Comparison with 1869 |
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confined to some one spot. Most marine animals have a wide range; and we have seen that with plants it is those which have the widest range, that oftenest present 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,
....... 1861 1866 1869 1872 | which 1859 1860 |
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
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, varieties, 1861 1866 1869 1872 | varieties 1859 1860 |
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 numerous 1861 1866 1869 | numerous, 1859 1860 1872 |
fine,
intermediate intermediate 1861 1866 1869 | intermediate, 1859 1860 1872 |
fossil links, by asking CHAP. IX. GEOLOGICAL RECORD.
ourselves
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
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, 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
discovering in a fossil state numerous intermediate gradations;
and such success
is is 1861 1866 1869 1872 |
seems to me 1859 1860 |
improbable in the highest degree. |
Text in this page (from paragraph 3110, sentence 100 to paragraph 3200, sentence 100, word 17) is not present in 1869 |