il and pouter
and carrier-pigeon with their diverse characters have taken their origin.

It is true that some biologists have urged certain technical objections to
the employment of domesticated animals and their history as analogies to
the processes and results in wild nature. To my mind, however, artificial
selection is truly a part of the whole process of natural selection. Man
is but one element of the environment of tame forms, and his fancy or need
is therefore one of the varied series of external criteria that must be
met if survival is to be the result; failing this, elimination follows as
surely as under the conditions of an area uninhabited or uninfluenced by
mankind. Congenital variation is real, selection is real and the heredity
of the more fit modification is equally real. Surely Darwin was right in
contending that the facts of this class amplify the conception of natural
selection developed on the basis of an analysis of wild life.

* * * * *

Knowing the elements of the selective process, it is possible to analyze
and to understand many significant phenomena of nature, and to gain a
clearer conception of the results of the struggle for existence,
especially when the human factor is involved. Let us see how much is
revealed when the foregoing results are employed in a further study of
some of nature's vital situations.

As a consequence of the many-sided struggle for existence, the
interrelations of a series of species will approach a condition of
equilibrium in an area where the natural circumstances remain relatively
undisturbed for a long time. For example, among the field-mice of one
generation, just as many individuals will survive as will be able to find
food and to escape hereditary foes such as cats and snakes and owls. The
number of owls, in their turn, will be determined by the number of
available mice and other food organisms, as well as by the severity of the
adverse circumstances that cause elimination of the less fit among the
fledglings brought into the world. The vital chain of connections is
sometimes astonishingly long and intricate. One remarkable illustration is
given by Fiske, as an elaboration of an example cited by Darwin. He points
out that the fine quality of the traditional roast beef of England is
directly determined by the number of elderly spinsters in that country.
The chain of circumstances is as follows: the quality of the clover
fields, fu