60 THE THEORY OF NATURAL SELECTION 
have arisen. This last consideration will account for 
the frequency with which apparently adaptive like- 
nesses are to be found in nature, even if we suppose 
that their origin was ‘accidental,’ or simply due to 
the operation of similar external causes. The same 
criticism applies to all cases of adaptation of whatever 
kind, so far as concerns their supposed method of origin 
by the action of natural selection upon individual 
differences. 
Perhaps a still more serious criticism of the methods 
of those who spend their time in seeking out or devising 
cases of adaptation has been made by Bateson, who 
points out the logical difficulty that we can never 
make any quantitative estimate of the amount of 
benefit or the reverse which any particular structure 
may afford to its possessor. It is easy enough to 
imagine particular circumstances in which an organ 
developed in a particular way may be of undoubted 
service, but whether the net amount of such service 
throughout the life of the creature considered is 
greater or less than the strain upon its resources caused 
by the development of such an organ is quite beyond 
our powers of determination. 
‘ The students of adaptation forget that even on the 
strictest application of the theory of selection it is 
unnecessary to suppose that every part an animal has, 
and everything which it does, is useful and for its good. 
We, animals, live not only by virtue of, but also in 
spite of what we are. It is obvious from inspection 
that any instinct or organ may be of use; the real 
question we have to consider is how much use it is. 
