Short notes on the mutation theory of de vries

Short notes on the mutation theory of de vries

Hugo de Vries (1840 – 1935) was a Dutch Botanist. In his book. The Mutation theory written originally in German and later translated to English, de Vries described a number of changes and new types in many species of plants that he had studied. In particular he made a detailed study of the genus Oenothera (evening primrose plant) belong­ing to the family Onagraceae. In the species Oenothera lamarckiana, he noticed several changes.

In 1887 de Vries noted two other species O. brevistylis and O. laevifolia. He collected the seeds from all these and sowed them to find out if they bred true. In the case of O. lamarckiana, some of the offspring showed some exceptional characters that were not present in the parents.

These changes which occurred suddenly were called Mutations by de Vries. A new type which appeared much larger than the parent was described by de Vries as a new species O.gigas. On the basis of these observations de Vries proposed the theory of muta­tion to account for evolution. According to this, mutations throw up sud­denly fresh variations which are then acted upon by natural selection. Since mutations were known to be random evolution was also considered a ran­dom process.

Many biologists thought that all variations are chance occurences and that there is no question of adaptation, de Vries continued the breeding experiments and discovered 15 different types of mutations and grouped them into 15 different species. As these were markedly different from the original plants he concluded that muta­tions constitute the basis of evolution.

He stated that origin of species or evolution takes place by sudden mutations and not by microvariations as proposed by Darwin. He announced this theory in 1901. However it should be pointed out that the so called mutations observed by de Vries were actually chromosomal rearrangements rather than the gene mutations or point mutations as it was belived by de Vries. But the theory of mutation proposed by de Vries as providing the basic raw material for evolution is essentially correct. Further, the mutation theory explains some objections raised against the natural selection theory.

The sudden changes or sports to which Darwin did not seem to attach much importance was regarded as very significant by de Vries. It is on the basis of mutations that one can explain how heriditary variations arise in individuals as against the superficial variations.