TEE FISHES OF JAPAN. 77 



The resemblance consists in the presence in the two regions of cer- 

 tain striking-looking fishes not found in other parts of the world. An 

 analysis of these resemblances takes away much of their impressiveness. 

 Most of the forms in question are widely distributed, ranging from 

 Japan through India to the Cape of Good Hope. Only three genera 

 are restricted to Japan and the Mediterranean. Eesemblances equally 

 strong exist between Japan and the West Indies, or between Japan 

 and Australia. The differences are equally marked. The types re- 

 garded as of Japanese origin are all wanting in the Mediterranean. 

 Those of Mediterranean origin are wanting in Japan. There are two 

 main reasons why one fish fauna may resemble another ; the one, actual 

 connection, so that fishes migrate from one region to another ; the other, 

 similarity of physical conditions, favoring in each region the develop- 

 ment of similar kinds of fishes. The evidence points toward the theory 

 that similarity of physical conditions is the chief source of resemblance 

 between Japan and the Mediterranean. The resemblance between 

 Japan and the West Indies is due to this cause, while that of Japan to 

 the East Indies is due largely to direct connection. If Japan and the 

 Mediterranean were ever connected, the Eed Sea must have been a 

 region of junction. Yet, while the Eed Sea in its fishes closely resem- 

 bles southern Japan, it has almost nothing in common with the Medi- 

 terranean. Except a few shallow water or brackish water types, the 

 shore fishes of the two regions are wholly distinct, none of the charac- 

 teristic genera of either sea being found in the other. 



Yet, geologists affirm that in Pliocene or Post-Pliocene times the 

 Isthmus of Suez was submerged. It is made up of Pliocene, deposits 

 with alluvium from the Nile and drifting sand-hills. Admitting this 

 to be true, the nature of the fishes shows that this channel must have 

 been very shallow and probably in part occupied by fresh water. No 

 bottom-fish or rock-fish has crossed it — only sting-rays, torpedoes, eels 

 and mullets appear to have passed from one side to the other. It must 

 have been impossible for Japan and the Mediterranean ever to have 

 exchanged their deep-water fishes in this way. The only other alterna- 

 tive is the Cape of Good Hope, and this barrier is, to this day, passed 

 by many characteristic fishes of both oceans. 



Four hundred and eighty-three genera of fishes are known from 

 Japan. For the purpose of our present study we must take from this 

 list all the fresh- water types, derived from China; all the northern 

 types, derived from Bering Sea and the general Arctic stock; all the 

 pelagic fishes, at home in the open sea, and all the bassalian fishes, or 

 those inhabiting great depths below the range of climatic changes. 

 After these are withdrawn, we have left the shore fishes of tropical, or 

 semi-tropical, origin. Of these, Japan has 334 genera; the Mediter- 

 ranean, 144; the Eed Sea, 191; India, 280; Australia, 344; New 



