ANIMAL LIFE 187 



as that of somewhat shallower water in the 

 north. The species seem in many cases to be 

 identical." 



Observations similar to those above men- 

 tioned form the foundation for a belief in 

 what has been called bipolarity in the distri- 

 bution of marine organisms. 



Cetacea. — Among the Cetacea, two families 

 (Balaenidae and Balaenopteridae) appear to 

 be limited to the cold and temperate seas 

 of both hemispheres, and Sir William Turner 

 states that Balcena hiscayensis of the north 

 and B. australis of the south are identical, 

 and not present in the intermediate tropical 

 zone. 



Carnivora. — Among the eared seals allied 

 species are found in the Antarctic and in the 

 North Pacific, but not in the tropical waters ; 

 in the Atlantic, however, no eared seals occur 

 in the northern hemisphere. 



Fishes. — A. C. Giinther states that the most 

 striking character of the shore fish-fauna of 

 the southern temperate zone is the re-appear- 

 ance of types inhabiting the corresponding 

 latitudes of the northern hemisphere and not 

 found in the intervening tropical zone, and he 

 mentions eleven species and twenty- nine genera 

 as illustrating this character. The Salmonidae 

 are represented in the southern hemisphere 

 by the fresh-water family Haplochitonidae, 



