| → irregular. 1859 1860 1861 |
| irregular, nor that it goes on continuously; it is far more probable that each form remains for long periods unaltered, and then again undergoes modification. 1866 1869 1872 |
|
| ↑ 1 blocks not present in 1859 1860 1861 1866; present in 1869 1872 |
| Nor do I suppose that the most divergent varieties are invariably preserved:
a medium form may often long endure, and may or may not produce more than one modified descendant; for natural selection will always act according to the nature of the places which are either unoccupied or not perfectly occupied by other beings; and this will depend on infinitely complex relations.
|
|
| → I am far from thinking 1859 1860 1861 |
| Nor do I suppose 1866 |
|
| → prevail and multiply: 1859 1860 1861 |
| preserved: 1866 |
|
| → I do not doubt that 1859 1860 1861 1866 1869 |
| no doubt 1872 |
|
|
the diagram, though in itself made somewhat
→irregular.
↑ →I am far from thinking
that the most divergent varieties
invariably
→prevail and multiply:
a medium form may often long endure, and may or may not produce more than one modified descendant; for natural selection will always act according to the nature of the places which are either unoccupied or not perfectly occupied by other beings; and this will depend on infinitely complex relations. But as a general rule, the more diversified in structure the descendants from any one species can be rendered, the more places they will be enabled to seize on, and the more their modified progeny will
In our diagram the line of succession is broken at regular intervals by small numbered letters marking the successive forms which have become sufficiently distinct to be recorded as varieties. But these breaks are imaginary, and might have been inserted
after intervals long enough to
the accumulation of a considerable amount of divergent variation. |
|
| As all the modified descendants from a common and widely-diffused species, belonging to a large genus, will tend to partake of the same advantages which made their parent successful in life, they will generally go on multiplying in number as well as diverging in character: this is represented in the diagram by the several divergent branches proceeding from (A). The modified offspring from the later and more highly improved branches in the lines of descent, will, it is probable, often take the place of, and so destroy, the earlier and less improved branches: this is represented in the diagram by some of the lower branches not reaching to the upper horizontal lines. In some cases
→I do not doubt that
the process of modification will be confined to a single line of descent, and the number of
|
