Origin of Species Variorum

Comparison with 1872

geological ages, that we only see that the forms of life are now different from what they formerly were.

In order that any great amount of modification should be effected in a species, a variety has once arisen, it again varies, after perhaps a long interval of time; vary or present individual differences of the same favourable nature as before; and these must be again preserved, and so onwards. Seeing that individual differences of the same kind perpetually recur, this can hardly be considered as an unwarrantable assumption. But whether it is true, we can judge only by seeing how far the hypothesis accords with and explains the general phenomena of nature. ↑ On the other hand, the general phenomena of nature.

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, 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 natural selection might be .. 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 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, a variety when once formed must again, perhaps after a long interval of time, vary or present individual differences of the same favourable nature, and these must be again preserved, and so onwards step by step. 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. ↑ On the other hand, the ordinary belief that the amount of possible variation is a strictly limited quantity is .. 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, ... 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 ... 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