of the Sexual Products. 159 



could recall to mind of my own observations upon the Cteno- 

 phora, the Geryonidaa, and the Mollusca was in favour of 

 Hackel's ideas ; and in the Pteropoda especially I had clearly 

 seen what I took to be the entire genital gland formed by a 

 scission of part of the inner lamella. These observations on 

 the Pteropoda are recorded in a memoir which will appear 

 immediately. 



Nevertheless the perusal of M. van Beneden's memoir and 

 certain contradictions to be met with in those authors who 

 have paid attention to this subject for the Mollusca, made me 

 wish for an opportunity of verifying afresh the correctness of 

 my opinions. Thus it is well known that most authors repre- 

 sent the hermaphroditic gland of the Mollusca as originating 

 from the posterior part of the liver — that is to say, from the 

 entoderm. My own observations were in support of this 

 view, as I had seen the gland in question separate by scission 

 from the wall of the nutritive sac in the Pteropoda. Now 

 the nutritive sac gives direct origin to the liver in many 

 Cephalophora, although this is not the case in the Pteropoda. 



But one author, whose opinion weighs heavily in the 

 balance, did not share this opinion. J. M tiller describes the 

 genital organs in Creseis as originating from a pyriform organ 

 which is suspended by the side of the stomach and the origin 

 of the nutritive sac. What is the origin of this organ ? and 

 what are the modifications it undergoes in order to give origin 

 to the sexual organs ? The observations of the great anato- 

 mist give no answer to these questions. 



Being at Messina during the months of February and 

 March in the present year, my first care was to resume the 

 question ab ovo. Chance was in my favour ; the larvae and 

 young of Creseis abounded in the sea at a depth of from 5 to 

 10 fathoms. 



I had no trouble in finding the pyriform body described by 

 J. Mtiller in young animals which had recently undergone 

 metamorphosis. It was moreover already indicated in some 

 of my previous drawings. A careful study of its structure 

 and relations showed me that it was composed of a great 

 number of not very distinct small cells, and connected with 

 the ectoderm by sarcodic prolongations of its substance. The 

 largest of these prolongations was attached to the ectoderm 

 in the region near the anus, and to the anus itself, by means 

 of a quantity of branched filaments of extreme tenuity. The 

 other sarcodic processes were attached to the portion of the 

 ectoderm that surrounds the branchial or pallial cavity. 



This body, which is situated, as well described by J. Mtiller, 

 on the left side of the stomach, afterwards takes on a very 



12* 



