ON MOLLUSCA. OTe 
tion, of greater or less extent, situated between the second 
branchial plate and the body. Before this termination the 
oviduct contains at a certain period a milky white liquor. 
Some authors, and among others MM. Bojanus and Mery,add 
to this essential part of the generative organ of the bivalves 
the organs which we have already described under the name 
of gills, and which they regard as depositaries for the eggs. 
In the monecious cephala, such as the patelle, haliotides, 
&c., the ovary is always single, and on one side. It is the 
same with the oviduct, which is constantly directed from 
behind to front, sometimes at the left, but more frequently at 
the right side, where it terminates by a very short tube in the 
respiratory cavity. 
The disposition which constitutes the union of two distinct 
sexes in the same individual obtains only among the cephalo- 
phorous malacozoaria, and only in a certain number. 
The female part is formed by a single ovary, situated pos- 
teriorly in the liver; from it proceeds a first oviduct, which 
originates by ramifications, like those of the biliary canal in 
the liver. Very fine at first, its bulk increases; it bends, runs 
into heaps more or less compact, approaches the male part, 
becomes intimately united with it, and finally opens into a 
second oviduct, much wider, with thick folded parietes, se- 
creting an abundant viscous matter, and which is sometimes 
designated under the name of matrix. Near its mediate or 
immediate termination at the exterior is remarked that of a 
canal more or less long, proceeding from an oval or spherical 
bladder, contained in the great visceral cavity, and the use of 
which is entirely unknown. Might it not be a sort of 
prostate ? 
The male part is also composed of a secretory organ or 
testicle, situated most usually on the left side, and in front of 
the ovary. ‘The deferential canal which springs from it, after 
an intimate union with the first oviduct, follows the passage 
