There remains for consideration Evolution in its narrower sense, in which its operations are restricted to organic nature, such Evolution being commonly, but incorrectly, identified with "Darwinism." Understood thus, "Evolution" signifies no more than that the various species of animals and plants have descended _genetically_ one from another, through a graduated series of intermediate forms which link them together. _Darwinism_ is one particular mode of explaining how such transformations may be accounted for,--namely, by what is known as "Natural Selection." The theory of Evolution, as thus concerned with Organic life in particular, is compendiously described as "Transformism," under which head Darwinism is evidently included. Transformism makes no pretence to account for the origin of life, whether animal or vegetable. Living things must exist before any question arises as to their transmutation. But, given the existence of life, Transformists undertake in the first place to show that Organic Evolution has, as a matter of fact, occurred, and is still in process of occurrence; and secondly, to exhibit the manner in which this process is actually worked out. As to the first point, all Transformists, whether Darwinians or others, are necessarily at one, for the fact of Evolution is equally essential for every explanation of its method. It is when they come to explain in what manner evolutionary transformations have been wrought that Transformists divide themselves into various schools, each of which relies upon some particular factor to furnish the required explanation. Thus besides Darwinians pure and simple, there are neo-Darwinians, Lamarckians, neo-Lamarckians, Weismannists, and others, ascribing the results to physiological selection, sexual-selection, or other forces, rather than natural selection. Of such systems, however, excepting only Darwinism, it will be unnecessary to speak in particular. The great fundamental question is whether genetic Evolution be really established as a fact,--which, as has been said, equally affects them all--and if it be advisable to treat more in detail of Darwinism, it is not because this does not hold good of it as of the rest--but because this particular system has obtained such a position, is so much in the mouths of men, and has been made the basis of so many and such far-reaching consequences, that it is impossible to pass it by. Much the same may indeed be said even of the assumed fact of Organic Evolution underlying all Transformist theories. This does not affect the fundamental problems with which we are concerned, and leaving untouched, as it does, the question of the origin of Life it makes even less pretence than the cosmic-nebular hypothesis just spoken of to trace the operations of Nature to their ultimate source. It might therefore appear superfluous to devote to it so much attention as, if treated at all, it must needs demand.