The Descent of Man

another in many ways, we may infer that in
most cases they are impelled by the same sense
of satisfaction or pleasure which they experience
in performing other instinctive actions; or by
the same sense of dissatisfaction as when other
instinctive actions are checked. We see this in
innumerable instances, and it is illustrated in a
striking manner by the acquired instincts of our
domesticated animals; thus a young shepherddog
delights in driving and running round a
flock of sheep, but not in worrying them; a
young fox-hound delights in hunting a fox,
whilst some other kinds of dogs, as I have witnessed,
utterly disregard foxes. What a strong
feeling of inward satisfaction must impel a bird,
so full of activity, to brood day after day
over her eggs. Migratory birds are quite miserable
if stopped from migrating; perhaps they
enjoy starting on their long flight; but it is hard
to believe that the poor pinioned goose, described
by Audubon, which started on foot at the
proper time for its journey of probably more