| → by the parasitic habits 1859 1860 1861 1866 1869 |
| would be a decided advantage to each successive individual 1872 |
|
| → Proteolepas, though effected by slow steps, would be a decided advantage to each successive individual of the 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| → in reducing and saving every 1859 1860 1861 1866 1869 |
| to reduce any 1872 |
|
| → is rendered 1859 1860 1861 1866 1869 |
| becomes, through changed habits, 1872 |
|
| → superfluous, 1859 1860 1861 1872 |
| by changed habits of life superfluous, 1866 1869 |
|
| ←Subtitle not present 1859 1860 1861 Multiple,
Rudimentary,
and
Lowly-organised
Structures
are
Variable
.
1866 1869 1872 |
| → structure of the 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| → number of the 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
|
instances could be given: namely, that when a cirripede is parasitic within another
is thus protected, it loses more or less completely
own shell or carapace. This is the case with the male Ibla, and in a truly extraordinary manner with the Proteolepas: for the carapace in all other cirripedes consists of the three highly-important anterior segments of the head enormously developed, and furnished with great nerves and muscles; but in the parasitic and protected Proteolepas, the whole anterior part of the head is reduced to the merest rudiment attached to the bases of the prehensile antennæ. Now the saving of a large and complex structure, when rendered
→by the parasitic habits
of the
→Proteolepas, though effected by slow steps, would be a decided advantage to each successive individual of the
species; for in the struggle for life to which every animal is exposed, each
would have a better chance of supporting itself, by less nutriment being
|
|
| Thus, as I believe, natural selection will
in the long run
→in reducing and saving every
part of the organisation, as soon as it
→is rendered
→superfluous,
without by any means causing some other part to be largely developed in a corresponding degree. And, conversely, that natural selection may perfectly well succeed in largely developing
without requiring as a necessary compensation the reduction of some adjoining part. →
|
| It seems to be a rule, as remarked by Is. Geoffroy St. Hilaire, both
varieties and
species, that when any part or organ is repeated many times in the
→structure of the
same individual (as the vertebræ in snakes, and the stamens in polyandrous flowers) the number is variable; whereas the
→number of the
same part or organ, when it occurs in lesser numbers, is constant. The same
|
