RELATIVE STABILITY OF LIVING MATTER 



315 



Space does not permit the enumeration of instances of acclima- 

 tization of domesticated animals and plants. References are full 

 of data of this sort, and common experience supplies a mass 

 of additional information. That both animal and plant species 

 possess and exercise large powers of adaptation to external condi- 

 tions is now no longer questioned. The only doubt is as to the 

 method. Whether the whole effect is produced through individ- 

 ual modification, whether it is largely the result of selection of 

 hardier strains, or whether there is some inheritance of modifica- 

 tion of this sort is yet an open question. 



Without a doubt individual modification has been underesti- 

 mated. It has been said that the powers of individual adaptation 

 are slight and that real acclimatization is secured through the 

 selection of the few individuals naturally endowed with powers 

 of high resistance. For example, it is a well-known fact that 

 when an entire field of corn (maize) has suffered from a killing 

 frost a few stalks here and there are unaffected. The same fact 

 has been noted among garden vegetables and fruits of various 

 sorts, many of which are mentioned by Darwin. 1 In changing 

 spring to winter wheat all but a few stalks are killed the first 

 winter, but those remaining give rise to winter strains. 



These and similar facts have given rise to the idea that accli- 

 matization is really through the selective process, and based on 

 inherent differences in constitution of the organism rather than 

 upon adaptability. Recent researches, however, have shown, 

 within limits, an unexpected degree of adaptability in the individ- 

 ual, and the examples already cited establish the fact that acclima- 

 tization is largely the result of modification of protoplasm. How 

 far this modification is possible and how far it is permanent, and 

 whether it is in any degree inherited, are now the absorbing 

 questions. That there is a high degree of permanence, at least 

 in some cases, is well established. Whether the modifications are 

 to any extent inherited is a subject that will be discussed in the 

 next chapter. 



Two facts are worthy of note in all studies in acclimatization : 

 first, the variations are functional, not morphological ; second, 

 the external forces involved are such as exercise an all-pervading 



1 Darwin, Animals and Plants under Domestication, II, 299-300. 



