Mr. Wallace's scheme has in view the prevention of marriage by the weak and worthless. He believes that if this can be done little more will be required, for the superior would be the only ones to procreate, and this would be quite sufficient in a few generations to produce a strong and healthy race. He calls his plan that of "human selection," but it may be considered practically as a modification of sexual selection. NATURAL SELECTION.--Natural selection is another process which takes place on an enormous scale and constantly among all organisms, whether animal or vegetable. Natural selection is the result of the operation of certain laws in the natural world which brings about the survival of those best fitted for their environment. It is a weeding-out system by the destruction of a certain portion, at least, if not all, of the weak and the bad, and it occurs because there is such a rapid increase of most organisms. We speak of it as the survival of the fittest, but it is also, at the same time, the destruction of the unfit. Mr. Darwin says: "We have seen that man is variable in body and mind, and that the variations are induced either directly or indirectly by the same general causes, and obey the same general laws as with the lower animals. Man has spread widely over the face of the earth, and must have been exposed during his incessant migrations to the most diversified conditions. They must have passed through many climates and changed their habits many times before they reached their present homes. They must have been exposed to a struggle for existence and, consequently, to the rigid law of natural selection. Beneficial variations of all kinds have been preserved and injurious ones eliminated. If, then, the progenitors of man, inhabiting any district, especially one undergoing some changed conditions, were divided into two equal bodies, the one-half including those with the best adapted powers for movement, for gaining a subsistence, for self-defence, would, on the average, have more offspring than the other and the less well endowed half."