More than that: some of these young will tend to possess those advantageous differences--this by the laws of variation as antidote needed just here for the laws of heredity--in even more marked degree than existed in the parents, while others will possess them in less degree and still others in about the same degree. Hence, the particular young showing the increased differences will be the individuals of this generation to survive in the struggle. These will then leave behind them new young again tending to possess in varying degree those advantageous variations from the old or species type that make them especially "fit for the conditions under which they must live." Thus there will result, in a series of many generations, a gradual shifting of the character of the species to the type characterized by an ever increasing and perfecting of the original advantageous differences. This is "species transformation," or the "origin of species" by natural selection. It is evolution on a basis of life and death struggle; extinction of the unfit; and survival of the fit, fitter or fittest. And just as with the different individuals inside the species, so with the different varying species. Each struggles with the other and the one or ones with the advantageous differences win at the expense of the others. There is no doubt of the fascinating plausibility and seeming reality and sufficiency of this explanation. It makes a strong appeal to the logical mind; to the theory-spinning brain. You can understand it, prove it, expand it, improve on it, and, all this almost without ever seeing an animal or a plant, or knowing anything of its actual life and relations to the world it lives in. No wonder it fascinated and seized a world demanding a logical explanation for the theory of evolution. No wonder that this explanation of Darwin, offered at the same time with a clear elucidation of the evolution theory itself to a world just ready for both, came to be the one all-sufficient explanation, came to be a scientific dogma of the most dogmatic type. * * * * *