MOLLUSCA— 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- 

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

 would be realised. 



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

 which is further found in other 

 Crphalaspidce [DoiHdium, Philinc, 

 Scaplmnder, Bulla) and all Ptcro- 

 poda. 



Tlie 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 nidaniental or 

 shell gland, .yields its outer pro- 

 tective envelope ; (2) tlie duct of 

 a globular vesicle (reeeptaculum 

 seminis, Schwammerdam's vesicle), 

 which receives the sjierniatozoa 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 

 which it is witlidrawn by means of 

 a retractor muscle. A gland called 

 the ))rostata opens into the penis. 

 The penis itself lies on the right ceptaculum seminis- 

 anteriorly, on 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 Acera do not essentially differ from 

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

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

 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, tlie vas deferens or seminal duct, and the oviduct. The 

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



Fig. 100.— Genital organs of Gastropteron Meckelii 

 (after VayssiSre). The penis and tlie seminal furrow 

 are not drawn. 1, Common genital aperture ; 2, genital 

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

 hermaphrodite duct ; (5, hermaphrodite gland ; 7, re- 



