DARWTN, AND THE ORIGIN- OF SPECIES 1 95 



tics which fail to attract the breeder's notice, and that, so far as he 

 is concerned, they may be without " selective value." 



The breeder may either destroy, promptly and utterly, the ani- 

 mals and plants which he discards, or else, if he have some use 

 for them which is independent of reproduction, as he has for 

 horses, he may cut them off, at once and forever, from all part 

 in history ; but it is a mistake to infer from this analogy that 

 extermination in the natural struggle for existence always or even 

 generally, means sudden death. Nothing could be further from 

 the truth ; for the total extinction of a genetic line is usually slow, 

 and it may be carried on for many generations before it is finally 

 consummated. Among the terrestrial animals and plants which 

 we know best, sudden death during the reproductive period, when 

 the living being is in its prime, is not uncommon, but each organ- 

 ism is so well adjusted to the dangers and hardships which it may, 

 on the average, expect that those which are cut off completely from 

 posterity are exceptional. "I must premise," says Darwin, "that I 

 use this term struggle for existence in a large and metaphorical 

 sense, including dependence of one being on another, and includ- 

 ing (which is more important) not only the life of the individual, 

 but success in leaving progeny. ... A plant which annually pro- 

 duces a thousand seeds, of which on an average only one comes 

 to maturity, may be said to struggle with the plants of the same 

 and other kinds which already clothe the ground." ^ 



In a long series of generations all degrees of success or failure 

 in rearing progeny are possible, and when we bear in mind that, 

 so far as natural selection is concerned, success in leaving de- 

 scendants is practically equivalent to survival, no matter what the 

 after-fate of the individual may be, it is plain that the process of 

 extinction, far from being sudden, may go on so slowly as to be 

 imperceptible, and that there may be many opportunities for 

 every useful quality, however slight its value, to count for some- 

 thing in the result. " Battle within battle must be continually 

 recurring with varying success ; and yet in the long run the forces 

 are so nicely balanced, that the face of nature remains for long 

 periods of time uniform, though assuredly the merest trifle would 

 give the victory to one organic being over another." ^ 



1" Origin," p. 50. ^ " Origin," p. 57. 



