| → an area, many of the older species 1869 1872 |
| a new area, they 1859 1860 1861 |
| a new area, these 1866 |
|
| → OMIT 1869 1872 |
| many of the old inhabitants; 1859 1860 1861 |
| many of the older species; 1866 |
|
| → regions, 1872 |
| parts of the world, 1859 1860 1861 1866 1869 |
|
|
With respect to the apparently sudden extermination of whole families or orders, as of Trilobites at the close of the palæozoic period and of Ammonites at the close of the secondary period, we must remember what has been already said on the probable wide intervals of time between our consecutive formations; and in these intervals there may have been much slow extermination. Moreover,
by sudden immigration or by unusually rapid development, many species of a new group have taken possession of
→an area, many of the older species
will have
in a correspondingly rapid
→OMIT
and the forms which thus yield their places will commonly be allied, for they will partake of
inferiority in common. |
|
| Thus, as it seems to me, the manner in which single species and whole groups of species become
accords well with the theory of natural selection. We need not marvel at extinction; if we must marvel, let it be at our
in imagining for a moment that we understand the many complex
on which the existence of each species depends. If we forget for an instant, that each species tends to increase inordinately, and that some check is always in action, yet seldom perceived by us, the whole economy of nature will be utterly obscured. Whenever we can precisely say why this species is more abundant in individuals than that; why this species and not another can be naturalised in a given country; then, and not
then, we may justly feel surprise why we cannot account for the extinction of
particular species or
of species. |
|
|
| Scarcely any palæontological discovery is more striking than the fact, that the forms of life change almost simultaneously throughout the world. Thus our European Chalk formation can be recognised in many distant
→regions,
under the most different climates, where not a fragment of the mineral chalk itself can be found;
in North America, in equatorial South America, in Tierra del Fuego, at the Cape of Good Hope, and in the peninsula of India. For at these distant points, the organic remains in certain beds present an unmistakeable
resemblance to those of the Chalk. It is not that the same species are met with; for in some cases not one species is identically the same, but they belong to the same families, genera, and sections of genera, and sometimes are similarly characterised in such trifling points as mere superficial sculpture.
other forms, which are not found in the Chalk of
|
