRACHEATA Peripatus (p. 1)
MYRIAPODA
Order. Family. POLYXENIDAE (p. 43), GLOMERIDAE (p. 48). SPHAEROTHERIIDAE (p. 48). JULIDAE (p. 48). BLANJULIDAE (p. 44). CHORDEUMIDAE (p. 44). POLYDESMIDAE (p. 44). POLYZONIIDAE (p. 44).
CHILOGNATHA (=DIPLOPODA) ;
LirHosiipAE (p. 45). SCOLOPENDRIDAE (p. 45).
— —_—_————
CHILOPODA | NoropHILipAE (p. 45). GEOPHILIDAE (p. 46). SCHIZOTARSIA CERMATIIDAE (=SCUTIGERIDAE) (p. 46). SYMPHYLA. SCOLOPENDRELLIDAE (p. 46), PAUROPODA : PAUROPIDAE (p. 47). INSECTA Order. Bea he Family. CAMPODEIDAE (p. 183), Thysanura JAPYGIDAE (p. 184). (p. 182) MAcHILIDAE (p. 184). LEPISMIDAE (p. 185).
APTERA (p. 180) .
. LIPURIDAE (p. 190). Se { PoDURIDAE (p. 190). Pp. SMYNTHURIDAE (p. 191).
SCHEME OF INSECTA
Order.
ORTHOPTERA J
(p. 198)
r
Division, Series, or Sub-Order.
Orthoptera cursoria
Orthoptera saltatoria
(Continucd on the next page.)
Family.
Tribe or Sub-Family.
ForFIcULIDAE (p. 202), HEMIMERIDAE (p. 217).
BLATTIDAE (p. 220)
MANTIDAE (p. 242)
PHASMIDAE (p. 260)
ACRIDIIDAE (p. 279)
LocusTipaE (p. 311)
- Ectobiides. Phyllodromiides. Nyctiborides. Epilamprides. Periplanetides. Panchlorides.
] Blaberides.
Corydiides.
Oxyhaloides.
Perisphaeriides,
Panesthiides.
? Geoscapheusides.
Orthoderides.
Amorphoscelides. f Mantides.
Vatides. Empusides.
| Harpagides.
; Lonchodides. Bacunculides. Bacteriides. Necroscides. Clitumnides. Acrophyllides. Cladomorphides. Anisomorphides. Phasmides. Aschipasmides. Bacillides. Phylliides.
Tettigides. Pneumorides. Mastacides. Proscopiides.
‘ Tryxalides.
Oedipodides. Pyrgomorphides. Pamphagides. Acridiides.
Phaneropterides. Meconemides. Mecopodides. Prochilides. Pseudophyllides. Conocephalides. Tympanophorides.
eae » Sagides.
Locustides. Decticides. Callimenides. Ephippigerides. Hetrodides. Gryllacrides.
| Stenopelmatides.
SCHEME OF INSECTA xi Order. one Family. Tribe or Sub-Family. Group. Tridactylides, Gryllotalpides. ORTHOPTERA Orthoptera | Gayrrtmpap Myrmecophilides. (continued) saltatoria (p. 330) Gryllides. (continued) P. Occanthides. ‘Trigonidiides. \ Eneopterides. Mallophaga i Leiotheides. (p. 345) Philopterides. EMBIIDAE (p. 351). Reaudoe Af ye (p. 356). neuroptera | Psocipan (p. 390). PERLIDAE (p. 398). Gomphinae. Cordulegasterinae. Anisopterides Aeschninae. alan tei ODONATA | i Corduliinae. fa 10-- (p. 409) pibelnhos : alepteryginae. Zyeoptondes re ee \ EPHEMERIDAE (p. 429). SIALIDAE Sialides. (p. 444) Raphidiides. NEUROPTERA PANORPIDAE (p. 449). (p. 341) Myrmeleonides (p. 454). Ascalaphides f Holophthalmi. (p. 459) \ Schizophthalmi. Neuroptera Nemopterides (p. 462), planipennia Hemerosrpa | Mantispides (p. sie pe Sa) Hemerobiides Nymphidina. (p. 465) Osmylina. Hemerobiina. Chrysopides (p. 469). \ Coniopterygides (p. 471). Phryganeides (p. 480). Limnophilides (p. 481). Sericostomatides (p. 482). Trichoptera ie IDAR Leptocerides (p. Bo, Bs Hydropsychides (p. 482). Rhyacophilides (p. 483). ‘ Hydroptilides (p, 484). CEPHIDAR (p. 504). heey il OryssIDAE (p. 506). sere S81!) SIRICIDAE (p. 507). iventres | TenTHREDINIDAE (p. 510). ; CYNIPIDAE (p. 523). PROCTOTRYPIDAE (p. 583). HYMENOPTERA | Soe eta (p. at (p. 487 CHNEUMONIDAE (p. 551). ‘ eae: BRACONIDAE (p. 558). lat t) STEPHANIDAE (p. 561). ata (par MEGALYRIDAE (p. 562). EVANIIDAE (p. 562). PELECINIDAE (p. 563).
