| → in imagination adapt 1859 1860 1861 1866 |
| take 1869 1872 |
|
| → a 1859 1860 1861 1866 1869 |
| it is a 1872 |
|
| → as I believe, is 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| → on my theory 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
|
the same rule will probably apply to both; and if we
→in imagination adapt
a varying species
a very large area, we shall have to adapt two varieties to two large areas, and a third variety to a narrow intermediate zone. The intermediate variety, consequently, will exist in lesser numbers from inhabiting a narrow and lesser area; and practically, as far as I can make out, this rule holds good with varieties in a state of nature. I have met with striking instances of the rule in the case of varieties intermediate between well-marked varieties in the genus Balanus. And it would appear from information given me by Mr. Watson, Dr. Asa Gray, and Mr. Wollaston, that
when varieties intermediate between two other forms occur, they are much rarer numerically than the forms which they
Now, if we may trust these facts and inferences, and
conclude that varieties linking two other varieties together
existed in lesser numbers than the forms which they connect,
we can understand why intermediate varieties should not endure for very long
as a general
they should be exterminated and disappear, sooner than the forms which they originally linked together. |
|
| For any form existing in lesser numbers would, as already remarked, run a greater chance of being exterminated than one existing in large numbers; and in this particular case the intermediate form would be eminently liable to the inroads of
forms existing on both sides of it. But
→a
far more important consideration,
→as I believe, is
during the process of further modification, by which two varieties are supposed
→on my theory
to be converted and perfected into two distinct species, the two which exist in larger
from inhabiting larger areas, will have a great advantage over the intermediate variety, which exists
|
