presents, further, individual variations which are more
distinct as it is less deeply fixed by heredity. Thus the divergent
instincts of two varieties, _e.g._, of insects, present more individual
variability and adaptability than do those instincts common to all
species of a genus. In short, if we carefully study the behaviour of
each individual of a species of insects with a developed brain (as has
been done by P. Huber, Lubbock, Wasmann, and myself, among others, for
bees, wasps, and ants), we are not long in finding noteworthy
differences, especially when we put the instinct under abnormal
conditions. We then force the nervous activity of these insects to
present a second and plastic aspect, which to a large extent has been
hidden from us under their enormously developed instinct.

(_b_) The _plastic_ or _adaptive_ activity is by no means, as has been
so often suggested, a derivative of instinct. It is primitive. It is
even the fundamental condition of the evolution of life. The living
being is distinguished by its power of adaptation; even the amoeba is
plastic. But in order that one individual may adapt itself to a host of
conditions and possibilities, as is the case with the higher mammals and
especially with man, the brain requires an enormous quantity of nerve
elements. But this is not the case with the fixed and specialised
adaptation of instinct.

In secondary automatism, or habit, which we observe in ourselves, it is
easy to study how this activity, derived from plastic activity, and ever
becoming more prompt, complex, and sure (technical habits), necessitates
less and less expenditure of nerve effort. It is very difficult to
understand how inherited instinct, hereditary automatism, could have
originated from the plastic activities of our ancestors. It seems as if
a very slow selection, among individuals best adapted in consequence of
fortunate parentage, might perhaps account for it.

To sum up, every animal possesses two kinds of activity in varying
degrees, sometimes one, sometimes the other predominating. In the lowest
beings they are both rudimentary. In insects, special automatic activity
reaches the summit of development and predominance; in man, on the
contrary, with his great brain development, plastic activity is elevated
to an extraordinary height, above all by language, and before all by
written language, which substitutes graphic fixation for secondary
automatism, and allows the accumulation ou