806 Fluctuations 



gression in the organic world. But the ex- 

 perience of the breeders does not support this 

 view, since the results of practice prove that 

 selection according 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 in- 

 dividuals, 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 far as 

 we know, changes her standard from time to 

 time only in consequence of the migrations of 

 the species, or of local changes of climate. 

 Afterwards the new standard remains un- 

 changed for centuries. 



Selection, according to a constant standard, 

 reaches its results in few generations. The 

 experience of Van Mons and other breeders of 

 apples shows that the limit of size and luscious- 

 ness may be soon 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 



