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1859
1860
1861
1866
1869
1872

Compare with:
1859
1861
1866
1869
1872

I. e. 1860 1861
i . e . 1859
i.e. 1866 1869 1872

species which have been 1859 1860 1861 1866
OMIT 1869 1872

long be preserved, 1859 1860 1861 1866
be preserved for a long time, 1869 1872

Hence the improved and modified descendants of a species will generally cause the extermination of the parent-species; and if many new forms have been developed from any one species, the nearest allies of that species, I. e. the species of the same genus, will be the most liable to extermination. Thus, as I believe, a number of new species descended from one species, that is a new genus, comes to supplant an old genus, belonging to the same family. But it must often have happened that a new species belonging to some one group
has
will have
seized on the place occupied by a species belonging to a distinct group, and thus
cause
have caused
caused
its
examination;
extermination.
extermination;
If
and if
any
many
allied forms be developed from the
success-
successful
ful intruder,
intruder,
many will have to yield their places; and it will generally be
the allied
allied
forms, which will suffer from some inherited inferiority in common. But whether it be species belonging to the same or to a distinct class, which
have yielded
yield
their places to other species which have been modified and
improved
improved,
species, a
a
few of the
suffers
sufferers
may often long be preserved, from being fitted to some peculiar line of life, or from inhabiting some distant and isolated station, where they
will have
have
escaped severe competition. For instance,
some
a single
species of Trigonia, a great genus of shells in the secondary formations,
survive
survives
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