Mutation

Abstract

THE term mutation in the modern sense means a discontinuous germinal change. Conceptions of continuity or discontinuity have played an important role in the history of thought not only in biology, but also in other sciences, notably physics and geology. In the latter science the earlier and cruder theories of catastrophism, in which the sudden extinction of floras and faunas was followed by the creation of new ones, were superseded by the uniformitarianism of Lyell. This, coupled with the slow and gradual modification of species as upheld by Darwin, led to a complete triumph of “continuity.” But with the followers of Darwin it frequently reached an extreme expression which was not in accordance with the facts of biological variation. It was thought that variations which were often spoken of as infinitesimal, could be accumulated in any direction to produce new species. But to produce a new species by this method, such accumulation of infinitesimals must take place simultaneously in several diverse directions, for species differ from each other in a number of independent characters.