Experiments of De Vries 



generation beyond nine. This was the limit 

 to be obtained by the most rigorous selection 

 of fluctuating variations. 



Selection, based on fluctuating variation, does 

 not, asserts De Vries, conduce to the production 

 of improved races. " Only temporary ameliora- 

 tions are obtained, and the selection must be 

 made in the same manner every year. More- 

 over, the improvement is very limited, and does 

 not give any promise of further increase." Not- 

 withstanding prolonged efforts, horticulturists 

 have not yet succeeded in breeding a biennial 

 race of either beetroots or carrots that does not 

 continually give rise to useless annual forms. 

 Writing of the beet, De Vries says useless 

 annual varieties " are sure to return each year. 

 They are ineradicable. Every individual is in 

 the possession of this latent quality, and liable to 

 convert it into activity as soon as the circum- 

 stances provoke its appearance, as is proved by 

 the increase of annuals in the early sowings" 

 that is to say, in circumstances favourable to 

 the annual variety. 



It will be urged perhaps that these experi- 

 ments, which seem to show that there is a limit 

 to which a species can be modified by the 

 accumulation of fluctuating variations, cannot 

 have been properly carried out, because all the 

 various breeds of pigeons and other domestic 

 animals clearly show that extraordinary differ- 



