202 THE ORIGIN OF SPECIES 



a very common flexibility of constitution, brought, under 

 peculiar circumstances, into action. 



How much of the acclimatization of species to any 

 peculiar climate is due to mere habit, and how much to 

 the natural selection of varieties having different innate 

 constitutions, and how much to both means combined, is 

 an obscure question. That habit or custom has some in- 

 fluence I must believe, both from analogy and from the 

 incessant advice given in agricultural works, even in 

 the ancient Encyclopedias of China, to be verv cautious 

 in transporting animals from one district to another. 

 And as it is not likely that man should have succeeded 

 in selecting so many breeds and sub-breedi with constitu- 

 tions specially fitted for their own districts, the result 

 mu^it, I think, be due to habit. On the other hand, 

 natural s^^lection would inevitably tend to preserve those 

 individuals which were born with constitutions best 

 adapted to any country which they inhabited. In trea- 

 tises on many kinds of cultivated plants, certain varieties 

 are said to withstand certain climates better than others; 

 this is strikingly shown in works on fruit-trees published 

 in the United States, in which certain varieties are ha- 

 bitually recommended for the Northern and others for the 

 Southern States; and as most of these varieties are of 

 recent origin, they cannot owe their constitutional differ- 

 ences to habit. The case of the Jerusalem artichoke, 

 which is never propagated in England by seed, and of 

 which consequently new varieties have not been pro- 

 duced, has even been advanced, as proving that acclima- 

 tization cannot be effected, for it is now as tender as 

 ever it was! The case, also, of the kidney-bean has 

 been often cited for a similar purpose, and with much 



