Order Polycladida Lang, 1884
Gut with numerous radiating branches sometimes anastomosing, with pharynx plicatus. Testes scattered, follicular, male pore almost invariably anterior to female pore; ovaries scattered, eggs entolecithal. Free-living, some symbiotic, mainly marine.
? Family Ditremageniidae Palombi, 1928
After a considerable period of relative neglect, the polyclads were the subject of two comprehensive reviews (Faubel, 1983-84; Prudhoe, 1985). The scheme adopted here is the most recent, and the essentially more conservative, view of Prudhoe. These two criteria — modernity and conservatism — determined this choice. Faubel's scheme is both extensive and revolutionary; its very comprehensiveness allows it to stand on its own. Faubel places great reliance on the nature of the prostate tissue — its presence, its form and its distribution — especially in relation to the lining of the prostatic vesicle. Prudhoe, however, claims these characters are unreliable as they are capable of change during the development and maturation of some species. Such divergent views as those of Prudhoe and Faubel, however, must lead to increased critical analysis of the taxon — an unarguably desirable occurrence.