THE GROWTH OF GROUPS 127 



at from the same point of view. Chemical reaction is 

 commonly regarded as a natural process, but mutation 

 is often spoken of as though it were supernatural. Un- 

 supported bodies fall to the ground, chemical substances 

 unite in various ways, animals and plants produce mutants. 

 All are events which have been observed ; why, then, must 

 we think that some of them are more supernatural than 

 others ? There is no doubt that to some biologists mutants 

 have a supernatural appearance. The Mutation Theory 

 brings back to their minds what they call the " doctrine 

 of special creation," and is repugnant for that reason. 

 But none of the older doctrines of creation could be 

 expressed in terms of perceptible events, whereas the 

 Mutation Theory is a description of events which have 

 been observed. 



It is perhaps this feeling that there is something 

 supernatural about mutants which leads Mr. Tower to the 

 opinion that they play a minor role in evolution. Like 

 Darwin, he is unable to believe that they play no part 

 at all. 



When describing his own observations Mr. Tower 

 appears to be almost convinced that mutants are of 

 importance; thus on page 259 of the Memoir we 

 read 



" The work of De Vries, however, shows conclusively 

 that in plants the rapid development of new forms occurs 

 also in nature, and it is now an established fact that it 

 is not confined to domestic races, but is common to both 

 wild and cultivated plants." 



And on page 282 we read, in reference to such forms 

 as pallida, " As far as I can judge, my variations from 

 decemlineata are as pure and strong as De Vries' mutants 



