| → have converted the animal 1872 |
| convert it 1859 1860 1861 1866 1869 |
|
| → certain bats in which 1872 |
| bats which have 1859 1860 1861 1866 |
| certain bats which have 1869 |
|
| → see 1859 1860 1861 1866 1872 |
| yet see actual 1869 |
|
| → OMIT 1872 |
| or were unknown, 1859 1860 1861 1866 1869 |
|
| → be the result of 1872 |
| have resulted from 1859 1860 1861 1866 1869 |
|
| → to show what diversified means of transition are at least 1872 |
| at least, to show what diversified means of transition are 1859 1860 1861 1866 1869 |
|
| → have survived to 1872 |
| continue to exist to 1859 1860 1861 1866 |
| exist at 1869 |
|
| → their successors, which were gradually rendered more 1869 1872 |
| the very process of 1859 1860 1861 1866 |
|
|
organs of flight are concerned, would
→have converted the animal
into a bat. In
→certain bats in which
the wing-membrane
from the top of the shoulder to the
the hind-legs, we perhaps
→see
traces of an apparatus originally
for gliding through the air rather than for flight. |
|
| If about a dozen genera of birds
become
→OMIT
who would have ventured to
that birds might have existed which used their wings solely as flappers, like the logger-headed duck (Micropterus of Eyton); as fins in the water and
on the land, like the penguin; as sails, like the ostrich; and functionally for no purpose, like the
Yet the structure of each of these birds is good for it, under the conditions of life to which it is exposed, for each has to live by a struggle; but it is not necessarily the best possible under all possible conditions. It must not be inferred from these remarks that any of the grades of wing-structure here alluded to, which perhaps may all
→be the result of
disuse, indicate the
steps by which birds
acquired their perfect power of flight; but they
→to show what diversified means of transition are at least
possible. |
|
| Seeing that a few members of such water-breathing classes as the Crustacea and Mollusca are adapted to live on the
and seeing that we have flying birds and mammals, flying insects of the most diversified types, and formerly had flying reptiles, it is conceivable that flying-fish, which now glide far through the air, slightly rising and turning by the aid of their fluttering fins, might have been modified into perfectly winged animals. If this had been effected, who would have ever imagined that in an early transitional state they had been
of the open ocean, and had used their incipient organs of flight exclusively, as far as we know, to escape being devoured by other fish? |
|
| When we see any structure highly perfected for any particular habit, as the wings of a bird for flight, we should bear in mind that animals displaying early
grades of the structure will seldom
→have survived to
the present day, for they will have been supplanted by
→their successors, which were gradually rendered more
through natural selection. Furthermore, we may conclude that
between structures fitted for very different habits of life will rarely have been developed at an early period in great numbers and under many subordinate forms. Thus, to return to our imaginary illustration of the
it does not seem probable that fishes capable of true flight would have been developed under many subordinate forms, for taking prey of many kinds in many ways, on the land and in the water, until their organs of flight
|
