y land upon the surface of the earth.

Slow-breeding man has been known to double his number in twenty-five
years, and according to Euler, this might occur in little over twelve
years. But assuming the former rate of increase, and taking the
population of the United States at only thirty millions, in six hundred
and eighty-five years their living progeny would have each but a square
foot to stand upon, were they spread over the entire globe, land and
water included. But millions of species are doing the same thing, so
that the inevitable result of this strife cannot be a matter of chance.
Evidently those individuals or varieties having some advantage over
their competitors will stand the best chance to live, while those
destitute of these advantages will be liable to destruction. Nature may
be said (metaphorically) to choose (like the will of man in artificial
selection) which shall be preserved and which destroyed.

That portion of the theory of development which maintains the common
descent of all species of animals and plants from the simplest common
origin, I have already stated with full justice should be called
Lamarckism. Progress is recognized by all scientists to be a law of
nature. Some of the more important facts which sustain the theory of
development, I propose now to present as briefly as possible.

RUDIMENTARY ORGANS.

One of the strongest arguments in favor of the hypothesis of a genetic
connection among all animals (including man), at least among all those
belonging to the same great types, is the presence of rudimentary parts.
By rudiments in anatomy are meant organs or structures imperfectly
developed, so as to be almost or entirely without functional use. "Each
of them represents in germ, as it were, in one animal (or plant), that
which is perfect and useful in another type."

For a few examples: The little fold of caruncle at the inner margin of
the eye in man, represents the nictitating membrane of birds. Eyes which
do not see form a striking example. These are found in very many animals
which live in the dark, as in caves or underground. Their eyes are often
perfectly developed but are covered by a membrane, so that no ray of
light can enter and they can never see. Such eyes, without the function
of sight, are found in several species of moles and mice which live
underground, in serpents and lizards, in amphibious animals (proteus,
caecilia) and in fishes; also in numerous invertebrate anima