THE THEORY OF MUTATIONS 99 



character, or, in other less frequent cases, to the 

 reassumption of a quality formerly lost. Some may 

 originate in a negative way, others in a positive 

 manner, but in both cases nothing really new is 

 acquired." (p. 247). 



We have now to examine the evidence on which 

 this far-reaching theory is built up, for far-reaching 

 it certainly is. If it be established that by muta- 

 tions alone is the development of a new species 

 possible, then Darwin's doctrine, or a large part 

 of it, absolutely falls to the ground. Darwin, as 

 we have seen, insisted that natural selection worked 

 only through the preservation and accumulation 

 of small inherited modifications. Some of his 

 followers have even contended that these modifi- 

 cations were so small that they could not be 

 appreciated until natural selection had taken hold 

 of them and made them obvious by a process of 

 adding change to change. " It is only natural 

 selection which accumulates those alterations, so 

 that they become appreciable to us and con- 

 stitute a variation which is evident to our senses."* 

 But beyond this Darwin also asserted that his 

 theory would " banish the belief of the continued 

 creation of new organic beings or of any great and 

 sudden modifications of their structure." But 

 apart from this purely negative effect, certain 

 positive results follow. Species regain something 

 of the dignity which they formerly possessed, and 

 the fact that mutations produce new species is a 

 demonstration that the cause of the variation lies 

 deep in the nature of life ; that it is not fortuitous, 



* Claus, Textbook of Zoology. 



