CHAPTER XXIV 
THE MUTATION THEORY 
[It will be recalled that Darwin, although depending upon the 
ever-present fluctuating variations as the material for natural selection 
to work upon, recognized the occasional occurrence of ‘‘sports’’ or 
“saltatory variations.” These, however, seemed to him to be so rare 
in nature as to offer no adequate basis for selection. During the latter 
part of the nineteenth century several investigators, feeling the 
inadequacy of fluctuating variations to produce qualitatively new 
characters, decided to make a more careful examination of animals 
and plants in nature in order to discover whether saltatory variations 
might not be of more frequent occurrence than Darwin had supposed. 
In England William Bateson collected a large number of instances 
of a type of variation which he called discontinuous in contradistinc- 
tion to the continuous type which we have been calling fluctuations. 
Such variations, instead of being in a closely graded series with the 
typical variations of a species, were frequently quite sharply different 
from the majority. Although no experiments were conducted in 
order to test the hereditability of these ‘‘discontinuous variations,” 
it is probable that some of them were ‘‘mutations”’ in the sense of 
De Vries. 
At about the same time Hugo De Vries in Holland, probably as 
the result of: his rediscovery of Mendel’s work and his confirmation of 
th latter’s laws of heredity, became convinced that new species arise 
not by the accumulation, through natural selection, of minute fluc- 
tuating variations, but by the sudden appearance in one generation 
of fully formed new elementary species. He began a systematic 
research for species of plants in nature that were giving rise to new 
species. Many species were examined in their natural surroundings 
and were then brought into the experimental garden for more careful 
observation, but for a long time the search for a species throwing off 
new elementary species was unsuccessful. Finally, however, in a 
field near Hilversum, in the vicinity of Amsterdam, he found what 
seemed to him to be just the kind of plant he had been looking for in 
the evening, primrose (Oenothera lamarckiana). 
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