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include few 1859 1860 1861 1866
do not include many 1869 1872

by catastrophes; and 1859 1860 1861 1866 1869
OMIT 1872

lapse of actual 1859 1860 1861 1866 1869
relative, though not actual lapse of 1872

quite incomprehensible by us, 1859 1860 1861 1866
OMIT 1869

a mere fragment of time, 1859 1860 1861 1866
short, 1869

was created. 1859 1860 1861 1866
appeared on the stage. 1869

stages as having been of vast duration. But we shall be able to gauge with some security the duration of these intervals by a comparison of the preceding and succeeding organic forms. We must be cautious in attempting to correlate as strictly contemporaneous two formations, which include few identical species, by the general succession of
the
their
forms of life. As species are produced and exterminated by slowly acting and still existing causes, and not by miraculous acts of
creation;
creation
and by catastrophes; and as the most important of all causes of organic change is one which is almost independent of altered and perhaps suddenly altered physical conditions, namely, the mutual relation of organism to organism,— the improvement of one
organism
being
entailing the improvement or the extermination of others; it follows, that the amount of organic change in the fossils of consecutive formations probably serves as a fair measure of the lapse of actual time. A number of species, however, keeping in a body might remain for a long period unchanged, whilst within
the
this
same period, several of these species, by migrating into new countries and coming into competition with foreign associates, might become modified; so that we must not overrate the accuracy of organic change as a measure of time. During early periods of the
earths
earth's
history, when the forms of life were probably fewer and simpler, the rate of change was probably slower; and at the first dawn of life, when very few forms of the simplest structure existed, the rate of change may have been slow in an extreme degree. The
whole
whole
history of the world, as at present known, although of
immense
a
length,
length
quite incomprehensible by us, will hereafter be recognised as a mere fragment of time, compared with the ages which
must have
have
elapsed since the first
organic beings,
creature,
the
progenitors
progenitor
of innumerable extinct and living descendants, was created.