82 
DARWINISM 
CHAP. Ill 
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. 
