254 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



It should be noted that a spermatheca and spermatocyst 

 occur on the vaginal portion of the reproductive apparatus 

 of certain Prosobranchs, as described by Bourne* in the 

 Neritacea. Here the spermatheca (sperm sac) receives sperma- 

 tophores, whose sperms when liberated pass into the spermato- 

 cyst (receptaculum seminis). A duct of unknown function, 

 called by Bourne the ductus enigmaticus, is thought by him 

 to serve for conveying the debris to the exterior. 



* Bourne, G. C. " Contributions to the Morphology of the Group 

 Neritacea of Aspidobranch Gastropods." Proc. Zool. Soc., 1908, p. 810-887. 



