..Not only the choice of a place for laying the eggs, but all the various acts for depositing and protecting them, are occasioned by the perception of the proper object, and the relation of this perception to the various stages of maternal impulse.When the burying beetle perceives a carrion, she is not only impelled to approach it and lodge her eggs in it, but also to go through the movements requisite for burying it; just as a bird who sees his hen-bird is impelled to caress her, to strut around her, dance before her, or in some other way to woo her; just as a tiger, when he sees an antelope, is impelled to stalk it, to pounce upon it, and to strangle it.When the tailor-bee cuts out pieces of rose-leaf, bends them, carries them into a caterpillar-or mouse-hole in trees or in the earth, covers their seams again with other pieces, and so makes a thimble-shaped case -- when she fills this with honey and lays an egg in it, all these various appropriate expressions of her will are to be explained by supposing that at the time when the eggs are ripe within her, the appearance of a suitable caterpillar- or mouse-hole and the perception of rose-leaves are so correlated in the insect with the several impulses in question, that the performances follow as a matter of course when the perceptions take place...."
The perception of the empty nest, or of a single egg, seems in birds to stand in such a close relation to the physiological functions of oviparation, that it serves as a direct stimulus to these functions, while the perception of a sufficient.number of eggs has just the opposite effect.It is well known that hens and ducks lay more eggs if we keep removing them than if we leave them in the nest.The impulse to sit arises, as a rule, when a bird sees a certain number of eggs in her nest.If this number is not yet to be seen there, the ducks continue to lay, although they perhaps have laid twice as many eggs as they are accustomed to sit upon....That sitting, also, is independent of any idea of purpose and is a pure perception-impulse is evident, among other things, from the fact that many birds, e.g.wild ducks, steal eggs from each other....The bodily disposition to sit is, it is true, one condition , but the perception of the eggs is the other condition of the activity of the incubating impulse.The propensity of the cuckoo and of the cow-bird to lay their eggs in the nests of other species must also be interpreted as a pure perception-impulse.These birds have no bodily disposition to become broody, and there is therefore in them no connection between the perception of an egg and the impulse to sat upon it.Eggs ripen, however, in their oviducts, and the body tends to get rid of them.And since the two birds just named do not drop their eggs any-where on the ground, but in nests, which are the only places where they may preserve the species, it might easily appear that such preservation of the species was what they had in view, and that they acted with full consciousness of the purpose.But this is not so....The cuckoo is simply excited by the perception of quite determinate sorts of nest, which already contain eggs, to drop her own into them, and throw the others out, because this perception is a direct stimulus to these acts.It is impossible that she should have any notion of the other bird com-ing and sitting on her egg."
INSTINCTS NOT ALWAYS BLIND OR INVARIABLE.
Remember that nothing is said yet of the origin of instincts, but only of the constitution of those that exist fully formed.How stands it with the instincts of mankind?
Nothing is commoner than the remark that Man differs from lower creatures by the almost total absence of instincts, and the assumption of their work in him by 'reason.' A fruitless discussion might be waged on this point by two theorizers who were careful not to define their terms.'Reason'
might be used, as it often has been, since Kant, not as the mere power of 'inferring,' but also as a name for the tendency to obey impulses of a certain lofty sort, such as duty, or universal ends.And 'instinct '
might have its significance so broadened as to cover all impulses whatever, even the impulse to act from the idea of a distant fact, as well as the impulse to act from a present sensation.Were the word instinct used in this broad way, it would of course be impossible to restrict it, as we began by doing, to actions done with no prevision of an end.We must of course avoid a quarrel about words, and the facts of the case are
