Japanese Freshwater Triclads. 50 



whole colder than it is at present but that it was never cold enough 

 to generate glaciers, and that during that period it was colder in 

 the earlier part than in the later. The temperature of the country 

 has gradually increased since the Pliocene epoch, attaining its 

 maximum in the Diluvial period and then again decreasing down 

 to the present time. This state of things is just the reverse of what 

 we hnd in Europe and America. Yabe'\ on the contraiy dis- 

 senting entirely from Yokoyama's view, infers that Japan has 

 undergone climatic changes nearly pai'allel to those which prevailed 

 in Europe and America. More recently, S(jme authorities (Tsujr- 

 MURA, Yamazaki, OzEKr, Ogawa and others), approaching the 

 question from the geographical point of view, have adduced argu- 

 ments of considerable weight in favour of the view that this part of 

 the globe has formerly been subjected to a climate cold enough to 

 generate glaciers. As evidence of the recent occurrence of a 

 glacial age, they cite the cirques and moraines found in the Hida 

 mountains, well-known as the Japanese Alps. At present, this 

 view, though still more or less open to obvious objection, appears 

 to 1)0 generally accepted. 



Drawing attention to Yokoya3ia's opinion, Breiim"'^ has men- 

 tioned that the freshwater fauna in Japan requires more investiga- 

 tion. In collecting the freshwater Triclads I liave paid most 

 attention to the condition of their distributions, upon which the 

 following is based. 



Central Japan presents us with four familiar planarians. such 

 as Bdellocephala hrunnea, Planaria gonocepliala. PL vlvlda and 

 Polycelis auricidata. Among them the last mentioned species is, 

 so far as my observation goes, chiefly confined to the northern 

 mountain districts, wdiile PL vivida, which is similar in external 

 feature to /''/. alplna in Europe, extends much failher soutli than 

 Poly, auricidata. It is, how^ever, of intei'est that PI. vivida in the 

 southern parts is always found either in cave (Geml)udo in province 



(2) Yabe, X, 1913. On the Cliuiate in Japan since the Pleistocene Epoch. Gendai no 

 Kagaku (Sei. Gaz.), V^ol. I. 



(3) Brehm, v., 1913. Die Badentung der japanischen Corallin-Age für den europäischen 

 Süsswasserhiologen. Zool. Anz., Bd >i LII. 



