od by which organisms evolve, putting all of the emphasis upon the
congenital causes of variation, although the reality of other kinds of
change is not questioned. But the contrast between Darwinism and the other
descriptions of secondary factors can best be made after a somewhat
detailed discussion of the former, which has gained the adherence of the
majority of the naturalists of to-day. However, we must not pass on
without pointing out that however much the explanations given by various
men of science may differ, they all agree in expressly recognizing the
complete naturalness of the secondary as well as of the primary factors of
evolution.

* * * * *

The doctrine of natural selection forms the best basis for the detailed
discussion of the way evolution has come about in the past and how it is
going on to-day. This is true because it was the first description of
nature's program to carry conviction to the scientific world, and because
its major elements have stood the test of time as no other doctrine has
done. Much has been added to our knowledge of natural processes during
post-Darwinian times, and new discoveries have supplemented and
strengthened the original doctrine in numerous ways, although they have
corrected certain of the minor details on the basis of fuller
investigation.

At the outset it must be clearly understood that Darwin's doctrine is
concerned primarily with the _method_ and not with the evidences as to the
actual _fact_ of evolution. Most of those who are not familiar with the
principles of science believe that Darwin discovered this process; but
their opinion is not correct. The reality of natural change as a universal
attribute of living things had been clearly demonstrated long before
Darwin wrote the remarkable series of books whose influence has been felt
outside the domains of biology and to the very confines of organized
knowledge everywhere. The "Origin of Species" was published in 1859, and
only the last of its fourteen chapters is devoted to a statement of the
evidence that evolution is true. In this volume Darwin presented the
results of more than twenty-five years of patient study of the phenomena
of nature, utilizing the observations of wild life in many regions visited
by him when he was the naturalist of the "Beagle" during its famous voyage
around the world. He also considered at length the results of the
breeder's work with domesticated animals,