On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life eBook

This eBook from the Gutenberg Project consists of approximately 532 pages of information about On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life.

On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life eBook

This eBook from the Gutenberg Project consists of approximately 532 pages of information about On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life.
degrees of inheritance and of reversion.  Variability is governed by many unknown laws, more especially by that of correlation of growth.  Something may be attributed to the direct action of the conditions of life.  Something must be attributed to use and disuse.  The final result is thus rendered infinitely complex.  In some cases, I do not doubt that the intercrossing of species, aboriginally distinct, has played an important part in the origin of our domestic productions.  When in any country several domestic breeds have once been established, their occasional intercrossing, with the aid of selection, has, no doubt, largely aided in the formation of new sub-breeds; but the importance of the crossing of varieties has, I believe, been greatly exaggerated, both in regard to animals and to those plants which are propagated by seed.  In plants which are temporarily propagated by cuttings, buds, etc., the importance of the crossing both of distinct species and of varieties is immense; for the cultivator here quite disregards the extreme variability both of hybrids and mongrels, and the frequent sterility of hybrids; but the cases of plants not propagated by seed are of little importance to us, for their endurance is only temporary.  Over all these causes of Change I am convinced that the accumulative action of Selection, whether applied methodically and more quickly, or unconsciously and more slowly, but more efficiently, is by far the predominant Power.

CHAPTER 2.  VARIATION UNDER NATURE.

Variability.  Individual differences.  Doubtful species.  Wide ranging, much diffused, and common species vary most.  Species of the larger genera in any country vary more than the species of the smaller genera.  Many of the species of the larger genera resemble varieties in being very closely, but unequally, related to each other, and in having restricted ranges.

Before applying the principles arrived at in the last chapter to organic beings in a state of nature, we must briefly discuss whether these latter are subject to any variation.  To treat this subject at all properly, a long catalogue of dry facts should be given; but these I shall reserve for my future work.  Nor shall I here discuss the various definitions which have been given of the term species.  No one definition has as yet satisfied all naturalists; yet every naturalist knows vaguely what he means when he speaks of a species.  Generally the term includes the unknown element of a distinct act of creation.  The term “variety” is almost equally difficult to define; but here community of descent is almost universally implied, though it can rarely be proved.  We have also what are called monstrosities; but they graduate into varieties.  By a monstrosity I presume is meant some considerable deviation of structure in one part, either injurious to or not useful to the species, and not generally propagated.  Some authors use the term “variation”

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On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life from Project Gutenberg. Public domain.