

c-KUSTACIA. 



.,,, 



_ f-. flg-'". *"T **"" "~ u " tKrir ""*" hT 



> of tli (UK-lli f. .mi ppradancw of the extremities belonging to 

 U moo : wbiU the inferior (WMn. wcfa a* the Ktomo*ra 

 have MMMKMd to UM external orifice* cither horn; tubes or pair 

 of nnobmoon* me* which onnUhi and transport them from place to 

 BUM. TtMw rarwtie* in the aceea*ory organs of generation are in 

 \nrnn CM.. MOrwot to distinguish the sexes; thus, among the 

 /hf !>' evc**i, UM fcmatoa are known at a gUooe by their 



. which is ooMtimea of .uch dimensions u to ooTer 



the whole sUrnnm " 



Tbe following ct will convey eome idea of the relative poaition of 

 the parU in the cunpace. 



Common *Vw-Crmb (Carrima mmat). open. 



b; ,, rrniialonrn; <-. hnrt ; < rf, bnnchto ; ,/,/,UTCT. 



Prma-Wstrr Cnr-FIh (Ailanajlirriniila], open. 

 ..,. toourh ; . f*alul onranii ; r, hesrt ; t, 4, d, d, d, liver ; t, . 

 VruKhi* ; /, /, aoiMles of tke mandibles. 



At oo time it was supposed that the young of the Crtulacea 

 underwent no change after being hatched from the ova, and this was 

 fomMfiy given a* a distinction between the Insects and Cnutacca. We 

 BOW know however that those anomalous forms of animal life known by 

 UM name of Zoat, aad referred by Bosc and others to the Kntomostra- 

 ou* OHSMCM. are truly the young of the higher forms of Uruttacea 

 undergoing OMtomorphoaia. FBlUKOinorODA.] The fact* of this pro- 

 eta* were fin* mad* out by Mr. V. Thompson in the year 1823, and 

 obcsqaeaUy the instances in which it has been observed are so 

 numerous that UMTS can be no doubt that metamorphosis takes place 

 in all the Mario* Ueoapodous Cnulaera. In the various forms of 

 Jfswrvwv, th* metamorphosis I* lea* decided than in the Brathy*ra; 

 and in the Freah-Water Cray Pish (A**r*,jl*rii>lu) no change Ukes 

 flac* at all The** bav* led *ome observers to doubt the correctness of 

 Mr. Tbompra's eooclusicaa. One of the last and most important series 

 Of ioT-rticatwos eoli>cUd on this ..il.ject was by Mr. R. Q. Couch, 

 of Pwmao*, CotnwsJI, who, diatMifto<l with the uncertainty and 

 0Mtr*diotioa ot former testimony, reiwlved to inveMigate the matter 

 lor himnlf. He obMrred the mt .morjihoais to occur in the following 

 fmttn : Camctr, ZmnOto. Pilummiu, Carcintu, Purtunut, Maia, 

 OSM****, y/emorw. and Palinmnu. The details of Mr. Couch's 

 otasrvBUoo* WOT* published in th* 'Prooseding* of the Cornwall 

 IViJ^iiliiilii Society ' for IMS. 



'"*f Bell says, " Eliminating, therefore, this exceptional case 

 (the* of ^*tenuj(wrMti7u), it will be found that the fact of a moU- 

 morpbusia * DMO dMDoo*traUd with mor* or IMS siicea in no less 

 thM **lsuU*u |*o*r of th* brach vur >u order of th* DrnipoJa, in 



which oriler th phenomenon i rnont deri.l.'.l mul i.1ivinu<, belonging 



t.> tin- f;imilitr A^I^/WKK/T, .l/>n'i>/.r, C'uncrr. /'mno- 



/.iW.r. In the Anomo" i it ha* been 



i tl . ^-nrra Paguriu, Farctllann, and (Jalalh >i. Kii.l mnongst 



the Uofrouni in ll;marur, I'nln.uria, Palirmon, and Crangon." 



