horse will hesitate to go upon thin ice
or upon a frail bridge, even though it has never had any experience
with thin ice or frail bridges. This, no doubt, is an inherited
instinct, which has arisen in its ancestors from their fund of general
experience with the world. How much with them has depended upon a
secure footing! A pair of house wrens had a nest in my well-curb; when
the young were partly grown and heard any one come to the curb, they
would set up a clamorous calling for food. When I scratched against
the sides of the curb beneath them like some animal trying to climb
up, their voices instantly hushed; the instinct of fear promptly
overcame the instinct of hunger. Instinct is intelligent, but it is
not the same as acquired individual intelligence; it is untaught.

When the nuthatch carries a fragment of a hickory-nut to a tree and
wedges it into a crevice in the bark, the bird is not showing an
individual act of intelligence: all nuthatches do this; it is a race
instinct. The act shows intelligence,--that is, it adapts means to an
end,--but it is not like human or individual intelligence, which
adapts new means to old ends, or old means to new ends, and which
springs up on the occasion. Jays and chickadees hold the nut or seed
they would peck under the foot, but the nuthatch makes a vise to hold
it of the bark of the tree, and one act is just as intelligent as the
other; both are the promptings of instinct. But when man makes a vise,
or a wedge, or a bootjack, he uses his individual intelligence. When
the jay carries away the corn you put out in winter and hides it in
old worms' nests and knot-holes and crevices in trees, he is obeying
the instinct of all his tribe to pilfer and hide things,--an instinct
that plays its part in the economy of nature, as by its means many
acorns and chestnuts get planted and large seeds widely disseminated.
By this greed of the jay the wingless nuts take flight, oaks are
planted amid the pines, and chestnuts amid the hemlocks.

Speaking of nuts reminds me of an incident I read of the deer or
white-footed mouse--an incident that throws light on the limitation of
animal intelligence. The writer gave the mouse hickory-nuts, which it
attempted to carry through a crack between the laths in the kitchen
wall. The nuts were too large to go through the crack. The mouse would
try to push them through; failing in that, he would go through and
then try to pull them after him. All night he