236 



COMPARATIVE ANATOMY 



CHAP. 



The oviduct which separates from the vas deferens at the end of the uterus is also 

 a vagina. It is a simple tube which opens outward to the right near the anus 

 through the genital aperture. Near the middle of its course it is joined by the 

 stalk-like duct of a globular vesicle, the receptaculum seminis (bursa copulatrix), and 

 by a long glandular cascal appendage. 



3rd Type. We find this in the Stylommatophora among the Pulmonala, and also 



Ps 



3D. 



PIG. 193. Anatomy of Helix pomatia (after Leuckart, Wandtafeln). The shell is removed 

 and the mantle hud back to the left, the organs of tin* visceral dome and head are isolated and 

 separated. To the left (in the figure) are the genital organs. L, Digestive gland (liver) ; Zd, her- 

 maphrodite gland; ./, intestine; N, kidney; V, ventricle; M, fore-stomach; F, foot; A, anus; 

 Al, edge of the mantle near the respiratory aperture ; Mr, retractor muscle ; G, cerebral ganglion ; 

 Fl, flagellum ; Sk, cesophageal bulb (pharynx) ; P, penis ; R, retractor of the tentacle ; Ps, dart sac ; 

 AD, digitate glands ; Vd, vas deferens ; X, lateral bulging of the stalk of the receptaculum seminis 

 (Rs); Od, portion of the uterus belonging to the oviduct ; Eil, albuminous gland ; Zg, hermaphrodite 

 duct. 



in all Nudibrancihia and a few Tcdibranchia (e.g. Pleurobranchcea). The herma- 

 phrodite gland gives rise to a hermaphrodite duct, which, as in the second type, 

 sooner or later divides into a male and a female duct. These, however, do not open 

 out through distinct apertures, but again unite to form a common atrium genitale or 

 a genital cloaca. This third type may be deduced from the second by suppos- 

 ing that the male and female apertures became approximated, and finally opened 

 together. 



