es of change, the accumulative
action of selection, whether applied methodically and quickly, or
unconsciously and slowly, but more efficiently, seems to have been the
predominant power.

_III.--Variation Under Nature_

Before applying these principles to organic beings in a state of nature,
we must ascertain whether these latter are subject to any variation. We
find variation everywhere. Individual differences, though of small
interest to the systematist, are of the highest importance for us, for
they are often inherited; and they thus afford materials for natural
selection to act and accumulate, in the same manner as man accumulates
in any given direction individual differences in his domesticated
productions. Further, what we call varieties cannot really be
distinguished from species in the long run, a fact which we can clearly
understand if species once existed as varieties, and thus originated.
But the facts are utterly inexplicable if species are independent
creations.

How have all the exquisite adaptations of one part of the body to
another part, and to the conditions of life, and of one organic being to
another being, been perfected? For everywhere we find these beautiful
adaptations.

The answer is to be found in the struggle for life. Owing to this
struggle, variations, however slight, and from whatever cause
proceeding, if they be in any degree profitable to the individuals of a
species in their infinitely complex relations to other organic beings
and to their physical conditions of life, will tend to the preservation
of such individuals, and will generally be inherited by the offspring.
The offspring, also, will thus have a better chance of surviving, for,
of the many individuals of any species which are periodically born, but
a small number can survive. I have called this principle, by which each
slight variation, if useful, is preserved, by the term Natural
Selection, in order to mark its relation to man's power of selection.
But the expression, often used by Mr. Herbert Spencer, of the Survival
of the Fittest, is more accurate.

We have seen that man, by selection, can certainly produce great
results, and can adapt organic beings to his own uses, through the
accumulation of slight but useful variations given to him by the hand of
Nature. Natural Selection is a power incessantly ready for action, and
is as immeasurably superior to man's feeble efforts as the works of
Nature are to those of Art.