(To be continued in Vol. VI.)
TRIGONALIDAE (p. 564).
PERIPATUS
BY
ADAM SEDGWICK, M.A, F.RS,
Fellow of Trinity College, Cambridge.
VOL. V £
CHAPTER I PERIPATUS
INTRODUCTION EXTERNAL FEATURES — HABITS BREEDING — ANATOMY — ALIMENTARY CANAL——NERVOUS SYSTEM— THE BODY WALL — THE TRACHEAL SYSTEM — THE MUSCULAR SYSTEM —-THE VASCULAR SYSTEM — THE BODY CAVITY — NEPHRIDIA——GENERATIVE ORGANS——-DEVELOPMENT——SYNOPSIS OF THE SPECIES—-SUMMARY OF DISTRIBUTION.
THE genus Peripatus was established in 1826 by Guilding? who first obtained specimens of it from St. Vincent in the Antilles. He regarded it as a Moilusc, being no doubt deceived by the slug -like appearance given by the antennae. Specimens were subsequently obtained from other parts of the Neotropical region and from South Africa and Australia, and the animal was vari- ously assigned by the zoologists of the day to the Annelida and Myriapoda. Its true place in the system, as a primitive member of the group Arthropoda, was first established in 1874 by Moseley,? who discovered the tracheae. The genus has been monographed by Sedgwick, who has also written an account of the development of the Cape species* A bibliography will be found in Sedgwick’s Monograph.
11, Guilding, ‘‘ Mollusca caribbaeana: an Account of a New Genus of Mollusca,” Zool. Journ. vol. ii. 1826, p. 443, pl. 14 ; reprinted in Jsis, vol. xxi. 1828, p. 158, pl. ii.
2 H. N. Moseley, ‘On the Structure and Development of Peripatus capensis,” Phil. Trans. elxiv. pls. lxxii.-lxxv. pp. 757-782 ; and Proc. &, S. xxii. pp. 344-350, 1874.
3 A. Sedgwick, ‘‘A Monograph of the Genus Peripatus,” Quart. Journ. of Mic. Science, vol. xxviii., and in Studies from the Morphological Laboratory of the Uni- versity of Cambridge, vol. iv.
4A. Sedgwick, ‘‘A Monograph of the Development of Peripatus capensis,” Studies from the Morphological Laboratory of the University of Cambridge, vol. iv.
4 PERIPATUS CHAP.
There can be no doubt that Peripatus is an Arthropod, for it possesses the following features, all characteristic of that group, and all of first-class morphological importance: (1) The presence of appendages modified as jaws; (2) the presence of paired lateral ostia perforating the wall of the heart and putting its cavity in communication with the pericardium; (3) the presence of a vas- cular body cavity and pericardium (haemocoelic body cavity) ; (+) absence of a perivisceral section of the coelom. Finally, the tracheae, though not characteristic of all the classes of the Arthropoda, are found nowhere outside that group, and constitute a very important additional reason for uniting Peripatus with it.
