370 Evolution and Adaptation 
Darwinian theory meets with difficulties at every turn by 
assuming that new forms are built up through the action 
of selection, the mutation theory escapes most of these diffi- 
culties, because it applies no such rigid test as that of selec- 
tion to account for the presence of new forms. 
LENGTH OF LIFE AS AN ADAPTATION 
It has been pointed out in the first chapter that the length 
of life of the individual has been supposed by some of the 
most enthusiastic followers of Darwin to be determined by 
the relation of the individual to the species as a whole. In 
other words, the doctrine of utility has been applied here also, 
on the ground that it would be detrimental to the species to 
have part of the individuals live on to a time when they can 
no longer propagate the race or protect the young. It is 
assumed that those varieties or groups of individuals (unfor- 
tunately not sharply defined) would have the best chance 
to survive in which the parent forms died as soon as they 
had lost the power to produce new individuals. Sometimes 
interwoven with this idea there is another, namely, that death 
ztself has been acquired because it was more profitable to 
supplant the old and the injured individuals by new ones, 
than to have the old forms survive, and thus deprive the 
reproducing individuals of some of the common food supply. 
This insidious form that the selection theory has taken in 
the hands of its would-be advocates only serves to show to 
what extremes its disciples are willing to push it. On the 
whole it would be folly to pursue such a will-o’-the-wisp, when 
the theory can be examined in much more tangible examples. 
If in these cases it can be shown to be improbable, the re- 
maining superstructure of quasi-mystical hypothesis will fall 
without more ado. 
That the problem of the length of life may be a real one 
for physiological investigation will be granted, no doubt, with- 