The following U Mr. < '..n, II'H account of the change* which take place 

 in the Common Sh. .iv-< 'rub (Cartintu manat). Having procured some 

 Rpecimena of the Crab laden with ripe ova, he aay " Tbeae were 

 tranaferred to captivity, placed in separate baains, and supplied with 

 m-watcr, and in about sixteen hours I had the gratification of fil 

 large numbers of the creatures alluded to above swimming about with 

 all the activity of young life. There could be but litllo doubt that 

 these creatures were the young of the captive crabs. In order how- 

 ever to secure accuracy of result, one of the crabs was removed to 

 another vessel and supplied with filtered water, that all insects might 

 be removed ; but in about au hour the same creatures were observed 

 swimming about as before. To render the matter if possible still 

 more certain, some of the ova were opened, and the embryos extracted, 

 but shortly afterwards I had the pleasure of witnessing beneath the 

 microscope the natural bursting and escape of one prpi-i*-ly similar in 

 form to those found so abundantly in the water. Thus then th. i H 

 no doubt that these grotesque-looking creatures are the young of the 

 Ciircinta mteruu ; but how different they are from the ftdult need 

 hardly be pointed out When they first escape they rarely exceed 

 half a line in length. The body is ovoid, the dorsal shield large and 

 inflated ; on its upper edge and about the middle is a long Hpiue, 

 curved posteriorly, and rather longer than the diameter of the body, 

 though it varies in length in different specimens ; it is hollow, and 

 the blood may be seen circulating through it. The upper portion of 

 the body is sap-green and the lower semitransparent. The eyes are 

 large, sessile, and situated in front, and the circumference of the 

 pupil marked with radiating lines. The lower margin of the nlii. !.! 

 nt waved, and at its posterior and lateral margin is a pair of natatory 

 feet. The tail is extended longer than the diameter of the shield, 

 and in composed of five equal simulations besides the terminal one ; 

 its extremity is forked, and the external angles long, slender, pointed, 

 and attached to the last aimulation by joints. Between the external 

 angles, and on each side of the median line, are three lesser spines, 

 also attached to the last ring by joints. Between the eyes and from 

 near the edge of the shield hangs a long stout and somewhat com- 

 pressed appendage, which as the animal moves is reflexed posteriorly 

 between the claws. Under each eye there is also another appendage, 

 shorter, and slightly more compressed. The claw* are in three pairs ; 

 each is composed of three joints, and terminates in four long slnuli r 

 hair-like appendages. These claws are generally bent on tin- 

 but stand in relief from it If the animal be viewed in front the 

 lower margin of the dorsal shield will ba found to be waved into 

 three semicircular festoons, the two external of which are occupied 

 by the eyes, and between which the middle one intervenes ; the 

 general direction of the claws will be seen to be at right angles to the 

 body. As the young lies inclosed within the membranes of the egg, 

 the claws are folded on each other, and the tail is flexed on them so 

 far as the margin of the shield ; and if long enough is reflected over 

 the front of the shield between the eyes. The dorsal spine is b.-nt. 

 backwards, and lies in contact with the dorsal shield ; for the young, 

 when it escapes from the egg, is quite soft, but it rapidly hardens and 

 solidifies by the deposition of calcareous matter ill what maybe called 

 its skin. The progress of this solidification may be very beautilully 

 observed by watching the circulation in the dorsal spine. When the 

 creature has just effected its liberation from the egg, the blood globules 

 may be seen ascending to the apex, but as the consolidation advances 

 the circulation becomes more and more limit'-. 1 in its extent, and is 

 finally confined to the base. These minute creatures, in thin early 

 state of their existence, are natatory and wonderfully activ.-. Tin y 

 are continually swimming from onn part of the vessel to the oth.-r, 

 and when observed free in their native pools, if posnible even more 

 active than when in confinement. Their swimming is produced by 

 flexions and extensions of the tail, and by repeated beating motion* 

 of th.-ir claws; this, together with their grotesque-looking forms, gives 

 them a most extraordinary appearance when under examination. As 

 the shell becomes more solid they get less active, and return to the 

 sand at the bottom of the vessel to cast their shells, and acquire a 

 new form. They are exceedingly delicate, and require great core and 

 attention to convey them through the first stage, for unless the water 

 be supplied very frequently and in groat abundance they soon die. 

 The second form of transmutation is equally as remarkable as the 

 first, and quite as distinct from the adult animal. I now 



nnil'T r .n^i.l. rition this second tnumformntion i marked by the dis- 

 appearance of the .:-.r-. I ..|.;in . tb 



depressed: the anterior jiortion in. .re li,.ri/. I. the 



three festoons having disappeared. The cy< *. from l-ing sessile, are 

 now elevated on foot-stalks; the infra-orbital appendages become 

 apparently converted into antennae. The claws undergo an entire 

 revolution ; the first pair become stouter than the others, and are 

 armed with a pair of nippers, the others being simple, but the 

 posterior pair are branched near the base, and one ,.f the branches 

 ends in a bushy tuft The toil is greatly diminished in its relative 

 size and proportions, and is sometimes partially bent under the Im.ly, 