Peripatus, though indubitably an Arthropod, differs in such important respects from all the old-established Arthropod classes, that a special class, equivalent in rank to the others, and called Prototracheata, has had to be created for its sole occupancy. This unlikeness to other Arthropoda is mainly due to the Anne- lidan affinities which it presents, but in part to the presence of the following peculiar features: (1) The number and diffusion of the tracheal apertures; (2) the restriction of the jaws to a single pair; (3) the disposition of the generative organs; (4) the tex- ture of the skin; and (3) the simplicity and similarity of all the segments of the body behind the head.
The Aunelidan affinities are superficially indicated in so marked a manner by the thinness of the cuticle, the dermo- muscular body wall, the hollow appendages, that, as already stated, many of the earlier zoologists who examined Peripatus placed it amongst the segmented worms; and the discovery that there is some solid morphological basis for this determination constitutes one of the most interesting points of the recent work on the genus. The Annelidan features are: (1) The paired nephridia in every segment of the body behind the first two (Saenger, Balfour!); (2) the presence of cilia in the generative tracts (Gaffron). It is true that neither of these features are absolutely distinctive of the Annelida, but when taken in con- junction with the Annelidan disposition of the chief systems of organs, viz. the central nervous system, and the main vascular trunk or heart, may be considered as indicating affinities in that
1 F, M. Balfour, ‘‘The Anatomy and Development of Peripatus capensis,” edited
by Professor H. N. Moseley and A. Sedgwick, Quart. Journ. Mic. Sci. xxiii. pp. 213-259, pls. xili.-xx. 1883.
I EXTERNAL FEATURES 5
direction. Peripatus, therefore, is zoologically of extreme interest from the fact that, though in the main Arthropodan, it possesses features which are possessed by no other Arthropod, and which connect it to the group to which the Arthropoda are in the general plan of their organisation most closely related. It must, therefore, according to our present lights, be regarded as a very primitive form; and this view of it is borne out by its extreme isolation at the present day. Peripatus stands absolutely alone as a kind of half-way animal between the Arthropoda and Anne- lida. There is no gradation of structure within the genus; the species are very limited in number, and in all of them the peculiar features above mentioned are equally sharply marked.
Peripatus, though a lowly organised animal, and of remark- able sluggishness, with but slight development of the higher organs of sense, with eyes the only function of which is to enable it to avoid the light—though related to those animals most re- pulsive to the aesthetic sense of man, animals which crawl upon their bellies and spit at, or poison, their prey—is yet, strange to say, an animal of striking beauty. The exquisite sensitiveness and constantly changing form of the antennae, the well-rounded plump body, the eyes set like small diamonds on the side of the head, the delicate feet, and, above all, the rich colouring and velvety texture of the skin, all combine to give these animals an aspect of quite exceptional beauty. Of all the species which I have seen alive, the most beautiful are the dark green individuals of Capensis, and the species which I have called Balfouri. These animals, so far as skin is concerned, are not surpassed in the animal kingdom. TI shall never forget my astonishment and delight when on bearing away the bark of a rotten tree-stump in the forest on Table Mountain, I first came upon one of these animals in its natural haunts, or when Mr. Trimen showed me in confinement at the South African Museum a fine fat, full-grown female, accompanied by her large family of thirty or more just- born but pretty young, some of which were luxuriously creeping about on the beautiful skin of their mother’s back.
External Features.
The anterior part of the body may be called the head, though it is not sharply marked off from the rest of the body (Fig. 1). The head carries three pairs of appendages, a pair of simple eyes,
6 PERIPATUS CHAP.
and a ventrally placed mouth. The body is elongated and vermiform; it bears a number of paired appendages, each termi- nating in a pair of claws, and all exactly alike’ The number varies in the different species. The anus is always at the
Fic. 1.—Peripatus capensis, drawn from life. Life size. (After Sedgwick. )
posterior end of the body, and the generative opening is on the ventral surface just in front of the anus; it may be between the legs of the last pair (Fig. 2), or it may be behind them. There is in most species a thin median white line extending the whole length of the dorsal surface of the body, on each side of which
Fic. 2.—Ventral view of hind -end of Fic. 3.—Ventral view of the head of P, LP. Novae-Zealandiue. (Alter Sedg- capensis. (After Sedgwick.) ant, An- wick.) gy, Generative opening; a, tennae ; or.p, oral papillae ; 7.7, first anus. leg ; 7, tongue.
