372 
DARWINISM 
CHAP. 
or perish, and all which come within sight of an island will 
struggle to reach it as their only refuge. But, with mountain 
summits the case is altogether different, because, being sur¬ 
rounded by land instead of by sea, no bird would need to fly, 
or to be carried by the wind, for several hundred miles at a 
stretch to another mountain summit, but would find a refuge 
in the surrounding uplands, ridges, valleys, or plains. As a 
rule the birds that frequent lofty mountain tops are peculiar 
species, allied to those of the surrounding district; and there 
is no indication whatever of the passage of birds from one 
remote mountain to another in any way comparable with 
the flights of birds which are known to reach the Azores 
annually, or even with the few regular migrants from 
Australia to New Zealand. It is almost impossible to con 
ceive that the seeds of the Himalayan primula should have 
been thus carried to Java; but, by means of gales of wind, 
and intermediate stations from fifty to a few hundred miles 
apart, where the seeds might vegetate for a year or two and 
produce fresh seed to be again carried on in the same 
manner, the transmission might, after many failures, be at 
last effected. 
A very important consideration is the vastly larger scale 
on which wind-carriage of seeds must act, as compared with 
bird-carriage. It can only be a few birds which carry seeds 
attached to their feathers or feet. A very small proportion of 
these would carry the seeds of Alpine plants ; while an almost 
infinitesimal fraction of these latter would convey the few 
seeds attached to them safely to an oceanic island or remote 
mountain. But winds, in the form of whirlwinds or tornadoes, 
gales or hurricanes, are perpetually at work over large areas 
of land and sea. Insects and light particles of matter are 
often carried up to the tops of high mountains ; and, from the 
very nature and origin of winds, they usually consist of 
ascending or descending currents, the former capable of 
suspending such small and light objects as are many seeds 
long enough for them to be carried enormous distances. For 
each single seed carried away by external attachment to the 
feet or feathers of a bird, countless millions are probably 
carried away by violent winds ; and the chance of conveyance 
to a great distance and in a definite direction must be many 
