Comparison with 1859 |
|
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,
on the common view, whether or not
these doubtful forms are
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
ranging species vary
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
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
spread, if
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 been 1859 1860 1866 1869 1872 | been, 1861 |
intermittent in their accumulation; and their duration,
I am inclined to believe, has
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
blank intervals of time;
for
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 deposited on the subsiding bed of the sea. During the alternate periods of elevation and of stationary level the record will be
blank. blank. 1859 1860 1869 1872 | generally blank. 1861 1866 |
During these latter periods there will probably be more variability in the forms of life; during periods of subsidence, more extinction. |
|
With respect to the absence of fossiliferous formations
beneath the lowest Silurian strata,
I can only recur
to the hypothesis given in the ninth
chapter.
↑1 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | With respect to the lapse of time not having been sufficient since our planet was consolidated for the assumed amount of organic change, and this objection, as urged by Sir William Thompson , is probably one of the gravest as yet advanced, I can only say, firstly, that we do not know at what rate species change as measured by years, and secondly, that many philosophers are not as yet willing to admit that we know enough of the constitution of the universe and of the interior of our globe to speculate with safety on its past duration.
|
That the geological record is imperfect all will admit; but that it is imperfect to the degree which I require,
few will be inclined to admit. If we look to long enough
intervals intervals 1859 1860 1866 1869 1872 | in- tervals 1861 |
|
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? ↑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. 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— 1861 1866 1869 1872 | local,— 1859 1860 |
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
....... 1861 1866 1869 1872 | im- 1859 1860 |
improved; improved; 1861 1866 1869 1872 | proved; 1859 1860 |
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 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, 1861 | been 1859 1860 1866 1869 1872 |
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
in most cases separated in most cases separated 1861 1866 1869 1872 |
separated 1859 1860 |
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 1861 1866 1869 1872 | formations, 1859 1860 |
thick enough to resist future
degradation degradation 1861 1866 1869 1872 | degradation, 1859 1860 |
can
generally be generally be 1861 1866 |
be 1859 1860 |
as a general rule be 1869 1872 |
accumulated only where much sediment is deposited on the subsiding bed of the sea. During the alternate periods of elevation and of stationary level the record will
be be 1859 1860 1861 1866 | generally be 1869 1872 |
generally blank. generally blank. 1861 1866 | blank. 1859 1860 1869 1872 |
During these latter periods there will probably be more variability in the forms of life; during periods of subsidence, more extinction. |
|
With respect to the absence
of fossiliferous formations of fossiliferous formations 1859 1860 1861 |
of strata rich in fossils 1869 1872 |
OMIT 1866 |
beneath the
lowest Silurian strata, lowest Silurian strata, 1859 1860 1861 |
lowest Silurian strata 1866 |
Cambrian formation, 1869 1872 |
I can only recur I can only recur 1859 1860 1861 |
of formations rich in fossils of many kinds, I can recur only 1866 |
I can recur only 1869 1872 |
to the hypothesis given in the
ninth ninth 1859 1860 1861 1866 1869 | tenth 1872 |
chapter. chapter. 1859 1860 1861 1866 1869 |
chapter; namely, that though our continents and oceans have endured for an enormous period in nearly their present relative positions, we have no reason to assume that this has always been the case; consequently formations much older than any now known may lie buried beneath the great oceans. 1872 |
That the geological record is imperfect all will admit; but that it is imperfect to the degree
which I require, which I require, 1859 1860 1861 1866 |
required by our theory, 1869 1872 |
few will be inclined to admit. If we look to long enough
in- tervals in- tervals 1861 | intervals 1859 1860 1866 1869 1872 |
|