The Genital Ducts of Some British Stenoglossan Prosobranchs

Extract

The foregoing pages include an account of the anatomy and histology of the male and female genital ducts of Ocenebra erinacea, Nucella lapillus, Nassarius reticulatus and Buccinum undatum. Observations have also been made on the mode of functioning of the ducts and the formation of the egg capsules.

In both male and female it is possible to divide the genital ducts into a narrow and thin-walled proximal section which leads from the gonad and opens into a thick-walled glandular distal region, and in this respect the Stenoglossa agree with the mesogastropods. Near the junction of these two portions, in the female, arises the gonopericardial duct, which puts the genital duct into communication with the pericardial cavity; in males this structure i s lost or reduced to a vestige lying in a similar position.

In males the upper part of the proximal region of the genital duct is used as a vesicula seminalis and the epithelium is capable of taking up and digesting effete or superfluous sperm. Sperms are passed from it into the anterior, distal region during the act of copulation, and secretion from the glands is mixed with them and provides the medium in which they are transferred to the female. In Ocenebra and Nucella this glandular region, the prostate, extends only as far as the opening of the mantle cavity, from which a continuation of the duct, without glandular walls, runs to the penis. The entire distal half of the male duct shows evidence of having been derived from an open seminal groove such as is found in Littorina.