HEREDITY, AND THE ORIGIN OF SPECIES. te 
vidual tree may find itself in a situation favorable to the 
preservation of a number of seedlings, which might endure 
until again reproductive; in such cases a marked variety 
may originate and make its way over the earth. 
“IT have often thought it probable that in time a few 
individuals of these suddenly introduced forms might 
again leap into new features, and then if they should be 
able to sustain themselves, we should have new species 
quite independently of any principle of natural selection; 
that principle, as I understand it, being governed chiefly 
by ‘environment.’ ”’ 
These utterances may be taken as prophetic in part, 
and in part as a natural expression of the inadequacy of 
explanations of the origin of species current at the time. 
Shortly afterward, Professor De Vries, impressed with the 
necessity for obtaining positive evidence upon the subject, 
began an examination of the plants in the vicinity of 
Amsterdam, Holland. Over a hundred species were 
brought into cultivation, and tested by guarded pedigree- 
cultures, and every precaution was taken to exclude inter- 
ference of agencies which might introduce errors. It is 
impossible to describe the enormous amount of work en- 
tailed in such investigations, but the truly splendid results 
well justify the tedious care by which lines of descent were 
carried through successive generations for two decades 
without allowing a trace of doubt as to the purity of the 
lineage involved. 
ring the last four years a partial duplication and 
an extension of these experiments has been carried on in 
New York. It seems unnecessary at this late date to go 
into the detail of the mutations of Lamarck’s evening- 
primrose, especially since the phenomena exhibited by them 
are also to be seen in many other species. By way of 
illustration it need only be said that this plant, as origi- 
nally observed by De Vries, was found to give from two 
