GENERATIVE ORGANS OF MOLLUSCA. 



383 



the reception of the copulatory organ. At the generative orifice, the 

 semen either passes directly into the subjacent and eversible copula- 

 tory organ, or, when this is some distance from the orifice, it is 

 carried to it by a ciliated groove. This arrangement is found in some 

 Opisthobranchiata, and in all the Thecosomatous Pteropoda. 



2) The efferent duct of the hermaphrodite gland is common for a 

 short distance only; it then divides, and each canal goes on its own way 

 to the generative orifice. At the point of division it may be connected 

 with secondary organs, or undergo a simpler 

 kind of differentiation as expressed by modi- 

 fications of the calibre of the canals. This 

 may also happen to the common tube an- 

 teriorly to its bifurcation. In the Opis- 

 thobranchiata it is often widened out for 

 a considerable distance, and so serves as a 

 receptacle for the generative products which 

 are about to be passed out. In the Neph- 

 ropneusta (Fig. 204) the common efferent 

 duct is divided into two portions. The 

 upper one (ve) from the hermaphrodite 

 gland (z) is simple, while the lower is 

 divided into two cavities for some distance ; 

 the narrower of these, which accompanies 

 the wider one in the form of a half-groove, 

 serves as a duct for the sperm, while the 

 wider one (u) belongs to the female appa- 

 ratus. At its upper end this latter has an 

 albuminiparous gland (Ed) attached to it, 

 and in the Helicina3 is beset with diverti- 

 cula, in which the ova obtain their envelope. 

 As the other canal is not completely shut 

 off from this uterus (u), the separation of 

 the ducts is not complete. It is only at 

 the termination of the uterus that the vas 

 deferens is continued on as an independent 

 canal (vd), which passes to the eversible 

 penis (p), which here forms a portion of the 

 efferent ducts. The more distal portion of 

 the canal secretes a substance which unites 

 the seminal masses into a seminal rope 



(Spermatophor). The uterus, finally, is continued into a terminal 

 portion, which is known as the "vagina;" this extends as far 

 as the common generative orifice, and may have a number of 

 appendages (ps, d) on its sides. In addition to a receptaculum 

 seminis (Rs), the Helicina3 have a group of larger glandular tubes 

 (//), which are connected to a thick-walled tube {ps). This latter 

 appendage is eversible, and contains a pointed calcareous concretion 

 (spiculum amoris), which appears to be moulded in its internal 

 cavity. 



Fig. 20k Generative ap- 

 paratus of Helix lior. 

 tensis. z Hermaphrodite 

 gland, ve Hermaphrodite 

 duct, u Uterus. Ed Al- 

 buminiparous gland, dd Ac- 

 cessory glands, pc Dart- 

 sac. Rs Keceptaculum 

 seminis. vd Seminal duct. 

 p Penis, fl Flagelliform 

 appendage. 



