Describe De-Vries mutation theory of evolution.

Explanation

He gave mutation theory of evolution. He studied mutations in Oenothera lamarckiaru (Evening Primrose) plant and proposed this theory as follows-
(i) The large discontinuous variation results in the origin of new elementary species. These species appear suddenly and attain full constancy at once.
(ii) The same new species are produces a large number of individuals.
(iii) Mutations are recurring so that the same mutants appear again and again, thereby increasing the chance of selection by nature.
(iv) Mutation occurs in all directions (directionless) because it means either gain or loss of any character while Darwinian variations are small and directional.
(v) Mutability is something fundamentally different from the fluctuating variability of Darwin. According to de Vries, new species originate suddenly and spontaneously from the normal individuals either by sudden jump (saltation) or through a single step large mutation (macrogenesis) without any transitional stages between them. Mutation causes evolution and not the minor variations (heritable) that Darwin talked about.