measured by years,
have probably been have probably been 1866 |
was, from the reasons lately assigned, probably 1869 |
was probably 1872 |
short in comparison with
the periods the periods 1866 | that 1869 1872 |
during which
these same species these same species 1866 |
it 1869 1872 |
remained without undergoing any change. We may infer that this has been the case, from there being no inherent tendency in organic beings to become modified or to progress in structure, and from all modifications depending, firstly on long-continued variability, and secondly on changes in the physical conditions of life, or on changes in the habits and structure of competing species, or on the immigration of new forms; and such contingencies will supervene in most cases only after long intervals of time and at a slow rate. These changes, moreover, in the organic and inorganic conditions of life will affect only a limited number of the inhabitants of any one area or country. |
It should not be forgotten, that at the present day, with perfect specimens for examination, two forms can seldom be connected by intermediate
varieties, varieties, 1861 1866 1869 1872 | varieties 1859 1860 |
and thus proved to be the same species, until many specimens
have been have been 1859 1860 1861 1866 | are 1869 1872 |
collected from many places; and
in the case of in the case of 1859 1860 1861 1866 1869 |
with 1872 |
fossil species this
could could 1859 1860 1861 1866 | can 1869 1872 |
rarely be
effected by palæontologists. effected by palæontologists. 1859 1860 1861 1866 1869 |
done. 1872 |
We shall, perhaps, best perceive the improbability of our being enabled to connect species by
numerous numerous 1861 1866 1869 | numerous, 1859 1860 1872 |
fine,
intermediate intermediate 1861 1866 1869 | intermediate, 1859 1860 1872 |
fossil links, by asking
...OMIT 1860 1861 1866 1869 1872 |
CHAP. IX. GEOLOGICAL RECORD. 1859 |
our-selves our-selves 1861 1866 | ourselves 1859 1860 1869 1872 |
whether, for instance, geologists at some future period will be able to
prove prove 1861 1866 1869 1872 | prove, 1859 1860 |
that our different breeds of cattle, sheep, horses, and dogs
have have 1859 1860 1861 1866 | are 1869 1872 |
descended from a single stock or from several aboriginal stocks; or, again, whether certain sea-shells inhabiting the shores of North America, which are ranked by some conchologists as distinct species from their European representatives, and by other conchologists as
distinct species from their European representatives, and by other conchologists as only distinct species from their European representatives, and by other conchologists as only 1866 |
only 1859 1860 1861 1869 1872 |
varieties, are really
varieties, varieties, 1861 1866 1869 1872 | varieties 1859 1860 |
or are, as it is called, specifically distinct. This could be effected
only by the future geologist only by the future geologist 1859 1860 1861 1866 1869 |
by the future geologist only by his 1872 |
discovering in a fossil state numerous intermediate
gra- dations; gra- dations; 1866 | gradations; 1859 1860 1861 1869 1872 |
|