390 PHYLUM MOLLUSCA. 
which can be protruded at the single genital aperture and 
retracted by a special muscle. Before the vas deferens 
enters the penis, a long process or flagel/um is given off. 
It is like the lash of a whip, and is as long as the common 
duct. Its secretion is used in forming a sperm-packet or 
spermatophore of a large number of spermatozoa, which are 
OT 
D.S 
Fic. 210.—Reproductive organs of Helix pomatia.— 
After Meisenheimer, 
O.T., Ovotestis ; H.D., hermaphrodite duct; 4.G., albumen gland; F.D., 
female side of common duct; J7.D., male side of common duct; O., 
oviduct; &.S., receptaculum seminis; JZ.G., mucus glands; D.3S., 
dart-sac; V.D., vas deferens; FL., flagellum; P., penis; AZ., retractor 
muscle of penis ; A/., genital aperture. 
compacted together at the time of sexual union partly in 
the flagellum, partly in the penis. Thé spermatophore is 
transferred by the penis into the genital aperture of another 
snail. 
(f) Continued from the oviducal side of the common 
duct, there is a separate ciliated ovéduct. This has a short 
course, and ends in the common genital aperture. Before 
