Japanese Freshwater Triclads.; 5 



discs of other Platocles. nor to that of the leech; it lacks the special 

 musculature so often elahorately developed in these. It appears to 

 be comparable, rather, to the frontal organ of the Aeoela, and 

 more particularly to the organ existing at the anterior end of 

 Mesostoma lingua, as mentioned 1)}^ Woodwortif. 



Digestive /System. — The mouth-opening lies slightly behind 

 the hind end of the middle third of the body. The pharynx, wliich 

 is cylindrical in shape, is inserted at about the middle of the body 

 and is about one-sixth the length of the entire body. The anterior 

 main trunk of the intestine gives rise to about 11 pairs of lateral 

 branches which are numerously subdivided, while the posterior 

 trunks are each provided with about 18 bifurcated or trifurcated 

 diverticulae. The wall of the gut is composed of an epithelium 

 comprising a number of cells which are known under the name of 

 Minot's glands. The general epithelial cells were seen to contain 

 minute spherical droplets or to be vacuolated. 



Nervous Sytem. — The brain is a bilobed organ, situated at the 

 anterior end of the body between the ventral wall and the anterior 

 termination of the intestinal trunk. Anteriorly each brain-mass 

 gives off a few sensory nerves and posteriorly is continuous with one 

 of the longitudinal trunks which run nearly parallel to each other 

 and extend to the hind end of the body. Throughout their entire 

 course, the trunks are connected by numerous transverse commis- 

 sures and also send out lateral branches towards the marginal 

 nerves, usually at points opposite to the union of the trunks with 

 transverse commissures. 



Geriital Organs. — The common genital opening is placed at a 

 point somewhat in front of the middle between the mouth-opening 

 and the posterior end of the body. It leads into the spacious pro- 

 longed atrium, which is provided with an irregularly folded wall, 

 and wliich may be generally divided into three portions, viz., the 

 anterior, the middle and the posterior. The anterior space extends 

 forward over the penis. The wall is made up of an epithehum of 

 columnar cells, resting upon a basement membrane, external to 

 which is a well-developed muscular coating, varying more or less 

 in thickness in different parts. 



