| → species. Seeing this difference in the process of selection, as carried on by man and nature, we need not be surprised at some difference in the result. 1861 |
| species. 1859 1860 1866 |
|
| ↑ 1 blocks not present in 1861 1869 1872; present in 1859 1860 1866 |
| Seeing this difference in the process of selection, as carried on by man and nature, we need not be surprised at some difference in the result.
|
|
| → is 1861 1866 1869 1872 |
| seems to me 1859 1860 |
|
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unconscious power of selection, for his own use and pleasure: he neither wishes to select, nor could select, slight differences in the reproductive system, or other constitutional differences correlated with the reproductive system. Domestic productions are less closely adapted to climate and to the other physical conditions of the countries which they inhabit than are those in a state of nature, for they can generally be removed to other and differently constituted countries with
impunity.
supplies his several varieties with the same food;
them in nearly the same
and does not wish to alter their general habits of life. Nature acts uniformly and slowly during vast periods of time on the whole organisation, in any way which may be for each creature's own good; and thus she may, either directly, or more probably indirectly, through correlation, modify the reproductive
the several descendants from any one
→species. Seeing this difference in the process of selection, as carried on by man and nature, we need not be surprised at some difference in the result.
↑
|
|
| I have as yet spoken as if the varieties of the same species were
fertile when intercrossed. But it
→is
impossible to resist the evidence of the existence of a certain amount of sterility in the few following cases, which I will briefly abstract. The evidence is at least as good as that from which we believe in the sterility of a multitude of species. The evidence is, also, derived from hostile witnesses, who in all other cases consider fertility and sterility as safe criterions of specific distinction. Gärtner kept during several years a dwarf kind of maize with yellow seeds, and a tall variety with red
growing near each other in his garden; and although these plants have separated sexes, they never naturally crossed. He then fertilised
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