1901II Isolation plus Flowing Seas 



"cosmopolitan," ranging widely through the open 

 sea. 



The shore fish-fauna of Hawaii is frankly and Tropkai 

 entirely tropical — all the kinds belonging to families ^"' . 



d, •• r ^ ' ^ T\ ' n distinct 



genera characteristic 01 the equatorial racmc; 



but the different species are usually distinct from 



those of Samoa and Tahiti. This fact is doubtless 



due to the relative isolation of Hawaii as compared 



with Polynesia, which is linked with the East Indies 



by an almost continuous chain of islands and atolls. 



Yet the effects of geographical isolation are in- influence 

 sistently emphasized and increased bv the antaso- °^ '^"'^'^ 

 nistic course of marine currents in that region. These 

 do not much influence free swimmers like the tunnies 

 and mackerels, but they no doubt serve to transport 

 young individuals of more "sedentary" sorts from 

 one area to another. Certainly the young of shore 

 fishes are often carried out to deep water, so that 

 every island becomes to a certain extent the center 

 of a "sphere of influence" so far as its own species 

 are concerned. And fry are often borne northward 

 by the Gulf Stream as far as Rhode Island. In the 

 same way, young of tropical forms reach Japan 

 through the Kuro Shio. Other ocean currents must 

 exercise a similar influence. 



One of these great streams, starting near the Philip- The great 

 pines, passes eastward between Melanesia and Micro- ^1"^^''"'^ 

 nesia, thence along the shores of Fiji, Tonga, Samoa, 

 and Tahiti; next, proceeding by way of the Mar- 

 quesas, it turns to the northeastward, touching the 

 Revillagigedos ^ and other offshore Mexican islands, 

 and leaving there a few Polynesian species, after 



^ Not to be confounded with Revillagigedo Island in Alaska. The principal 

 members of the Mexican group are Clarion and Socorro. 



1:93 3 



stream 



