| → natural and artificial, 1859 1860 1861 |
| those naturally and those artificially produced, 1866 1869 1872 |
|
| → is probably 1859 1860 1861 |
| has at some periods probably been 1866 1869 1872 |
|
| → the number of species has 1859 1860 1861 |
| species have 1866 1869 1872 |
|
|
agency. I may repeat what I published in 1845, namely, that to admit that species generally become rare before they become extinct— to feel no surprise at the rarity of a species, and yet to marvel greatly when
ceases to exist, is much the same as to admit that sickness in the individual is the forerunner of death— to feel no surprise at sickness,
when the sick man dies, to wonder and to suspect that he died by some
deed of violence. |
|
| The theory of natural selection is grounded on the belief that each new variety, and ultimately each new species, is produced and maintained by having some advantage over those with which it comes into
and the consequent extinction of
forms almost inevitably follows. It is the same with our domestic
when a new and slightly improved variety has been raised, it at first
the less improved varieties in the same neighbourhood; when much improved it is transported far and near, like our short-horn cattle, and takes the place of other breeds in other countries. Thus the appearance of new forms and the disappearance of old forms, both
→natural and artificial,
are bound together. In
flourishing groups, the number of new specific forms which have been produced within a given time
→is probably
greater than
of the old
which have been exterminated; but we know that
→the number of species has
not gone on indefinitely increasing, at least during the later geological
so
looking to later
we may believe that the production of new forms has caused the extinction of about the same number of old forms. |
|
| The competition will generally be most severe, as formerly explained and illustrated by examples, between the forms which are most like each other in all respects.
|
