: 



('IRKIPKDIA. 



1100 



one of the royal medals, followed up by the report of bin dincovery of 

 similar change* exhibited by three specie* of two other genera of the 

 econd tribe of thin family, namely, the Ispadn. The Tame of thin 

 tribe, like thoM of the Bauan, hare the external appearance of Bivalve 

 Monocnli. furnished with locomotive organs, in the form of three 

 pain of members, the moet anterior of which are simple, and the 

 other bifid. The back of the animal in covered by an ample shield, 

 terminating anteriorly in two extended horns, and poiiteriorly in a 

 ingle elongated ipinons process. Thus they posses* considerable 

 power* of locomotion, which, with the assistance of an organ of vision, 

 enable them to seek their future permanent place of residence. The 

 author is led from his researches to the conclusion that the Cirripedes 

 do not constitute, as modern naturalists have considered them, a dis- 

 tinct class of animals, but that they occupy a place intermediate 

 between the L'rtataeta dtrapwia (with which the Rolani have a marked 

 affinity) and the Cnutacea mtomtatrata, to which the Lepade* are 

 allied '; and that they have no natural affinity with the Testaceous 

 MiJImca, as was supposed by Linnaras, and all the older systematic 

 writers on Ecology." 



Mr. Thompson does not seem to have been aware of a paper by 

 Dr. J. Martin-Saint-Ange, read at the Academy of Sciences on the 

 14th July 1834, and published in the 'Havana Etrangera' (tome vi.), 

 and separately by Baillicre (1835). The following is the summary of 

 the principal facts stated by him in the course of a very laborious 

 and acute investigation : The mouth of the Pedunculated Cirripedes 

 is composed of pieces entirely comparable to those of the mouths of 

 many Crtutarra, and especially of the Phyllotomet ; the upper lip, 

 the palpi, and the mandibles are so analogous that the resemblance 

 extends even to the form. The three jaw-feet (pieds-mftchoires), 

 which are met with most commonly in the Crtuitatra, are conjoined 

 in a single jaw-foot which receives the nervous trunks ; at its base are 

 always found from two to four bronchia;. The ten ordinary feet of 

 the Criutatm are faithfully represented in the Anatifex (Cnmjiylnto- 

 mtita) ; at the base of many among them are found branchiic disposed 

 like those of certain Ortutafta, and the number even is sometimes 

 repeated. There exists in each foot a double canal, fit for establish- 

 ing a circulating current, and traversing all the articulations of the 

 cirri. The body is composed of a certain number of rings, or of 

 articulations, very distinct, each of which supports a pair of feet. In 

 the interior of the body there are a dorsal vessel (like that in a great 

 number of the Articulated Animals), and a double series of ganglions ; 

 of which the number, accordingto l)r. Martin-Saint-Ange' s researches, 

 is equal to that of the feet; there is besides another pair on the 

 lateral parts of the stomach. The pedicle may be regarded an 

 analogous to the tail of many Crustacea ; it is in this cavity, and not, 

 as has been said, on the back, that the eggs are found ; these pass 

 afterwards by a conduit, not yet indicated, in the envelope, which, by 

 its resemblance to the mantle of the .!/"/'.". establishes tl 

 possible analogy between the (.'impedes and the last-named animal*. 

 The organs placed upon the back, which Cuvier described as eggs, are 

 the generative apparatus of the male, of which the disposition is very 

 remarkable. Finally, the stomach and intestinal canal inclo.se in the 

 interior a membranous sac of a retort-shape ; the disposition and use 

 of which establish, according to the researches of M. Serres, an 

 additional approximation between the Cirripedes and the Annelides. 

 1 >r. Mart in-Saint Ange then proposes, as the last result of his labours, to 

 place the class Cirrijiedia at the end of the Crtutacea, so as to estab- 

 lish a natural link or passage between the superior Articulated Animals 

 and the Annelida. Such are the conclusions drawn in the Memoir 

 of Dr. Martin-Saint-Ange, who refers with approbation to the dis- 

 coveries of Mr. Thompson, published in 1830 ; and before we proceed 

 to give a further account of the structure of the Cirriptdia we will 

 state Mr. Thompson's view of the ovarial system. " In the whole of 

 the tribe of the Cirripedes," observes Mr. Thompson, in his paper 

 in the '1'hilosophical Transactions' above quoted, "the ova, after 

 expulsion from the ovarium, appear to be conveyed by the ovipositor 

 into the cellular texture of the pedicle, just beneath the body of the 

 animal, which they fill to the distance of about an inch. When first 

 placed in thin situation, they seem to be amorphous and inseparable 

 (rum the pulpy substance in which they are imbedded ; but us they 

 approach to maturity they become of an oval shape, pointed at both 

 ends, and are easily detached. Sir Kvcmrd Home has given a very 

 good representation of them, at this stage of their progress, in his 

 Lectures on Comparative Anatomy,' from the elegant pencil of Mr. 

