Whe. Shell Collectors Handbook. 13 
pigmented retina, and leads back by an optic nerve — 
which when the tentacle is invaginated into the body 
is coiled up in a beautiful fashion—to the nerve to 
the tentacle, of which it forms a branch. 
THE Ouractory OrGans.—Most probably the 
olfactory organ is the pedal gland which has already 
been described. Still there are authors who localise 
the sense of smell in the anterior tentacles, or in the 
lobate processes surrounding the mouth. 
THe RepropuctTivE OrGans.—The Opisthobran- 
chiata and Pulmonata are monecious with the 
exception, perhaps, of Limax levis, which, according 
to the recent researches of Simroth, has the sexes 
distinct (vide 8. B. Ges. Leipsig, 1883, p. 74). The 
principal reproductive organ is the hermaphrodite 
gland or ovotestis, a yellowish gland situated in the 
left lobe of the digestive gland, and near the inner 
side of the second whorl. This combines the functions 
of ovary and testis, and although the cells composing 
it are microscopically alike, yet the regions where the 
ova and spermatozoa are developed are distinct and 
well defined from one another. Histologically the 
ovotestis consists of digitate follicles, in each of which 
the ova are developed on the outer wall, and the 
spermatozoa in the more central portions, Lodged 
in the right lobe of the digestive gland is a yellowish- 
white tongue-shaped organ—the albumen gland—from 
which a duct arises which unites in some portion of 
its extent with another duct from the hermaphrodite 
gland—the hermaphrodite duct—forming a common 
duct which at length divides into two—one, the 
longer, called the vas deferens, and the other the oviduct. 
