DE VRIES, HUGO. - Dutch botanist and biologist, born in Haarlem on 16 February 1848, died in Lunteren on 20 May 1935; he was professor of botany at Amsterdam from 1878 to 1918. His scientific work falls into two distinct periods: the first (1877-88) concerns chiefly cellular physiology, the second (1889-1918) the origin of plant forms through “mutation.”
Conceptually, DE VRIES’s work as a theorist of evolution is rooted in Darwinism. Darwin had seen in the varieties of nascent species the gradual emergence of new forms; DE VRIES, however, began from the observation that, in certain cases, varieties arise suddenly, in a single season, without gradual transitions and without the need for long periods of time.
He found in *Oenothera Lamarckiana* a plant that in nature exhibits rapid character variations and, when cultivated, lends itself to the experimental study of these mutations, which give rise to well-defined races that he called elementary species, absolutely constant from the outset. These would coincide with pure lines. The mutation theory (1901-1906), when it intersected with Mendelism and genetics, represented a significant phase in the history of biology and for a time offered the hope of rationally and experimentally producing new species, thus bringing evolutionism into the realm of inductive, experimental science. But when doubts arose that the plant chosen by DE VRIES for study, *Oenothera*, was itself hybrid and that the new forms it produced were in reality the original species, the mutation theory in its original sense lost much of its appeal (cf. LOTSY).
Moreover, like all partial and interpretive hypotheses that, from time to time in the history of biology, converge toward the more general hypothesis of evolution, the mutation theory has been judged by theorists of different schools in opposing ways. F. LE DANTEC saw in it a tendency toward antitransformism and denounced it as a factor in the crisis of transformism. Others see in random mutations a triumph of chance and the a-teleological, that is, the true and profound motives of classical evolutionism. Today, a mutation is understood to mean a hereditary variation. But whether a new species has ever arisen through mutation remains a matter of debate. It is certain, however, that new organs do not originate through mutation.
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