INTRODUCTION 
THE NATURAL REGIONS OF THE GLOBE 
THE modern interest in the facts of the distribution 
of animals, as indeed the modern interest in so many 
of the problems connected with biology, dates from 
the publication 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 publication 
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 
