Discartemon stenostomus van Benthem Jutting, 1954  

The genital system of Discartemon stenostomus – “The ovotestis consists of irregular lobes which, in the present specimens, contained stages of spermatogenesis and many mature spermatozoa and relatively few oocytes up to 55 μ in diameter. These oocytes were usually located singly and far apart. The little hermaphrodite duct consists of two distinct regions. The upper (i.e. apical as opposed to lower abapical) region is narrow and lined by a single layer of cuboidal ciliated cells with a thin muscular investment. The lower region is much wider with an irregular, labyrinthine, ciliated lumen and a substantial muscular investment. Where the upper region of the little hermaphrodite duct joins the lower, it is joined by the large seminal vesicle. This contained mature spermatozoa and the lining epithelium included secretory cells with their tips constricted off to varying extents. The little hermaphrodite duct passes into the glandular large hermaphrodite duct (or spermoviduct) at the base of the albumen gland where there is embedded a small talon. The large hermaphrodite duct is externally divisible into the large but compact prostate gland and the glandular wall of the female tract. From the lower (abapical) end of the large hermaphrodite duct the vas deferens emerges from the prostatic tissue and the oviduct continues from the glandular female tract. Sections reveal that the vas deferens arises from a deep ciliated groove extending from the main lumen of the large hermaphrodite duct into the prostatic tissue and receiving the latter’s products. This groove is almost partitioned off from the female lumen by a conspicuous flap running almost the whole length of the large hermaphrodite duct. In addition to those groove, a separate duct leaves the lower (abapical) end of the lumen of the large hermaphrodite duct at a point well below the origin of the vas deferens. It passes through the prostatic tissue to the upper (apical) end of the large hermaphrodite duct into which it reopens. This duct is wider at each end than in the middle and contained spermatozoa in both specimens sectioned. The prostate gland is not arranged in definite follicles, but irregular interstices among the cuboidal secretory cells lead to the deep prostatic groove. The lining of the female tract varies along its length. The upper (apical) third of its length it lined by large secretory cells up to 40 μ tall with many narrow ciliated cells wedged between them. The middle third (approximately) is lined by continuous ciliated epithelium resting on a basement membrance. This epithelium is thrown into pits and ridges and overlies many sub-epithelial gland cells. The lower (abapical) third of the glandular female tract is lined by a ciliated epithelium with markedly fewer secretory cells and this region passes without abrupt change into the relatively narrow oviduct. The vagina is swollen and highly muscular with an elaborately folded and pitted lining. The epithelium at the bottoms of the pits and furrows is normal and cuboidal but that at the tops of the ridges is compressed and stratified. The vagina receives the duct of the bursa copulatrix which comprises a folded epithelium of tall ciliated cells and a surrounding layer of muscle fibres. The lining of the bursa itself is similar but with more elaborate folds and larger cells. The vagina and penis pass into the genital atrium whose walls resemble those of the vagina until they merge with the skin of the head just below the right oculiferous tentacle. The vas deferens is well supplied with muscle fubres and leads into the proximal end of the penis. The muscular penis sheath does not quite reach the point of attachment of the retractor muscle to the terminal loop of the vas deferens. Where the vas deferens enters the side of the penis proper it bears within it a hollow stylet and this presumably protrudes from near the tip of the everted penis during mating. The inner surface of the penis is lined by heavily corrugated, stratified epithelium which will face outward during erection but there are no hooks or spines.” (Berry, 1965)