46 Experimental Zoology 
when the environment that has caused them is altered. De 
Vries answers this question in the following way: If the seeds 
of the best-nourished ordinary plants are selected and planted 
under the most favorable conditions, the average plants of the 
next generation will not only be as vigorous as the former, but 
their seeds themselves will have a higher average of size. If 
this process is continued, the average of the race will be in- 
creased in the direction of selection, and in time the race, 7.e. 
all the individuals, may be brought to and maintained near the 
highest plane to which fluctuating variation ever reaches. 
There is a counteracting principle that must also be con- 
sidered, viz., what Galton has called regression toward medi- 
ocrity. If variations that depart from the average of the type 
are united, their descendant will tend in some degree to return 
to the average or to mediocrity, as Galton has shown. If, 
however, we pick out in each generation those that are most’ 
above the average, the average of the descendants in each gen- 
eration rises, despite the regression, and in time the average may 
be brought near to the highest point to which individual varia- 
tions reach. In other words, the character that appeared in 
the first generation as a somatic variation of one individual 
has become temporarily transferred to the seeds; but unless the 
same favoring external conditions are vigorously maintained, 
there will be a return to mediocrity. 
This fastening, as it were, of the individual variation upon 
the race is due, de Vries thinks, to the action of the nourish- 
ment on the germ-cells. 
If a plant is well nourished, it produces larger seeds that are 
better supplied with nourishment. Hence on an average they 
will give rise to more vigorous plants, and these in turn will 
produce an average of larger or at least of better-nourished 
seeds, and the plants from these will be still stronger. Thus 
by slow degrees the seeds acquire the same sort of characteris- 
tics as those shown by the best-nourished plants in any one 
generation. The curious thing about this is that the seeds do 
not respond completely in the first generation, but it takes sev- 
