128 Evolution and Adaptation 



" Mere chance, as we may call it, might cause one variety 

 to differ in some character from its parents, and the off- 

 spring of this variety again to differ from its parent in the 

 very same character and in a greater degree ; but this alone 

 would never account for so habitual and large a degree of 

 difference as that between the species of the same genus. 

 As has always been my practice, I have sought light on this 

 head from our domestic productions." 



Then, after pointing out that under domestication two 

 different races, the race-horse and the dray-horse, for in- 

 stance, might arise by selecting different sorts of variations, 

 Darwin inquires : — 



" But how, it may be asked, can any analogous principle 

 apply in nature ? I believe it can and does apply most 

 efficiently (though it was a long time before I saw how), from 

 the simple circumstance that the more diversified the descen- 

 dants from any one species become in structure, constitution, 

 and habits, by so much will they be better enabled to seize 

 on many and widely diversified places in the polity of nature, 

 and so be enabled to increase in numbers." 



Here we touch on one of the fundamental principles of the 

 doctrine of evolution. It is intimated that the new form of 

 animal or plant first appears (without regard to any kind of 

 selection), and then finds that place in nature where it can 

 remain in existence and propagate its kind. Darwin refers 

 here, of course, only to the less extensive variations, the in- 

 dividual or fluctuating kind ; but as we shall discuss at greater 

 length in another place, this same process, if extended to 

 other kinds of variation, may give us an explanation of evolu- 

 tion without competition, or selection, or destruction of the 

 individuals of the same kind taking place at all. 



