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THE COEFFICIENT OF MUTATION IN OENOTHERA 



BIENNIS L. 



The significance of the discovery of the mutability of Oenothera 

 Lamar cki ana, 0. 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 

 by slow and almost invisible changes as was assumed by Darwin. 

 The theory itself does not, of course, depend on this or other single 

 instances; it is founded upon general considerations taken from 

 almost all branches of biological and paleontological research, as 

 _-i I have often pointed out. 1 ) 



One of the main arguments is the statement that adaptations 

 •cannot, as a rule, have been produced by slow improvements, and 



i) The mutation theory, 2 vols., igoa-iqio; Species and varieties, 

 their origin by mutation, 2d ed., igo6; Die Mutationen in der Erblich- 

 keitslehre. Opera VI, p. 514. The principles of the theory of mutation. 

 Science 40:77 — 84, 1914. 



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