GASTROPODA. 



41 



but the ovaries and testes are, with a few exceptions (Actceon, Janus), 

 united in one hermaphrodite gland, which is usually imbedded 

 among the lobes of the liver. The ova and spermatozoa arise 

 either in different but adjacent follicles of the lobed or branched 

 hermaphrodite gland (Nudibranchiata), the ovarian follicles being 

 placed peripherally to the semeniferous follicles (^Eolis) or the 

 epithelium of the same follicle produces in one part ova, in another 

 part spermatozoa, not however usually at the same time, the maturity 

 of the male element preceding that of the female (terrestrial snails). 

 The efferent duct of the 

 female is nearly always 

 provided with a separated 

 albumen gland, and a re- 

 ceptaculum seminis (fig. 51 7). 

 In the Helicidce the vagina 

 bears two tufts of finger- 

 shaped glandular tubes and a 

 peculiar sac the dart-sac 

 which produces in its interior 

 a dart- like calcareous rod. 

 The latter - - the so-called 

 love-dart is attached to a 

 papilla at the base of the 

 sac ; it is protruded during 

 copulation, and seems to play 

 the part of a stimulating 

 organ. It is. usually broken 

 during use and is replaced Fia. 517. Sexual organs of the Eoman Snail (Helix 



poinatia). Zd, hermaphrodite gland; Zg, its duct ; 

 EJ, albumen gland ; Od, oviduct and seminal 

 groove ; Vd, vas deferens ; P, protrusible penis ; 

 Fl, flagellum ; Rs, receptaculum seminis ; D, 

 finger-shaped gland ; Z, Spiculum arnoris ; Go, 

 common genital opening. (After Baasen). 



later by a new one. The 

 male generative opening is 

 always in connection with a 

 protrusible penis, and usually 

 opens with the female into a common lateral cloaca. 



The structure of the generative organs in the dioacious Gastropods 

 resembles that of the hermaphrodite forms. A receptaculum 

 seminis and an albumen gland may be present in the female 

 (Paludina). The ovaries and testes lie hidden among the lobes of 

 the liver, and the sexual orifices are placed laterally. The males 

 almost always possess a projecting penis, which is either perforated 

 by the terminal part of the vas deferens (Buccinuni) or traversed by 

 a furrow, at the base of which the sexual opening is placed. When 



