| → may conclude 1869 1872 |
| are thus led to infer, as previously remarked, 1866 |
|
| → bond which 1869 1872 |
| law or bond 1866 |
|
| → with that 1869 1872 |
| and of first crosses, with the infertility 1866 |
|
| → offspring, and we are led to extend the same view to first crosses and hybrids; 1869 1872 |
| and hybrid offspring; 1866 |
|
| → except 1866 1869 |
| whatever, either in structure or in constitution, relatively to external conditions, and yet be sterile when united 1872 |
|
|
of the same species by the improper union of certain forms, whilst ordinary hybrids are produced from an improper union
so-called distinct species. We have also already seen that there is the closest similarity in all respects between first illegitimate unions and first crosses between distinct species.
will perhaps be made more fully apparent by an
we may suppose that a botanist found two well-marked varieties (and such occur) of the long-styled form of the trimorphic Lythrum salicaria, and that he determined to try by crossing whether they were specifically distinct. He would find that they yielded only about one-fifth of the proper number of seed, and that they behaved in all the other above specified respects as if they had been two distinct species. But to make the case sure, he would raise plants from his supposed hybridised seed, and he would find that the seedlings were miserably dwarfed and utterly sterile, and that they behaved in all other respects like ordinary hybrids. He might then maintain that he had actually proved, in accordance with the common view, that his two varieties were as good and as distinct species as any in the world; but he would be completely mistaken. |
|
| The facts now given on dimorphic and trimorphic plants are
because they show us,
that the physiological test of lessened fertility, both in first crosses and in hybrids, is no safe criterion of specific distinction; secondly, because we
→may conclude
that there
some unknown
→bond which
the infertility
of illegitimate unions
→with that
of their illegitimate
→offspring, and we are led to extend the same view to first crosses and hybrids;
thirdly, because we find, and this seems to me of especial
that two or three forms of the same species may exist and may differ in no
→except
|
