S. H A TT A. 



25 



marinas and assigning Gbay's name Lampetra to the portion represented 

 by ßuviatilis, planer i, m/itsukurii, wilden', &c. 



T>. Distribution of the Lampreys in Japan. 



The smaller Lamprey, Lampetra mitsuJcurii, is found in almost all 

 localities of the empire, while the larger form, L. japonica, is limited to 

 the rivers and ponds on the slope facing the Japan Sea on the main island 

 (the Hondo); the latter is especially abundant in the Shinauo River, the 

 Mogami Rivet', the Omono River, the Jintsu River, the Lake Kawakita, 

 the Kozan Pond, &c. It has been maintained by some persons that the 

 larger Lamprey is occasionally met with in the marshy regions of the 

 Kwanto-Plain and in -the mouth of the Kiso River and of the Kitakami 

 River and their adjacent waters. As these localities all belong to the 

 Pacific side, I have been at great pains to obtain the specimen from 

 them, but all my efforts were unfortunately so far proved fruitless. 



Let us now try to explain this peculiarity in the distribution of the 

 Lampreys on the main island. 



As is well known, the long chain of the islands, of which our empire 

 is composed, extends from the parallel of about 52° north to the parallel 

 of 22° with an oblique north-east or south-west direction. As regards 

 the main island, the long range of high mountains running lengthwise 

 in the central part constitutes the water-shed which divides rivers into 

 two sets of systems: the rivers on the slops facing the Asiatic Continent 

 empty their water into the Japan Sea, and the streams on the opposite 

 slope flow into the Pacific Ocean. The rivers on the Pacific slope have 

 in general a very steep incline, and their waters rush down in torrents 

 after heavy rains, and in most of the rivers, almost drying up or dwind- 

 ling into mere threads of water at other times. Thus their bed consists, 

 in most parts, of sand and gravel. On the contrat - }', the rivers on the 

 opposite side are less steep, and their bed is muddy. Thsse topograph- 

 ical conditions exert, it seems to me, a great influence up m the distribu- 

 tion of Lampreys in Japan, as the following considerations will show. 



