Page:Popular Science Monthly Volume 73.djvu/552

548 beginning; thus a too susceptible organism would quickly be thrown out of gear and would perish; a too conservative one, unless adapted to practically unchanging types of life, would equally perish. There would be a certain optimum susceptibility, which would be preserved, and would differ for different groups. More than this, certain kinds of susceptibility would be favored, and being once developed might, like bad habits, become harmful through the accumulation of results, resulting in extinction. Thus rapid evolution would usually go with a high percentage of failures, and a considerable number of grotesque forms, such as we see among the vertebrates. According to this view, the initiation of any evolutionary trend, except the oscillatory movements above described, would be exceedingly slow, and quite beyond the reach of experimental methods, other than those furnished by nature in the course of ages; hence, as Osborn has indicated, the great importance of paleontological researches. At the same time, while the processes which change the fundamental character of animals and plants may be too slow to observe, it is not to be doubted that very much light may be obtained by the experimental method, if only by way of showing us what it is that has been evolved—a thing we seem not to have clearly known. If the control of orthogenetic changes is reserved, as it were, for the gods—and we, doubtless, should only make a mess of it—we may be well satisfied if we can take advantage of the oscillation processes, which experimental researches are showing to be far more extensive and much easier to control than had previously been suspected.