174 INTELLIGENT BEHAVIOUR 
claims of instinct are the stronger. Taking animals as we 
actually find them, however, they afford numberless examples 
of behaviour at first instinctive but subsequently modified, 
in greater or less degree, in accordance with the teachings 
of experience. Let us, first, assume that the environment is 
slowly changing, or has changed, in some definite manner. 
Such change would, of course, be relative, and might be due, 
either to new conditions brought to bear on the animal, or to 
the animal being itself brought, in the expansion of its life, 
within their influence. The old instinct is no longer quite 
adapted to the changed circumstances. If the change were 
sufficient in amount, and occurred somewhat suddenly, variations 
of instinct might not occur soon enough to enable the animal 
to reach adaptation by the gradual process of natural selection. 
If dependent on instinct alone the animal would, under these 
circumstances, be eliminated. But if intelligence were able to 
modify the behaviour to meet the new conditions this elimina- 
tion would be prevented. In successive generations intelligence 
would constantly modify behaviour in the same manner and in 
a definite direction. Meanwhile congenital variations in 
different directions would occur. Those which were in direc- 
tions antagonistic to that dictated by intelligence would tend 
to thwart accommodation and render it less effectual ; but 
those which were coincident in direction would conspire with 
accommodation and render it more effectual. The individuals 
in which variations of instinct tended to thwart intelligence 
would be eliminated ; while those in which coincident variations 
assisted and aided intelligent modification would survive. 
Thus intelligence would lead the way along lines which con- 
genital variations would follow. And in the course of a number 
of generations the new instinct would reach the fully adaptive 
level, and further modification by intelligence would become 
unnecessary unless the environment continued to change yet 
more. Individual accommodation of behaviour would in this 
way determine the direction of instinctive variation ; and yet 
throughout the process there would be, strictly speaking, no 
transmission of the intelligently acquired characters of the 
behaviour. 
