chap, iv.] ZOOLOGICAL KEGIONS. 51 



or a group of animals, is a matter of the first importance ; and, 

 as regards the general history of life upon the globe, may be 

 considered to be one of its essential characters. The structure, 

 affinities, and habits of a species, now form only a part of its 

 natural history. We require also to know its exact range at 

 the present day and in prehistoric times, and to have some 

 knowledge of its geological age, the place of its earliest appear- 

 ance on the globe, and of the various extinct forms most nearly 

 allied to it. To those who accept the theory of development as 

 worked out by Mr. Darwin, and the views as to the general 

 permanence and immense antiquity of the great continents and 

 oceans so ably developed by Sir Charles Lyell, it ceases to be a 

 matter of surprise that the tropics of Africa, Asia, and America 

 should differ in their productions, but rather that they should 

 have anything in common. Their similarity, not their diversity, 

 is the fact that must frequently puzzles us. 



The more accurate knowledge we have of late years obtained 

 of the productions of many remote regions, combined with the 

 greater approaches that have been made to a natural classifica- 

 tion of the higher animals, has shown, that every continent or 

 well-marked division of a continent, every archipelago and 

 even every island, presents problems of more or less complexity 

 to the student of the geographical distribution of animals. If 

 we take up the subject from the zoological side, and study any 

 family, order, or even extensive genus, we are almost sure to 

 meet with some anomalies either in the present or past distri- 

 bution of the various forms. Let us adduce a few examples of 

 these problems. 



Deer have a wonderfully wide range, over the whole of Europe, 

 Asia, and North and South America ; yet in Africa south of 

 the great desert there are none. Bears range over the whole of 

 Europe, Asia, and North America, and true pigs of the genus 

 Sus, over all Europe and Asia and as far as New Guinea ; yet 

 both bears and pigs, like deer, are absent from Tropical and 

 South Africa. 



Again, the West Indian islands possess very few Mammalia, 

 all of small size and allied to those of America, except one 



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