III. The wonderful performances attributed to instinct in animals appear less incomprehensible when viewed in juxtaposition with some of the feats of lucid cataleptics. The term instinct is a very vague one. It is commonly used to denote the intelligence of animals as opposed to human reason. Instinct is, therefore, a compound phenomenon; and I must begin by resolving it into its elements. They are three in number:— 1. Observation and reasoning of the same kind with that of man, but limited in their scope. They are exercised only in immediate self-preservation, and in the direct supply of the creature’s bodily wants or simple impulses. A dog will whine to get admission into the house, will open the latch of a gate; one rook will sit sentry for the rest; a plover will fly low, and short distances, as if hurt, to wile away a dog from her nest. But in this vein of intelligence, animals make no further advance. Reflection, with the higher faculties and sentiments which minister to it, and with it constitute reason, is denied them. So they originate no objects of pursuit in the way that man does, and have no source of self-improvement. But, in lack of human reflection, some animals receive the help of— 2. Special conceptions, which are developed in their minds at fitting seasons. Of this nature, to give an instance, is the notion of nest-building in birds. It may be observed of these conceptions that they appear to us arbitrary, though perfectly suited to the being of each species: thus, in the example referred to, we may suppose that the material and shape of the nest might be varied without its object being the less perfectly attained,—at least, as far as we can see. The conception spontaneously developed in the mind of the bird is then carried out intelligently, through the same quick and just observation, in a little way, which habitually ministers to its appetites, as I explained in a preceding paragraph. The special conception is sometimes characterized by the utmost perfectness of mechanical design. Here, however, is nothing to surprise us. The supreme wisdom which preordained the development of an idea in an insect’s mind, might as easily as not have given it absolute perfectness. But—