. Elements of Comparative Anatomy. GENEEATIVE ORGANS OF MOLLUSCA. 383 tlie reception of tlie 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
. Elements of Comparative Anatomy. GENEEATIVE ORGANS OF MOLLUSCA. 383 tlie reception of tlie 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 («) belongs to the female appa- ratus. At its upper end this latter has an albnminiparous gland (Ed) attached to it, and in the Helicinae 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 u
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