VOLUME LIX NUMBER 3 
f Us & 
DOTANICAL GAZETIE 
MARCH 1915 
THE COEFFICIENT OF MUTATION IN OENOTHERA 
Huco DEVRIES : 
The significance of the discovery of the mutability of Oenothera 
Lamarckiana, O. biennis, and allied forms is a double one. In the 
first place, it provides us with material for experimental investi- 
gations into the laws which govern the origin of living forms by 
means of the production of new characters and of the loss of exist- 
ing ones. The knowledge of such laws must become of the highest 
practical value as soon as the evidently limited possibilities of 
producing new forms through the recombination of characters by 
means of crossing becomes exhausted. This conclusion seems 
especially well founded, since the old conception of improving 
agricultural races after the principle of slow and continued selections 
has now generally been abandoned and replaced by the direct 
selection of elementary types out of the mixtures which constitute 
the so-called agricultural races and varieties. 
The appearance of really new characters seems to be a very 
rare phenomenon in nature, and a case in which such changes 
regularly occur in one or more per cent of all the individuals affords 
material for experiments, the results of which may be expected 
to apply to a large series of other species also, including, probably, 
an important number of agricultural crops. 
In the second place, the mutability of the evening primroses 
has a distinct bearing upon the theory of mutation, or of the origin 
of all living species from one another by sudden leaps instead of 
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