f the weaker bodily structure of others. So again, in
some few cases, certain instincts cannot be considered as absolutely
perfect; but as details on this and other such points are not
indispensable, they may be here passed over.

As some degree of variation in instincts under a state of nature, and
the inheritance of such variations, are indispensable for the action of
natural selection, as many instances as possible ought to have been here
given; but want of space prevents me. I can only assert, that instincts
certainly do vary--for instance, the migratory instinct, both in extent
and direction, and in its total loss. So it is with the nests of birds,
which vary partly in dependence on the situations chosen, and on the
nature and temperature of the country inhabited, but often from causes
wholly unknown to us: Audubon has given several remarkable cases of
differences in nests of the same species in the northern and southern
United States. Fear of any particular enemy is certainly an instinctive
quality, as may be seen in nestling birds, though it is strengthened by
experience, and by the sight of fear of the same enemy in other animals.
But fear of man is slowly acquired, as I have elsewhere shown, by
various animals inhabiting desert islands; and we may see an instance
of this, even in England, in the greater wildness of all our large birds
than of our small birds; for the large birds have been most persecuted
by man. We may safely attribute the greater wildness of our large birds
to this cause; for in uninhabited islands large birds are not more
fearful than small; and the magpie, so wary in England, is tame in
Norway, as is the hooded crow in Egypt.

That the general disposition of individuals of the same species, born in
a state of nature, is extremely diversified, can be shown by a multitude
of facts. Several cases also, could be given, of occasional and strange
habits in certain species, which might, if advantageous to the species,
give rise, through natural selection, to quite new instincts. But I am
well aware that these general statements, without facts given in detail,
can produce but a feeble effect on the reader's mind. I can only repeat
my assurance, that I do not speak without good evidence.

The possibility, or even probability, of inherited variations
of instinct in a state of nature will be strengthened by briefly
considering a few cases under domestication. We shall thus also be
enabled to see the