and the constant changes taking place in their
surroundings. "Natural Selection" are the words chosen to express the
action of animals under these conflicting forces. The power of external
influence upon structure is exhibited in the remarkable results of man's
treatment of plants and animals. The varieties of pears and apples are
of his producing; and the different breeds of domestic animals are the
direct consequences of his influence. The most astonishing instance of
his power is shown in pigeons, which are made, by skilful breeders, to
assume a great variety of shapes, colors, and habits. To what is this
change due? If a rock-pigeon were left to itself, it would produce only
rock-pigeons, unless some new influences were brought to bear by natural
causes. Man gives a rock-pigeon some peculiar food, subjects it to some
peculiar treatment, and the creature begins at once to change; that is,
to accommodate itself to the new circumstances by which it is
surrounded. The plastic nature undergoes an alteration correspondent to
the new state of existence. In a few generations these varieties are
indefinitely multiplied; and then, by crossing these varieties, new ones
are again produced. What is then the state of affairs? We have a series
of birds which, were they discovered in new countries, would be
considered to be new species. They differ in shape and color, in the
number of their vertebrae and ribs, the number of wing and tail feathers,
the number of scales on their toes, and various other anatomical
peculiarities. Here then is proof that animals, when exposed to
influences different from those which surrounded their ancestors, take
on new forms and characteristics. This is man's work. But is not man one
of the many agents in the work of the Great Prime Mover? Let us suppose
that the peculiar circumstances which produced a pouter or a fan-tail
were to remain in force for centuries; would not pouters or fan-tails
continue to procreate, and thus a new species be added to the genus?
What, then, becomes of special creation of every species of animal, if
man in a few years can produce a dozen forms out of one, any one of
which dozen is so distinct as to be deemed a new species, were it
Nature's work and not man's? The fact is thus demonstrated that animals
become varied in accordance with variations in their surroundings. This
simple fact, once substantiated, is the key to the whole subject. Man's
influence ceases when he leave