the skin pigment is darker than elsewhere. The colour varies considerably in the different species, and even in different indi- viduals of the same species. The ventral surface is nearly always flesh-coloured, while the dorsal surface has a darker colour. In the
I EXTERNAL FEATURES 7
South African species the colour of the dorsal surface varies from a dark green graduating to a bluish gray, to a brown vary- ing to a red orange. The colour of the Australasian species varies 1n like manner, while that of the Neotropical species (S. American and W. Indian) is less variable. The skin is thrown into a number of transverse ridges, along which wart-like papillae are placed. The papillae, which are found everywhere, are specially developed on the dorsal surface, less so on the ventral. Each papilla carries at its extremity a well-marked spine.
The appendages of the head are the antennae, the jaws and the oral papillae.
The antennae, which are prolongations of the dorso-lateral parts of the head, are ringed, and taper slightly till near their termination, where they are slightly enlarged. The rings bear a number of spines, and the free end of the antennae is covered by a cap of spiniferous tissue like that of the rings.
The mouth is at the hinder end of a depression called the buceal cavity, and is surrounded by an annular tunid hp, raised into papilliform ridges and bearing a few spines (Fig. 3). Within the buccal cavity are the two jaws. They are short, stump-like, muscular structures, armed at their free extremities by a pair of cutting blades or claws, and are placed one on each side of the mouth. In the median line of the buccal cavity in front is placed a thick muscular protuberance, which may be called the tongue, though attached to the dorsal instead of to the ventral wall of the mouth (Fig. 3). The tongue bears a row of small chitinous teeth. The jaw- claws (Figs. 4 and 5), which re- semble in all essential points the claws borne by the feet, and like these are thickenings of the scat aie se oe cuticle, are sickle-shaped. They — pensis. (After pensis. (After have their convex edge directed — ?#/0"™) ee forwards and their concave or cutting edge turned backwards. The inner cutting plate (Fig. 4) usually bears a number of cutting teeth. The jaws appear to be used for tearing the food, to which the mouth adheres by means of the tumid suctorial lips. The oral papillae are placed at the sides of the head (Fig. 3). The
8 PERIPATUS CHAP.
ducts of the slime-glands open at their free end. They possess two main rings of projecting tissue, and their extremities bear papillae irregularly arranged.
The ambulatory appendages vary in number. There are seventeen pairs in P. capensis and eighteen in P. Balfouri, while in P. £dieardsii the number varies from twenty-nine to thirty-four pairs. They consist of two main divisions, which we may call the leg and the foot (Figs. 6 and 7). The leg (2) has the form of a truncated cone, the broad end of which is attached to the ventro-lateral wall of the body, of which it is a prolonga- tion. It is marked by a number of rings of papillae placed
Fic. 6.—Ventral view of last leg of a Fic, 7.—Leg of P. capensis seen from the male P. capensis. (After Sedg- front. (After Sedgwick.) f, Foot; 2, leg; wick.) , Foot; J, leg; p, spini- P, spiniferous pads. ferous pads. The white papilla on the proximal part of this leg is characteristic of the male of this species.
transversely to its long axis, the dorsal of which are pigmented
like the dorsal surface of the body, and the ventral like the
ventral surface. At the narrow distal end of the leg there are on the ventral surface three spiniferous pads, each of which is continued dorsally into a row of papillae.
The foot is attached to the distal end of the lee. It is slightly narrower at its attached extremity than at its free end. Tt bears two sickle-shaped claws and a few papillae. The part of the foot which carries the claws is especially retractile, and is generally found more or less telescoped into the proximal part. The legs of the fourth and fifth pairs differ from the others in
E HABITS 9
the fact that the proximal pad is broken up into three, a small central and two larger lateral. The enlarged nephridia of these legs open on the small central division.
The males are generally rather smaller than the females. In those species in which the number of legs varies, the male has a smaller number of legs than the female.
