248 ENTOMOLOGY 
De Vries has produced new species by experimental means 
and without the aid of selection. Moreover, he has produced 
them at once, showing that a species does not necessarily re- 
quire hundreds of years to develop, by means of a long-con- 
tinued process of selection. 
It has long been customary to draw a distinction between 
individual variations and sports. Darwin recognized the dis- 
tinction and was one of the first to notice the extraordinary 
persistence with which sports are transmitted, as compared 
with the relative instability of individual variations. Not a 
few dominant races of plants and animals are known to have 
arisen from sports, and the belief has been gaining ground 
with Bateson and others that species also have to some extent 
arisen from sports, rather than from individual variations ; 
though the rarity of sports as compared with individual varia- 
tions is the strongest objection to this theory as a theory of 
the origin of species in general. 
De Vries, however, was the first to make extensive experi- 
ments on sports, or mutations, as he calls them, and to formu- 
late a definite theory of the subject from a considerable body 
of evidence. He regards the qualities of organisms as being 
built up of definite but sharply separated units, or elements, 
which combine in groups. The addition of a new unit means 
a mutation, a sudden departure from the normal specific form; 
in other words, a new species may arise from the parent form 
without any evident gradation. The mutable condition exists 
only at times, and some species are more mutable than others. 
Acting upon this as a hypothesis, De Vries made a preliminary 
study of a great number of plants in order to find one in its 
period of mutation, and at length selected Genothera Lamarck- 
iana (probably a variety of our FE. biennis, introduced into 
Holland from America), because of its exceptionally vigorous 
multiplication, dispersion and variation. | By careful cultivation 
and by means of artificial pollination, he succeeded in obtaining 
seven or more new species. Most of these remained con- 
stant from year to year in spite of intercrossing. Moreover, 
