ORGANIC EVOLUTION 289 
germinated, there would appear among the seedlings a few that were 
very different from the others. These few being brought under culti- 
vation developed into individuals with all the marks of species distinct 
from the parent. Moreover, they " came true," generation after gen- 
eration, which is regarded as the final test of a species. In this way 
O. Lamarckiana was observed to give rise to several new species, in 
some cases the same species appearing repeatedly. Not all of these 
suddenly produced species would have survived in nature, but some of 
them had already stood this test in the vacant field. This immediate 
appearance of a fully equipped new species, without any intermediate 
stages or any building up by selection, DeVries called mutation, the 
forms thus produced being mutants. The role of natural selection in 
this case is not to produce species, but to select among those already 
produced. It is evident that a mutant is simply a large variation, such 
as are called " sports." 
DeVries investigated the results of plant breeders, as Darwin had 
done, and distinguished between improved forms and really new forms. 
The former evidently arose from the continuous selection of small varia- 
tions, and were always inconstant. The very few new forms produced 
were constant, and, so far as records of their pedigree were available, 
were found to have arisen in each case from some individual that had 
suddenly appeared among the cultures. In other words, new forms 
were found, not produced; and when found, they remained constant. 
Naturally DeVries concluded that all the new and permanent forms that 
have appeared in connection with plant breeding have been mutants, 
and have not been built up by continuous selection. 
It is entirely unknown whether this mutating condition is of general 
occurrence. Cultures of plants and animals are being carried on by 
numerous investigators, and the results may indicate presently whether 
mutation is to be regarded as a general method in the origin of species 
or as only an occasional one. It is becoming more and more evident 
that new species may have arisen in several ways, perhaps including all 
the methods heretofore suggested, and certainly including some that 
remain to be discovered. Whether mutation stands or falls as an 
explanation of evolution, the most important contribution of DeVries to 
evolutionary science is its transfer from the field of observation and 
comparison to the field of experimental work. 
Orthogenesis. Natural selection utilizes small variations in building 
up new species, and mutation calls large variations species. In both 