Habits.
They live beneath the bark of rotten stumps of trees, in the crevices of rock, and beneath stones. They require a moist atmosphere, and are exceedingly susceptible to drought. They avoid light, and are therefore rarely seen. They move with great deliberation, picking their course by means of their antennae and eyes. It is by the former that they acquire a knowledge of the ground over which they are travelling, and by the latter that they avoid the light. The antennae are extra- ordinarily sensitive, and so delicate, indeed, that they seem to be able to perceive the nature of objects without actual contact. When irritated they eject with considerable force the contents of their slime reservoirs from the oral papillae. The force is sup- plied by the sudden contraction of the muscular body wall. They can squirt the slime to the distance of almost a foot. The slime, which appears to be perfectly harmless, is extremely sticky, but it easily comes away from the skin of the animal itself.
I have never seen them use this apparatus for the capture of prey, but Hutton describes the New Zealand species as using it for this purpose. So far as I can judge, it is used as a defensive weapon; but this of course will not exclude its offensive use. They will turn their heads to any part of the body which is being irritated and violently discharge their slime at the offending object. Locomotion is effected entirely by means of the legs, with the body fully extended.
Of their food in the natural state we know little; but it is probably mainly, if not entirely, animal. Hutton describes his specimens as sucking the juices of flies which they had stuck down with their slime, and those which I kept in captivity eagerly devoured the entrails of their fellows, and the developing young from the uterus. They also like raw sheep’s liver. They move their mouths in a suctorial manner, tearing the food with their jaws. They have the power of extruding their jaws from
10 PERIPATUS CHAP,
the mouth, and of working them alternately backwards or for- wards. This is readily observed in individuals immersed in water.
Breeding.
All species are viviparous. It has been lately stated that one cf the Australian species is normally oviparous, but this has not been proved. The Australasian species come nearest to laying eggs, inasmuch as the eges are large, full of yolk, and enclosed ina shell; but development normally takes place in the uterus, though, abnormally, incompletely developed eggs are extruded,
The young of P. capensis are born in April and May. They are almost colourless at birth, excepting the antennae, which are yreen, and their length is 10 to 15 mm. A laree female will produce thirty to forty young in one year. The period of vesta- tion is thirteen months, that is to say, the ova pass into the oviduets about one month before the young of the preceding year are born. They are born one by one, and it takes some time for a female to get rid of her whole stock of embryos; in fact, the embryos in any given female differ slightly in age, those next the oviduct being a little older (a few hours) than those next the vagina. The mother does not appear to pay any special attention to her young, which wander away and get their own food.
There does not appear to be any true copulation. The male deposits small, white, oval spermatophores, which consist of small bundles of spermatozoa cemented together by some glutinous substance, indiscriminately on any part of the body of the female. Such spermatophores are found on the bodies of both males and females from July to January, but they appear to be most nume- rous in our autumn, It seems probable that the spermatozoa make their way from the adherent spermatophore through the body wall into the body, and so ly trayersiny the tissues reach the ovary. The testes are active from June to the following March. From March to June the vesiculae of the male are empty.
There are no other sexual differences except in some of the South African species, in which the last or penultimate lee of the male bears a small white papilla on its ventral surface (Fig. 6).
Whereas in the Cape species embryos in the same uterus are all practically of the same age (except in the month of April, when two broods overlap in P. capensis), and birth takes place at a fixed season; in the Neotropical species the uterus, which is
I ALIMENTARY CANAL ba
alvays pregnant, contains embryos of different aves, and births probably take place all the year round.
In all species of Peripatus the young are fully formed at birth, and differ from the adults only in size and colour.
ANATOAY The Alimentary Canal (Tig. 8).
