VII 



MOLLUSC A GENITAL ORGANS 



233 



This lies more or less far forward in front of the genital aperture, near the right 

 tentacle. 



If we imagine the testis of a male Monotocardian transformed into a herma- 

 phrodite gland, and the vas deferens into a hermaphrodite duct, the above condition 

 would be realised. 



Gastropteron may be chosen as a good example of this arrangement (Fig. 190), 

 which is further found in other 

 Cephalaspidce (Doridium, Pkiline, 

 Scaphander, Bulla) and all Ptcro- 

 poda. 



The hermaphrodite gland or ovo- 

 testis, which lies between the lobes 

 of the liver in the posterior part of 

 the body, gives rise to a herma- 

 phrodite duct, which, after a long 

 coiled course, enters a short but 

 much widened terminal section 

 known as the uterus or genital 

 cloaca. This cloaca opens outward 

 in front of the base of the gills 

 through the genital aperture. Into 

 the cloaca open : (1) the common 

 efferent duct of two glands, one 

 of which, the albuminous gland, 

 supplies the egg with albumen, 

 while the other, the nidamental or 

 shell gland, yields its outer pro- 

 tective envelope ; (2) the duct of 

 a globular vesicle (receptaculum 

 seminis, Schwammerdam's vesicle), 

 which receives the spermatozoa dur- 

 ing copulation. From the genital 

 aperture, which has a more or less 

 median position on the right side of 

 the body, the seminal furrow runs 

 forward to the penis. The latter is 

 enclosed in a special sheath, out of 

 which it can be protruded, and into FIG. 190. Genital organs of Gastropteron Meckelii 

 which it is withdrawn by means of ( after Vayssiere). The penis and the seminal furrow 



a retractor muscle. A gland called a , re not dra ' V Coml " n genital aperture ; o genital 



cloaca ; 3, albuminous gland ; 4, nidamental gland ; 5, 



3 prostata opens into the penis, hermaphrodite duct; 6, hermaphrodite gland; 7, re- 

 The penis itself lies on the right ceptaculum seminis. 

 anteriorly, 011 the boundary between 



the head and the foot. When it is at rest its sheath lies in the cephalic cavity, 

 near the buccal mass. 



The very complicated ducts of Aplysia and Accra do not essentially differ from 

 that above described. The hermaphrodite duct, on reaching the region of the 

 albuminous gland, coils back upon itself, the ascending and descending portions of 

 this coil surrounding the albumen gland with their spiral coils. The penis has no 

 prostata. 



2nd Type. The hermaphrodite gland gives rise to a hermaphrodite duct, which 

 soon divides into two parts, the vas deferens or seminal duct, and the oviduct. The 

 former runs to the male copulatory apparatus, the latter to the female genital 



