THE DAKWIXIAN THEORY 53 



cent., that is to say, none V)iit individuals of this fittest type will be 

 left surviving. 



This does not yet exhaust the process, however, for we can infer 

 from the results of artificial breed-forming that the selected charac- 

 ters may intensify from generation to generation, and that they will 

 continue to do so as long as it gives them any advantage in the struggle 

 for existence, for so long will it lead to the more frequent survival 

 of its possessors. The increase will only stop when it has reached 

 the highest degree of usefulness, and in this way new characters 

 may be formed, just as, in artificial selection, the short upward- 

 turning feathers of the Jacobin pigeon have been intensified into 

 the peruke, a feather canopy covering the head. 



A few examples of natural selection will make the process 

 clearer. Our hare is well secured from discovery by his fur of 

 mixed brown, yellow, white, and black, when he cowers in his form 

 among the dry leaves of the underwood. It is easy to pass close 

 to him without seeing him. But if the ground and the bushes are 

 covered with snow, he contrasts conspicuously with them. Suppose, 

 now, that our climate became colder, and that the winter brought 

 lasting snow, the hares which had the largest mixture of white 

 in their fur would have an advantage in their ' struggle for 

 existence' over their darker fellows; they would be less easily 

 discovered l)y their enemies — the fox, the badger, the horned owl, 

 and the wild cat. Of the numerous hares which would annually 

 become the prey of these enemies, there would be, on an average, more 

 dark than light individuals. The percentage of light-coloured hares 

 would, therefore, increase from generation to generation, and the 

 longer the winter the keener would be the selection between dark 

 and light hares, until finally none but light ones would remain. At 

 the same time, the colour of the hares would become increasingly 

 light, first, because it would hajjpen more and more frequently that 

 two light hares would pair, and secondly, because, after a time, the 

 struggle for existence would no longer be between light and dark 

 bares, but between light hares and still lighter ones. Thus ulti- 

 mately a race of white hares would arise, as has actually happened 

 in the Arctic regions and on the Alps. 



Or let us think of a herbaceous plant, in appearance something 

 like a belladonna, rich in leaves and very juicy, but not poisonous. 

 It would doubtless be a favourite food with the animals of the forest, 

 and it would not, therefore, attain to more than a sparse occurrence, 

 since few of the individuals would be able to form seeds. But noAV 

 let us assume that a stuff of very unpleasant taste develops in 



