by the selection of mere external differences, and
not of differences in the reproductive system. | not of differences in the reproductive system. 1859 1860 1861 1866 |
| that they have not been long exposed to uniform conditions of life. 1869 1872 |
| 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 | | Nor
should it
be forgotten
that long-continued domestication apparently
tends to eliminate sterility, and is therefore little likely to induce this same quality.
|
| In 1859 1860 1861 |
| Excluding the subject of fertility, in 1866 |
| respects, 1859 1860 1861 | | respects 1866 |
| excluding fertility, 1859 1860 1861 | excluding fertility, 1866 |
| close 1859 1860 1861 | | closest 1866 |
| the facts briefly 1859 1860 |
| although we are profoundly ignorant in every case of the precise cause of sterility, the facts briefly 1861 |
| although we are profoundly ignorant in every case of the precise cause of the sterility of first crosses and of hybrids, the facts briefly 1866 |
| although we are profoundly ignorant of the precise cause of the sterility of first crosses and of hybrids, the facts 1869 |
| although we are as ignorant of the precise cause of the sterility of first crosses and of hybrids as we are why animals and plants removed from their natural conditions become sterile, yet the facts 1872 |
| to, but even rather to support the view, that there is no fundamental distinction between species and varieties. 1859 1860 |
| to, but even rather to support in some respects the view, that there is no fundamental distinction between species and varieties. 1861 |
| to the view, that there is no fundamental distinction between species and varieties. 1866 |
| to the belief that varieties and species are not fundamentally different. 1869 |
| to the belief that species aboriginally existed as varieties. 1872 |
|
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