HERMAPHRODITISM IN MOLLTJSOA. 27 



of the ovotestis (P. glaber, maximus, flexuosus). The 

 male region is thus nearer the genital aperture than the 

 female region. 



(5) Cycladidse. 



A. Cyclas. — The hermaphroditism of this genus has been 

 known from the time of v. Siebold (24). But the conformation 

 of the genital organs has not been completely described even 

 by subsequent authors (25) ; Stepanoff has merely made known 

 that one portion of the gland is male and the other female. 



In C. cornea (fig. 12) the genital gland has a superficial 

 position upon each side of the posterior part of the body. It 

 is of scarcely any extent except in length (from liver to 

 nephridium), its height and depth being inconsiderable. It is 

 transversely divided into two portions of different appearance 

 and size, separated by a constriction in which there is merely 

 a ciliated duct uniting the two portions (fig. 11, iii). The 

 most anterior division is more elongated and more appreciably 

 lobulated than the other ; it extends as far as the liver. This 

 is the male region of the gland ; the other is exclusively female 

 (fig. 11, II). 



The hermaphrodite gland is thus seen to be here divided 

 into two portions of different sexes ; and these are no longer 

 in immediate contact (as in Pecten), but already separated 

 from one another, though connected by the intermediation of 

 a duct. 



Lastly, the posterior (female) portion of the gland is con- 

 tinued backwards by an hermaphrodite duct which terminates 

 at the genital orifice. The latter, which has escaped notice 

 hitherto) is situated outside the visceral commissure, near the 

 most ventral point of the nephridium (where the aperture of 

 this organ is placed), and in front of the posterior retractor 

 muscle of the foot (fig. 12, vi). 



B. Pisidium (26) and Corbicula (fide v. Jhering in 

 lit era) are also hermaphrodite. The conformation of the 

 genital gland appears to be the same in them as in C y c 1 a s (27) . 



