| → time as estimated by years— 1869 1872 |
| our palæontological collections— 1859 1860 1866 |
| our palæntological collections— 1861 |
|
| → our palæontological collections— 1869 1872 |
| geological formations— 1859 1860 |
| granitic areas— 1861 1866 |
|
| → geological formations— 1861 1866 1872 |
| intermediate varieties in any one formation— 1859 1860 |
| granitic areas— 1869 |
|
| → denudation of granitic areas— On the absence of intermediate varieties in any one formation— On the 1872 |
| sudden appearance of groups of species— On their 1859 1860 |
| absence of intermediate varieties in any one formation— On the 1861 1866 |
| intermittence of geological formations— On the absence of intermediate varieties in any one formation— On the 1869 |
|
| → of groups of species— On their sudden appearance in 1861 1866 1869 1872 |
| in 1859 1860 |
|
| → strata— Antiquity of the habitable earth. 1869 1872 |
| strata. 1859 1860 1861 1866 |
|
| → OMIT 1869 1872 |
| on the earth, 1859 1860 1861 1866 |
|
|
CHAPTER
|
| ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. |
| On the absence of intermediate varieties at the present day— On the nature of extinct intermediate varieties; on their number— On the
lapse of time, as inferred from the rate of
and of
On the
of
→time as estimated by years—
On the
of
→our palæontological collections—
On the
of
→geological formations—
On the
→denudation of granitic areas— On the absence of intermediate varieties in any one formation— On the
sudden appearance
→of groups of species— On their sudden appearance in
the lowest known fossiliferous
→strata— Antiquity of the habitable earth.
|
| IN the sixth chapter I enumerated the chief objections which might be justly urged against the views maintained in this volume. Most of them have now been discussed. One, namely the distinctness of specific forms, and their not being blended together by innumerable transitional links, is a very obvious difficulty. I assigned reasons why such links do not commonly occur at the present
under the circumstances apparently most favourable for their presence, namely on an extensive and continuous area with graduated physical conditions. I endeavoured to show, that the life of each species depends in a more important manner on the presence of other already defined organic forms, than on climate; and, therefore, that the really governing conditions of life do not graduate away quite insensibly like heat or moisture. I endeavoured, also, to show that intermediate varieties, from existing in lesser numbers than the forms which they connect, will generally be beaten out and exterminated during the course of further modification and improvement. The main cause, however, of innumerable intermediate links not now occurring everywhere throughout
on the very process of natural selection, through which new varieties continually take the places of and
their parent-forms. But just in proportion as this process of extermination has acted on an enormous scale, so must the number of intermediate varieties, which have formerly
→OMIT
be truly enormous. Why then is not every geological formation and every stratum full of
|
