242 The Geographical Distribution of Fishes 



must explain the resemblance of the Arctic and Antarctic 

 faunae, there being in no case a barrier in the sea that may not 

 some time be crossed. Like forms lodge in like places. 



Agency of Ocean Currents. We may consider again for a 

 moment the movements of the great currents in the Pacific as 

 agencies in the distribution of species. 



A great current sets to the eastward, crossing the ocean 

 just south of the equator. It extends past Samoa and passes 

 on nearly to the coast of Mexico, touching the Galapagos Islands, 

 Clipperton Island, and especially the Revillagigedos. This 

 may account for the number of Polynesian species found on 

 these islands, about which they are freely mixed with immi- 

 grants from the mainland of Mexico. 



From the Revillagigedos * the current moves northward 

 and westward, passing the Hawaiian Islands and thence onward 

 to the Ladrones. The absence in Hawaii of most of the charac- 

 teristic fishes of Polynesia and Micronesia may be in part due 

 to the long detour made by these currents, as the conditions 

 of life in these groups of islands are not very different. North- 

 east of Hawaii is a great spiral current, moving with the hands 

 of the watch, forming what is called Fleurieu's Whirlpool. 

 This does not reach the coast of California. This fact may 

 help to account for the almost complete distinction in the shore 

 fishes of Hawaii and California.! 



No other group of islands in the tropics has a fish fauna 

 so isolated as that of Hawaii. The genera are largely the 

 ordinary tropical types. The species are largely peculiar to 

 these islands. 



The westward current from Hawaii reaches Luzon and For- 

 mosa. It is deflected to the northward and, joining a north- 

 ward current from Celebes, it forms the Kuro Shiwo or Black 

 Stream of Japan, which strews its tropical species in the rock 

 pools along the Japanese promontories as far as Tokio. Then, 

 turning into the open sea, it passes northward to the Aleutian 

 Islands, across to Sitka. Thence it moves southward as a cold 



* Clarion Island and Socorro Island. 



j- A few Mexican shore fishes, Chcetodon humeralis, Galeichthys dasycephalus, 

 Hypsoblennius parvipinnis , have been. wrongly accredited to Hawaii by some 

 misplacement of labels. 



