558 
This is the only proof which he offers for the action of 
Natural Selection as an agent in the transmutation of 
species. Now we venture to protest against the method 
of this argument. The advocate of Mixed Darwinism 
has no right to assert that certain phenomena which can 
not have been brought about by the inherited effects of 
use or disuse, must have been produced by Natural Selec 
tion, until he has proved that they cannot have been pro 
duced by the direct action of the medium. He has no 
right to argue that what cannot be brought about by 
Natural Selection, must have been brought about by the 
direct action of the medium, until he has proved that 
they are not due to the inherited effect of use or disuse. 
Believing as he does that the direct action of the medium 
is a very potent influence in Organic Evolution, he scarcely 
does justice to his convictions, when he regards this factor 
as coming in to supplement the action of the other two 
factors. And in point of fact he argues subsequently that 
the direct action of the medium was the cause of the first 
modification of primordial living matter. 
But we venture to protest not only against the method 
of this argument, but also against the conclusions arrived 
at in the consideration of details. Mr. Spencer’s first reason 
for regarding Natural Selection as a factor is that, by it, 
adjustments, which are not the result of the effect of 
inherited use, are made comprehensible. His second 
reason is that Natural Selection alone accounts for the 
appearance of new parts. His third reason is derived 
from the changes in the arrangement and attachment 
of muscles. His fourth reason is based on the phe 
nomenon of mimicry. With respect to the third of these 
classes of phenomena, he says : “ Here again, then, we 
have a class of structural changes to which Mr. Darwin’s 
hypothesis gives the key, and to which there is no other