. Bulletin of the British Museum (Natural History). The tubular excretory system is 'Y"-shaped. It has a short, sinuous stem which divides into two sinuous arms dorsally to, and at the level of, the posterior union of the gut-caeca. Initially one arm is in the dorsal and the other in the ventral plane, but the ventral arm soon passes dorsally. They then both extend forward in the dorso-lateral region of the hindbody, enveloped by the uterine loops. At the level of the peduncle the arms pass ventrally and deep into the peduncle, before reflexing and running forward ventro-laterally in the
. Bulletin of the British Museum (Natural History). The tubular excretory system is 'Y"-shaped. It has a short, sinuous stem which divides into two sinuous arms dorsally to, and at the level of, the posterior union of the gut-caeca. Initially one arm is in the dorsal and the other in the ventral plane, but the ventral arm soon passes dorsally. They then both extend forward in the dorso-lateral region of the hindbody, enveloped by the uterine loops. At the level of the peduncle the arms pass ventrally and deep into the peduncle, before reflexing and running forward ventro-laterally in the forebody and re-uniting dorsally to the pharynx. There are 16 and 18 oval testes in the two specimens. These are arranged in irregular pairs along the anterior two-thirds of the hindbody. A tubular seminal vesicle extends sinuously, tapering gently, from just anterior to the base of the peduncle, medially between the caeca, to a level about 0-5 mm posteriorly to the pharynx. The distal region is very narrow and has a more muscular wall than the remainder of the seminal vesicle. It leads into the pars prostatica through a stout sphincter. The tubular pars prostatica is broader than the distal region of the seminal vesicle and has a wider lumen. It extends forward, curving antero-ventrally, to about the level of the posterior margin of the pharynx. It gradually tapers anteriorly and only the less muscular anterior half is surrounded by external gland-cells (Fig. 18A). The distal extremity of the pars prostatica might be termed an ejaculatory duct, as it also lacks external gland-cells, but a lining of villous cells is present. This region is linked to the hermaphroditic duct by a sphincter. This latter duct is relatively long, passes antero-ventrally, enters a tubular sinus-organ and opens at its terminus. The sinus-organ lies in a deep genital atrium, which opens mid-ventrally close to the posterior margin of the ventral sucker. In other material the sinus-organ is commonly foun
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