CH. i] OF NATURAL SELECTION 5 



the old species would tend to become discontinuous in its distri- 

 bution by being replaced in some of its area by the new ones. 



On the face of it, this suggested mechanism for the carrying on 

 of evolution, to which Darwin gave the name of Natural Selection 

 ("or the preservation of favoured races in the struggle for life") 

 seemed eminentlv reasonable, and one that could do the work 

 required. But the struggle was necessarily of each individual of a 

 species for itself alone, and if one individual showed a favourable 

 variation while its neighbours did not, the variation would soon 

 tend to be lost by crossing. This was shown by Fleeming 

 Jenkin (21) in a criticism which Darwin considered as the best 

 that was ever made of his work. It therefore became necessary to 

 stipulate for the same variation to appear in many more or less 

 adjacent individuals of the species, scattered as a rule over a 

 considerable area. Crossing would then be useful, rather than 

 injurious. This in turn meant that the variation must probably 

 have been controlled, directlv or indirectlv. bv the external con- 

 ditions, and these would most likely be those of climate or of soil, 

 for the biological conditions largely depend upon which particular 

 plants may happen to surround the individual concerned at any 

 given place. 



Instead of an external force, there might of course have been 

 some compelling internal force which made a whole lot of indi- 

 viduals vary in the same way, and in this case one would certainly 

 expect all to vary. Whether the force were external or internal, 

 unless all varied alike over a considerable area, the advantage 

 would be lost by crossing. In either case, it is a little difficult to 

 see where natural selection got any leverage, for there would be 

 no competition between the new and the old, except at the margin 

 between them, where the new would in any case tend to be lost 

 by crossing. When Darwin gave way, as he was forced to do, to 

 this criticism of Fleeming Jenkin, the freedom of the natural 

 selection theory was really lost. 



The struggle for existence, felt as it was in every community 

 and family, was such a commonplace of everyday life, that the 

 principle had a very great psychological appeal, and was soon 

 taken up on all hands. The long neglected theory of evolution 

 rose "in the attitude of claimant to the throne of the world of 

 thought, from the limbo of hated, and as many hoped, of for- 

 gotten things " (66). Rarely has any h\^othesis met with greater 

 success than did natural selection. A mechanism familiar to 

 everyone seemed able to operate the long wished for process of 



