Japanese Freshwater Triclads. 23 



the bod}", the deep ends of the anterior being located behind the 

 brain. 



D'ujedlve System. — The month-opening is situated at about 

 tlie commencement of the posterior third of the body. The 

 pharynx, which is inserted a short distance in front of the middle 

 of the body, is a cylindrical tube, terminating conically at the free 

 end. The anterior gut trunk gives rise to 4-6 pairs of lateral 

 branches, while the posterior trunk is usually provided with 12-14 

 lateral branches and about as many inwardly directed very short 

 branches. 



Of the excretory canals I could not obtain from any of the 

 sections available more insight than a few loops, which he in 

 dorso-lateral parts of the body and open out at some points on the 

 dorsal surface. 



Nervous System. — The brain conforms to the type observed by 

 MicoLETZKY (53) in PI. alphia. The longitudinal nerve cord of 

 each side forms anteriorly a well-developed brain-mass, those of 

 the two sides being connected by a strong commissure in which 

 there can be distinguished three sets of transverse fibres. From 

 each brain-mass spring some sensory nerves directed forwardly and 

 laterally. The first and second nerves, taking their origin at the 

 anterior corner of the brain-mass, proceed forwards to join the 

 marginal nerve. The third nerve breaks up into branches whilst 

 proceedmg towards the body- margin and extends to the tentacular 

 region, associated with the remainder, From the inner lateral 

 region of the '"Substanzinsel" arises a nerve extending to the eye. 

 Immediately below the first nerve is a very fine anterior trunk 

 which is connected with its fellow of the opposite side b}^ some 

 transverse commissures. The posterior longitudinal trunks proceed, 

 running parallel to each other, to the hind end of the body and 

 are connected together by about 45 transverse commissures. At 

 points opposite to the union of the said commissures the trunks 

 give off lateral nerves towards the marginal nerves. 



Oenital Organs. — The common genital aperture lies behind 

 the mouth-opening at a distance equal to about one-third that be- 

 tween the mouth-opening and the posterior end of the body. The 



