| → SELECTION; OR THE SURVIVAL OF THE FITTEST. 1869 1872 |
| SELECTION. 1859 1860 1861 1866 |
|
| → the results of Natural 1869 1872 |
| Natural 1859 1860 1861 1866 |
|
| → beings— Advance in organisation— Low forms preserved— Convergence of character— Indefinite multiplication of species— Summary. 1872 |
| beings. 1859 1860 |
| beings— Advance in organisation— Low forms preserved— Objections considered— Indefinite multiplication of species— Summary. 1861 |
| beings — Advance in organisation— Low forms preserved— Objections considered— Indefinite multiplication of species— Summary. 1866 |
| beings— Advance in organisation— Low forms preserved— Objections considered— Uniformity of certain characters due to their unimportance and to their not having been acted on by Natural Selection— Indefinite multiplication of species— Summary. 1869 |
|
| → briefly discussed 1869 1872 |
| discussed too briefly 1859 1860 1861 1866 |
|
| → the 1869 1872 |
| it be borne in mind in what an 1859 1860 1861 1866 |
|
| → slight variations and individual differences occurring in 1872 |
| strange peculiarities 1859 1860 1861 1866 |
| peculiar variations in 1869 |
|
| → be borne in mind; as well as the strength of 1869 1872 |
| vary; and how strong 1859 1860 1861 1866 |
|
|
CHAPTER IV. |
| NATURAL
→SELECTION; OR THE SURVIVAL OF THE FITTEST.
|
| Natural Selection— its power compared with
selection— its power on characters of trifling importance— its power at all ages and on both sexes— Sexual Selection— On the generality of intercrosses between individuals of the same species— Circumstances favourable and unfavourable to
→the results of Natural
Selection, namely, intercrossing, isolation, number of individuals— Slow action— Extinction caused by Natural Selection— Divergence of
related to the diversity of inhabitants of any small area, and to naturalisation— Action of Natural Selection, through Divergence of
and Extinction, on the descendants from a common parent— Explains the
of all organic
→beings— Advance in organisation— Low forms preserved— Convergence of character— Indefinite multiplication of species— Summary.
|
|
will the struggle for existence,
→briefly discussed
in the last chapter, act in regard to variation? Can the principle of selection, which we have seen is so potent in the hands of man, apply
nature? I think we shall see that it can act most
Let
→the
endless number of
→slight variations and individual differences occurring in
our domestic productions, and, in a lesser degree,
under nature,
→be borne in mind; as well as the strength of
the hereditary
Under domestication, it may be truly said that the whole organisation becomes in some degree plastic. But the variability, which we almost universally meet with in our domestic productions, is not directly produced, as Hooker and Asa Gray have well remarked, by man; he can neither originate varieties, nor prevent their occurrence; he can only preserve and accumulate such as do
Unintentionally he exposes organic beings to new and changing conditions of life, and variability ensues; but similar changes of conditions might and do occur under nature. Let it
borne in mind how infinitely complex and
are the mutual relations of all organic beings to each other and to their physical conditions of
and consequently what infinitely varied diversities of structure
be of use to each being under changing conditions of life. Can it, then, be thought improbable, seeing that variations useful to man have
|
