806 Fluctuations 



the organic world. But the experience of the 

 breeders does not support this view, since 

 the results of practice prove that selection ac- 

 cording to a constant standard soon reaches a 

 limit which it is not capable of transgressing. 

 In order to attain further improvements the 

 method of selection itself must be improved. A 

 better and sharper method assures the choice 

 of more valuable representatives of the race, 

 even if these must be sought for in far larger 

 numbers of individuals, as is indicated by the 

 law of Quetelet. 



Continuous or even prolonged improvement 

 of a cultivated race is not the result of frequent- 

 ly repeated selection, but of the improvement of 

 the standard of appreciation. Nature, as we 

 know, changes her standard only from time to 

 time in consequence of the migrations of the spe- 

 cies, or of local changes of climate. Afterwards 

 the new standard remains unchanged for cen- 

 turies. 



Selection, according to a constant standard, 

 reaches its results in few generations. The 

 experience of Van Mons and other breeders of 

 apples shows how soon the limit of size and 

 lusciousness may be attained. Vilmorin's ex- 

 periments with wild carrots and those of Car- 

 riere with radishes lead to the same conclusion 

 as regards roots. Improvements of flowers in 



