| → C. livia, whether 1866 1869 1872 |
| whether 1859 1860 |
| (C. livia), whether 1861 |
|
| → ever existed directly intermediate between them, 1859 1860 1861 1866 1869 |
| directly intermediate between them ever existed, 1872 |
|
|
two breeds, moreover, have become so much modified,
if we had no historical or indirect evidence regarding their origin, it would not have been possible to have
from a mere comparison of their structure with that of the
→C. livia, whether
they had descended from this species or from some other allied
such as C. oenas. |
|
| So with natural species, if we look to forms very distinct, for instance to the horse and tapir, we have no reason to suppose that links
→ever existed directly intermediate between them,
but between each and an unknown common parent. The common parent will have had in its whole organisation much general resemblance to the tapir and to the horse; but in some points of structure may have differed considerably from both, even perhaps more than they differ from each other.
in all such cases, we should be unable to recognise the parent-form of any two or more species, even if we closely compared the structure of the parent with that of its modified descendants, unless at the same time we had a nearly perfect chain of the intermediate links. |
|
| It is just possible by
theory, that one of two living forms might have descended from the other; for instance, a horse from a tapir; and in this case
intermediate links will have existed between them. But such a case would imply that one form had remained for a very long period unaltered, whilst its descendants had undergone a vast amount of change; and the principle of competition between organism and organism, between child and parent, will render this a very rare event; for in all cases the new and improved forms of life
tend to supplant the old and unimproved forms. |
|
| By the theory of natural selection all living species
|
