346 DARWINISM AND THE PROBLEMS OF LIFE 



can only gradually have been evolved from variations. 

 The complete adaptations cannot possibly have arisen 

 from a modification of the organism by mutation ; that 

 would be an excessive trust in the fortune of chance. 

 On this theory a mutation of a butterfly's wing would 

 imply that all its parts suddenly developed different 

 colours. But we must not expect that in this hap- 

 hazard variation the colours would harmonise in such 

 a way as to form a picture of a leaf ! Even if an 

 imperfect leaf-design were formed, it would not be 

 improved at the next mutation, as the colours of all the 

 parts would change at once ; even if the colours that were 

 wanting before now made their appearance, the parts 

 that had been rightly coloured would be destroyed. 

 Let us recall our illustration of the twenty dice. 

 Suppose the adaptation consisted in all the dice showing 

 the six. The shaking of them in the cup and throwing 

 them would represent a mutation. However many 

 times we try the experiment we shall scarcely succeed 

 in making all the dice show the six. It can only be 

 done by throwing each die separately until it gives a 

 six, and then letting it stand. But that is just the way 

 in which variations occur, and the fixing of them is left 

 to natural selection. 



Another objection to the theory of de Vries is that 

 the mutations must be neutralised by amphimixis with 

 normal animals, as they occur in so few individuals. It 

 will very rarely happen for them to be of so favourable 

 a character and at the same time for such a crisis to 

 come upon the species that all the individuals without 

 the mutation will perish. 



