I THE DARWINIAN HYPOTHESIS 7 



distribution of animals and plants it seems 

 utterly hopeless to attempt to understand the 

 strange and apparently capricious relations which 

 they exhibit. One would be inclined to suppose 

 a priori that every country must be naturally 

 peopled by those animals that are fittest to live 

 and thrive in it. And yet how, on this hypothesis, 

 are we to account for the absence of cattle in the 

 Pampas of South America, when those parts of 

 the New World were discovered ? It is not that 

 they were unfit for cattle, for millions of cattle 

 now run wild there ; and the like holds good of 

 Australia and New Zealand. It is a curious 

 circumstance, in fact, that the animals and plants 

 of the Northern Hemisphere are not only as well 

 adapted to live in the Southern Hemisphere as 

 its own autochthones, but are, in many cases, 

 absolutely better adapted, and so overrun and 

 extirpate the aborigines. Clearly, therefore, the 

 species which naturally inhabit a country are not 

 necessarily the best adapted to its climate and 

 other conditions. The inhabitants of islands are 

 often distinct from any other known species of 

 animal or plants (witness our recent examples 

 from the work of Sir Emerson Tennent, on 

 Ceylon), and yet they have almost always a sort 

 of general family resemblance to the animals and 

 plants of the nearest mainland. On the other 

 hand, there is hardly a species of fish, shell, or 

 crab common to the opposite sides of the narrow 



