expect to
discover, owing to the imperfection of the geological record. discover, owing to the imperfection of the geological record. 1859 1860 1861 1866 |
find so many links. 1869 1872 |
↑1 blocks not present in 1859 1860; present in 1861 1866 1869 1872 | If two or three, or even more linking forms were discovered, they would simply be ranked as
so many new species, more especially if found in different geological sub-stages, let their differences be ever so slight.
|
Numerous existing doubtful forms could be named which are probably varieties; but who will pretend that in future ages so many fossil links will be discovered, that naturalists will be able to
decide, decide, 1859 1860 1861 | decide 1866 1869 1872 |
on the common view, whether or not on the common view, whether or not 1859 1860 1861 |
whether or not on the common view 1866 |
whether or not 1869 1872 |
these doubtful forms
are are 1859 1860 1861 1866 |
ought to be called 1869 1872 |
varieties? As long as most of the links between any two species are unknown, if any one link or intermediate variety be discovered, it will simply be classed as another and distinct species. Only a small portion of the world has been geologically
explored. Only organic beings of certain classes can be preserved in a fossil condition, at least in any great number. ↑1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 | Many species when once formed never undergo any further change,
but become extinct without leaving modified descendants; and the periods, during which species have undergone modification, though long as measured by years, have probably been short in comparison with the periods during which they have
retained the same form.
|
Widely Widely 1859 1860 1861 |
It is the dominant and widely 1866 1869 1872 |
ranging species
vary vary 1859 1860 1861 |
which vary most frequently and vary 1866 1869 1872 |
most, and varieties are often at first
local,— local,— 1859 1860 | local— 1861 1866 1869 1872 |
both causes rendering the discovery of intermediate links
less less 1859 1860 1861 |
in any one formation less 1866 1869 1872 |
likely. Local varieties will not spread into other and distant regions until they are considerably modified and
im- im- 1859 1860 | im- 1861 1866 1869 1872 |
proved; proved; 1859 1860 | improved; 1861 1866 1869 1872 |
and when they
do do 1859 1860 1861 1866 | have 1869 1872 |
spread,
if if 1859 1860 1861 1866 | and are 1869 1872 |
discovered in a geological formation, they will
appear as if suddenly created there, and will be simply classed as new species. Most formations have been
intermittent in their accumulation; and their
duration, duration, 1859 1860 1861 | duration 1866 1869 1872 |
I am inclined to believe, has I am inclined to believe, has 1859 1860 1861 |
has probably 1866 1869 1872 |
been shorter than the average duration of specific forms. Successive formations are
separated separated 1859 1860 |
in most cases separated 1861 1866 1869 1872 |
from each other by
enormous enormous 1859 1860 1861 1866 | enormous 1869 1872 |
blank intervals of
time; time; 1859 1860 1861 1866 | time 1869 1872 |
for for 1859 1860 1861 1866 |
of great length; for 1869 1872 |
fossiliferous
formations, formations, 1859 1860 | formations 1861 1866 1869 1872 |
thick enough to resist future
degradation, degradation, 1859 1860 | degradation 1861 1866 1869 1872 |
can
be be 1859 1860 |
generally be 1861 1866 |
as a general rule be 1869 1872 |
accumulated only where much sediment is
|