566 



SCIENCE. 



[N. S. Vol. XIV. No. 354. 



DISTRIBUTION OF LITTORAL FISHES BY COAST- 

 LINES. 



Their distribution is best indicated, not 

 by realms or areas, but as forming four 

 parallel series, corresponding to the four 

 great north and south continental outlines. 

 Each of these series may be represented as 

 beginning at the north in the Arctic fauna, 

 practically identical in each of the four 

 series, actually identical in the two Pacific 

 series. Passing southward, forms are ar- 

 ranged according to temperature. One by 

 one in each series, the Arctic types disap- 

 pear ; sub-arctic, temperate and semi-trop- 

 ical types take their places, giving way in 

 turn to south-temperate and Antarctic 

 forms. The distribution of these is modi- 

 fied by barriers and by currents, yet though 

 genera and species may be different, each 

 isotherm is represented in each series by 

 certain general types of fishes. 



Passing southward, the two American 

 series, the East Atlantic and the East Pa- 

 cific, pass on gradually through temperate 

 to antarctic types. These are analogous to 

 those of the arctic, and in a few cases they 

 are generically identical. The West Pacific* 

 (East Asian) series is very much broken 



* The minor faunal areas of shore fishes may be 

 grouped as follows : 



EAST ATLANTIC. 



Icelandic, 



British, 



Mediterranean, 



Guinean, 



Cape. 



WEST ATLANTIC. 



Greenlandic, 



New England, 



Virginian, 



Austroriparian, 



Floridian, 



Antillsean, 



Caribbean, 



Brazilian, 



Argentinan, 



Patagonian. 



EAST PACIFIC. 



Arctic, 



Aleutian, 



Sitkan, 



Californian, 



San Diegan, 



Sinaloan, 



Panaman, 



Peruvian, 



Revillagigedan, 



Galapagan, 



Chilian, 



Patagonian. 



WEST PACIFIC. 



Arctic, 



Aleutian, 



Kurile, 



Hokkaido, 



Nippon, 



Chinese, 



East-Indian, 



Polynesian, 



Hawaiian, 



Indian, 



Arabian, 



Madagascarian, 



Cape, 



North Australian, 



Tasmanian, 



New Zealand, 



Antarctic. 



by the presence of Australia, the East- 

 Indies and Polynesia. The irregularities 

 of these regions make a number of sub- 

 series, which break up the simplicity ex- 

 pressed in the idea of four parallel series. 

 Yet the fauna of Polynesia is strictly East- 

 Indian, modified by the omission or alter- 

 ation of species, and that of Australia is 

 Indian at the north, and changes to the 

 southward much as that of Africa does. 

 In its marine fishes, it does not constitute 

 a distinct ' realm. ' The East Atlantic 

 (Europe-African) series follows the same 

 general lines of change as that of the West 

 Atlantic. It extends, however, only to the 

 South Temperate Zone, developing no Ant- 

 arctic elements. The relative shortness of 

 Africa explains in large degree, as already 

 shown, the similarity between the tropical 

 elements in the two Old World series, as 

 the similarity in tropical elements in the 

 two American series must be due to a 

 former depression of the connecting Isth- 

 mus. The practical unity of the Arctic 

 marine fauna needs no explanation in view 

 of the present shore lines of the Arctic 

 Ocean. 



EQUATORIAL FISHES MOST SPECIALIZED. 



In general, the different types are most 

 highly specialized in equatorial waters. 

 The processes of specific change, through 

 natural selection or other causes, if other 

 causes exist, take place most rapidlj^ there 

 and produce most far-reaching modification. 

 As I have elsewhere stated, the coral reefs 

 of the tropics are the centers of fish-life, the 

 cities in fish-economy. The fresh waters, 

 the arctic waters, the deep sea and the open 

 sea, represent forms of ichthyic backwoods, 

 regions where change goes on more slowly, 

 and in them we find survivals of archaic 

 or generalized types. For this reason, the 

 study in detail of the distribution of marine 

 fishes of equatorial regions is in the highest 

 degree instructive. 



