| → world; in some few cases, however, as by the breaking of an isthmus and the consequent irruption of a multitude of new inhabitants, or by the final subsidence of an island, the extinction may have been comparatively rapid. 1861 1866 |
| world. 1859 1860 1869 1872 |
|
| ↑ 1 blocks not present in 1859 1860 1861 1866; present in 1869 1872 |
| In some few cases, however, as by the breaking of an isthmus and the consequent irruption of a multitude of new inhabitants into an adjoining sea, or by the final subsidence of an island, the process of extinction may have been rapid.
|
|
| → a whole group of species 1866 1869 1872 |
| the species of a group 1859 1860 1861 |
|
| → of a group 1866 |
| of a group of species 1859 1860 1861 |
| OMIT 1869 1872 |
|
| → increase 1859 1860 1861 1866 |
| the early increase 1869 1872 |
|
| → sudden relatively to that of most other groups. 1861 1866 |
| sudden. 1859 1860 1869 1872 |
|
| → whole subject of the 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → at the extinction of species, than I have done. 1859 1860 1861 1866 |
| than I have done at the extinction of species. 1869 1872 |
|
|
species gradually disappear, one after another, first from one spot, then from another, and finally from the
→world; in some few cases, however, as by the breaking of an isthmus and the consequent irruption of a multitude of new inhabitants, or by the final subsidence of an island, the extinction may have been comparatively rapid.
↑
Both single species and whole groups of species last for very unequal periods; some groups, as we have seen,
endured from the earliest known dawn of life to the present day; some
disappeared before the close of the palæozoic period. No fixed law seems to determine the length of time during which any single species or any single genus endures. There is reason to believe that the
extinction of
→a whole group of species
is generally a slower process than their production: if
appearance and disappearance
→of a group
be represented, as before, by a vertical line of varying thickness, the line is found to taper more gradually at its upper end, which marks the progress of extermination, than at its lower end, which marks the first appearance and
→increase
in
of the species. In some cases, however, the extermination of whole
as of
towards the close of the secondary period, has been wonderfully
→sudden relatively to that of most other groups.
|
|
| The
→whole subject of the
extinction of species has been involved in the most gratuitous mystery. Some authors have even supposed
as the individual has
definite length of life, so have species a definite duration. No one
can have marvelled more
→at the extinction of species, than I have done. When I found in La Plata the tooth of a horse embedded with the remains of Mastodon, Megatherium, Toxodon, and other extinct monsters, which all co-existed with still living shells at a very late geological period, I was filled with
|
