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 {Bcric/it, dent. 

 Bot. GiSilL, Hd. 13, p. 303, 1895). 



DeVries concedes that species might originate b)- more than 

 one metht)d. l)ut he holds that natural selection may account tor 

 neither the origin, noi' the prcscrxation 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 \ariation or mutation. {MntationstJicorie. 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 b)- mu- 

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

 that phrase. Natural selection implies constant and progressive 

 variation in one or many directions, the individuals distinguished 

 by the greatest improvements constituting the fittest and surviv- 

 ing from successive generations. The constant and repeated 

 survival of the fittest and most improved effecting in time such 

 an amount of departure from the original as to constitute a new 

 type. The mutants which arise in discontinuous variability are 

 seen to depart in all directions from the original, but none of 

 these may be fitter than the parent type and may perish. It is 

 prob-^.ble that many thousands of mutants come into existence 

 for every one that is capable of existence in competition with the 

 parent type. The repeated failure of the successive series of 

 mutants can in nowise affect the character of the later crops 

 of discontinuous derivatives, and hence the failure of the non-fit 

 and the endurance of the improved form are \\(A dependent upon 

 natural selection. Every mutant that survives must not only be 

 suitable for its environment but must be of a structure and habit 

 that will enable it to compete successfully with existing types, 

 in comparison with which it is enormously weaker in numerical 

 strength. It must therefore gain a foothold at once, with but 

 little opportunity for adaptations of any kind. Every mutant is 



