The Making of Species 
believe that this long course of development from 
the simple to the complex is due to the action 
of a blind force, to the survival of those whose 
fortuitous variations happen to be best adapted 
to the environment. The result seems out of 
all proportion to the cause. There must be some 
potent force inherent in protoplasm, or behind 
organisms, impelling them upwards. This objec- 
tion is as difficult to refute as it is to establish. 
It is purely speculative. 
3. A very serious objection to the Darwinian 
theory is that the beginnings of new organs 
cannot be explained by the action of natural 
selection on fortuitous minute variations, and 
natural selection can act on an organ only when 
that organ has attained sufficient size to be of 
practical utility to its possessor. When once 
an organ has come into being it is not difficult 
to understand how it can be improved, modified 
and developed by natural selection. But how 
can we explain the origin of an organ such as 
a limb by the action of natural selection on 
minute variations ? 
The theory of the change of function goes 
some way towards meeting the difficulty, for by 
means of it we are able to understand how certain 
organs, as, for example, the lung of air-breathing 
animals, might have come into existence. This 
is said to have been developed from the 
swimming-bladder of fishes. This bladder is 
36 
