176 THE ORIGIN OF SPECIES 



Zealand, and to a lesser degree in Australia, and have 

 beaten the natives; whereas extremely few southern forms 

 have become naturalized in any part of the northern 

 hemisphere, though hides, wool, and other objects likely 

 to carry seeds have been largely imported into Europe 

 during the last two or three centuries from La Plata and 

 during the last forty or fifty years from Australia. The 

 Neilgherrie Mountains in India, however, offer a partial 

 exception ; for here, as I hear from Dr. Hooker, Austra- 

 lian forms are rapidly sowing themselves and becoming 

 naturalized. Before the last great Glacial period, no 

 doubt the intertropical mountains were stocked with en- 

 demic Alpine forms; but these have almost everywhere 

 yielded to the more dominant forms generated in the 

 larger areas and more efficient workshops of the north. 

 In many islands the native productions are nearly 

 equalled, or even outnumbered, by those which have 

 become naturalized; and this is the first stage toward 

 their extinction. Mountains are islands on the land, and 

 their inhabitants have yielded to those produced within 

 the larger areas of the north, just in the same way as 

 the inhabitants of real islands have everywhere yielded 

 and are still yielding to continental forms naturalized 

 through man's agency. 



The same principles apply to the distribution of 

 terrestrial animals and of marine productions, in the 

 northern and southern temperate zones, and on the in- 

 tertropical mountains. When, during the height of the 

 Glacial period, the ocean-currents were widely different 

 to what they now are, some of the inhabitants of the 

 temperate seas might have reached the equator; of these 

 a few would perhaps at once be able to migrate south- 



