seed, tubers, &c., from one soil or climate to another, and back again. During the convalescence of animals,
we plainly see that | we plainly see that 1859 1860 1861 1866 |
| OMIT 1869 1872 |
| the 1859 1860 1861 1866 1869 | | their 1872 |
| abundant 1859 1860 1861 1866 1869 | | the clearest 1872 |
| evidence 1861 1866 1869 1872 | | evidence, 1859 1860 |
| very distinct 1859 1860 1861 1866 | very distinct 1869 1872 |
| that is between members of different strains or sub-breeds, 1859 1860 1861 1866 |
| which differ to a certain extent, 1869 1872 |
| offspring. 1859 1860 1861 1866 |
| offspring; and that close interbreeding continued during several generations between the nearest relations, especially if these be kept under the same conditions of life, almost always induces weakness and sterility. 1869 |
| offspring; 1872 |
| I believe, indeed, from the facts alluded to in our fourth chapter, that a certain amount of crossing is indispensable even with hermaphrodites; 1859 1860 1861 1866 |
| OMIT 1872 |
| interbreeding 1859 1860 1866 1872 | | inter-breeding 1861 |
| especially 1859 1860 1861 1866 | especially 1872 |
| always induces weakness and sterility in the progeny. 1859 1860 1861 1866 |
| almost always leads to decreased size, weakness, or sterility. 1872 |
|
Hence it seems that, on the one hand, slight changes in the conditions of life benefit all organic beings, and on the other hand, that slight crosses, that is crosses between the males and females of the same
species | species 1859 1860 1861 1866 | | species, 1869 1872 |
| varied and become 1859 1860 1861 1866 1869 |
| been subjected to 1872 |
| different, 1859 1860 1861 1866 1869 | | different 1872 |
| give 1859 1860 1861 1866 1869 |
| conditions, or which have slightly varied, give 1872 |
| But 1859 1860 1861 1866 1869 | | But, 1872 |
| we 1859 1860 1861 1866 1869 | | as we 1872 |
| seen 1859 1860 1861 1866 1869 | | seen, 1872 |
| that greater changes, or changes of a particular nature, often render 1859 1860 1861 1866 1869 |
| OMIT 1872 |
| in some degree 1859 1860 1861 1866 1869 |
| long habituated to certain uniform conditions under a state of nature, when subjected, as under confinement, to a considerable change in their conditions, very frequently are rendered more or less 1872 |
| that greater crosses, that is 1859 1860 1861 1866 1869 |
| we know that a 1872 |
| crosses 1859 1860 1861 1866 1869 | | cross 1872 |
| males and females which 1859 1860 1861 1866 1869 |
| two forms, that 1872 |
| generally sterile 1859 1860 1861 1866 1869 | | almost always 1872 |
| degree. 1859 1860 1861 1866 1869 | | degree sterile. 1872 |
| cannot persuade myself 1859 1860 1861 1866 1869 |
| am fully persuaded 1872 |
| parallelism is 1859 1860 1861 1866 1869 |
| double parallelism is by no means 1872 |
| 3 blocks not present in 1859 1860 1861 1866 1869; present in 1872 | | He who is able to explain why the elephant and a multitude of other animals are incapable of breeding when kept under only partial confinement in their native country, will be able to explain the primary cause of hybrids being so generally sterile.
He will at the same time be able to explain how it is that the races of some of our domesticated animals, which have often been subjected to new and not uniform conditions, are quite fertile together, although they are descended from distinct species, which would probably have been sterile if aboriginally crossed.
The above two parallel series of facts seem to be connected together by some common but unknown bond, which is essentially related to the principle of life; this principle, according to Mr. Herbert Spencer, being that life depends on, or consists in, the incessant action and reaction of various forces, which, as throughout nature, are always tending towards an equilibrium; and when this tendency is slightly disturbed by any change, the vital forces gain in power.
|
| life; this principle apparently being that life, as Mr. Herbert Spencer has remarked, depends on, or consists in, the incessant action and reaction of various forces, which, as throughout nature, are always tending towards an equilibrium; and when this ten- dency is slightly disturbed by any change, the vital forces apparently gain in power. 1866 |
| life. 1859 1860 1861 |
| life; this principle apparently being that life, as Mr. Herbert Spencer has remarked, depends on, or consists in, the incessant action and reaction of various forces, which, as throughout nature, are always tending towards an equilibrium; and when this tendency is slightly disturbed by any change, the vital forces apparently gain in power. 1869 |
|
