live on the
land; land; 1860 1861 1866 1869 1872 | land, 1859 |
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
the inhabitants the inhabitants 1869 1872 | inhabitants 1859 1860 1861 1866 |
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? |
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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
transitional transitional 1859 1869 1872 | tran- sitional 1860 1861 1866 |
grades of the structure will seldom
exist at exist at 1869 |
continue to exist to 1859 1860 1861 1866 |
have survived to 1872 |
the present day, for they will have been supplanted by
their successors, which were gradually rendered more their successors, which were gradually rendered more 1869 1872 |
the very process of 1859 1860 1861 1866 |
perfect perfect 1869 1872 | perfection 1859 1860 1861 1866 |
through natural selection. Furthermore, we may conclude that
transitional transitional 1860 1861 1866 1869 1872 | transi- tional 1859 |
states states 1869 1872 | grades 1859 1860 1861 1866 |
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
flying-fish, flying-fish, 1859 1860 1861 1869 1872 | flying-fish; 1866 |
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 had come to a high stage of perfection, so as to have given them a decided advantage over other animals in the battle for life. Hence the chance of discovering species with transitional grades of structure in a fossil condition will always be less, from their having existed in lesser numbers, than in the case of species with fully developed structures. |
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I will now give two or three instances
of of 1859 1860 1861 1866 1869 | both of 1872 |
diversified and of changed habits in the individuals of the same
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