282 Miscellaneous, 



experimentale,' I stated, in speaking of the relations between the 

 kidney and the coelome in Cirripedes, that there was no communi- 

 caiion between the renal sacs and the exterior or the general bodj-- 

 cavity. Herein, as throughout my paper, I took into consideration 

 only the adult forms. 



It was iuteresting to ascertain whether, at a certain stage of 

 development, any communication whatever existed between the 

 kidney and the body-cavity. As I had at my disposal some larvie 

 and very young examples of Lepas pecturata, obtained at the Arago 

 Laboratory, I have been able to make certain investigations upon 

 this subject, the result of which I will briefly detail. 



On examining series of transverse sections of larvae and young 

 specimens of Lepas pecturata, we are able to perceive how the 

 reciprocal relations between the kidney and the body-cavity are 

 modified. 



In the Cypris larva we find an extremely small cf.vity in direct 

 communication with the exterior by means of a pair of orifices 

 situated upon the palps of the lower lip, and which evidently represents 

 the coelome as it is met with in the adult. At the very bottom of 

 this cavity — that is to say, on the side opposite to the external 

 aperture — we notice a little cluster of scarcely differentiated cells 

 with a narrow central lumen ; this is the beginning of the renal 

 gland. 



In proportion as the coelome enlarges, the lumen of the renal 

 gland increases more and more, and in individuals which are quite 

 young and have scarcely emerged from their larval shell there exists 

 a distinct commnnieation between the body-cavity and the kidney. 

 Then, as the animal grows, the renal cells become more and more 

 differentiated, and the sac is entirely reconstituted, destroying the 

 communication which had existed for a time between the two 

 cavities in question. 



At a certain period of their development, therefore, Cirripedes, 

 or at least the species that I have been studying (and there is no 

 reason that the conditions should not be the same in the remaining 

 forms), possess a pair of veritable segmental organs, formed by an 

 excretory band scarcely differentiated, it is true, but in direct com- 

 munication with the exterior. 



The accumulative pseudo-kidneys (pseudo-reins d'accumulation) 

 that I have described in the adult would therefore be, at this period 

 of life, genuine organs for the direct elimination of excrementitious 

 products to the exterior. 



The body- cavity of the adult would be primitively a simple excre- 

 tory canal, which has become, so to speak, passive in consequence of 

 the obliteration of the renal sacs, the products of which it still 

 eliminates to the exterior indeed, but in a manner altogether indirect, 

 by the aid of the incessant osmotic exchanges which take j^lace 

 between the general body-cavity and the kidneys of the adult. 



We know that in the Crustacea the shell-gland generally opens 

 upon the second pair of maxillaB. In reality the position of the 

 excretory orifice of this gland varies enormously, not onl}' in the 

 different groups, but even according to the genera and species. 



