Japanese Freshwater Triclads. 21 



The paired ovaiy occupies a ventral position in front of the 

 first pair of the gut branches. It is of small size and is composed 

 of ova in several stages of development. In front of the ovary 

 there exists a large and lobed cellular mass which may be desig- 

 nat-ed under the name of the paraovary. 



The vitelline glands are branching cords of cells which are 

 arranged in two or more rows, and are extensively distriljuted 

 posteriorly from the ovarian region and in the interstices between 

 the gut diverticulae. The mode of the connexion between them 

 and the oviduct has not come under observation. 



The oviduct, which arises from the ovary in the form of 

 a funnel-like passage, soon assumes the cliaracter of a narrow tube 

 running backwards just along the outer side of the nerve cord. 

 S]ightl.y in front of the genital aperture the oviduct takes an inward 

 and upward course to unite with its fellow of the opposite side into 

 a wide single duct which opens into an elongate atrial passage be- 

 tween the penis-sheath and the vestibulum on the dorsal side. 



Plantiria vivida Ij. et Kab. 

 (PL I., figs. 9-11. -Text figs. 8, 9.) 



This species is widely distributed throughout the mainland 

 •of the Empire and commonly found in cool running waters in the 

 hilly districts. 



Form and Dimension. — In sliape the species closely resemldes 

 PI. alpina Dana. The frontal margin of the body in the living 

 condition is subtruncate and gently arched in the middle parts, 

 which laterally pass into the frontal margin of the moderately long, 

 obtusely pointed tentacles. The head is very fiat, without being 

 .marked oft' from the trunk by any neck-like narrowing of the body. 

 The trunk is slender, only weakly convex above and almost 

 uniformly Itroad for the greater part of its length, in the hind parts 

 tapering to an obtusely pointed, or sometimes rounded, extremity. 

 •Large specimens may reach 22 mm. in length and 4 mm. in 

 breadth at the pharyngeal region, the ratio of the breath to the 

 length being 1: 8-10. The worms, however, are usually smaller. 



