Abstract
A study was made of morphology, taxonomy, ecology, reproduction, and distribution in freshwater planarians of the species Phagocata kawakatsui OKUGAWA. The specific character in the present form of the copulatory apparatus is as follows : penis large with well-developed bulb and slender, long, finger-shaped papilla ; sperm ducts enter the penis bulb separately ; single bulbar cavity ; copulatory bursa rather small or moderate or large ; slender bursa stalk with thick radial musculature on the vagina. This species is distributed in Middle Japan (Honshu and Shikoku). Specimens from different localities show some variation in miaute details of the copulatory apparatus. This species in found in shallow spring-fed streams with a slow current. The planarians become sexually mature in winter to early spring (about six months after hatching). Their active breeding season is spring (March to May). After breeding, adult worms begin to die. One worm lays 1 to 2 ovoid-shaped cocoons in one breeding season. The number of juveniles per cocoon ranges from 2 to 10. An analysis was made of the factors affecting the seasonal change of the population size of Phagocata kawakatsui, and the taxonomic relation and speciation of the three Phagocata species (kawakatsui, teshirogii and iwamai) were also discussed.
