358 
REPRODUCTIVE ORGANS— GONADS. 
Near to the vaginal apertures of the digitate glands is the opening 
of the Stylo]diore, or dart sac, which commonly consists of an ovoid 
muscular sac within which is secreted a pointed calcareous spiculum 
used in the preludes leading up to sexual conjugation. 
The spermatheca or copulatory pouch often develops an additional 
and more capacious diverticulum, which may attain a considerable 
length, and usually receives the sperniatophore transferred during 
copulation. 
The male organs are chietly augmented by the development of 
the dagellum, a blind glandular diverticulum at the distal end of the 
l)enis sheath, within which or in an intermediate epiphallial tract 
the sperniatophore is moulded; these spermatophoral tracts may be 
separated from the penis sheath by a strong and outwardly visible 
s})hincter muscle, or the separation may be less distinct. 
The Reproductive System of the Dioeciate species have fewer con- 
stituent parts than the gastropodous Monoecia, in which a variety of 
auxiliary organs have been developed, sujiplementing or more perfectly 
discharging the neces.sary functions in connection with reproduction. 
The CfoNADS (yoi'os, seed) or germinal glands, the essential organs 
of the sexual system, are paired and symmetrical in the Pelecypoda 
but single in the Gastropoda. These organs possess a structureless 
outer wall, the internal germinal epithelium being composed of 
rounded cells, and derived from the walls of the cadomic or secondary 
body cavity of which they form a more or less definite part. 
In the Dimciate Gastropods and Pelecypods there are male gonads 
or testes, producing only spermatozoa or zoosperms, and female 
gonads or ovaries, producing eggs only, but in the ovotestis of the 
Monoeciate or hermaphrodite species both eggs and spermatozoa may 
Fig. G.).1. Fig. G54. 
Fig. (U),!.— Ovotestis of Limnaa peregra (Miill.), X .1, showing its lobiilated arrangement. 
Fig. (DI. — Ovotestis of Helix aspersa Miill., X 3, showing its sometimes tufted character. 
be itroduced by the same gland, although in the hermaphrodite 
Pelecypods Spharium, Pisidium, etc., the male and female gonads 
are separated in two regions, an anterior male region and a female 
more posterior one, with, however, a common efferent duct. 
In the Gastropoda, the richly lobed and convergent diverticula 
forming the gland vary greatly in their compactness and general 
