STUDIES ON THE REPRODUCTIVE SYSTEMS OF SEA-STARS. II. THE MORPHOLOGY AND HISTOLOGY OF THE GONODUCT OF ASTERIAS VULGARIS.

In Asterias vulgaris there are 10 separate units of the reproductive system, each with its own distinct gonoduct. The gonoduct forms late in the life of the sea-star as an outgrowth of the inner sac of the gonad. During its formation, each gonoduct grows from the gonad to the body wall where it burrows through a layer of connective tissue located below the parietal peritoneum. The gonoduct follows this subperitoneal connective tissue into a coelomic pocket (which ends externally in several dermal branchiae) and ultimately penetrates the dermis, where it divides into subsidiary ducts which open separately in the external epithelium of the interradius. The gonoduct consists of an outer elastic connective tissue layer continuous with both walls of the haemal sinus of the inner sac of the gonad and an inner epithelial layer continuous with the germinal epithelium of the gonad. Near the point where the gonoduct opens into the lumen of the gonad, the epithelial layer of the gonoduct forms cross-ridges which span the lumen of the duct and imbricate, partially blocking the lumen.