CHARLES DARWIN 227 



under nature, be borne in mind ; as well as the strength of the heredi- 

 tary tendency. Under domestication, it may be truly said that the 

 whole organization becomes in some degree plastic. But the varia- 

 bility, which we almost universally meet with in our domestic produc- 

 tion, is not directly produced, as Hooker and Asa Gray have well 

 remarked, by man ; he can neither originate varieties, nor prevent 

 their occurrence ; he can only preserve and accumulate such as do 

 occur. Unintentionally he exposes organic beings to new and chang- 

 ing conditions of life, and variability ensues ; but similar changes of 

 conditions might and do occur under nature. Let it also be borne 

 in mind how infinitely complex and close-fitting are the mutual rela- 

 tions of all organic beings to each other and to their physical condi- 

 tions of life ; and consequently what infinitely varied diversities of 

 structure might be of use to each being under changing conditions 

 of life. Can it then be thought improbable, seeing that variations 

 useful to man have undoubtedly occurred, that other variations useful 

 in some way to each being in the great and complex battle of life, 

 should occur in the course of many successive generations? If such 

 do occur, can we doubt (remembering that many more individuals are 

 born than can possibly survive) that individuals having any advantage, 

 however slight, over others, would have the best chance of surviving 

 and of procreating their kind? On the other hand, we may feel 

 sure that any variation in the least degree injurious would be rigidly 

 destroyed. This preservation of favourable individual dififerences 

 and variations, and the destruction of those which are injurious, I 

 have called Natural Selection, or the Survival of the Fittest. Varia- 

 tions neither useful nor injurious would not be afifected by natural 

 selection, and would be left either a fluctuating element, as perhaps 

 we see in certain polymorphic species, or would ultimately become 

 fixed, owing to the nature of the organism and the nature of the con- 

 ditions. 



Several writers have misapprehended or objected to the term Nat- 

 ural Selection. Some have even imagined that natural selection in- 

 duces variability, whereas it implies only the preservation of such 

 variations as arise and are beneficial to the being under its conditions 

 of life. No one objects to agriculturists speaking of the potent efifects 

 of man's selection ; and in this case the individual differences given 

 by nature, which man for some object selects, must of necessity first 



