69 
by de Vries as varieties, in a narrow sense of the word imposed 
by himself. Of the new forms, at least nine have ever since 
bred true.. In this connection we may note that de Vries has 
shown that “‘ varieties are as constant as the best species, if kept 
free from hybrid admixtures.’’ Darwin, on the other hand, be- 
lieved that species were strongly marked and permanent varie- 
ties, that each species first existed as riety. But de Vries 
is disposed to limit the use of the term ‘“ eer ” to retrograde, . 
or negative forms and to apply the name “ elementary species”’ 
to secondary forms having progressive characters. 
Mutations, which de Vries has now placed on a sound scien- 
tific foundation, as parts of the order of nature, were formerly 
included with “ sports,’ and were looked upon as monstrosities, 
or, at least, accidents. But de Vries has shown that mutatio 
“must be a universal phenomenon, although affecting a cal 
proportion of the inhabitants of any region at one time. 
The evening primroses are not the only family in which de 
Vries has actually witnessed the origination of new species and 
varieties. He has recorded so many cases of observed mutation 
and so many facts supporting its probability, that it is undoubt- 
marck’s evening all of its derivatives were destroyed, 
or had never been heard of, the results of experimental studies 
which have been made of other species would serve to establish 
the fact that mutations have occurred in a number of cases rep- 
resenting diverse groups. The observations of de Vries on the 
evening primroses has exceptional interest for us, because of the 
fact that many of his experiments have been repeated at the New 
ork Botanical Garden with results entirely confirmatory of 
those obtained by him, as has been reported in Doctor Mac- 
Dougal’s paper in the February number of this journal, and as 
is more particularly set forth in a recent publication of the Car- 
negie Institution. 
There are many points at which, while it appears opposed to 
some of Darwin’s ideas, the mutation theory really illuminates 
and reénforces the theory of derivation by means of natural selec- 
tion. For example, Darwin was much troubled by the absence 
