Eggs deposited in a cocoon after copulation.
It is probable that they acquire special sensibility at the breeding season and serve as " guides " in copulation.
In this duct and sac the spermatophores received in copulation from another snail are lodged.
It is supposed to act in some way as a stimulant in copulation, but possibly has to do with the calcareous covering of the egg-capsule.
Spermatheca or receptacle of the sperm in copulation, opening into the female duct.