Mutations 



53 



of Professor de Vries, botanist, of Amsterdam, Holland, 

 who denies that natural selection is competent to produce 

 species, or that organic ascent is the product of small 

 differences gradually enlarging into great ones. According 

 to de Vries' view, species-characters arise suddenly, or 

 all at once, and they are ordinarily stable from the moment 

 they arise. 



-15 16-20 20-25 26-80 



70-75 75-SO 80-Si 8i-90 00-95 05- !l 



FIG. 9. Variations in statures of (Enothera nanella (left), a mutant, 

 and (Enothera Lamarkiana (right), its parent. (Enothera nanella : 

 Range, 7-35 cm. ; M., 22.81 == 1.02 cm. ; <r, 7.26 0.72 cm. ; C. V., 

 31.84 3. 16 per cent. (Enothera Lamarkiana: Range, 77-96 cm. ; 

 M., 88.68 == 0.55 cm. ; v, 4.76 0.39 cm. ; C. V. 5.37 == 0.44 per 

 cent. 



De Vries conceives that variations, or differences, are of 

 two general categories : (1) Variations proper, or small, 

 fluctuating, unstable differences peculiar to the individual 

 (only partially transmitted to offspring) ; and (2) muta- 

 tions, or differences that are usually of marked character, 

 appear suddenly and without transition to other forms 

 and are at once the starting-points of new species or races. 

 Variations proper may be due to the immediate environ- 



