Japanese Freshwater Triclads. jk 



inserted at a point in front of the middle of the body, sliowing an 

 average length in relation to the body-length of 1: 3.5. The un- 

 paired anterior gut Wunk generally gives ofï 5 pairs of subbranched 

 lateral diverticulae, while the posterior trunks are each provided 

 Avith 15-17 diverticulae outwardly directed. A point of interest 

 is the occurrence of a transverse comnnssure, joining together tlie 

 two posterior trunks. Internally, the connecting canal is lined 

 with an epithelium made up of small cylindrical cells of a glandular 

 nature, which shows features apparently differing from the geneial 

 epithelium of the intestine. Externally there exists a muscular 

 coating of considerable thickness, consisting of circular fibres for 

 the most part. The muscular layer is less developed in the im- 

 mature than in the mature individual. To me, the connecting 

 canal appears to serve as a glandular organ. 



The exact arrangement of the nervous system could not be 

 ascertained, but it seemed to be quite similar to that observed in 

 the preceding species. 



Genital Organs. — The genital apparatus is similar in appea- 

 rance to that of Foly. auricidata. The common genital opening 

 lies nearly midway between the mouth-opening and the posterior 

 end of the body, and leads into the vestibulum, which receives the 

 openings of the vagina and the unpaired common oviduct from 

 above, as well as of the penis-sheath from the front. The penis- 

 sheath is provided with a strongly developed muscular layer of 

 circular fibres, which in the living state may be easily discerned as 

 a lighter colour. The muscular layer gradually increases in thick- 

 ness posteriorly, and is thickest at the end of the sheath. In 

 cross section the muscular layer shows a uniform thickness, unlike 

 that in Foly. auriculaia in which it is much thinner on the ventral 

 than on the dorsal side. Between the penis-sheath and the ves- 

 tibulum there exists no sign of the funnel-like body, which is 

 observed in Poly, auricidata. 



Numerous testes occur close together in the ventral position, 

 arranged on either side of the anterior main trunk of the intestine. 

 They extend from behind the ovaries to the insertion of the 

 pharynx. The vasa deferentia proceed backwards close along the 



