GEOGRAPHICAL DISTRIBUTION 199 



altTiougli the next nearest continent, is so enormously 

 remote that the fact becomes an anomaly. Bat this 

 difficulty partially disappears on the view that New Zea- 

 land, South America, and the other southern lands have 

 been stocked in part from a nearly intermediate though 

 distant point, namely, from the antarctic islands, when 

 they were clothed with vegetation, during a warmer 

 tertiary period, before the commencement of the last 

 Glacial period. The affinity, which, though feeble, I am 

 assured by Dr. Hooker is real, between the flora of the 

 southwestern corner of Australia and of the Cape of 

 Good Hope, is a far more remarkable case; but this 

 affinity is confined to the plants, and will, no doubt, 

 some day be explained. 



The same law which has determined the relationship 

 between the inhabitants of islands and the nearest main- 

 land is sometimes displayed on a small scale, but in a 

 most interesting manner, within the limits of the same 

 archipelago. Thus each separate island of the Galapagos 

 Archipelago is tenanted, and the fact is a marvellous 

 one, by many distinct species; but these species are re- 

 lated to each other in a very much closer manner than 

 to the inhabitants of the American continent, or of any 

 other quarter of the world. This is what might have 

 been expected, for islands situated so near to each other 

 would almost necessarily receive immigrants from the 

 same original source, and from each other. But how is 

 it that many of the immigrants have been differently 

 modified, though only in a small degree, in islands 

 situated within sight of each other, having the same 

 geological nature, the same height, climate, etc. ? This 

 long appeared to me a great difficulty: but it arises in 



