No- 443] MUTATION IN PLANTS. 745 



of procedure may have been followed in the development of the 

 prevalent types of vegetal organism. This view of the subject 

 has been thoroughly discussed by von Wettstein and need not 

 occupy our attention further at the present time (Hcricf/t, dent. 

 Bot. GeselL, Bd. 13, p. 303, 1895). 



DeVries concedes that species might originate by more than 

 one method, but he holds that natural selection may account for 

 neither the origin, nor the preservation and continuance of spe- 

 cies. He furthermore calls attention to the fact that Darwin 

 repeatedly asserted that characteristics or qualities were formed 

 very slowly but might disappear suddenly, or in other words that 

 retrogressive and digressive species formation might ensue by 

 discontinuous variation or mutation. {Mutationsthcoric. Bd. 2: 

 661. 1903.) 



It is necessary to point out that the use of the term natural 

 selection as applying in any sense to the origin of species by mu- 

 tation is wrong in view of the special meaning long attached to 

 that phrase. Natural selection implies constant and progressive 



by the greatest improvements constituting the fittest and surviv- 



these may be titter than the ] 

 pn ibable that main thousand: 

 for every one that is capable < 



