GASTEROPODA. 401 



rived, which is at first thin and slender, but, soon becoming wider 

 and more capacious (M), it gradually expands into an extremely 

 convoluted intestiniform viscus, to which the name of uterus has 

 been improperly given, and ultimately terminates in a canal de- 

 rived from the spermatheca, to be described hereafter. It is during 

 their passage through this enormous oviduct that the eggs attain 

 their full growth preparatory to their expulsion from the body. 



Another viscus, called by Cuvier simply " the bladder," is, from 

 the constancy of its occurrence, evidently an organ of importance ; 

 and there seems to be little room to doubt that it is intended to 

 be a receptacle for the seminal fluid, analogous in function to the 

 copulatory pouches we have already met with in Insects and some 

 Crustacea. The reservoir in question, which we have called sper- 

 matheca (Jig- 183, t), is in the snail placed above the stomach; 

 and the canal derived from it accompanies the sacculated oviduct, 

 which it ultimately joins near its termination, in such a manner 

 that the ova must pass the orifice of its duct as they are expelled 

 from the body. It must nevertheless be confessed that the office 

 here assigned to the "bladder" is rather probable than positively 

 established ; for in the Slug, so nearly allied to the snail in its 

 general organization, the excretory duct of this organ opens into 

 the common generative sac by an aperture distinct from that which 

 leads into the oviduct, although even here the two are closely 

 approximated. Cuvier suggests that perhaps it may furnish some 

 material useful in forming an envelope for the ova, but experiments 

 are still wanting upon this subject. 



There is still another set of organs connected with the canal by 

 which the eggs escape from the oviduct of the snail ; and these, 

 although peculiar to the genus we are examining, no doubt furnish 

 a secretion of importance to their economy. They are called the 

 multifid vesicles (fig. 183,^), and are composed of a series of 

 branched cseca derived from two excretory ducts by which a milky 

 fluid, secreted by the caeca, is poured into the egg-passage prior to 

 its termination. 



(439.) Although it will be convenient to speak in more general 

 terms concerning the nervous system of the GASTEROPODA than 

 the examination of a particular species would permit, we deem it 

 necessary, before closing our description of the snail, to describe 

 with some minuteness the senses possessed by these terrestrial mol- 

 lusks, and more especially the extraordinary mechanism provided 

 for withdrawing the most important instruments of sensation into 



2 D 



