rrun
enormously the means of support. If all the seeds of a plant, all the
spawn of a fish, were to arrive at maturity, in a very short time the
world could not contain them. Hence of necessity arises a struggle for
life. Only a few of the myriads born can possibly live.

Fourth, here comes in the law of Natural Selection, or the Survival of
the Fittest. That is, if any individual of a given species of plant or
animal happens to have a slight deviation from the normal type,
favorable to its success in the struggle for life, it will survive. This
variation, by the law of heredity, will be transmitted to its offspring,
and by them again to theirs. Soon these favored ones gain the
ascendency, and the less favored perish; and the modification becomes
established in the species. After a time another and another of such
favorable variations occur, with like results. Thus very gradually,
great changes of structure are introduced, and not only species, but
genera, families, and orders in the vegetable and animal world, are
produced. Mr. Darwin says he can set no limit to the changes of
structure, habits, instincts, and intelligence, which these simple laws
in the course of millions or milliards of centuries may bring into
existence. He says, "we cannot comprehend what the figures 60,000,000
really imply, and during this, or perhaps a longer roll of years, the
land and waters have everywhere teemed with living creatures, all
exposed to the struggle for life, and undergoing change." (p. 354). "Mr.
Croll," he tells us, "estimates that about sixty millions of years have
elapsed since the Cambrian period, but this, judging from the small
amount of organic change since the commencement of the glacial period,
seems a very short time for the many and the great mutations of life,
which have certainly occurred since the Cambrian formation; and the
previous one hundred and forty million years can hardly be considered as
sufficient for the development of the varied forms of life which
certainly existed toward the close of the Cambrian period." (p. 379).
Years in this connection have no meaning. We might as well try to give
the distance of the fixed stars in inches. As astronomers are obliged to
take the diameter of the earth's orbit as the unit of space, so
Darwinians are obliged to take a geological cycle as their unit of
duration.

_Natural Selection._

As Natural Selection which works so slowly is a main element in Mr.
Darwin's th