CHAPTER III - STRUGGLE FOR EXISTENCE
BEFORE entering on the subject of this chapter, I must make a few
preliminary remarks, to show how the struggle for existence bears on
Natural Selection. It has been seen in the last chapter that amongst
organic beings in a state of nature there is some individual
variability: indeed I am not aware that this has ever been disputed.
It is immaterial for us whether a multitude of doubtful forms be
called species or sub-species or varieties; what rank, for instance,
the two or three hundred doubtful forms of British plants are entitled
to hold, if the existence of any well-marked varieties be admitted.
But the mere existence of individual variability and of some few
well-marked varieties, though necessary as the foundation for the
work, helps us but little in understanding how species arise in
nature. How have all those exquisite adaptations of one part of the
organisation to another part, and to the conditions of life, and of
one organic being to another being, been perfected? We see these
beautiful co-adaptations most plainly in the woodpecker and the
mistletoe; and only a little less plainly in the humblest parasite
which clings to the hairs of a quadruped or feathers of a bird; in the
structure of the beetle which dives through the water; in the plumed
seed which is wafted by the gentlest breeze; in short, we see
beautiful adaptations everywhere and in every part of the organic
world.
Again, it may be asked, how is it that varieties, which I have
called incipient species, become ultimately converted into good and
distinct species which in most cases obviously differ from each
other far more than do the varieties of the same species? How do those
groups of species, which constitute what are called distinct genera,
and which differ from each other more than do the species of the
same genus, arise? All these results, as we shall more fully see in
the next chapter, follow from 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,
and is sometimes equally convenient. 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. But Natural
Selection, as we shall hereafter see, 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.
We will now discuss in a little more detail the struggle for
existence. In my future work this subject will be treated, as it
well deserves, at greater length. The elder De Candolle and Lyell have
largely and philosophically shown that all organic beings are
exposed to severe competition. In regard to plants, no one has treated
this subject with more spirit and ability than W. Herbert, Dean of
Manchester, evidently the result of his great horticultural knowledge.
Nothing is easier than to admit in words the truth of the universal
struggle for life, or more difficult- at least I have found it so-
than constantly to bear this conclusion in mind. Yet unless it be
thoroughly engrained in the mind, the whole economy of nature, with
every fact on distribution, rarity, abundance, extinction, and
variation, will be dimly seen or quite misunderstood. We behold the
face of nature bright with gladness, we often see superabundance of
food; we do not see or we forget, that the birds which are idly
singing round us mostly live on insects or seeds, and are thus
constantly destroying life; or we forget how largely these
songsters, or their eggs, or their nestlings, are destroyed by birds
and beasts of prey; we do not always bear in mind, that, though food
may be now superabundant, it is not so at all seasons of each
recurring year.
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