How to Solve One of the Problems of Science [pp. 787-793]

How TO SOLVE ONE OF
from that all the different kinds of plants and animals useful
to man have been begotten. This is called artificial selection.
Now, what gardeners, dog-fanciers, and cattle-breeders have
been able to do, Nature has done, and her method is called
natural selection. But Nature works much more slowly than
man, and it is because we cannot see the changes which she
produces coming about in one life-time that so many persons,
not scientists, do not believe that any changes take place. What
,these doubters need above all things is to close, at least for a
brief period, their books of grammar and rhetoric, to cut loose
from old methods and old ideas, and to cultivate their observing powers by studying the Creator's work under the blue sky.
An American naturalist, Professor J. A. Allen, has recently
discovered among the birds of the United States an even
greater amount of variation in color, size, length of bill and
wing, between individuals of the same species, than anybody had
imagined.* And it is now admitted that variation takes place
not only externally but internally: every part of the organism
varies; there is variation in the deepest cells, and without this
natural variability natural selection could not operate. And we
may add that fossils indicate that in past geological ages variability.also existed, and that from one species several varieties
branched off just as they do to-day. In fact the study of the
life-system as revealed by fossils in the rocks everywhere strengthens the hypothesis of evolution. We are able in not a few
cases plainly to mark the transition from one group of animals
to another group. Far back in the Jurassic strata, for instance,
we light upon the earliest bird, Archaeopteryx, which has not
yet entirely cut loose from the reptile stem; and nearly all
scientists are agreed that birds have developed from reptiles;
and, moreover, no naturalists have done more to establish intermediate, transition forms than our American investigatorsHyatt, Marsh, Cope, -and Leidy.
The curious facts, too, of embryology cannot be explained
except by the theory of evolution. Embryology gives in an
abridged form the whole history of the organism. Just as the
primitive amphibians had their origin in fishes, so does embryology show that all the higher vertebrates have been evolved
from fishes: it distinctly reveals the tracks of this long development. We may express it by a zoological rule-of-three, in
the words of the Catholic scientist, St. George Mivart: "As the
young of living kinds are to living adults, so are animals of
X Mammals and Winter Birds of Florida.
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[Mar.,