| → OMIT 1869 1872 |
| in most cases 1859 1860 1861 1866 |
|
| → which 1869 1872 |
| and therefore we might expect that such variability 1859 1860 1861 1866 |
|
| → would augment 1872 |
| be super-added to 1859 1861 |
| be superadded to 1860 1866 |
| be added to 1869 |
|
| → OMIT 1869 1872 |
| cross or in the first 1859 1860 1861 1866 |
|
| → that in 1872 |
| their extreme variability in 1859 1860 1861 1866 |
| OMIT 1869 |
|
| → of one of 1869 1872 |
| on 1859 1860 1861 1866 |
|
| → OMIT 1869 1872 |
| it is due to 1859 1860 1861 1866 |
|
| → fails under these circumstances to perform 1869 1872 |
| being thus often rendered either impotent or at least incapable of 1859 1860 1861 1866 |
|
| → closely similar in all respects to 1872 |
| identical with 1859 1860 1861 1866 |
| identical in all respects with 1869 |
|
| → degrees and kinds of resemblance 1866 1869 1872 |
| resemblance 1859 1860 1861 |
|
| → So I believe it to be with varieties of plants; and with 1872 |
| With 1859 1860 1861 1866 1869 |
|
|
tried on natural varieties), and this implies
→OMIT
that there has been recent
→which
would often continue and
→would augment
that arising from the
act of crossing. The slight
of
in
the first
→OMIT
generation, in contrast with
→that in
the succeeding generations, is a curious fact and deserves attention. For it bears on
the view which I have taken
→of one of
the
of ordinary
namely, that
→OMIT
the reproductive system
eminently sensitive to
conditions of life,
→fails under these circumstances to perform
its proper function of producing offspring
→closely similar in all respects to
the parent-form. Now hybrids in the first generation are descended from species (excluding those
which have not had their reproductive systems in any way affected, and they are not variable; but hybrids themselves have their reproductive systems seriously affected, and their descendants are highly variable. |
|
| But to return to our comparison of mongrels and hybrids: Gärtner states that mongrels are more liable than hybrids to revert to either parent-form; but this, if it be true, is certainly only a difference in degree. Moreover, Gärtner expressly states that hybrids from
plants are more subject to reversion than hybrids from species in their natural state; and this probably explains the singular difference in the results arrived at by different observers: thus, Max Wichura doubts whether hybrids ever revert to their
and he experimented on uncultivated species of willows; whilst Naudin, on the other hand, insists in the strongest terms on the almost universal tendency to reversion in hybrids, and he experimented chiefly on cultivated plants. Gärtner further
that when any two species, although most closely allied to each other, are crossed with a third species, the hybrids are widely different from each other;
if two very distinct varieties of one species are crossed with another species, the hybrids do not differ much. But this conclusion, as far as I can make out, is founded on a single experiment; and seems directly opposed to the results of several experiments made by Kölreuter. |
|
|
alone are the unimportant
which Gärtner is able to point
between hybrid and mongrel plants. On the other hand, the
→degrees and kinds of resemblance
in mongrels and in hybrids to their respective parents, more especially in hybrids produced from nearly related species,
according to Gärtner the same laws. When two species are crossed, one has sometimes a prepotent power of impressing its likeness on the
→So I believe it to be with varieties of plants; and with
animals one variety certainly often has this prepotent power over another variety.
|
