expect to
find so many links. find so many links. 1869 1872 |
discover, owing to the imperfection of the geological record. 1859 1860 1861 1866 |
If two or three, or even more linking forms were discovered, they would simply be ranked
as as 1861 1866 1869 |
by many naturalists as 1872 |
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 1866 1869 1872 | decide, 1859 1860 1861 |
whether or not whether or not 1869 1872 |
on the common view, whether or not 1859 1860 1861 |
whether or not on the common view 1866 |
these doubtful forms
ought to be called ought to be called 1869 1872 |
are 1859 1860 1861 1866 |
varieties? ↑1 blocks not present in 1861 1866 1869 1872; present in 1859 1860 | 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 geologically 1859 1860 1861 1869 1872 | geological 1866 |
explored. Only organic beings of certain classes can be preserved in a fossil condition, at least in any great number. Many species when once formed never undergo any further
change change 1869 1872 | change, 1866 |
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.
It is the dominant and widely It is the dominant and widely 1866 1869 1872 |
Widely 1859 1860 1861 |
ranging species
which vary most frequently and vary which vary most frequently and vary 1866 1869 1872 |
vary 1859 1860 1861 |
most, and varieties are often at first
local— local— 1861 1866 1869 1872 | local,— 1859 1860 |
both causes rendering the discovery of intermediate links
in any one formation less in any one formation less 1866 1869 1872 |
less 1859 1860 1861 |
likely. Local varieties will not spread into other and distant regions until they are considerably modified and
....... 1861 1866 1869 1872 | im- 1859 1860 |
improved; improved; 1861 1866 1869 1872 | proved; 1859 1860 |
and when they
have have 1869 1872 | do 1859 1860 1861 1866 |
spread,
and are and are 1869 1872 | if 1859 1860 1861 1866 |
discovered in a geological formation, they
will will 1859 1860 1861 1866 1869 | will 1872 |
appear as if suddenly created there, and will be simply classed as new species. Most formations have
been been 1859 1860 1866 1869 1872 | been, 1861 |
intermittent in their accumulation; and their
duration duration 1866 1869 1872 | duration, 1859 1860 1861 |
has probably has probably 1866 1869 1872 |
I am inclined to believe, has 1859 1860 1861 |
been shorter than the average duration of specific forms. Successive formations are
in most cases separated in most cases separated 1861 1866 1869 1872 |
separated 1859 1860 |
from each other by
....... 1869 1872 | enormous 1859 1860 1861 1866 |
blank intervals of
time time 1869 1872 | time; 1859 1860 1861 1866 |
of great length; for of great length; for 1869 1872 |
for 1859 1860 1861 1866 |
fossiliferous
formations formations 1861 1866 1869 1872 | formations, 1859 1860 |
thick enough to resist future
degradation degradation 1861 1866 1869 1872 | degradation, 1859 1860 |
can
as a general rule be as a general rule be 1869 1872 |
be 1859 1860 |
generally be 1861 1866 |
accumulated only where much sediment is
|