Comparison with 1861 |
|
geological ages, that we
only see only see 1859 1860 1861 1866 | see only 1869 1872 |
that the forms of life are now different from what they formerly were. |
|
In order that any great amount of modification
should thus in the course of time be produced, it is necessary to believe that when should thus in the course of time be produced, it is necessary to believe that when 1861 1866 |
in any part should be effected, 1869 |
should be effected in a species, 1872 |
a variety
has has 1861 1866 | when 1869 1872 |
once
arisen, it again varies, after perhaps arisen, it again varies, after perhaps 1861 1866 |
formed must again, perhaps after 1869 1872 |
a long interval of
time; time; 1861 1866 | time, 1869 1872 |
and that its varieties, if favourable, are and that its varieties, if favourable, are 1861 1866 |
vary or present individual differences of the same favourable nature, and these must be 1869 |
vary or present individual differences of the same favourable nature as before; and these must be 1872 |
again preserved, and so
onwards. onwards. 1861 1866 |
onwards step by step. 1869 1872 |
↑2 blocks not present in 1859 1860 1861 1866; present in 1869 1872 | Seeing that individual differences of all
kinds
perpetually recur, this can hardly be considered as an unwarrantable assumption.
But whether all this has actually taken place must be judged by
how far the hypothesis accords with and explains the general phenomena of nature.
|
That varieties more or less different from the parent-stock occasionally arise, few will deny; but that the process of variation should be thus indefinitely prolonged is an assumption, the truth of which must be judged of by how far the hypothesis accords with and explains the general phenomena of nature. ↑1 blocks not present in 1859 1860 1861 1869; present in 1866 1872 | On the other hand, the general phenomena of nature.
|
On the other hand, the ordinary belief that the amount of possible variation is a strictly limited quantity is
likewise likewise 1861 1866 | likewise 1869 |
a simple assumption. |
|
Although natural selection can act only through and for the good of each being, yet characters and structures, which we are apt to consider as of very trifling importance, may thus be acted on. When we see leaf-eating insects green, and bark-feeders mottled-grey; the alpine ptarmigan white in winter, the red-grouse the colour of heather,
and the black-grouse that of peaty earth, and the black-grouse that of peaty earth, 1859 1860 1861 1866 |
OMIT 1869 1872 |
we must believe that these tints are of service to these birds and insects in preserving them from danger. Grouse, if not destroyed at some period of their lives, would increase in countless numbers; they are known to suffer largely from birds of prey; and hawks are guided by eyesight to their prey,—
so much so, that on parts of the Continent persons are warned not to keep white pigeons, as being the most liable to destruction. Hence
I can see no reason to doubt that I can see no reason to doubt that 1859 1860 1861 1866 |
OMIT 1869 1872 |
natural selection might be most
effective in giving the proper colour to each kind of grouse, and in keeping that colour, when once acquired, true and constant. Nor ought we to think that the occasional destruction of an animal of any particular colour would produce little effect: we should remember
|
geological ages, that we
see only see only 1869 1872 | only see 1859 1860 1861 1866 |
that the forms of life are now different from what they formerly were. |
|
In order that any great amount of modification
in any part should be effected, in any part should be effected, 1869 |
should thus in the course of time be produced, it is necessary to believe that when 1861 1866 |
should be effected in a species, 1872 |
a variety
when when 1869 1872 | has 1861 1866 |
once
formed must again, perhaps after formed must again, perhaps after 1869 1872 |
arisen, it again varies, after perhaps 1861 1866 |
a long interval of
time, time, 1869 1872 | time; 1861 1866 |
vary or present individual differences of the same favourable nature, and these must be vary or present individual differences of the same favourable nature, and these must be 1869 |
and that its varieties, if favourable, are 1861 1866 |
vary or present individual differences of the same favourable nature as before; and these must be 1872 |
again preserved, and so
onwards step by step. onwards step by step. 1869 1872 |
onwards. 1861 1866 |
Seeing that individual differences of
all
kinds
perpetually recur, this can hardly be considered as an unwarrantable assumption. But whether
all this has actually taken place must be judged by all this has actually taken place must be judged by 1869 |
it is true, we can judge only by seeing 1872 |
how far the hypothesis accords with and explains the general phenomena of nature. ↑1 blocks not present in 1859 1860 1869 1872; present in 1861 1866 | That varieties more or less different from the parent-stock occasionally arise, few will deny; but that the process of variation should be thus indefinitely prolonged is an assumption, the truth of which must be judged of by how far the hypothesis accords with and explains the general phenomena of nature.
|
On the other hand, the ordinary belief that the amount of possible variation is a strictly limited quantity is
....... 1869 | likewise 1861 1866 |
a simple assumption. |
|
Although natural selection can act only through and for the good of each being, yet characters and structures, which we are apt to consider as of very trifling importance, may thus be acted on. When we see leaf-eating insects green, and bark-feeders mottled-grey; the alpine ptarmigan white in winter, the red-grouse the colour of heather,
...OMIT 1869 1872 |
and the black-grouse that of peaty earth, 1859 1860 1861 1866 |
we must believe that these tints are of service to these birds and insects in preserving them from danger. Grouse, if not destroyed at some period of their lives, would increase in countless numbers; they are known to suffer largely from birds of prey; and hawks are guided by eyesight to their
prey— prey— 1860 1861 1866 1869 1872 | prey,— 1859 |
so much so, that on parts of the Continent persons are warned not to keep white pigeons, as being the most liable to destruction. Hence
...OMIT 1869 1872 |
I can see no reason to doubt that 1859 1860 1861 1866 |
natural selection might be
most most 1859 1860 1861 1866 1869 | most 1872 |
effective in giving the proper colour to each kind of grouse, and in keeping that colour, when once acquired, true and constant. Nor ought we to think that the occasional destruction of an animal of any particular colour would produce little effect: we should remember
|