| → points of structure. 1859 1860 1861 |
| respects. 1866 1869 1872 |
|
| → be compelled to 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| ↑ 1 blocks not present in 1859 1860; present in 1861 1866 1869 1872 |
| Look again at the later tertiary deposits, which include many shells believed by the majority of naturalists to be identical with existing species; but some excellent naturalists, as Agassiz and Pictet, maintain that all these tertiary species are specifically distinct, though the distinction is admitted to be very slight; so that here, unless we believe that these eminent naturalists have been misled by their imaginations
and that these late tertiary species really present no difference whatever from their living representatives, or unless we believe that the great majority of naturalists are wrong and that the
tertiary species are all truly distinct from the recent, we have evidence of a very general
slight modification
of form of
the kind required.
|
|
| → namely, 1859 1860 |
| of time, namely, 1861 1866 1869 1872 |
|
| → but to this subject I shall have to return 1859 1860 |
| so that here again we have undoubted evidence of change, though not strictly of variation, 1861 1866 |
| so that here again we have undoubted evidence of change 1869 1872 |
|
| → following 1859 1860 |
| direction required by my theory; but to this latter subject I shall have to return in the following 1861 1866 |
| direction required by the theory; but to this latter subject I shall have to return in the following 1869 |
| direction required by the theory; but to this latter subject I shall return in the following 1872 |
|
| → One other consideration is worth notice: 1859 1860 1861 |
| OMIT 1866 1869 1872 |
|
|
of B and C, and yet
not
necessarily be strictly intermediate between them in all
→points of structure. So that we might obtain the parent-species and its several modified descendants from the lower and upper beds of
formation, and unless we obtained numerous transitional gradations, we should not recognise their
and should consequently
→be compelled to
rank them
as distinct species. |
|
| It is notorious on what excessively slight differences many palæontologists have founded their species; and they do this the more readily if the specimens come from different sub-stages of the same formation. Some experienced conchologists are now sinking many of the very fine species of
and others into the rank of varieties; and on this view we do find the kind of evidence of change which on
theory we ought to find. ↑
we look to rather wider
→namely,
to distinct but consecutive stages of the same great formation, we find that the embedded fossils, though
universally ranked as specifically different, yet are far more closely
to each other than are the species found in more widely separated formations;
→but to this subject I shall have to return
in the
→following
chapter. |
|
|
→One other consideration is worth notice:
animals and plants that
propagate rapidly and
not
there is reason to suspect, as we have formerly seen, that their varieties are generally at first local; and that such local varieties do not spread widely and supplant their parent-forms until they have been modified and perfected in some considerable degree. According to this view, the chance of discovering in a formation in any one country all the early stages of transition between any two
is small, for the successive changes are supposed to have been local or
|
