| → than in other parts of their organisation; compare, for instance, 1859 1860 1861 1866 1869 |
| are strongly displayed, with 1872 |
|
| → males of gallinaceous birds, in which secondary sexual characters are strongly displayed, with the amount of difference between the females; and the truth of this proposition will be granted. 1869 |
| males of gallinaceous birds, in which secondary sexual characters are strongly displayed, with the amount of difference between their females; and the truth of this proposition will be granted. 1859 1860 1861 1866 |
| females. 1872 |
|
| → parts of the organisation; for secondary sexual characters have been 1859 1860 1861 1866 1869 |
| for they are 1872 |
|
| → their sexual characters, 1859 1860 1861 1866 1869 |
| these 1872 |
|
| → parts of their structure. 1859 1860 1861 1866 1869 |
| respects. 1872 |
|
| → two instances in illustration, the first 1869 |
| in illustration two instances, the first 1859 1860 1861 1866 |
| in illus- tration the two first instances 1872 |
|
|
secondary sexual
→than in other parts of their organisation; compare, for instance,
the amount of difference between the
→males of gallinaceous birds, in which secondary sexual characters are strongly displayed, with the amount of difference between the females; and the truth of this proposition will be granted. The cause of the original variability of
characters is not manifest; but we can see why
should not have been rendered as constant and uniform as
→parts of the organisation; for secondary sexual characters have been
accumulated by sexual selection, which is less rigid in its action than ordinary selection, as it does not entail death, but only gives fewer offspring to the less favoured males. Whatever the cause may be of the variability of secondary sexual characters, as they are highly variable, sexual selection will have had a wide scope for action, and may thus
have
in giving to the species of the same group a greater amount of difference in
→their sexual characters,
than in other
→parts of their structure.
|
|
| It is a remarkable fact, that the secondary
differences between the two sexes of the same species are generally displayed in the very same parts of the organisation in which the
species of the same genus differ from each other. Of this fact I will give
→two instances in illustration, the first
which happen to stand on my list; and as the differences in these cases are of a very unusual nature, the relation can hardly be accidental. The same number of joints in the tarsi is a character
common to very large groups of beetles, but in the Engidæ, as Westwood has remarked, the number varies greatly; and the number likewise differs in the two sexes of the same
in
hymenoptera, the
of
the
|
