140 LAWS OF VARIATION. Chap. V. 



We may infer this from our frequent inability to pre- 

 dict whether or not an imported plant will 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 



