44 DARWINIANA. 



upon natural selection by separated extracts. The 

 following must serve to show how the principle is sup- 

 posed to work : 



" If during the long course of ages, and under varying condi- 

 tions of life, organic beings vary at all in the several parts of 

 their organization, and 1 think this cannot be disputed ; if there 

 be, owing to the high geometrical powers of increase of each 

 species, at some age, season, or year, a severe struggle for life, 

 and this certainly cannot be disputed : then, considering the 

 infinite complexity of the relations of all organic beings to each 

 other and to their conditions of existence, causing an infinite di- 

 versity in structure, constitution, and habits, to be advantageous 

 to them, I think it would be a most extraordinary fact if no 

 variation ever had occurred useful to each being's own welfare, 

 in the same way as so many variations have occurred useful to 

 man. * But if variations useful to any organic being do occur, 

 assuredly individuals thus characterized will have the best 

 chance of being preserved in the struggle for life ; and from the 

 strong principle of inheritance they will tend to produce off- 

 spring similarly characterized. This principle of preservation 

 I have called, for the sake of brevity, Natural Selection." (pp. 

 126, 127.) 



" In order to make it clear how, as I believe, natural selec- 

 tion acts, I must beg permission to give one or two imaginary 

 illustrations. Let us take the case of a wolf, which preys on 

 various animals, securing some by craft, some by strength, and 

 some by fleetness ; and let us suppose that the fleetest prey, a 

 deer for instance, had from any change in the country increased 

 in numbers, or that other prey had decreased in numbers, 

 during that season of the year when the wolf is hardest pressed 

 for food. I can under such circumstances see no reason to 

 doubt that the swiftest and slimmest wolves would have the 

 best chance of surviving, and so be preserved or selected pro- 

 vided always that they retained strength to master their prey 

 at this or at some other period of the year, when they might be' 

 compelled to prey on other animals. I can see no more reason 

 to doubt this than that man can improve the fleetness of his 



