Assertion: natural selection | /r/HasProperty | effective
Facets:
value: in keeping that colour
type: OTHER
Source sentences:
text: Hence 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.
text: Hence 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.