INTRODUCTION 



THE NATURAL REGIONS OF THE GLOBE 



The modern interest in the facts of the distribution 

 of animals, as indeed the modem interest in so many 

 of the problems connected with biology, dates from 

 the pubhcation of the Origin of Species. Darwin in his 

 famous voyage on the Beagle was much struck by the 

 curious phenomena of distribution which that voyage 

 brought before his eyes, and it was these phenomena 

 which helped to direct his attention to that line of 

 thought which resulted ultimately in the pubhcation 

 of his theory of Natural Selection. The two facts which 

 especially struck him were the two set forth in the 

 chapters on distribution in the Origin of Species. These 

 are, first, that similarity of physical conditions does not 

 necessarily result in a similar fauna, and conversely. 

 For example, there is considerable uniformity in the 

 fauna of South America throughout its length and 

 breadth, even though we find there every variety of 

 physical conditions, from the cold deserts of the high 

 Andes to the luxuriance of the Brazilian forest, or from 

 the burning deserts of Chile to the grassy plains of the 

 Argentine. On the other hand, there is very little 

 resemblance between the animals of the grassy plains 

 of South America and those of Africa, despite the 

 similarity in physical conditions. The second point 

 which struck him was that the resemblances or differ- 

 ences between the faunas of two areas are directly 



