EVOLUTION OF FEELING AND EMOTION 287 
We have already seen that, if the claim for the inheritance 
of acquired characters be, on the evidence, judged unproven, 
and if instinct cannot be ascribed to transmitted habit, or re- 
garded as a legacy of that which has been ancestrally acquired, 
the only scientific explanation of instinctive behaviour is one 
which involves the principle of natural selection. But no one 
doubts that, in the course of experience, animals acquire modes 
of procedure which are beneficial to the race. This is well seen 
in the play of animals as interpreted by Professor Groos. Now, 
why do animals play ? From the psychological point of view, 
because they like it ; from the biological point of view, because 
they thus gain practice and preparation for the serious business 
of their after-life. But why do they like it? because, under 
natural selection, those who did not like it, and therefore did 
not play, proved unfit for life’s struggle, and were eliminated. 
Suppose that an animal were born with a rooted hereditary 
aversion to everything nutritious and an inherited hunger for 
anything harmful and unfit for food. What chance would it 
stand of survival? Hereditary likes and dislikes determine 
the general course of acquired behaviour, just as hereditary 
nerve-connections determine the course of instinctive behaviour. 
Wherein, then, lies the difference between the two? In the 
fact that in the one case the nerve-connections are transmitted 
ready-made, while in the other they result from association or 
coalescence in the course of individual life. But in both cases 
the pursuit and attainment of the beneficial brings satisfaction. 
Now, the consonance of end has long been regarded as an 
inevitable deduction from the hypothesis of evolution. “That 
pains are correlatives of actions injurious to the organism,” 
wrote Mr. Herbert Spencer in his “ Principles of Psychology,” * 
‘‘ while pleasures are the correlatives of actions conducive to its 
welfare, is an induction not based on the vital functions only. 
It is an inevitable deduction from the hypothesis of evolution, 
that races of sentient creatures could have come into existence 
under no other conditions. Those races of beings only can 
* Vol. i, pt. ii., ch. ix., §124. I quote from the valuable “ Epitome ” 
prepared by Mr. Howard Collins, p. 214. 
