remarkable than the contingent operation of the instincts of many
species of animals. "It is remarkable," says Kirby, "that many of the
insects which are occasionally observed to emigrate are not usually
social animals, but seem to congregate, like swallows, merely for the
purpose of emigration." When certain rare emergencies occur, which
render it necessary for the insects to migrate, a contingent instinct
develops itself, and renders an unsocial species gregarious.

It is probable that most of our domesticated species, exhibiting as
they do in that condition attainments foreign to their natural habits
and faculties in a wild state, were endowed with provisional instincts
with a view to their association with man. But generally the docility
of animals does not extend to attainments which are radically different
from their habits and faculties in a wild state. Casual acquirements,
which have no relation to their exigencies in their natural condition,
never become hereditary, and are not, therefore, instinctive. A young
pointer-dog, which has never been in the fields before, will not only
point at a covey of partridges, but will remain motionless, like a
well-trained dog. The fact that the sagacity of the pointer is
hereditary shows that it is the development of an instinctive
propensity; for simple knowledge is not transmitted by blood from one
generation to another. We have heard of a pig that pointed game, and of
another that was learned in letters; but we ascertain in every such
instance that their foreign acquirements do not reappear in their
progeny, but end with the pupils of the time being. The pig's
peculiarity of pointing did not arise from the development of a
provisional instinct, because it does not become hereditary; but the
same act in the pointer-dog is instinctive,--for, when once brought out
by associating with man, it has remained with the breed, being a part
of the animal's nature, which existed in embryo till it was developed