| → by our fir-trees, so 1866 1869 1872 |
| in order 1859 1861 |
|
| →
the Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection. 1869 |
|
of Chapter
.—
1859 1861 |
|
the Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection.
1866 |
|
the Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection
. 1872 |
|
| → We 1859 1861 1866 1869 1872 |
|
Summary of Chapter.
— We
1860 |
|
|
of
→by our fir-trees, so
that a few granules may be wafted by
chance
on to the ovules? |
|
→
the Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection.
|
|
→We
have in this chapter discussed some of the difficulties and objections which may be urged against
theory. Many of them are
but I think that in the discussion light has been thrown on several facts, which on the
of independent acts of creation are utterly obscure. We have seen that species at any one period are not indefinitely variable, and are not linked together by a multitude of intermediate
partly because the process of natural selection
always
very slow, and
at any one
on a
few forms; and partly because the very process of natural selection
implies the continual supplanting and extinction of
and intermediate
Closely allied species, now living on a continuous area, must often have been formed when the area was not continuous, and when the conditions of life did not insensibly graduate away from one part to another. When two varieties are formed in two districts of a continuous area, an intermediate variety will often be formed, fitted for an intermediate zone; but from reasons assigned, the intermediate variety will usually exist in lesser numbers than the two forms which it connects; consequently the two latter, during the course of further modification, from existing in greater numbers, will have a great advantage over the less numerous intermediate variety, and will thus generally succeed in supplanting and
it. |
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| We have seen in this chapter how cautious we should be in concluding that the most different habits of life
|
