Another mode of accounting for the succession of organized beings on the surface of the globe, and consequently also their successive extinction and outgoing, as seen in the fossiliferous rocks, is that which is termed THE THEORY OF DEVELOPMENT, or the doctrine of the transmutation of species. The same has been a very ancient and favorite notion among mankind. Early in this century it assumed the form of a system, under the adaptive principle of Lamarck, who conceived that animals, according to the circumstances in which they are placed, by the use or disuse of certain organs, the frequency and degree of exertion or strain upon particular parts of the body, were themselves the agents in inducing all the variety of structures by which they are distinguished into so many orders and families. The aquatic fowl, for example, is attracted to the waters in quest of food, and so in time becomes web-footed. The heron dislikes to plunge into the flood, or will only venture into the shoals, and hence he becomes a wader, and is equipped with long legs. The woodpecker rejoices in those little aphides and creatures that nestle under the bark of trees, and thus, from constant exercise, acquires his strength of bill. The eagle seeks the blaze of the sun, and soars to the gates of heaven, and hence his penetrating eye and speed of descent upon his all-unconscious victim beneath. And, in like manner, through the whole range of animated nature, and in all past ages, genera and species have all acquired their adaptive powers, and distinctive forms of organization, arising from a certain plastic character in their different constitutions, and their own voluntary attempts to supply their constantly increasing wants. There were a few great leading stamps or dies of nature’s own molding; but all the rest—even man himself—are merely offsets from the primitive type, with such extension of organs and modification of excrescences as were required in each particular case; succeeding races always retaining a strong affinity to their immediate predecessors, and a tendency to impress their own features on their kindred which succeed them. There is a limit of divergence; but within that limit, the human family have their place assigned them among the monkeys and wild men of the woods.