PRELIMINARY DESCRIPTIONS OF SOME JAPANESE TRICLADS. 169 



Genital aperture at about the middle of the posterior third of body. 

 Atrium divided into two chambers, the penis sheath and the vestibulum,. 

 separated by a strongly muscular and tubular diaphragm, the free end 

 of which is retroverted into the former. Penis sheath with muscular wall 

 continuous with that of penis and thickest on the dorsal side. Testes 

 numbering about 19-21 on either side of body, occupying ventral position 

 on both sides of anterior gut trunk and limited in their distribution to be- 

 tween ovaries and pharynx insertion. Vasa deferentia in the posterior 

 parts make forward turn, rising upward at the same time, before they open 

 separately into penis. Vesicula seminalis wide, with somewhat folded walk 

 passing gradually into wide ejaculatory duct which opens at tip of penis. 

 Intromittent part of penis conical, horizontal. Ovaries two, spherical,, 

 placed ventrally between first and second pairs of gut branches. Oviducts 

 united at the end into a short single duct at a point dorsal to atrial dia- 

 phragm, opening into vestibulum just behind the latter. Receptaculum 

 seminis simply tubular at an early stage of development ; later the anterior 

 blind end becomes bent to the right or branches somewhat in the shape of 

 Y. Vagina opening dorsally into vestibulum on the left of median line. 



Localities : — Both running and standing waters at following localities : 

 Nikko ; Mt. Iwate in Prov. Rikuchu ; Towada Lake in Prov. Mutsu ; 

 Özawa in Prov. Ugo ; Mt. Bantai in Prov. Iwashiro, Collected by Ijima, 

 1S86, and by Kaburaki, 1914 and 1915. 



12. Polycelis karafto, n. sp. 



Woodcuts 23 and 24. 



Head end shaped nearly as in the preceding species, but tentacles 

 somewhat longer and more pointed at end. Trunk slender, nearly uni- 

 formly broad in most parts, obtusely pointed at posterior end. 



A large specimen in the creeping state measured 12 mm. in length 

 and 2 mm. in greatest breadth. Commonly smaller, breadth equalling 

 about one-fifth or one-sixth the length. 



Color of dorsal surface dark brown ; showing two, longitudinally 