 Bauer. During the stay of the ova in the pedicle, they render this 

 part more opaque and of a bluish tint ; the ova themselves and the 

 cellular texture with which they are surrounded, being of a pale or 

 azure-blue colour. It is difficult to conceive in what manner the 

 ova are extricated from the situation above indicated ; but it is 

 certainly not by the means suggested by Sir Kverard Home in the 

 above-meut ", namely, by piercing outwards through the 



membrane* of the pedicle, for the ova are subsequently found funning 

 a pair of leaf like expansions, placed between either side of the body 

 of the animal and the lining membrane of the shells in Isjtai (Pen- 

 tnlamu), or of the feathery internal tunic in Cinr-rai. These leaves 

 have each a separate attachment at the sides of the animal to the 

 septum, which divides the cavity occupied by the animal from that 

 of the pedicle ; they are at first comparatively small, have a rounded 



outline, and possess the same bluish colour which the ova had in the 

 pedicle; but as the ova advance in progress these leaven . n.l in 

 every dimension, and lap over each other on the back, j>a*iiig through 

 various lighter shade* of colour into pale-pink, ami I'm. illy, when 

 ready to hatch, become nearly white. Then leave* appear to be com- 

 posed of a layer of ova irregularly placed, and imbedded in a kind of 

 parenchymatous texture, out of which they readily fall when about 



to hatch, on its substance being torn asunder : in<l 1, it apjwars at 



length to become so tender a* to fall entirely away, so that after the 

 period of gestation is past no vestige of these leafy oonceptacles is to 

 be found. When the larva:, barely visible to the naked eye, 

 forth from the ova, their development goes on with such rapidity that 

 they seem to grow sensibly while under observation. The larva of 

 the Lepada then is a tailed Monocultu, with three pairs of members, 

 the most anterior of which arc simple, the other- 

 back covered with an ample shield, terminating anteriorly i: 

 extended horns, and posteriorly in a single elongated spinous pr 



The following observations on the development of the i. 

 animals, by Mr. Darwin, are amongst the latest contributions 

 interesting inquiry : " The ova, and consequently the larvtc of the 



lie, in the first stage, whilst within the sac of the parent. 

 in length from '007 to '009 in l^ptu, to '02:! of an inch in 

 My chief examination of these Ian , 



St-aJfitlluM wlgare ; but I saw them in all the other g> 

 larva is somewhat depressed, but nearly globular; the carapace 

 anteriorly is truncated with lateral horns : the sternal surface is flat 

 and broad, and formed of thinner membranes than tin' dorsal. The 

 horns just alluded to are long in Lrpat and short in Scalprllam ; their 

 ends are either rounded and excessively t, or. as in lli/n, 



furnished with an abrupt minute sharp point, Within these horns I 

 distinctly saw a long h'liformod organ, bearing excessively tine hairs 

 in lines, so exactly like the long plumose spines on the pie! 

 antenna; of the larva; in the last stage, that I have not the least doubt 

 that these horns are the cases in which antenna; are in process of 

 formation. Posteriorly to them on the sternal surface, near each 

 other, there are two other minute doubly-curved pointed horns, about 

 004 in length, directed posteriorly ; and within these I again saw a 

 most delicate articulated filifonned organ and a thicker pedicle. In 

 an excellent drawing by Mr. C. S. Bate, of the larv.c of a ( 'hi I,- 



< of British authors), after having been kept alive 

 and moulted once, these organs are distinctly shown as 

 antenna; (without a case), directed forwards : hence, before tie 

 moult in Scalpdlum we have two pairs of antennae in process of 

 formation. Anteriorly to the bases of these smaller antenna 1 is seated 

 the heart-shaped eye (as I believe it to be), "001 of an inch in dim 

 with apparently a single lens, surrounded, except at the apex, by dark- 

 redilish pigment-cells. In some cases, as in Home 

 the larvtc, when first excluded from the egg, have not an c\ 

 imperfect one. There are three pairs of limbs, seated c! 

 in a longitudinal line, but some way apart in a transvcr.-. dir. 

 The first pair always consists of a single spinosc minus ; it is imt 

 articulated in >v, ( /y,, HUM. Imt is multi-articulate in some genera ; it is 

 directed forwards. The other two pairs have each two ram!, 

 supported on a common haunch or pedicle ; in I Kith pairs the longer 

 minus is multi-articulate, and the shorter ramns is without articula- 

 tions, or with only trace-- of them; the longer spines bm 

 limbs (at least in > <///. iVi and t'lilhiiimilnx) are finely pli 

 The abdomen terminates a little beyond the posterior end 

 carapace in a slightly upturned horny point, A short <li 

 anteriorly to this point, a strong spinose forked projection depends 

 from the abdominal surface. Messrs. V. Tliotnp . and 



Bate have kept alive for several days the larva; of Lepcu, Cunrhudermn, 

 it ii/, i ma, Verruca, and Chthamaltu, and have described the changes 

 which supervene between the first and third exuviations. The most 

 conspicuous new character is the great elongation of t! 

 ixiint of the carapace into an almost lilit'onn spinose point in / 

 Uonchoderma, C'/ilhnmnliu, and Bnlnnna, but not, according to 

 Qoodsir, in one of the species of the latter genus. The p. 



point also of the abdomen becomes developed in Balanta(0 Isir) 



into two very long spear-like processes, serrated <m their 

 in Lepat and Conchodtrtna, according to Thompson, into a 

 ta]H<ring spinqsc projection ; and in I'litlmmalta, as figured by Mi 

 the posterior bilid point, as well ;H the depending ventral fork, 

 increases much in size. Another important change, whi 

 particularly attended to by Mr. Bate, is the appearance of spinose 

 projections and spines (some of which are thick, curved, and strongly 

 plumose or almost pectinated along their inner sides) on the p< 

 and lower segments of the shorter ratui of the two po 

 of limbs." In this stage of the growth of the larva, Mr. Darwin 

 found the month in > x < seated on a MTV slight 



prominence in a most remarkable situation, namely, in a < 

 point between the bases of the three pairs of legs. Mr. Darwin 

 continues:"! traced by dissection the oesophagi little 



way, until lost in the cellular and oily matter tilling the. whole 

 animal, and it was directed anteriorly, which i* the direction that 

 might have been expected from the course followed by th- 

 in the larva in the last stage, and iu the mature < in >prd. " 



The larva, iu its second stage of development, is known only 