The buceal cavity, as explained above, is a secondary furma- tion around the true mouth, which is at its dorsal posterior end. It contains the tongue and the jaws, which have already been
. 8.—Perilpatus capensis dissected so as to show the alimentary canal, slime glands, and salivary glands. (After Balfour.) The dissection is viewed from the ventral side, and the lips (Z) have been cut through in the middle line behind and pulled outwards so as to expose the jaws (j), which have been turned outwards, and the tongue (7) bearing a median row of chitinous teeth, which branches behind into two. The muscular pharynx, extend- ing back into the space between the first and second pairs of legs, is followed by a short tubular oeso- phagus. The latter opens into the large stomach with plicated walls, extending almost to the hind end of the animal. The stomach at its point of junc- tion with the rectum presents an §-shaped ventro- dorsal curve. .1, Anus; af, antenna; J.J, 2.2, first and second feet; j, jaws; JZ, lips; oe, oesophagus ; o7.p, oral papilla; pk, pharynx; R, rectum ; s.d/, salivary duct; s.g, salivary gland ; si.d, slime reservoir; si.g, portion of tubules of slime gland; s¢, stomach; 7, tongue in roof of mouth,
described, and into the hind end of it there opens ventrally by a median opening the salivary glands (sy). The mouth leads into a muscular pharynx (ph), which is connected ly a short oeso- phagus (ve) with a stomach (sé). The stomach forms by far the
12 PERIPATUS CHAP.
largest part of the alimentary canal. It is a dilated soft-walled tube, and leads behind into the short narrow rectum (#), which opens at the anus. There are no glands opening into the alimentary canal.
Nervous System.
The central nervous system consists of a pair of supra- oesophageal ganglia united in the middle line, and of a pair of widely divaricated ventral cords, continuous in front with the supra-oesophageal ganglia (Fig. 9).
The ventral cords at first sight appear to be without gangh- onic thickenings, but on more careful examination they are found to he enlarged at each pair of legs (Fig. 9). These enlarge- ments may be regarded as imperfect ganglia. There are, there-
Fic. 9.—Brain and anterior part of the ventral nerve- cords of Peripatus capensis enlarged and viewed from the ventral surface. (After Balfour.) The paired appendages (d@) of the ventral surface of the brain are seen, and the pair of sympathetic nerves (sy) arising from the ventral surface of the hinder part. From the commencement of the oesopha- geal commissures pass off on each side a pair of nerves to the jaws (Jn). The three anterior commissures between the ventral nerve-cords are placed close together; immediately behind them the nerve-cords are swollen, to form the ganglionic enlargements from which pass off to the oral papillae a pair of large nerves on each side (077). Behind this the cords present a series of enlarge- ments, one pair for each pair of feet, from which a pair of large nerves pass off on each side to the feet (pn). atn, Antennary nerves; co, commissures between ventral cords; d, ventral appendages of brain ; HZ, eye; en, nerves passing outwards from ventral cord ; /.g.1, ganglionic enlargements from which nerves to feet pass off ; jn, nerves to jaws ; org, ganglionic enlargement from which nerves to oral papillae pass off ; orn, nerves to oral papillae ; pe, posterior lobe of brain; pn, nerves to feet ; sy, Sympathetic nerves,
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fore, as many pairs of ganglia as there are pairs of legs. There is in addition a ganglionic enlargement at the commencement of the oesophageal commissures, where the nerves to the oral papillae are given off (Fig. 9, 07.9).
The ventral cords are placed each in the lateral compart- ments of the hody cavity, immediately within the longitudinal layer of muscles. They are connected with each other, rather like the pedal nerves of Chiffon and the lower Prosobranchiata, by a number of commissures. These commissures exhibit a
I NERVOUS SYSTEM AND BODY WALL 13
fairly regular arrangement from the region included between the first and the last pair of true feet. There are nine or ten of them between each pair of feet. They pass along the ventral wall of the body, perforating the ventral mass of longitudinal muscles. On their way they give off nerves which innervate the skin.
Posteriorly the two nerve-cords nearly meet immediately in front of the generative aperture, and then, bending upwards, fall into each other dorsally to the rectum. They give off a series of nerves from their outer borders, which present throughout the trunk a fairly regular arrangement. From each ganglion two large nerves (pn) are given off, which, diverging somewhat from each other, pass into the feet.
