GEOGRAPHICAL RANGE OF ANIMALS. 49 



range, in investigating their associations, or the faunae, we 

 must distinguish between zoological realms, zoological 

 provinces, zoological counties, zoological fields, as it were; 

 that is, between zoological areas of unequal value, over 

 the widest of which range the most extensive types, while 

 in their smaller and smaller divisions we find more and 

 more limited types, sometimes overlapping one another, 

 sometimes placed side by side, sometimes concentric to 

 one another, but always and everywhere impressing a 

 special character upon some part of a wider area, which is 

 thus made to differ from any other part within its natural 

 limits. 



These various combinations of smaller or wider areas, 

 equally well defined in different types, have given rise to 

 the conflicting views prevailing among naturalists respect- 

 ing the natural limits of faunae ; but, with the progress of 

 our knowledge, these discrepancies cannot fail to disap- 

 pear. In some respect, every island of the Pacific upon 

 which distinct animals are found may be considered as 

 exhibiting a distinct fauna; yet several groups of these 

 islands have a common character, which unites them into 

 more comprehensive fauna? ; the Sandwich Islands for in- 

 stance, compared with the Fejees or with New Zealand. 

 What is true of disconnected islands or of isolated lakes 

 is equally true of connected parts of the mainland and of 

 the ocean. 



Since it is well known that many animals are limited 

 to a very narrow range in their geographical distribution, 

 it would be a highly interesting subject of inquiry to 

 ascertain what are the narrowest limits within which ani- 

 mals of different types are circumscribed, as this would 

 furnish the first basis for a scientific consideration of the 

 conditions under winch animals have been created. The 



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