=Evolution not necessarily progress.=--No excessive space has been devoted to this distinction between the fittest and the best and to the real meaning of Spencer's famous phrase, if perchance it should avail in any degree to dispel one of the commonest of the many common delusions regarding the nature of organic evolution and its outcome. This delusion is that progress is an inevitable law of nature.[12] The great process of history, as revealed by biology, displays as its supreme fact the occurrence of progress. The principles of evolution teach that this progress--as, for instance, in the evolution of man--is a product of the survival of the fittest; whilst we are also reminded that the survival of the fittest is a necessary truth: but it does not follow that progress is inevitable. In the first place, natural selection involves selection. Where all the young members of a new generation of any species survive, and parenthood becomes not a privilege but a common and universal function, plainly the process is in abeyance: and, in the second place, since the survival of the fittest is not the survival of the best, but only the survival of the best adapted, the process may at any time take the form of retrogression rather than that of progress. The assumption that, because progress has been effected through natural selection, we need do no more than fold our hands, or unfold them merely to applaud, involves the denial of one of the most familiar facts of natural history--the fact of racial degeneration. The parasitic microbes, the parasitic worms, the barnacles, innumerable living creatures both animal and vegetable, individuals and races of mankind, to-day as in all ages--these prove only too clearly that the process of the survival of the fittest may make as definitely for retrogression in one case as for progress in another.