Anyone who has worked in Science for forty years can be much surprised to realize how little he now hears about evolution, compared with such former times. At present, evolution seems to be accepted as an axiomatic or universal principle, while the mechanism of it is not much considered, except by a small group of specialists, who work on the subject in greatly limited ways. This is practically a reversal of the former emphasis. The chemist would probably suggest that the change is due to a better realization of the chemical difficulties involved in the mechanics of evolution, and his own change in viewpoint. The chemical difficulties will have increased to an almost incredible degree in this period, and his viewpoint will have changed correspondingly. A glance at some of these changes should illuminate the progress made in both subjects in this period.