tends to become general, since it is advantageous, and we thus fall back into a particular case of the great principle of natural selection formulated by Darwin. Let us go on. Thus far this instinct is but little complicated, since it has only the significance of a habit that one individual may have been able to take up with its share of intelligence. Now that it is seen rooted under the form of instinct, each individual in its turn, with its own share of intelligence, may be able to add something to it of its own accord. If that addition is still favorable, and again gets transmitted, it will tend in the same way to become general; the acquired instinct will grow so much the more complex; and, exactly as organic modifications scarcely perceptible, but accumulated successively, to a sufficient number, have been able to multiply animal forms infinitely, so instinct, by almost imperceptible but continuous additions, may be able to end by reaching that state of perfection in which philosophers had supposed they saw the convincing proof of a preestablished harmony.
Some naturalists even now are not, very fortunately, inspired when they attempt to prove to us that the corporeal organization of every animal is conceived and framed with regard to its instincts. We need not go far to learn, as indeed we might expect from what has gone before, that instinct is in many cases independent of external forms. All birds, whether they are masons, like the swallow; weavers, like the warbler; carpenters, like the crow; mound-builders, like the mégapode—have the same beak, the same claws, and forms almost the same. The European beaver, inhabiting the affluents of the Rhone and the Danube, is scarcely to be distinguished from the American beaver, yet he has quite a different kind of work to do. The American beaver, on his lakes and great, lonely rivers, builds the famous houses so well known; the European beaver burrows long galleries underground in the manner of moles. If he has always done so, what becomes of that supposed necessary correlation between the organs and the instinct of a burrowing animal on one continent, a building animal on the other, with the same members for two objects so different? If the European beaver did once build huts, where shall we find more decisive testimony in favor of the theory of mutability in instincts? Pursued for his warm covering and his flesh, he has changed his instincts, before invading civilization, more rapidly than his external form. It is a point well established at this day that the contact with man has had a decisive effect on the instinct of many animals. It is thus that in inhabited countries large birds take flight at his approach, while they still allow him to come close to them in countries visited by travellers for the first time. Wherever they have been hunted like a prey that is worth the trouble of pursuit for their flesh or their feathers, they have formed the habit, and then have had the instinct of taking flight.
Let us return to insects. Two instincts, the most remarkable among all, are presented by them; that of the bee, with its mathematical
