| → monstrosities, or such 1861 |
| OMIT 1866 1869 1872 |
|
| → Monsters are very apt to be sterile; and 1861 |
| OMIT 1866 1869 1872 |
|
| → at least with animals, 1861 |
| OMIT 1866 1869 1872 |
|
| ↑ 3 blocks not present in 1859 1860 1861; present in 1866 1869 1872 |
| Under domestication monstrosities sometimes
occur which resemble
normal structures
in widely different animals. Thus pigs have occasionally
been born with a sort of proboscis,
and if any wild species
of the same genus
had naturally possessed a proboscis, it might have been argued that this had
appeared
as a monstrosity; but I have as yet failed
to find, after diligent search,
cases of monstrosities resembling
normal structures in nearly allied forms, and these alone bear on the question.
If monstrous forms of this kind ever do appear in a state of nature and are capable of reproduction
(which is not always the case), as they occur rarely and singly, their preservation would depend on unusually favourable circumstances.
|
|
| ↑ 1 blocks not present in 1859 1860 1861 1869 1872; present in 1866 |
| If perpetuated in this crossed state, their preservation will be almost necessarily due to the modification being in some way beneficial to the animal under its then existing conditions of life; so that, even in this case, natural selection will come into play.
|
|
| ←Subtitle not present 1859 1860 1861
Individual
Differences. 1866 |
|
say that the dwarfed condition of shells in the brackish waters of the Baltic, or dwarfed plants on Alpine summits, or the thicker fur of an animal from far northwards, would not in some cases be inherited for at least
few generations? and in this case I presume that the form would be called a variety. |
|
| It may
be doubted whether
→monstrosities, or such
sudden and
deviations of structure
we occasionally see in our domestic productions, more especially with plants, are ever permanently propagated in a state of nature.
→Monsters are very apt to be sterile; and
every part of every organic
→at least with animals,
is so beautifully related to its complex conditions of life that it seems as improbable that any part should have been suddenly produced perfect, as that a complex machine should have been invented by man in a perfect state. ↑ ↑
I have not, at least, been able to find good cases of species in a state of nature presenting modifications of structure resembling monstrosities observed in allied forms. If such have occurred, their perpetuation will have been due to their beneficial nature, so that natural selection will have come into play. Many cases are known of plants which regularly produce on different branches, or on the circumference and in the centre of umbels, &c., flowers of a widely different structure; and if the plant ceased to produce flowers of the one kind, a great change might perhaps suddenly be effected in the specific character; but then we do not at present know by what steps, or for what good, a plant produces two kinds of flowers. With cultivated plants, in the few cases known of a variety habitually bearing flowers or fruit slightly different from each other, the production of the variety has been sudden. →
|
| Again, we have many slight differences which may be called individual differences, such as are known
|
