Varieties and Elementary Species 
As we have seen, De Vries does not believe 
that new species can arise by the accumulation 
of fluctuating variations. By means of these 
the race may be greatly improved, but nothing 
more can be accomplished. These variations 
follow Quetelet’s law, which says that, for 
biological phenomena, deviations from the aver- 
age comply with the same laws as the devia- 
tions from the average in any other case, if ruled 
by chance alone. 
Very different in character are mutations. By 
means of these, new forms, quite unlike the 
parent species, suddenly spring into being. 
Mutations are said by De Vries to be of two 
kinds—those that produce varieties and those 
which result in new elementary species. 
According to De Vries, those species of plants 
which are in a state of mutation (he refers to the 
species of the systematic botanists) are of a com- 
posite nature, being made up of a collection of 
varieties and elementary species. His concep- 
tion of a variety is a plant that differs from the 
parent plant in the loss or suppression of one or 
more characters, while an elementary species 
differs from the parent form in the possession of 
some new and additional character. But we will 
allow him to speak for himself: ‘“ We can con- 
sider (page 141 Sfeczes and Varretzes) the follow- 
ing as the principal difference between elementary 
species and varieties: that the first arise by the 
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