140 LAWS OF VAEIATION. Chap. V. 
We may infer this from our frequent inability to pre¬ 
dict whether or not an imported plant wull endure our 
climate, and from the number of plants and animals 
brought from warmer countries which here enjoy good 
health. We have reason to believe that species in a 
state of nature are limited in their ranges by the com¬ 
petition of other organic beings quite as much as, or 
more than, by adaptation to particular climates. But 
whether or not the adaptation be generally very close, we 
have evidence, in the case of some few plants, of their 
becoming, to a certain extent, naturally habituated to 
different temperatures, or becoming acclimatised: thus 
the pines and rhododendrons, raised from seed collected 
by Dr. Hooker from trees growing at different heights 
on the Himalaya, were found in this country to possess 
different constitutional powers of resisting cold. Mr. 
Thwaites informs me that he has observed similar facts 
in Ceylon, and analogous observations have been made 
by Mr. H. C. Watson on European species of plants 
brought from the Azores to England. In regard to 
animals, several authentic cases could be given of 
species within historical times having largely extended 
their range from warmer to cooler latitudes, and con¬ 
versely ; but we do not positively know that these ani¬ 
mals were strictly adapted to their native climate, but 
in all ordinary cases we assume such to be the case; 
nor do we know that they have subsequently become 
acclimatised to their new homes. 
As I believe that our domestic animals were origin¬ 
ally chosen by uncivilised man because they were use¬ 
ful and bred readily under confinement, and not because 
they were subsequently found capable of far-extended 
transportation, I think the common and extraordinary 
capacity in our domestic animals of not only withstand¬ 
ing the most different climates but of being perfectly 