From the oesophageal commissures, close to their junction with the supra-oesophageal ganglia, a nerve arises on each side which passes to the jaws, and a little in front of this, apparently from the supra-oesophageal ganglion itself, a second nerve to the jaws also takes its origin.
The supra-oesophageal ganglia (Fig. 9) are large, somewhat oval masses, broader in front than behind, completely fused in the middle, but free at their extremities. Each of them is pro- longed anteriorly into an antennary nerve, and is continuous behind with one of the oesophageal commissures. On the ventral surface of each, rather behind the level of the eye, is placed a hollow protuberance (Fig. 9, d), of which I shall say more in dealing with the development. About one-third of the way back the two large optic nerves take their origin, arising laterally, but rather from the dorsal surface (Fig. 9). Each of them joins a large ganglionic mass placed immediately behind the retina.
The histology of the ventral cords and oesophageal commis- sures is very simple and uniform. They consist of a cord almost wholly formed of nerve-fibres placed dorsally, and of a ventral layer of ganglion cells.
The Body Wall.
The skin is formed of three layers. (1) The cuticle. (2) The epidermis or hypodermis. (3) The dermis. The cuticle is a thin layer. The spines, jaws, and claws are special developments of it. Its surface ig not, however, smooth,
I4 PERIPATUS CHAP.
but is everywhere, with the exception of the perioral region, raised into minute secondary papillae, which in most instances bear at their free extremity a somewhat prominent spine. The whole surface of each of the secondary papillae just described is in its turn covered by numerous minute spinous tubercles.
The epidermis, placed immediately within the cuticle, is composed of a single layer of cells, which vary, however, a good deal in size in different regions of the body. The cells excrete the cuticle, and they stand in a very remarkable relation to the secondary papillae of the cuticle just described. Each epidermis cell is in fact placed within one of these secondary papillae, so that the cuticle of each secondary papilla is the product of a single epidermis cell. The pigment which gives the characteristic colour to the skin is deposited in the protoplasm of the outer ends of the cells in the form of small granules.
At the apex of most, if not all, the primary wart-like papillae there are present oval aggregations, or masses of epidermis cells, each such mass being enclosed in a thickish capsule and bearing a long projecting spine. These structures are probably tactile organs. In certain regions of the body they are extremely numerous ; more especially is this the case in the antennae, lips, and oral papillae. On the ventral surface of the peripheral rings of the thicker sections of the feet they are also very thickly set and fused together so as to form a kind of pad (Figs. 6 and 7). In the antenuae they are thickly set side hy side on the rings of skin which give such an Arthropodan appearance to these organs in Peripatus.
The Tracheal System.
The apertures of the tracheal system are placed in the depres- sions between the papillae or ridges of the skin. Each of them leads into a tube, which may be called the tracheal pit (Fig. 10), the walls of which are formed of epithelial cells bounded towards the lumen of the pit by a very delicate cuticular membrane con- tinuous with the cuticle covering the surface of the body, The pits vary somewhat in depth ; the pit figured was about 0°09 mm. It perforates the dermis and terminates in the subjacent muscular layer.
Internally it expands in the transverse plane and from the expanded portion the tracheal tubes arise in diverging bundles. Nuclei similar in character to those in the walls of the tracheal
I TRACHEAL, MUSCULAR AND VASCULAR SYSTEM 15
pit are placed between the tracheae, and similar but slightly more elongated nuclei are found along the bundles. The tracheae are minute tubes exhibiting a faint transverse striation which is prob- ably the indication of a spiral fibre. They appear to branch, but
Fic, 10,—Section through a tracheal pit and diverging bundles of tracheal tubes taken transversely to the long axis of the body. (After Balfour.) ¢7, Tracheae, showing rudimentary spiral fibre ; tr.c, cells resembling those lining the tracheal pits, which occur at intervals along the course of the tracheae ; ¢r.o, tracheal stigma ; ir.p, tracheal pit.
only exceptionally. The tracheal apertures are diffused over the surface of the body, but are especially developed in certain regions.
The Muscular System.
The general muscular system consists of—(1) the general wall of the body; (2) the muscles connected with the mouth, pharynx, and jaws; (3) the muscles of the feet ; (+) the muscles of the alimentary tract.
