124 Variability 



them both high, till the trammels of protoplasm are 

 transcended. 



§14. (C) Variability. 



The third great idea in Darwinism is Variability — 

 the mysterious welling up of novelties, so that chil- 

 dren differ from their parents and two peas may be 

 very far from like. These variations furnish the raw 

 materials of evolution, and their origin is the most 

 difficult problem in biology. Darwin relied chiefly on 

 minute fluctuations, a little more of this and a little 

 less of that; he was interested in brusque freakish 

 novelties, but he thought they were bound to be 

 swamped by inter-crossing. He confessed that he did 

 not know how variations arose except in the case of 

 those acquired novelties or modifications which are 

 directly due to peculiarities in surroundings, food, 

 and habits — which we now call modifications. Darwin 

 called the inborn variations fortuitous, but he simply 

 meant that the combinations of causes that give rise 

 to a new departure remained obscure or beyond 

 analysis. He thought of novelties as sometimes con- 

 tinuing along the same line generation after genera- 

 tion, and accumulating like compound interest, as he 

 saw in his studies on domesticated animals and cul- 

 tivated plants, but he was also aware of discontinuous 

 variations which crop up, so to speak, without 

 warning. Darwin had hold of the useful idea of cor- 

 related variations, that a change in one structure 

 may have in its wake a change in another structure. 

 One change may have several outcrops. 



