CHAPTER II 



EVOLUTION 



EVOLUTION may be defined as progress involving dif- 

 ferentiation, an ever-growing complication of things 

 which accompanies almost all the operations of Nature. 

 The idea of a differentiation of this kind may be en- 

 forced by a homely and quite imaginary illustration 

 of such a process. Imagine the proper ingredients of 

 a plum cake to be very finely minced and intimately 

 mixed together, so as to form a more or less homo- 

 geneous material. Then, if by any means the separate 

 particles of currants, raisins, peel, and so forth, could 

 be made to segregate out in such a way as to give rise 

 to the ordinary structure of this pleasant confection, 

 we should have arrived at the structure of a plum cake 

 by a process of evolution involving considerable dif- 

 ferentiation. 



The progressive increase in complexity which is 

 characteristic of so many natural processes is in great 

 part occasioned by the fact that a single * cause J is 

 followed as a general rule by more than one * effect.' 

 This apparently simple circumstance was pointed out 



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