214 Experimental Zoology 
anatomy, embryology, and paleontology. Charles Darwin 
occupies a unique position. Like his predecessors, he argued 
for the theory of evolution on the basis of comparative anatomy 
and paleontology, but in addition he brought forward his theory 
of natural selection to account for the ‘‘origin of species,” as 
the result of the survival of the individuals that are better 
adapted. In support of his theory of natural selection he 
introduced the evidence from artificial selection as carried out 
by man. Here almost for the first time the experimental study 
of evolution was begun. Darwin’s more immediate followers, 
however, did not carry on the experimental work much beyond 
the stage at which he left it. In the last decade, however, great 
activity has begun along experimental lines with most promising 
results, and at the present time the study of evolution has passed 
into an experimental stage. 
The results that de Vries has obtained with plants in his experi- 
mental garden have opened a new era in the study of evolution, 
for he has shown that the process may not be so slow that it can 
only be detected by elaborate mathematical calculations, or at 
least that it may at times be rapid and easily detected; and, 
what is more important, he has shown that this process is going 
onat the present time. De Vries’s results will be described later, 
and his evidence compared with that obtained by zodlogists for 
animal forms; but before taking up de Vries’s work, certain 
other considerations must first be dealt with. 
The Analogy with Artificial Selection 
If, as Darwin supposed, the domesticated races have been 
formed largely by the selection of fluctuating variations, a strong 
argument, at least, would have been established in favor of an 
analogous method in nature having produced wild species; but 
it is probable that Darwin relied too extensively on the statements 
of breeders and amateurs as to the process by which their results 
were obtained. It is clear that many of these breeders lack the 
scientific training and appreciation of the value of evidence to 
make their conclusions trustworthy, and however interesting 