The muscular wall of the body is formed of—(1) an external layer of circular fibres; (2) an internal layer of longitudinal muscles.
The main muscles of the body are unstriated and divided into fibres, each invested by a delicate membrane. The muscles of the
jaws alone are transversely striated.
The Vascular System.
The vascular system consists of a dorsal tubular heart with paired ostia leading into it from the pericardium, of the pericar- dium, and the various other divisions of the perivisceral cavity (Fig. 14, D). As in all Arthropoda, the perivisceral cavity is a haemocoele ; i.e. it contains blood and forms part of the vascular system. The heart extends from close to the hind end of the body to the head.
16 PERIPATUS CHAP.
The Body Cavity.
The body cavity is formed of four compartments—one central, two lateral, and a pericardial (Fig. 14, D). The former is by far the largest, and contains the alimentary tract, the generative organs, and the slime glands. It is lined by a delicate endo- thelial layer, and is not divided into compartments nor traversed by muscular fibres. The lateral divisions are much smaller than the central, and are shut off from it by the inner transverse band of muscles. They are almost entirely filled with the nerve-cord and salivary gland in front and with the nerve-cord alone behind, and their lumen is broken up by muscular bands. They further contain the nephridia. They are prolonged into the feet, as is the embryonic body cavity of most Arthropoda. The pericardium con- tains a pecuhar cellular tissue, probably, as suggested by Moseley, equivalent to the fat-bodies of insects.
Nephridia.
In Peripatus capensis nephridia are present in all the legs. In all of them (except the first three) the following parts may be recognised (Fig. 11) :—
(1) A vesicular portion opening to the exterior on the ventral
surface of the legs hy a narrow passage.
(2) A coiled portion, which is again subdivided into several
sections.
(3) A section with closely packed nuclei ending hy a some-
what enlarged openine.
(4) The terminal portion, which consists of a thin-walled
vesicle.
The last twelve pairs of these organs are all constructed in a very similar manner, while the two pairs situated in the fourth and fifth pairs of legs are considerably larger than those behind and are in some respects very differently constituted.
It will be convenient to commence with one of the hinder nephridia. Such a nephridium from the ninth pair of legs is represented in Fig. 11. The external opening is placed at the outer end of a transverse groove at the base of one of the legs, while the main portion of the organ lies in the body cavity in the base of the leg, and extends into the trunk to about the level
2
I NEPHRIDIA 17
of the outer edge of the nerve-cord of its side. The external opening (0s) leads into a narrow tube (s.d), which gradually dilates into a large sac (s). The narrow part is lined by small epithelial cells, which are directly continuous with and perfectly similar to those of the epidermis. The sac itself, which forms a kind of bladder or collecting vesicle for the organ, is provided with an extremely thin wall, ined with very large flattened cells. The second section of the nephridium is formed by the coiled tube, the epithelial lining of which varies slightly in the different parts. The third section (s.0.¢), constitutes the most distinct portion of the whole organ. Its walls are formed of columnar cells almost filled by oval nuclei, which absorb colouring matters with very great avidity, and thus render this part extremely Fic. 11.—Nephridium from the 9th pair of legs of P. capensis. o.s, External opening of seg- mental organ; p,f, internal opening of nephridium into the body cavity (lateral com- partment) ; s, vesicle of seg- mental organ; s.¢.1, 8.6.2, 5.6.3, 8.c.4, successive regions of coiled portion of neplii- dium; s.0.¢, third portion of nephridium broken off at p.f
from the internal vesicle, which is not shown.
conspicuous. The nuclei are arranged in several rows. It ends by opening into a vesicle (Fig. 14, D), the wall of which is so delicate that it is destroyed when the nephridium is removed from the body, and consequently is not shown in Fig. 11.
The fourth and fifth pairs are very considerably larger than those behind, and are in other respects peculiar. The great mass of each organ is placed behind the leg on which the external opening is placed, immediately outside one of the lateral nerve- cords. The external opening, instead of being placed near the base of the leg, is placed on the ventral side of the third ring (counting from the outer end)