THE DOGMA OF EVOLUTION 



And, second, it is not clear to me why, if continual 

 physical conditions are of so little moment as you 

 suppose, variation should occur at all."^^ Evidence 

 has accumulated that offspring frequently differ from 

 their parents by well-marked characteristics. DeVries, 

 on this evidence, assumes that variation of species may 

 thus progress by jumps, or mutations, rather than by 

 the gradual variation which proceeds in the same di- 

 rection through many generations. The idea is de- 

 structive to scientific theory, as it really does away 

 with the whole idea of continuity which should be the 

 basis of an evolution theory ; and it certainly, if true, 

 forbids any foretelling of future events since no one 

 knows how great such mutations may be. The thought 

 at once occurs that each of the surprising breaks in the 

 pal aeon tological record, such an one as separates the 

 reptile from the feathered bird, may have been taken 

 at a single leap during an overstimulated period of 

 Nature. If the theory of jumps is ever accepted, evo- 

 lution parts company with physics and chemistry and 

 would not differ essentially from the belief in special 

 creation. All other sciences are based on the law, that 

 nature does not proceed by jumps. 



We have so far considered the theory of natural 

 selection from the standpoint of its general philo- 

 sophical adequacy, and have found it to be based on 

 principles which are now discredited and that its 

 weakness is largely due to Darwin's temperamental 



15 Darwin, Life and Letters, vol. II, p. 27. 



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