Hooge MD 2003 (citation) - Male-mature specimens approximately 575 µm long and 150 µm wide (Figs. 17, 18A, B, 19). Body cylindrical. Anterior end rounded; posterior end more blunt. Epidermis completely ciliated. Few rhabdoids present at posterior end. Mucoid glands prevalent at anterior end. Body color dark brown in transmitted light, due to brown epidermal pigment granules (Fig. 18C), and dark cells lining digestive central syncytium (Figs. 18A, B). Musculature with circular muscles that encircle the body along entire length of animal; straight longitudinal muscles present between frontal organ and anterior edge of mouth; longitudinal-cross-over muscles (fibers with a longitudinal orientation anteriorly, but bend medially to cross diagonally) present in both dorsal and ventral body wall; ventral body wall of anterior end with sigmoid-shaped diagonal muscles positioned between outer circular and inner longitudinal muscles (Fig. 19). Brain poorly developed; few nuclei located anterior to statocyst. Frontal organ well developed. Cell bodies of frontal glands positioned ~75 µm behind frontal pore (Fig. 17B). Mouth opening on ventral surface, anterior half of body. Digestive central syncytium extends from frontal glands posteriorly to level of seminal vesicle. Ovary unpaired, ventral; extends from level of mouth posteriorly to seminal bursa (Fig. 17B). Testes paired, ventral, at lateral edges of body; positioned behind ovary; extending from level of seminal bursa to false seminal vesicle positioned immediately anterior to male copulatory organ (Fig. 17B). Female gonopore absent. Seminal bursa with wall; positioned immediately behind largest egg (Figs. 17, 20A). Male gonopore terminal at posterior end; opens to ciliated male antrum (Figs. 17B, 20). Male copulatory organ composed of highly muscular seminal vesicle with epithelial lining (Figs. 17, 18D, E, F, 20, 21). Seminal vesicle surrounded by network of suspensory muscles (Fig. 21). Lumen of seminal vesicle with sperm (Figs. 18E, F). Wall of seminal vesicle composed of 5 sets of alternating longitudinal and circular muscles: widely-spaced outer-longitudinal muscles, double layer of interdigitating outer-circular muscles, thick (~ 5 µm wide) middle-longitudinal muscles, inner-circular muscles, and inner-longitudinal muscles that underlie epithelium of seminal vesicle lumen (Fig. 21). Invaginated penis absent.[From Hooge MD (2003)]
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