e intelligence of man is that
instincts are to a large extent fixed and mechanical. The proper
performance of an instinct demands the presence of exactly the right
external conditions for its accomplishment. In the absence of these
conditions, the call to perform the instinctive action is equally
great, and results in useless performances. In many of the higher
animals these elaborate instincts are more general in their character,
and are supplemented by a considerable but varying aptitude for
modification of instinctive action to suit varieties of surrounding
circumstances. As this intelligence becomes more and more developed,
the blind, mechanical instinct becomes weaker. A large number of
instances might be given of such instincts modified by dawning
intelligence. The chief factors in producing the change are, as has
been shewn by Professor Groos, the possession of a general instinct to
imitate and to experiment, and the existence of a period of youth in
which the young creature may practise these instincts, and so prepare
itself for the more serious purposes of adult life. The anthropoid
apes seem to possess these experimental instincts to an extent much
greater than that observed in any other class of animals, and, as they
have a long period of youth, they have the opportunity of putting them
into practice to the fullest possible extent.

From the natural history of the anthropoid apes, Huxley passed to
consideration of their relation to man, prefacing his observations
with a passage defending the utility of the enquiry, a passage
necessary enough in these days of prejudice, but now chiefly with
historical interest:

"It will be admitted that some knowledge of man's position in the
animate world is an indispensable preliminary to the proper
understanding of his relations to the universe; and this again
resolves itself in the long run into an enquiry into the nature
and the closeness of the ties which connect him with those
singular creatures whose history has been sketched in the
preceding pages.

"The importance of such an enquiry is, indeed, intuitively
manifest. Brought face to face with these blurred copies of
himself, the least thoughtful of men is conscious of a certain
shock; due perhaps not so much to disgust at the aspect of what
looks like an insulting caricature, as to the awakening of a
sudden and profound mistrust of time-honoured th