| → distinct 1859 1860 1861 1866 |
| new and distinct 1869 |
| new, though closely allied 1872 |
|
| → plainly leads to the 1861 1866 1869 1872 |
| leads me to 1859 1860 |
|
| → which 1859 1860 1861 |
| though only some of them, which 1866 1869 1872 |
|
| → and as they would be found embedded in slightly different sub-stages of the same formation, they 1861 1866 1869 1872 |
| they 1859 1860 |
|
|
great period of subsidence over the whole or part of the archipelago, together with a contemporaneous accumulation of sediment, would
the average duration of the same specific forms; and these contingencies are indispensable for the preservation of all the transitional gradations between any two or more species. If such gradations were not
preserved, transitional varieties would merely appear as so many
→distinct
species. It
probable that each great period of subsidence would be interrupted by oscillations of level, and that slight climatal changes would intervene during such lengthy periods; and in these cases the inhabitants of the archipelago would
migrate, and no closely consecutive record of their modifications could be preserved in any one formation. |
|
| Very many of the marine inhabitants of the archipelago now range thousands of miles beyond its confines; and analogy
→plainly leads to the
that it would be chiefly these far-ranging
→which
would oftenest produce new varieties; and the varieties would at first
be local or confined to one place, but if possessed of any decided advantage, or when further modified and improved, they would slowly spread and supplant their parent-forms. When such varieties returned to their ancient homes, as they would differ from their former
in a nearly uniform, though perhaps extremely slight degree,
→and as they would be found embedded in slightly different sub-stages of the same formation, they
would, according to the principles followed by many palæontologists, be ranked as new and distinct species. |
|
| If
there be some degree of truth in these remarks, we have no right to expect to
in our geological formations, an infinite number of those fine transitional
on
have
|
