186 READINGS IN EVOLUTION, GENETICS, AND EUGENICS ‘ 
there can be no real racial progress; and evolution is nothing more or 
less than racial, as opposed to individual, progress. So obvious did 
this seem that Charles Darwin accepted as axiomatic the general facts 
of variation and heredity and proceeded at once to a discussion 
of the directive factors of evolution. Since variation and heredity 
are now universally conceded to be primary factors, and selection, 
the Lamarckian factor, isolation, orthogenesis, etc., as secondary 
‘or guiding factors, it would seem more natural to proceed first to 
a discussion of variation and heredity. So much of our present 
knowledge of variation and heredity, however, is dependent upon the 
background furnished by Darwin that it seems to us a more effective 
pedagogical order to-consider that vast and intricate conception -of 
evolution which was first given life and unity by Charles Darwin, 
and has come now to be known as “ Darwinism.”’ 
Just how broad the scope of Darwin’s work and how important a 
réle he played in the development of evolutionary biology is indicated 
in the following appreciation of Darwin which we have summarized 
largely from the admirable statement in Professor J. Arthur Thom- 
son’s book Darwinism and Human Life. 
WHAT WE OWE TO DARWIN 
1. The.web -of life—the idea of linkages, interdependencies, cor- 
relations in the living world. The idea is essentially ecological and has 
been expressed elsewhere as “organic equilibrium.” 
‘2. The struggle for existence—the inevitable consequence of Mal- 
‘thus’ idea of overproduction. This struggle is both inter- and intra- 
‘specific, or may be a mere struggle against fate or against hard condi- 
»tions of inorganic environment. 
3. Variability of living creatures—an idea derived from the study of 
changes under domestication and of diversity among wild individuals 
belonging to the same species. 
-4. Natural selection—the central idea which is to be studied pres- 
ently. 
5. Vindication of the evolution idea.—Darwin was the first effec- 
tively to marshal the evidences of evolution in sufficient force to com- 
pel the acceptance of the fact of evolution. Much that has already 
been presented under the head of “Evidences of Evolution” belongs 
to Darwin. The placing of the fact of evolution on a sure foundation 
is believed by many to have been Darwin’s principal contribution to 
science. 
