| → OMIT 1869 1872 |
| species which have been 1859 1860 1861 1866 |
|
| → be preserved for a long time, 1869 1872 |
| long be preserved, 1859 1860 1861 1866 |
|
| → 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 |
|
|
which
their places to other
→OMIT
modified and
few of the
may often
→be preserved for a long time,
from being fitted to some peculiar line of life, or from inhabiting some distant and isolated station, where they
escaped severe competition. For instance,
species of Trigonia, a great genus of shells in the secondary formations,
in the Australian seas; and a few members of the great and almost extinct group of Ganoid fishes still inhabit our fresh waters. Therefore the utter extinction of a group is generally, as we have seen, a slower process than its production. |
|
| 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,
|
