134 ACCLIMATIZATION. 



by Dr. Hooker from the same species growing at different 

 heights on the Ilimahiyas, were found to possess in this 

 country different constitutional powers of resisting cold. 

 Mr. Thwaites informs me that he has observed similar 

 facts in Ceylon; analogous observations have been made 

 by Mr. H. 0, Watson on European species of flants 

 brought from the Azores to England; and I could give 

 other cases. In regard to animals, several autbeiitic 

 instances could be adduced of species having h.rgely 

 extended, within historical times, their range f rom wiiinier 

 to colder latitudes, and conversely; but w^e do not posi- 

 tively know that these animals were strictly adapted to 

 their native climate, though in all ordinary casos we 

 assume such to be the case; nor do we know that they 

 have subsequently become specially acclimated to their 

 new homes, so as to be better fitted for them than they 

 ■were at first. 



As we may infer that our domestic animals were origin- 

 ally chosen by uncivilized man because they were useful, 

 and because they bred readily under confinement, and not 

 because they were subsequently found capable of far- 

 extended transportation, the common and extraordinary 

 capacity in our domestic animals of not only withstanding 

 the most different climates, but of being perfectl} fertile 

 (a far severer test) under them, may be used as an argument 

 that a large proportion of other animals liow in a state of 

 nature could easily be brought to bear widely dilferent 

 climates. We must not, however, push the foregoing 

 argument too far, on account of the probable origin of 

 some of our domestic animals from several wild stocks; the 

 blood, for instance, of a tropical and arctic wolf may per- 

 haps be mingled in our domestic breeds. The rat and 

 mouse cannot be considered as domestic animals, but they 

 have been transported by man to many parts of the world, 

 and now have a far wider range than any other rodent; for 

 they live under the cold climate of Faroe in the north and 

 of the Falklands in the south, and on many an island in 

 the torrid zones. Hence adaptation to any special climate 

 may be looked at as quality readily grafted on an innate 

 wide flexibility of constitution, common to most animals. 

 On this view, the capacity of enduring the most dilferent 

 climates by man himself and by his domestic animals, and 



