Comparison with 1869 |
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varieties; so
that, that, 1866 1869 1872 | that 1859 1860 1861 |
with shells and other marine animals, it is
probable probable 1869 1872 |
probably 1859 1860 |
highly probable that 1861 1866 |
that those which have that those which have 1869 |
those which have 1859 1860 1861 1866 |
that those which 1872 |
had the widest range, far exceeding the limits of the known geological formations of Europe, which
have oftenest given rise, first to local varieties and ultimately to new species; and this again would greatly lessen the chance of our being able to trace the stages of transition in any
one one 1859 1860 1866 1869 1872 | ony 1861 |
geological formation. |
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It is a more important consideration, clearly
leading to the same result, as lately insisted on by Dr. Falconer, namely, that the periods
during which species have been undergoing
modification, though very
long as measured by years, have probably been
short in comparison with the periods
during which these same species
remained without undergoing any change. ↑2 blocks not present in 1859 1860 1861 1869 1872; present in 1866 | 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.
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It should not be forgotten, that at the present day, with perfect specimens for examination, two forms can seldom be connected by intermediate varieties
and thus proved to be the same species, until many specimens
are are 1869 1872 | have been 1859 1860 1861 1866 |
collected from many places; and in the case of
fossil species this
can can 1869 1872 | could 1859 1860 1861 1866 |
rarely be effected by palæontologists. We shall, perhaps, best perceive the improbability of our being enabled to connect species by numerous,
fine, intermediate,
fossil links, by asking CHAP. IX. GEOLOGICAL RECORD.
ourselves ourselves 1859 1860 1869 1872 | our-selves 1861 1866 |
whether, for instance, geologists at some future period will be able to prove,
that our different breeds of cattle, sheep, horses, and dogs
are are 1869 1872 | have 1859 1860 1861 1866 |
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 only
varieties, are really varieties
or are, as it is called, specifically distinct. This could be effected only by the future geologist
discovering in a fossil state numerous intermediate gradations;
and such success seems to me
improbable in the highest degree. |
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It has been asserted over and over again, by writers who believe in the immutability of species, that geology
....... 1866 1869 1872 | has 1861 |
yields yields 1866 1869 1872 | yielded 1861 |
no linking forms. This assertion
is entirely
erroneous. As
Sir J. Sir J. 1866 1869 1872 | Mr. 1861 |
Lubbock has
....... 1866 1869 1872 | recently 1861 |
remarked,
"Every "Every 1866 1869 1872 | "Every 1861 |
species is a link between other allied
forms." We clearly see this if forms." We clearly see this if 1866 1869 |
forms." We clearly see this if 1861 |
forms." If 1872 |
we take a genus having
|