methods, which belong to its structure and may be re-
garded as hereditary, but it appears to vary and adjust
them from moment to moment in relation to the be-
haviour of an external object. If this is the case the
action is sensori-motor. ¹ With regard to higher animals
that follow the turnings and twistings of a prey, or,
if themselves dogged, the rapidly changing movements of
an enemy, the case admits of no doubt. Mechanism may
be wholly hereditary or may be improved by experience
as the case may be, but the combination and adjustment
from moment to moment require the combination of
many co-present elements, and the only question which
we shall have to raise later on will be whether we must
not carry some of these actions a grade higher and
frankly regard them as purposive.

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