| Comparison with 1860 |
|
|
yet are far more closely allied
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:
with
animals and plants that can
propagate rapidly and are
not highly locomotive,
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 forms,
is small, for the successive changes are supposed to have been local or 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
with shells and other marine animals, it is probably
those which have
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
geological formation. ↑| 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 | | 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.
|
|
|
| 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 have been
collected from many places; and in the case of
fossil species this could
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
|
yet are far more closely
allied | allied 1859 1860 | | related 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: | One other consideration is worth notice: 1859 1860 1861 |
| OMIT 1866 1869 1872 |
| with 1859 1860 1861 | | With 1866 1869 1872 |
| can 1859 1860 1861 | can 1866 1869 1872 |
| are 1859 1860 1861 | | do 1866 1869 1872 |
| highly locomotive, 1859 1860 1861 | | wander much, 1866 1869 1872 |
| forms, 1859 1860 1861 1872 | | such forms, 1866 1869 |
| that 1859 1860 1861 | | that, 1866 1869 1872 |
| probably 1859 1860 |
| highly probable that 1861 1866 |
| probable 1869 1872 |
| those which have 1859 1860 1861 1866 |
| that those which have 1869 |
| that those which 1872 |
| which 1859 1860 | which 1861 1866 1869 1872 |
| one 1859 1860 1866 1869 1872 | | ony 1861 |
| 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 | | 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.
|
|
|
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 1859 1860 | | varieties, 1861 1866 1869 1872 |
| have been 1859 1860 1861 1866 | | are 1869 1872 |
| in the case of 1859 1860 1861 1866 1869 |
| with 1872 |
| could 1859 1860 1861 1866 | | can 1869 1872 |
| effected by palæontologists. 1859 1860 1861 1866 1869 |
| done. 1872 |
| numerous, 1859 1860 1872 | | numerous 1861 1866 1869 |
| intermediate, 1859 1860 1872 | | intermediate 1861 1866 1869 |
|
