Hypothesis of Mutations 693 



natively mutating and constant species. Some 

 may at the present moment be mutating ; others 

 may momentarily be constant. The mutating 

 ones will probably sooner or later revert to the 

 inactive state, while the powers of development 

 now dormant may then become awakened on 

 other branches. 



The view of permanency represents life as 

 being surrounded with unavoidable death, the 

 principle of periodicity follows in the same 

 way the idea of resurrection, granting the 

 possibility of future progression for all living 

 beings. At the same time it yields a more hope- 

 ful prospect for experimental inquiry. 



Experience must decide between the two main 

 theories. It demonstrates the existence of poly- 

 morphous genera, such as Draba and Viola and 

 hundreds of others. They clearly indicate a 

 previous state of mutability. Their systematic 

 relation is exactly what would be expected, if 

 they were the result of such a period. Perhaps 

 mutability has not wholly ceased in them, but 

 might be found to survive in some of their mem- 

 bers. Such very rich genera however, are not 

 the rule, but are exceptional cases, indicating 

 the rarity of powerful mutative changes. 



On the other hand, species may remain in a 

 state of constancy during long, apparently dur- 

 ing indefinite, ages. 



