Origin of Species Variorum

→ It is the dominant and widely 1866 1869 1872

Widely 1859 1860 1861

→ which vary most frequently and vary 1866 1869 1872

vary 1859 1860 1861

→ in any one formation less 1866 1869 1872

less 1859 1860 1861

→ has probably 1866 1869 1872

I am inclined to believe, has 1859 1860 1861

→ in most cases separated 1861 1866 1869 1872

separated 1859 1860

→ of great length; for 1869 1872

for 1859 1860 1861 1866

→ as a general rule be 1869 1872

be 1859 1860

generally be 1861 1866

→ of strata rich in fossils 1869 1872

of fossiliferous formations 1859 1860 1861

OMIT 1866

→ Cambrian formation, 1869 1872

lowest Silurian strata, 1859 1860 1861

lowest Silurian strata 1866

→ I can recur only 1869 1872

I can only recur 1859 1860 1861

of formations rich in fossils of many kinds, I can recur only 1866

chapter. 1859 1860 1861 1866 1869

→ required by our theory, 1869 1872

which I require, 1859 1860 1861 1866

→ species have all 1869 1872

all species have 1859 1860 1861 1866

→ required by the theory, 1872

which my theory requires, 1859 1860 1861 1866

required, 1869

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 ranging species →which vary most frequently and vary most, and varieties are often at first

local,—

local—

both causes rendering the discovery of intermediate links →in any one formation less likely. Local varieties will not spread into other and distant regions until they are considerably modified and

im-

proved;

and when they

spread,

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

intermittent in their accumulation; and their

duration,

duration

→has probably been shorter than the average duration of specific forms. Successive formations are →in most cases separated from each other by

enormous

....

blank intervals of

time;

time

→of great length; for fossiliferous

formations,

formations

thick enough to resist future

degradation,

degradation

can →as a general rule be 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

generally be

generally blank.

blank.

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 strata rich in fossils beneath the →Cambrian formation, →I can recur only to the hypothesis given in the

ninth

tenth

→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. 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 →required by our theory, few will be inclined to admit. If we look to long enough

in- tervals

intervals

of time, geology plainly declares that →species have all changed; and they have changed in the manner →required by the theory, for they have