82 DARWINISM 



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

 is clear that Mr. Darwin 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, perhaps after a long 

 interval of time, vary or present individual differences of the 

 same favourable nature 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 expressions are hardly consistent with 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 

 writers as proofs of the extreme difficulties 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 

 Darwinian theory of the origin of species, that this chapter 

 has been written. 



