380 
GEOGRAPHICAL DISTRIBUTION, 
Chap. XI. 
were enabled to beat the less powerful southern forms. 
Just in the same manner as we see at the present day, 
that very many European productions cover the ground 
in La Plata, and in a lesser degree in Australia, and 
have to a certain extent beaten the natives; whereas 
extremely few southern forms have become naturalised 
in any part of Europe, though hides, wool, and other 
objects likely to carry seeds have been largely im¬ 
ported into Europe during the last two or three cen¬ 
turies from La Plata, and during the last thirty or forty 
years from Australia. Something of the same kind 
must have occurred on the intertropical mountains: no 
doubt before the Glacial period they were stocked with 
endemic Alpine forms; but these have almost every¬ 
where largely yielded to the more dominant forms, 
generated in the larger areas and more efficient work¬ 
shops of the north. In many islands the native pro¬ 
ductions are nearly equalled or even outnumbered by 
the naturalised; and if the natives have not been actu¬ 
ally exterminated, their numbers have been greatly 
reduced, and this is the first stage towards extinction. 
A mountain is an island on the land; and the inter¬ 
tropical mountains before the Glacial period must have 
been completely isolated; and I believe that the pro¬ 
ductions of these islands on the land yielded to those 
produced within the larger areas of the north, just in 
the same way as the productions of real islands have 
everywhere lately yielded to continental forms, natu¬ 
ralised by man’s agency. 
I am far from supposing that all difficulties are re¬ 
moved on the view here given in regard to the range 
and affinities of the allied species which live in the 
northern and southern temperate zones and on the 
mountains of the intertropical regions. Very many 
difficulties remain to be solved. I do not pretend to 
