| → excepting in the first main divisions; 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → are 1859 1860 1861 1866 |
| and embryo, are 1869 1872 |
|
| ↑ 2 blocks not present in 1859 1860 1861 1866; present in 1869 1872 |
| So again in formerly discussing certain
morphological characters
which are not functionally
important, we have seen that they are often of the highest service in classification.
This depends on their constancy throughout many allied groups; and their
constancy chiefly depends
on any slight deviations not
having been preserved and accumulated by natural selection, which acts only on serviceable
characters.
|
|
|
Owen, in speaking of the dugong, says, "The generative
being those which are most remotely related to the habits and food of an animal, I have always regarded as affording very clear indications of its true affinities. We are least likely in the modifications of these organs to mistake a merely adaptive for an essential character."
how remarkable it is that the organs of vegetation, on which their
life
are of little
→excepting in the first main divisions;
whereas the organs of reproduction, with their product the
→are
of paramount importance! ↑
|
|
| We must not, therefore, in classifying, trust to resemblances in parts of the organisation, however important they may be for the welfare of the being in relation to the outer world. Perhaps from this cause it has partly arisen, that almost all naturalists lay the greatest stress on resemblances in organs of high vital or physiological importance. No doubt this view of the classificatory importance of organs which are important is generally, but by no means always, true. But their importance for classification, I believe, depends on their greater constancy throughout large groups of species; and this constancy depends on such organs having generally been subjected to less change in the adaptation of
species to their conditions of life. That the mere physiological importance of an organ does not determine its classificatory value, is almost
by the
fact, that in allied groups, in which the same organ, as we have every reason to suppose, has nearly the same physiological value, its classificatory value is widely different. No naturalist can have worked
any group without being struck with this fact; and it has been
fully acknowledged in the writings of almost every author. It will suffice to quote the highest authority, Robert Brown,
in speaking of certain organs in the
|
