14 The Shell-Collector’s Handbook. 
The vas deferens belongs to the male portion of the 
generative organs, the oviduct to the female portion. 
We will take these separately. 
The vas deferens runs along the side of the female 
organs, under the retractor muscle of the tentacle, 
and terminates in the penis sac. Before its termina- 
tion, a diverticulum is given off as the flagellum, in 
which the spermatozoa become, as it were, glued 
together to form the spermatophore. 
The penis sac is the continuation of the vas 
' deferens, and opens to the exterior at the genital 
aperture, a little below and behind the right dorsal 
tentacle. This tube contains a conical intromittent 
organ (penis), and may be everted, at the pleasure of 
the animal, by contracting the retractor muscle which 
has its origin from the floor of the mantle-cavity and 
its insertion into the penis sac just above the penis. 
The female reproductive organs are none the less 
complicated. Like the vas deferens the oviduct has a 
diverticulum, which, in this case, is called the recepta- 
culum seminis or spermatheca, and serves to lodge a 
spermatophore received from another snail. In some 
snails this receptaculum seminis is single, and consists 
of not more than one diverticulum. But in the 
majority of species—and notably in Helix aspersa— 
there is another diverticulum, which becomes dilated 
at its cecal extremity, and ends near the division of 
the aorta. Below this point the oviduct may be 
spoken of as the vagina. The vagina ends in the 
penis sac, thus producing a common gential canal or 
vestibule. Into the vagina opens the two ducts of the 
tufted muctparous glands, and just above or below 
