no. 3638 TURBELLARIA — KAWAKATSU 17 



recorded from many caves. They are all white, eyeless cave-dwellers 

 with an adhesive organ in the center of the anterior margin. The 

 copulatory apparatus follows the plan of the genus Phagocata, from 

 which the Kenkiidae presumably derive (Hyman, 1951b). In the 

 Japanese Islands no specialized forms of planarians have been recorded 

 from caves (Kawakatsu, 1960). The Japanese Islands are the con- 

 tinental islands of the Asiatic Continent and consist of younger strata 

 than those of the North American Continent. Moreover, in the Neo- 

 gene, the greater part of the Old Japanese Islands had sunk beneath 

 the waves; this may have had a fatal effect upon the old Japanese flora 

 and fauna (Kawakatsu, 1965a). On the other hand, a number of un- 

 described species belonging to the family Kenkiidae (probably 

 SpeophUa) has been recorded from the subterranean waters in Middle 

 Japan (Kawakatsu 1965a, b, c). 7 Knowledge is scanty concerning the 

 Japanese subterranean water fauna although some troglobionts of the 

 ancient type or preglacial relics — Bathynella, Parabathynella, Al- 

 lobathynella, Phreatodytes, and Morimotoa — have been found in 

 subterranean waters in the Japanese Islands (M. U6no, 1960; S.-I. 

 Ueno, 1957). 



One of the speculations about the speciation of the genus Phagocata 

 is that the members of the North American cave-dwelling Kenkiidae 

 are the old immigrants to the New World, and at the same time a 

 group more adapted to the cave habitat than those of the present 

 North American Phagocata species. The speciation of the Japanese 

 Phagocata species, which apparently originated from the Eurasian 

 Continent, may not be so differentiated as the North American cave 

 inhabitants except for a number of the above-mentioned true sub- 

 terranean forms. More light could be thrown on this question by a 

 more thorough study of the turbellarian fauna of the North Pacific 

 areas of the Far East. 



7 Dr. Hyman kindly examined my photomicrographs of one of the forms that 

 occurs in a well in Himeji City, near Osaka, Middle Japan (coll. Mr. Y. Morimoto). 



