118 Prof. M'lutosli on </ie 



Attempts have been made to divide this vast area into 

 regions characterized by special features. For instance, 

 Prof. Forchhammer, of the Chair of Mineralogy in the 

 University of Copenhagen, in 1862 described no less than 

 eleven regions distinguished by the mean quantity of solid 

 matter in the water, the tropical regions containing the 

 greatest amount. 



For facility in describing the collections made by the 

 ' Challenger,' seven regions of the ocean were made, viz. the 

 North Atlantic, the South Atlantic, the South Indian or 

 Kerguelen, the Australian, the Philippine or Japanese, the 

 North Pacific, and the South Pacific. Taking the seals, 

 sirenians, and whales as a basis. Dr. Sclater has compara- 

 tively recently (1899) made six regions, viz. North Atlantic, 

 mid- Atlantic, Indian, North Pacific, mid-Pacific, and Antarctic, 

 This classification is useful in emphasizing, amongst other 

 things, the fact that even with the continuous medium, which 

 permits migration in various directions, certain forms cling- 

 to special areas. It lacks, however, corroboration from the 

 other divisions of marine animals, and embraces so wide a 

 .subject that further consideration of all the facts is desirable. 



In passing therefore the distribution of the chief groups of 

 marine forms under review, tiie first amongst the marine 

 mammals are the sea-otters [Enhydris), which often swim 

 10 to ] 5 miles from land, and are confined to the area of the 

 Nortli Pacific, They do not appear to be spreading, but, as 

 Beddard says, persecution by man has made them more 

 purely oceanic. 



The eared seals are chiefly confined to the south Polar 

 ocean. Tin-ee species are found all over the North Pacific 

 area, whilst two frequent the west coast of South America 

 (Sclater). Tiie walruses are Arctic, the san;e species probably 

 occurring in the North Atlantic and the Nortli Pacific, though 

 the latter by some is considered distinct. The seals (Phocidaj) 

 are most numerous in the Arctic and Antarctic seas and in 

 certain intermediate areas. In the North Pacific three out 

 of four seals ave identical with those in the North Atlantic. 

 The true seals of the Antarctic Ocean are all distinct from 

 those of the Arctic seas (Sclater) . Thus the seals, as a whole, 

 do not support the theory of the bipolarity of marine forms. 



The peculiar range of the living Sirenians and their struc- 

 tural features would seem to point to an inaptitude for 

 migration, especially in the case of the manatees, yet the 

 dugong and Steller's sea-cow might have passed from islet to 

 coast-line and spread over a greater area, unless temperature 

 or other circumstance {e.g. food) had proved inimical. 



