XII 



PHYLUM MOLLUSCA 



097 



herrn.nl 



Tierm.cL 



rec.sem 



The nephridia of the Gastropoda are dorsal ly placed glandular 

 tubes or chambers, which communicate internally with the peri- 

 cardium, and open on the exterior close to the anus, either 

 directly or through a duct the ureter. Both right and left neph- 

 ridia may be present, though unequal in size, the one situated to 

 the right of the anus being larger than that situated to the 

 left; or the former may alone be developed (Eutliyneura). In a 

 very limited number 

 of Gastropoda the 

 gonad opens into the 

 nephridium. 



The sexes are separ- 

 ate in nearly all the 



i/ 



Streptoneura, united 

 in the Euthyneura. 

 Special gonoducts are 

 present, except in one 

 or two forms in which 

 the nephridia perform 

 that function. In the 

 unisexual forms the 

 reproductive apparatus 

 is of a comparatively 

 simple character, con- 

 sisting merely of a 

 racemose reproductive 

 organ, ovary or testis, 

 as the case may be, 

 situated dorsally in the 

 visceral spiral, with the 

 goiioduct opening far 

 forwards on the right- 

 hand side, and, in the 

 male a penis, which is 

 grooved longitudinally 

 and non-retractile. In 

 the hermaphrodite 

 forms, such as the 

 Pulmonata (Fig. 603), 

 on the other hand, a 



considerable degree of complexity is observable. There is a 

 hermaphrodite gland (Jierm. gl., Fig. 604, A), some of the follicles 

 of which produce ova, while others produce sperms, a convoluted 

 hermaphrodite duct (herm. d.}, an albumen gland, in which 

 the albumen of the relatively large eggs is formed, separate 

 oviduct and spermiduct leading to a common genital opening. 

 In addition there is a receptaculum seminis (rec. sem.~) connected 



Kin. 003. Reproductive organs of Helix, all. <jl. albumen 

 gland ; d. s. dart sac ; flag, flagellum of the penis ; 

 herm. <il. hermaphrodite gland ; 1 ,-m. <> . hermaphrodite 

 duct; nine, r/l. mucous gland ; mac. <//. ap. apertures of 

 mucous glands into vestibule ; or'nl. ovidueal part of the 

 common duct ; o rid. up. aperture of oviduct into vesti- 

 bule; pen. penis; nc. sem. receptaculum semiuis ; rec. 

 ." TO. ap. aperture of receptaculum seminis; sp. </. sperm 

 duct ; sp. d'. spermiducal part of common duct. (After 

 Pelseneer.) 



