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- 
71 
