Mutation

Mu·ta′tion, n. 1. (Biol.) Gradual definitely tending variation, such as may be observed in a group of organisms in the fossils of successive geological levels.

2. (Biol.) (a) As now employed (first by de Vries), a sudden variation (the offspring differing from its parents in some well-marked character or characters) as distinguished from a gradual variation in which the new characters become fully developed only in the course of many generations. The occurrence of mutations, and the hereditary transmission, under some conditions, of the characters so appearing, are well-established facts; whether the process has played an important part in the evolution of the existing species and other groups of organisms is a disputed question. (b) The result of the above process; a suddenly produced variation.