cry about a hawk or an owl, or boldly attack him, they show intelligence in its simpler form, the intelligence that recognizes its enemies, prompted again by the instinct of self-preservation. When a hawk does not know a man on horseback from a horse, it shows a want of intelligence. When a crow is kept away from a corn-field by a string stretched around it, the fact shows how masterful is its fear and how shallow its wit. When a cat or a dog or a horse or a cow learns to open a gate or a door, it shows a degree of intelligence—power to imitate, to profit by experience. A machine could not learn to do it. If the animal were to close the door or gate behind it, that would be another step in intelligence. But its direct wants have no relation to the closing of the door, only to the opening of it. To close the door involves an afterthought that an animal is not capable of. A 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 enter 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, it is not showing an individual act of intelligence: all nuthatches do this; it is a race instinct. It is intelligent—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 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 or his companion seems to have kept up this futile attempt, fumbling and dropping the nut every few moments. It never occurred to the mouse to gnaw the hole larger, as it would instantly have done had it been too small to admit its own body. It could not project its mind that far; it could not get out of itself sufficiently to regard the nut in its relation to that hole, and it is doubtful if any vertebrate animal is capable of that degree of reflection and comparison. Nothing in its own life or in the life of its ancestors had prepared it to meet that kind of a difficulty with nuts. And yet the writer who made the above observation says that when confined in a box the slides of which are of unequal thickness, the deer-mouse, on attempting to gnaw out, almost invariably attacks the thinnest side. How does he know which is the thinnest side? Probably by a delicate and trained sense of feeling or hearing. In gnawing through obstructions from within, or from without, he and his kind have had ample experience.
Now when we come to insects we find that the above inferences do not hold. It has been observed that when a solitary
