82 DARWINISM chap, hi 



the last edition of The Origin of Species was preimred ; and it 

 is clear that Mr. Dar-\\an himself did not fully recognise the 

 enormous amount of variability that actually exists. This 

 is indicated by his frequent reference to the extreme slowness 

 of the changes for which variation furnishes the materials, 

 and also by his use of such expressions as the following : "A 

 variety when once formed must again, lyerluqjs after a long 

 interval of time, vary or present indi\'idual differences of the 

 same favourable natiu:e as before" (Origin, p. 66). And 

 again, after speaking of changed conditions " affording a better 

 chance of the occurrence of favourable variations," he adds : 

 " Unless such occur natural selection can do nothing" (Origin, 

 p. 64). These exj^ressions are hardly consistent A^^th the 

 fact of the constant and large amount of variation, of every 

 part, in all directions, which evidently occurs in each genera- 

 tion of all the more abundant species, and which must afford 

 an ample supply of favourable variations whenever required ; 

 and they have been seized upon and exaggerated by some 

 Avriters as proofs of the extreme difhculties in the way of the 

 theory. It is to show that such difficulties do not exist, and 

 in the full conviction that an adequate knowledge of the 

 facts of variation affords the only sure foundation for the 

 Dar-onnian theory of the origin of species, that this chapter 

 has been "\AT.itten. 



