| → on an average, most varieties. 1861 1866 1869 1872 |
| most varieties or incipient species. 1859 1860 |
|
| → long-continued 1859 1860 1861 1866 1872 |
| long - continued 1869 |
|
| → has 1869 1872 |
| may readily have 1859 1860 1861 1866 |
|
| → we have reason to believe that it 1872 |
| it 1859 1860 1861 1866 1869 |
|
| → of beneficial differences which has 1872 |
| through natural selection, of such differences, when beneficial to the individual, that 1859 1860 1861 1866 |
| through natural selection, of beneficial differences that has 1869 |
|
| → the more important 1859 1860 1861 1866 1872 |
| those 1869 |
|
| → in relation to the habits of each species. 1872 |
| by which the innumerable beings on the face of this earth are enabled to struggle with each other, and the best adapted to survive. 1859 1860 1861 1866 |
| which are the most important for the welfare of each species. 1869 |
|
| →on an average, most varieties. Secondary sexual characters are highly variable, and such characters differ much in the species of the same group. Variability in the same parts of the organisation has generally been taken advantage of in giving secondary sexual differences to the
of the same species, and specific differences to the several species of the same genus. Any part or organ developed to an extraordinary size or in an extraordinary manner, in comparison with the same part or organ in the allied species, must have gone through an extraordinary amount of modification since the genus arose; and thus we can understand why it should often still be variable in a much higher degree than other parts; for variation is a
→long-continued
and slow process, and natural selection will in such cases not as yet have had time to overcome the tendency to further variability and to reversion to a less modified state. But when a species with any extraordinarily-developed organ has become the parent of many modified
which on
view must be a very slow process, requiring a long
of
in this case, natural selection
→has
succeeded in giving a fixed character to the organ, in however extraordinary a manner it may
developed. Species inheriting nearly the same constitution from a common
and exposed to similar
naturally tend to present analogous variations,
these same species may occasionally revert to some of the characters of their ancient progenitors. Although new and important modifications may not arise from reversion and analogous
such modifications will add to the beautiful and harmonious diversity of nature. |
|
| Whatever the cause may be of each slight difference
the offspring
their
and a cause for each must
→we have reason to believe that it
is the steady
→of beneficial differences which has
rise to all
→the more important
modifications of
→in relation to the habits of each species.
|
