| → percentage system of 1859 1860 1861 1866 1869 |
| proportion between the 1872 |
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|
CHAPTER
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| ON THE GEOLOGICAL SUCCESSION OF
BEINGS. |
| On the slow and successive appearance of new species— On their different rates of change— Species once lost do not reappear— Groups of species follow the same general rules in their appearance and disappearance as do single species— On
On simultaneous changes in the forms of life throughout the world— On the affinities of extinct species to each other and to living species— On the state of development of ancient forms— On the succession of the same types within the same areas— Summary of preceding and present
|
| LET us now see whether the several facts and
relating to the geological succession of organic
accord
the common view of the immutability of species, or with that of their slow and gradual modification, through
and natural selection. |
|
| New species have appeared very slowly, one after another, both on the land and in the waters. Lyell has shown that it is hardly possible to resist the evidence on this head in the case of the several tertiary stages; and every year tends to fill up the blanks between
and to make the
→percentage system of
lost and
forms more gradual. In some of the most recent beds, though undoubtedly of high antiquity if measured by years, only one or two species are
and only one or two are
having
for the first time, either locally, or, as far as we know, on the face of the earth. If we may trust the observations of Philippi in Sicily, the successive changes in the marine inhabitants of that island have been many and most gradual. The secondary formations are more broken; but, as Bronn has remarked, neither the appearance
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