TAXONOMY AND GEOGRAPHICAL-DISTRIBUTION OF DUGESIA-JAPONICA AND D-RYUKYUENSIS IN THE FAR-EAST

Dugesia japonica Ichikawa et Kawakatsu, 1964, is a common and polymorp hic species of freshwater planarian distributed widely in the Far East . In 1976 the geographic populations were separated into 2 subspecies (D. j. japonica and D. j. ryukyuensis). The taxonomy of this species i s reconsidered once again from the morphological, anatomical, histolog ical, and karyological viewpoints. From the result of these studies, D . j. ryukyuensis is elevated to the rank of species: D. ryukyuensis Ka wakatsu, 1976. D. japonica (n = 8, 2x = 16, 3 x = 24) differs from D. ryukyuensis (n = 7, 2x = 14, 3x = 21) in having an asymmetrical penis papilla without a well-developed Valve surrounding its basal part, and a well-developed vagina (distribution: the Japanese Islands, Taiwan, the Korean Peninsula, China, and Primorskiy, Northeast Siberia, in Rus sia). D. ryukyuensis is characterized by an asymmetrical penis papilla with a well-developed valve surrounding its basal part, and a less-de veloped vagina (distribution: the Southwest Islands of Japan).