THE AMERICAN NATURALIST [Vol. XL V 



eral trends of evolution, which are apparent in so many phytoge- 

 nies. This larger problem, which may not be amenable to direct 



that the larger tendencies can be sufficiently accounted for by the 

 same means, without the intervention of other factors. 



While the supreme importance of DeVries's investigations on 

 mutation in Oenothera is fully recognized, his premutation 

 theory has always seemed to the reviewer unsatisfactory as a 

 hypothesis to explain the material basis of these phenomena. 

 The cytological investigations of myself and others on these 



new types. They have, moreover, shown that different cyto- 

 logical processes are involved in the origin of different mutants, 

 and in this way have thrown much light on the relationships of 

 some of the mutants to their parent form. It is probable that 

 the whole question of the relation of the mutants to their parent 

 will be found to be much more complex than at present supposed. 



K. R. Gates. 



