PHYSIOLOGY OF THE INVERTEBRATA. 449 



gland the spermatozoa and ova are developed, but never at 

 the same time. In terrestrial snails the maturity of the 

 spermatozoa precedes that of the ova ; the object of this 

 arrangement being to prevent self -impregnation. The narrow, 

 common, hermaphrodite duct leads from the ovotestis, but 



Fig. 78. — Reproductive Organs of Helix. 



a = flag or sperm gland, b = retractor muscle of penis. -: = penis. 



d = genital vestibule. e = dart sac. / = dart. £' = vagina. 



A = mucous glands, i = spermatheca. k = ovotestis. mo = her- 

 maphrodite duct. n = albumin gland, fi = prostate. 



soon dilates. In this dilated portion it receives the secretion 

 of a large albumin gland. Beyond this point it divides into 

 two ducts — one for the spertnatic fluid, and the other for the 

 ova. The oviduct passes into the vagina, while the narrower 

 branch of the common duct is continued into a separate vas 

 deferens, the extremity of which leads into a long penis. 



2 F 



