1. Boyer BC, Smith GW (1982) Sperm morphology and development in two acoel turbellarians from the Philippines. Pac Sci 36:365?380
2. Brooks DR, O'Grady RT, Glen DR (1985) The phylogeny of the Cercomeria Brooks, 1982 (Platyhelminthes). Proc Helminthol Soc Wash 52:1?20
3. Ehlers U (1985) Das phylogenetische System der Plathelminthes. Gustav Fischer, Stuttgart New York
4. Farnesi RM, Marinelli M, Tei S, Vagnetti D (1977) Ultrastructural research on spermatogenesis inDugesia lugubris SL. Riv Biol 70:113?136
5. Franquinet R, Lender T (1972) Quelques aspects ultrastructuraux de la spermiogenèse chezPolycelis tenuis etPolycelis nigra (Planaires). Z Mikrosk-Anat Forsch 86:481?495