ISLANDS TO THOSE OF THE MAINLAND. 419 



brought with earth and stones on icebergs, drifted by the 

 prevailing currents, this anomaly disappears. Xew Zealand 

 in its endemic planes is much more closely related to Aus- 

 tralia, the nearest mainland, than to any other region: and 

 this is what might have been expected; but it is also 

 plainly related to South America, which, although the 

 next nearest continent, is so enormously remote, that the 

 fact becomes an anomaly. But this difficulty partially dis- 

 appears on the view that New Zealand, 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 south-western 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 be- 

 t-ween the inhabitants of islands and the nearest mainland, 

 is sometimes displayed on a small scale, but in a most in- 

 teresting manner, within the limits of the same archi- 

 pelago. Thus each separate island of the Galapagos 

 Archipelago is tenanted, and the fact is a marvelous 

 one, by many distinct species; but these species are 

 related 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 

 some original source, and from each other. But how is it 

 that many of the immigrants have been differently modi- 

 fied, though only in a small degree, in islands situated 

 within sight of each other, having the same geolog- 

 ical nature, the same height, climate, etc. ? This long 

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

 part from the deeply-seated error of considering the phys- 

 ical conditions of a country as the most important; 

 whereas it cannot be disputed that the nature of the 

 other species with which eacli has to compete, is at 

 least as important, and generally a far more import- 



