The views of Darwin and Wallace have now become the established doctrine of science. They have led to the universal recognition of “the origin of species by descent with modification.” That is a statement, in other words, to the effect that all the various kinds of living things have been gradually produced by natural birth from predecessors which differ from them only slightly in the later stages of time, but become simpler and less like their descendants as we go further back, until we reach the simplest living things. It has led to the conviction that there has been no exceptional or “miraculous” suspension of the order of Nature in this process, but that all has come about in due and regular course, in virtue of the properties of natural things, which we know as the laws of physics and chemistry. Most important and dominating of all these results is the inevitable one that man himself has come from animal ancestors, in the same way, and—(this is the greatest and most far-reaching conclusion of all)—that he is still subject to those natural processes of change and development by which he has reached his present phase; that he must completely understand them and control them (so far as such control is possible) in order to maintain a healthy, happy, and improving race of men on the face of the globe. This great possession—the earth and all that lives on it—is, as Lord Bacon phrased it three hundred years ago—the Kingdom of Man. Man has but to use his intelligence in order to take control of it. The knowledge of his own relation to it, and of the ways in which the human race is affected for good and for ill, through the operation of the self-same processes which affect the breeding, the improvement, the health, the disease, the destruction, and the perfecting of other living things, has once and for all been placed within man’s reach by the discoveries of Darwin and Wallace.