GEOGRAPHICAL RANGE OF ANIMALS. 43 



beings standing in close relation to the one or the other 

 of these mediums, it is in the nature of things that no 

 single species, either of animals or plants, should be uni- 

 formly distributed over the whole globe. Yet there are 

 some types of the animal, as well as of the vegetable king- 

 dom, which are equably distributed over the whole surface 

 of the land, and others which are as widely scattered in 

 the sea; while others are limited to some continent or 

 some ocean, to some particular province, to some lake, 

 nay, to some very limited spot of the earth's surface. 1 



As for as the primary divisions of animals are con- 

 cerned, and the nature of the medium to which they are 

 adapted does not interfere, representatives of the four 

 great branches of the animal kingdom are everywhere 

 found together. Eadiata, Mollusks, Articulata and Verte- 

 brata occur together in every part of the ocean, in the 

 Arctics as well as under the equator and near the 

 southern pole, as far as man has penetrated : every bay, 

 every inlet, every shoal is peopled by them. So universal 

 is this association, not only at present but in all past 

 geological ages, that I consider it as a sufficient reason to 

 believe that fishes will be found in those few fossilife- 

 rous beds of the Silurian System in which thus far they 

 have not been found. 2 Upon land we find equally every- 

 where Vertebrata, Articulata and Mollusks, but no Ea- 

 diata, this whole branch being limited to the waters ; 

 but, as far as terrestrial animals extend, we find repre- 



1 The human race affords an ex- be circumscribed in the sea, and that 



ample of the wide distribution of a of the Goniodonts of South America 



terrestrial type : the Herring and the in the fresh waters. The Chaca of 



Mackerel families have an equally Lake Baikal is found nowhere else. 



wide distribution in the sea. The This is equally true of the Blindfish 



Mammalia of New Holland show how (Amblyopsis) of the Mammoth Cave, 



some families may be limited to one and of the Proteus of the caverns of 



continent, the family of Labyrinth id Carinthia. 

 of the Indian Ocean how fishes may 2 See above, Sect. 7. 



