CHAPTER XXIV. 



NATURAL SELECTION, 



Natural 



selection 



defined 



to be 

 among 

 sponta- 

 neous 

 variations. 



IN the chapter on Distribution, while stating my belief 

 that the remarkable similarity, without identity, 

 between the living species inhabiting the same region 

 ckiring successive geological periods is due to the bond of 

 descent, I said also that the species inhabiting any region 

 at present are not the direct lineal descendants of those 

 which dwelt there in the last geological age ; but that the 

 descent has been modified in accordance with a peculiar 

 law. The law I mean is that of " natural selection, or the 

 preservation of favoured races in the struggle for life." 

 (I quote these words from the title-page of Darwin's work 

 on " The Origin of Species.") But as Darwin's work, in 

 which the law of natural selection was first stated and 

 proved, is a well-known and very readable book, it is 

 needless for me to go into much detail. I speak of it as a 

 law that is proved. There is the greatest possible differ- 

 ence of opinion as to how much the law will account for ; 

 but no one who has the slightest knowledge of the subject 

 can doubt that it is a truly operative law. 



Before there can be selection, there must be something 

 among which to select ; and the full designation of the 

 theory is " natural selection among spontaneous variations!' 

 In the chapters on Habit and Variation, we have seen that 

 species are not absolutely constant in their characters, but 

 are liable to slight, and sometimes considerable variations, 

 which may become very great if they are added up and 

 accumulated through successive generations. We have 

 seen also that variation is stimulated by change of the 



