216 SUPPLEMENT 
known. The organ, however, is contained in a pouch open- 
ing by a very small orifice into the upper and anterior part of 
the branchial cavity, according to M. Bojanus, which has led 
him to think that this organ is a true lung, those which have 
been hitherto regarded as gills being, in his opinion, the 
organs for the deposition of the eggs. According to many this 
organ is behind, and under the rectum, which appears to be 
more in analogy. 
The apparatus of generation, which is more or less com- 
pletely known in all the animals of this type, is often very’ 
complicated, and at other times reduced to the greatest pos- 
sible simplicity. In fact, it is sometimes composed of the 
female part only, as in all the acephala and some cephala, 
which causes all the individuals of one species to be similar. 
There are found a tolerably great number of mollusca in which 
the sexes are distinct, but both existing in the same indivi- 
dual, from which it results that they again are all similar. 
Finally, there are also many in which the sexes are separated, 
thus producing in the same species the distinction of male 
and female individuals. 
The female apparatus of generation, in the cases where it 
exists alone, is formed but of one or two secretory organs or 
ovaries, situated a little differently in the acephala from the 
cephala. From this ovary there proceeds a canal or oviduct, 
which, after being for some time swelled in a part of its extent, 
directs itself forward or backward, and terminates on one 
side or the other, but more usually on the right than on the 
left. 
In the acephala the ovary may be single in its origin, and 
capable, by its successive enlargements, of extending itself 
into all parts of the mantle. It appears always to be prolonged 
by two distinct oviducts, which are placed, being directed 
from front to rear, on each side of the abdomen, where they 
terminate by a rounded orifice, at the extremity of an elonga- 
