Suddenly, in the last geological epoch, man, the descendant of a group which like all others had led the narrow life of the preparatory ages, appears upon the scene. At first, and in his lower human estate, his position was not noticeably higher than that of his kindred, but there was in him the seed of a great unlikeness, of very new things, in that his desires had an element of the unlimited which was to grow apace, and in time to make him greedy of on-going. As this innovating creature sought for agents of power in the wilderness about him, he blindly laid hands upon such of the fellow tenants of the wilds as might serve his immediate needs. This species, both animals and plants, endowed with the capacity for variation, the plasticity which is in general a characteristic of all organic forms, were early led by their new master, as of old they had been guided by the old organic laws. They changed according to his choice, abandoning their ancient ways for the novel paths of civilization. With this association of the higher forms of the earth under the leadership of man, there began an entirely new and unprecedented condition of the world's affairs. In place of the ancient law of nature there came the control of our species which had been, in a way, chosen to be the overlord of life. At first, the number of species of animals and plants which man brought under his control was very limited; it was indeed confined to those which might readily be subjugated to meet immediate needs. Gradually, however, the list has been extended until it included thousands of forms, which, while they meet no need such as the savage recognizes, are gratifying to the taste or the ambitions of civilized peoples. These aesthetic devices, or those of necessity, are advancing so rapidly that each generation sees hundreds of new animal and plant species added to our living collections, so that our plant and animal gardens now contain a large share of the more attractive forms which are to be found in the various geographical realms. Our tilled fields yield perhaps a hundred times as many varieties of plants as they did in the earliest historic agriculture. The advance in the process of domestication is not so rapid as regards the animal kingdom as it is with the realm of plants, and this mainly for the reason that animals have a will of their own which has to be bent or broken to that of man. Still it goes on apace. We of to-day have at our command many times the number of sentient species contributive to our pleasure or profit that had been made captive at the beginning of our era. Naturally, in the early days of domestication, men brought under their control the greater number of the animals which gave promise of utility. As no new species of any economic importance have been created within the last geologic period, the field for the extension of economic domestication has of late been very limited. But