e modification of the machine.

==Consciousness.==--It may be well here to refer to one other factor in
the problem, because it has somewhat recently been brought into
prominence. This factor is consciousness on the part of the animal.
Among plants and the lower animals this factor can have no significance,
but consciousness certainly occurs among the higher animals. Just when
or how it appeared are questions which are not answered, and perhaps
never will be. But consciousness, after it had once made its appearance,
became a controlling factor in the development of the machine. It must
not be understood by this that animals have had any consciousness of the
development of their body, or that they have made any conscious
endeavours to modify its development. This has not always been
understood. It has been frequently supposed that the claim that
consciousness has an influence upon the development of an animal means
that the animal has made conscious efforts to develop in certain
directions. For example, it has been suggested that the tiger, conscious
of the advantage of being striped, had a desire to possess stripes, and
the desire caused their appearance. This is absurd. Consciousness has
been a factor in the development of the machine, but an _indirect_ one.
Consciousness leads to effort, and effort has a direct influence in
development. For example, an animal is conscious of hunger, and this
leads to efforts on his part to obtain food. His efforts to obtain food
may lead to migration or to the adoption of new kinds of food or to
conflicts with various kinds of rivals, and all of these efforts are
potent factors in determining the direction of development.
Consciousness, again, may lead certain animals to take pleasure in each
other's society, or to recognize that in mutual association they have
protection against common enemies. Such a consciousness will give rise
to social habits, and social habits are a very potent factor in
determining the direction in which the inherited variations will tend;
not, perhaps, because it effects the variations themselves, but rather
because it determines which variations among the many shall be preserved
and which rejected by natural selection. Consciousness may lead the
antelope to recognize that he has no chance in a combat with a lion, and
this will induce him to flee. The _habit_ of flight would then develop
the _power_ of flight, not because the antelope desired such power, but
b