Darwinism does not explain Variation 
should suffice to satisfy any unbiassed person ; 
firstly, that natural selection is an important 
factor in evolution; secondly, that the position 
taken up by Wallace and his followers, that 
natural selection, acting on minute variations, 
is the one and only factor in organic evolution, 
is untenable. 
1. It has been urged that the Darwinian 
theory makes no attempt to explain variation, 
and that, until we know what it is that causes 
variations, we are not in a position to explain 
evolution. This of course is quite true, but the 
objection is scarcely a fair one, since, as we have 
seen, Darwin freely admitted that his theory 
made no attempt to explain the origin of varia- 
tions. It is not reasonable to object to a theory 
because it fails to explain phenomena with which 
it expressly states that it is not concerned. On 
the other hand, the objection is one that must be 
reckoned with, for, as we shall see, it makes a 
great difference to the importance of natural 
selection as a factor in evolution if variations 
appear indiscriminately in all directions, as 
Darwin tacitly assumed they do, or whether, 
as some biologists believe, they are determinate 
in direction, being the result of a growth-force 
inherent in all organisms. 
2. Very similar to the above-mentioned objec- 
tion is that which points out that it is a long 
journey from Amoeba to man. It is difficult to 
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