We have now noticed the chief characteristics of instinct: its existence prior to all experience or instruction; its incapacity of improvement, except within the narrow sphere of domestication; its limitation to a few objects, and the certainty of its action within these limits; the distinctness and permanence of its character for each species; and its constant hereditary nature. In regard to the uniformity of instinct throughout each species, it may be further remarked, that this seems to be very constantly preserved in the lowest divisions of the animal kingdom. Among the Articulates, also, instinct appears almost unvarying; and it is in this department among the insect tribes that the most striking manifestations of instinct are to be met with. When we arrive among the higher orders of the Vertebrates, we find in some species that each individual is capable of some modification of its actions, according to the particular circumstances in which it finds itself placed. But throughout the long series of animals, from the polype to man, there is instinctive action more or less in amount in every species, with, perhaps, the exception of man alone. The variety of that endowment, which is adapted to definite objects, means, and results, in each particular one of the five hundred thousand species estimated to be now living, may well call forth our admiration and astonishment at the magnitude and extent of the prospective contrivance of the Creator. How various the relations of all these animals to each other and to the inanimate world about them! and yet how admirable the adjustments of that immaterial principle which regulates their lives, so as to secure the well-being of each and the symmetry of the general plan! There has been much diversity of opinion as to the existence of instincts in the human species,--some making the whole mind of man nothing but a bundle of instincts, and others wholly denying him any endowment of this nature, while others still have given him a complex mental nature, and have, moreover, declared that intellect and instinct in him are so interwoven that it is impossible to tell where the one begins and the other ends. But we believe, with the author of "Ancient Metaphysics," that in Nature, however intimately things are blended together and run into each other like different shades of the same color, the species of things are absolutely distinct, and that there are certain fixed boundaries which separate them, however difficult it may be for us to find them out. In regard to intelligence and instinct, the two principles seem to us to be not more distinctly and widely separated in their nature than in the provinces of their operation.