346 M. Souleyet on the Gasteropod Mollusca. 



but which, it seems to me, in many relations, must be placed by 

 the side of the Eolides, Phylliroe, the liver occurs in the form of 

 caeca which open detached into the stomachal cavity, and thus 

 presents a disposition which leads to that which is observed in 

 all the mollusca of the family of the Eolides ; only that, in these 

 last, the cseca of the liver, instead of remaining internal, become 

 external, propelling, so to speak, the skin before them, — a re- 

 markable and wholly exceptional peculiarity, which belongs per- 

 haps to some biological circumstances in these mollusca. 



In his last communication to the Academy, M. de Quatrefages 

 has expressed the opinion that this division of the liver was ne- 

 cessitated by the ramified disposition of the digestive cavity ; but 

 this necessity is not very evident, and, according to what I have 

 said above, this position of the liver around ramifications of the 

 stomach is, on the contrary, wholly in contradiction to the func- 

 tions which that naturalist assigns to them. 



I have already said that this gastro-biliary apparatus always 

 opens into the stomachal cavity, and in fact M. de Quatrefages 

 is wrong in making it terminate thus in the intestine or in the 

 buccal cavity. As I cannot enter here into details on this sub- 

 ject, I shall only remark that, in all these mollusca, the intestine 

 properly so called has escaped the researches of this naturalist ; 

 this has caused him to assign a false position to the anus, or has 

 led him to mistake the existence of that aperture*. 



In the statement which I have just given of the result of my 

 researches on the Eolides and the other genera which belong to 

 the same group, I have mentioned only what appeared to me to 

 have a reference to the general questions raised by M. de Quatre- 

 fages ; but I should observe, that on several other points my ob- 

 servations disagree with those of that naturalist, and especially 

 on the organs of generation, whose conformation appears to me 

 not at all to resemble the description which he has given of them : 

 I shall show in fact that this apparatus is wholly analogous to 

 that of the other Nudibranch Mollusca, and especially of the 

 Tritonice. 



Amongst the other genera of Mollusca which M. de Quatre- 

 fages has arranged after the Eolidians, in his order Phlebenterata, 

 is Oken's Acteon, and which is identical, as I have assured my- 

 self, with the genus described by M. Risso under the name Ely- 

 sia. The observations which I have made on this small mollusk 

 are quite opposed to those of M. de Quatrefages, who moreover 



* The description which M. de Quatrefages has given of the gastro-biliary 

 apparatus in the Eolidma is wholly inexact ; the canals which lead from the 

 stomachal cavity never terminate in lateral trunks, as is represented in the 

 figure given by that naturalist. 



