In the first place, a consideration presents itself, which appears to furnish the most formidable of all difficulties in the way of Mr. Darwin's hypothesis. How can this struggle for existence be supposed to have any tendency to promote organic development to ever higher and more perfect types, in the orderly sequence which has in fact occurred? The "Survival of the fittest" means only the survival _of the fittest to survive_,--of such as can find means of living where others cannot. Unless it can be shown that increased complexity of organization necessarily brings with it such increased vitality, Natural Selection can do nothing for organic development. If the mere power of living be the only factor in the process, as on Mr. Darwin's showing it is, a man is only a more complicated and delicate machine for securing the same object which can equally well, or better, be attained by a mole, a cockroach, or a microbe. And who will say that, so far as this particular end is concerned, he is better equipped than creatures which all the resources of civilization are powerless to exterminate? That practical advantage in the struggle for existence must necessarily accompany increased specialization of organs, and thus produce a "higher" organization, was a prime point of Mr. Darwin's argument, though at the same time he found himself compelled to encumber it with qualifications which go very far to neutralize its force; for he had to explain the obvious fact that so many creatures which represent the lowest and least specialized forms of life, have survived down to our own time. Thus he writes:[222] The degree of differentiation and specialization of the parts in organic beings, when arrived at maturity, is the best standard, as yet suggested, of their degree of perfection or highness. As the specialization of parts is an advantage to each being, so natural selection will tend to render the organization of each being more specialized and perfect, and in this sense higher; not but that it may leave many creatures with simple and unimproved structures fitted for simple conditions of life, and in some cases will even degrade or simplify the organization, yet leaving such degraded beings better fitted for their new walks of life. By this fundamental test of victory in the battle of life, as well as by the standard of the specialization of organs, modern forms ought, on the theory of Natural Selection, to stand higher than ancient forms. Is this the case? A large number of palæontologists would answer in the affirmative; and it seems that this answer must be admitted as true, though difficult of proof.