intervals of time, is widely different in different groups. The extinction of species and of whole groups of species, which has played so conspicuous a part in the history of the organic world, almost inevitably follows
on on 1859 1860 1861 1866 | from 1869 1872 |
the principle of natural selection; for old forms
will be will be 1859 1860 1861 1866 | are 1869 1872 |
supplanted by new and improved forms. Neither single species nor groups of species
reappear reappear 1859 1860 1861 1866 1869 | re-appear 1872 |
when the chain of ordinary generation
has has 1859 1860 1861 1866 | is 1869 1872 |
once
been been 1859 1860 1861 1866 | been 1869 1872 |
broken. The gradual diffusion of dominant
forms, forms, 1859 1860 1861 1869 1872 | forms 1866 |
with the slow modification of their descendants, causes the forms of life, after long intervals of time, to appear as if they had changed simultaneously throughout the world. The fact of the fossil remains of each formation being in some degree intermediate in character between the fossils in the
formations formations 1859 1860 1861 1869 1872 | formation 1866 |
above and below, is simply explained by their intermediate position in the chain of descent. The grand fact that all extinct
organic organic 1859 1860 1861 1866 | organic 1869 1872 |
beings
belong to the same system with belong to the same system with 1859 1860 1861 1866 |
can be classed with all 1869 1872 |
recent beings,
falling either into the same or into intermediate groups, falling either into the same or into intermediate groups, 1859 1860 1861 1866 |
naturally 1869 1872 |
follows from the living and the extinct being the
off-spring off-spring 1861 | offspring 1859 1860 1866 1869 1872 |
of common parents. As
the groups which have descended from an ancient progenitor the groups which have descended from an ancient progenitor 1859 1860 1861 1866 |
species 1869 1872 |
have generally diverged in
character, character, 1859 1860 1861 1866 | character 1869 1872 |
the progenitor with its early descendants will often be intermediate in character in comparison with its later descendants; and thus the progenitor with its early descendants will often be intermediate in character in comparison with its later descendants; and thus 1859 1860 1861 1866 |
during their long course of descent and modification, 1869 1872 |
we can
see see 1859 1860 1861 1866 | understand 1869 1872 |
why
the the 1859 1860 1861 1866 |
it is that the 1869 1872 |
more ancient
a fossil is, the oftener it stands a fossil is, the oftener it stands 1859 1860 1861 1866 |
forms, or early progenitors of each group, so often occupy a position 1869 1872 |
in some degree intermediate between existing
and allied and allied 1859 1860 1861 | allied 1866 | and allied 1869 1872 |
groups. Recent forms are generally looked
at at 1859 1860 1861 1866 1869 | upon 1872 |
as being,
on the whole, higher on the whole, higher 1861 1866 |
in some vague sense, higher 1859 1860 |
on the whole, higher in the scale of organisation 1869 1872 |
than ancient
and extinct and extinct 1859 1860 1861 1866 | and extinct 1869 1872 |
forms; and they
are are 1859 1860 1861 1866 |
must be higher, 1869 1872 |
in so far higher in so far higher 1859 1860 1861 |
higher in so far 1866 |
in so far 1869 1872 |
as the later and more improved forms have conquered the older and less improved
organic beings organic beings 1859 1860 1861 1866 | forms 1869 1872 |
in the struggle for
life; they will also generally have had their organs more specialised for different functions. life; they will also generally have had their organs more specialised for different functions. 1861 1866 |
life. 1859 1860 |
life; they have also generally had their organs more specialized for different functions. 1869 |
life; they have also generally had their organs more specialised for different functions. 1872 |
This fact is perfectly compatible with numerous beings still retaining
a
simple and
little improved organisation little improved organisation 1861 1866 |
but little improved structures, 1869 1872 |
|