5. In organic evolution, when a higher factor appears, it immediately assumes control, and previous lower factors sink into a subordinate position, though still underlying and conditioning the higher. But in human evolution, the higher rational factor, when it comes in with man, not only assumes control, but transforms all other factors and uses them in a new way and for its own higher purposes. In fact, as already said, it is much more than a mere factor. It determines a new kind of evolution--evolution on a new and higher plane though, indeed, underlaid and conditioned by the laws of organic evolution. As _external physical_ Nature uses many factors to carry forward organic evolution, so the _internal spiritual_ nature, characteristic of man alone, uses these same factors in a new way to carry forward human evolution or progress. Thus, for example, one organic factor--the environment--is modified or even totally changed so as to effect suitably the human organism. This is _hygiene_. Again, use and disuse--another factor--is similarly transformed. The various organs of the body and faculties of the mind are deliberately used in such wise and degree (determined by reason) as to produce the highest efficiency of each part and the greatest strength and beauty of the whole. This is _education_--physical, mental, moral. So also the selective factors are similarly transformed, and _natural_ selection becomes _rational_ selection. We all know how this method is applied to domestic animals and cultivated plants in the formation of useful or beautiful varieties. Why should it not be applied also to the improvement of our race in the selection of our mates in marriage, or in the selection of our teachers, our law-makers, our rulers? Alas! how little even yet does reason control our selection in these matters! How largely are we yet under the law of organic evolution! _Application of these principles to some questions of the day_: