kind of food;

"2. Of yielding to sexual fecundation which excites in them certain
sensations;

"3. Of avoiding pain;

"4. Of seeking pleasure or happiness.

"To satisfy these wants they contract different kinds of habits,
which are transformed into so many propensities, which they can
neither resist nor change. From this originate their habitual
actions, and their special propensities to which we give the name
of instinct.[187]

"This propensity of animals to preserve their habits and to renew
the actions resulting from them being once acquired, is then
propagated by means of reproduction or generation, which preserves
the organization and the disposition of parts in the state thus
attained, so that this same propensity already exists in the new
individuals even before they have exercised it.

"It is thus that the same habits and the same _instinct_ are
perpetuated from generation to generation in the different species
or races of animals, without offering any notable variation,[188] so
long as it does not suffer change in the circumstances essential to
the mode of life."

"_On the Industry of Certain Animals._

"In those animals which have no brain that which we call _industry_
as applied to certain of their actions does not deserve such a name,
for it is a mistake to attribute to them a faculty which they do not
possess.

"Propensities transmitted and received by heredity (_generation_);
habits of performing complicated actions, and which result from
these acquired propensities; finally, different difficulties
gradually and habitually overcome by as many emotions of the organic
sense (_sentiment interieur_), constitute the sum of actions which
are always the same in the individuals of the same race, to which we
inconsiderately give the name of _industry_.

"The instinct of animals being formed by the habit of satisfying the
four kinds of wants mentioned above, and resulting from the
propensities acquired for a long time which urge them on in a way
determined for each species, there comes to pass, in the case of
some, only a complication in the actions which can satisfy these
four kinds of wants, or certain of them, and, indeed, only the
different difficulties necessary to be overcome have gradually
compelled the animal to extend and make contrivances, and have led
it, without choice or any intellectual act, but only by t