The building of her nest by a bird is an instinctive action; it is done with a purpose, but it is arbitrary to say that the bird has no knowledge of that purpose. Some hold that birds when they are building their nest know as well that they mean to bring up a family in it as a young married couple do when they build themselves a house. This is the conclusion which would be come to by a plain person on a _primâ facie_ view of the facts, and Von Hartmann shows no reason for modifying it. A better definition of instinct would be that it is inherited knowledge in respect of certain facts, and of the most suitable manner in which to deal with them. * * * * * Von Hartmann speaks of “a mechanism of brain or mind” contrived by nature, and again of “a psychical organisation,” as though it were something distinct from a physical organisation. We can conceive of such a thing as mechanism of brain, for we have seen brain and handled it; but until we have seen a mind and handled it, or at any rate been enabled to draw inferences which will warrant us in conceiving of it as a material substance apart from bodily substance, we cannot infer that it has an organisation apart from bodily organisation. Does Von Hartmann mean that we have two bodies—a body-body, and a soul-body? * * * * * He says that no one will call the action of the spider instinctive in voiding the fluids from its glands when they are too full. Why not? * * * * * He is continually personifying instinct; thus he speaks of the “ends proposed to itself by the instinct,” of “the blind unconscious purpose of the instinct,” of “an unconscious purpose constraining the volition of the bird,” of “each variation and modification of the instinct,” as though instinct, purpose, and, later on, clairvoyance, were persons, and not words characterising a certain class of actions. The ends are proposed to itself by the animal, not by the instinct. Nothing but mischief can come of a mode of expression which does not keep this clearly in view. * * * * * It must not be supposed that the same cuckoo is in the habit of laying in the nests of several different species, and of changing the colour of her eggs according to that of the eggs of the bird in whose nest she lays. I have inquired from Mr. R. Bowdler Sharpe of the ornithological department at the British Museum, who kindly gives it me as his opinion that though cuckoos do imitate the eggs of the species on whom they foist their young ones, yet one cuckoo will probably lay in the nests of one species also, and will stick to that species for life. If so, the same race of cuckoos may impose upon the same species for generations together. The instinct will even thus remain a very wonderful one, but it is not at all inconsistent with the theory put forward by Professor Hering and myself.