| → Knight. 1859 1860 1861 1866 1869 |
| Knight, and Kölreuter. 1872 |
|
| → showing, 1859 1860 1861 1866 1869 |
| and made so many experiments, showing, 1872 |
|
| → (utterly ignorant though we be of the meaning of the law) 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → intervals— 1859 1860 1861 1866 |
| intervals of time— 1869 1872 |
|
|
suggested by
→Knight. We shall presently see its importance; but I must here treat the subject with extreme brevity, though I have the materials prepared for an ample discussion. All vertebrate animals, all insects, and some other large groups of animals, pair for each birth. Modern research has much diminished the number of supposed hermaphrodites, and of real hermaphrodites a large number pair; that is, two individuals regularly unite for reproduction, which is all that concerns us. But still there are many hermaphrodite animals which certainly do not habitually pair, and a vast majority of plants are hermaphrodites. What reason, it may be asked, is there for supposing in these cases that two individuals ever concur in reproduction? As it is impossible here to enter on details, I must trust to some general considerations alone. |
|
| In the first place, I have collected so large a body of facts,
→showing,
in accordance with the almost universal belief of breeders, that with animals and plants a cross between different varieties, or between individuals of the same variety but of another strain, gives vigour and fertility to the offspring; and on the other hand, that
close
interbreeding diminishes vigour and fertility; that these facts alone incline me to believe that it is a general law of nature
→(utterly ignorant though we be of the meaning of the law)
that no organic being
itself for
of generations; but that a cross with another individual is occasionally— perhaps at
long
→intervals—
indispensable. |
|
| On the belief that this is a law of nature, we can, I think, understand several large classes of facts, such as the following, which on any other view are inexplicable. Every hybridizer knows how unfavourable exposure to wet is to the fertilisation of a flower, yet what a multitude of flowers have their anthers and stigmas fully
|
