ZOOLOGICAL REGIONS. I// 



first strikes our attention. The animals of a single 

 group, belonging to one country, though they may 

 consist of many species, yet show a close relation to 

 each other, and thus form a unit. Every naturalist 

 who has had the opportunity of travel, or of exami- 

 ning collections from different localities, has been 

 struck with this fact. As he roams through the 

 forests of South America, he finds many distinct 

 species of monkeys, differing much from each other, 

 and yet all having a fundamental likeness by which 

 they can at a glance be distinguished from the 

 monkeys of the Old World. A collection of beetles, 

 of birds, or almost any other class of animals shows 

 a like result. And this is not simply that the species 

 and genera are different, but there is evident funda- 

 mental difference between the species of two separ- 

 ated countries. This fact has found recognition with 

 all students of geographical distribution, and has 

 been expressed by the division of the world into 

 zoological regions, in each of which the fauna and 

 flora are found to show a fundamental likeness. 

 These zoological regions are always separated from 

 each other by physical barriers, which effectually 

 prevent at the present time any migration from one 

 to the other, and although they sometimes have 

 identical climate, the fauna and flora are always dis- 

 tinct. It is true that different students of distribu- 

 tion have not agreed exactly upon the extent, or 

 even the number, of these regions, their limits 

 varying according to the class of animals which is 

 taken as a basis for the division. Wallace, using the 

 mammals as a guide, distinguishes six, while others 



