The Making of Species 
from accepting his theory of mutations 2% éofo. 
We are, however, convinced that he, like Bate- 
son, is on the right track. There can be no 
doubt that a great many new forms have 
originated suddenly, by jumps, and not by 
imperceptibly slow degrees. Before giving a 
list of the names of some of the races, both 
plant and animal, which appear to have come 
into existence suddenly, it will be of advantage 
to consider for a little some of the more 
important conceptions of De Vries. 
That eminent botanist, as we have already 
seen, insists on the distinction between fluc- 
tuating variations and mutations. The former 
correspond, for all practical purposes, to the 
continuous variations of Bateson, and the latter 
seem to be equivalent to his discontinuous 
variations, 
According to De Vries, all plants display 
fluctuating variation, but only a small percentage 
exhibit the phenomenon of mutation. The 
most daring of his conceptions is, that the history 
of every species is made up of alternating 
periods of inactivity, when only fluctuating 
variations occur, and of activity when “ swarms 
of species” are produced by mutation, and of 
these only a few at the most survive; natural 
selection, which De Vries likens to a sieve, 
determining which shall live and which shall 
perish. 
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