M Database Inspector (cheetah)
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|OriginOfSpecies - 475 Rows|
|01 - Variations Under Domestication||01-09 - Principles of Selection anciently followed, and their Effects||40||
The same principles are followed by horticulturists; but the variations are here often more abrupt.
No one supposes that our choicest productions have been produced by a single variation from the aboriginal stock.
We have proofs that this has not been so in several cases in which exact records have been kept; thus, to give a very trifling instance, the steadily-increasing size of the common gooseberry may be quoted.
We see an astonishing improvement in many florists' flowers, when the flowers of the present day are compared with drawings made only twenty or thirty years ago.
When a race of plants is once pretty well established, the seed-raisers do not pick out the best plants, but merely go over their seed-beds, and pull up the "rogues," as they call the plants that deviate from the proper standard.
With animals this kind of selection is, in fact, likewise followed; for hardly any one is so careless as to breed from his worst animals.
|01 - Variations Under Domestication||01-09 - Principles of Selection anciently followed, and their Effects||50||
In regard to plants, there is another means of observing the accumulated effects of selection- namely, by comparing the diversity of flowers in the different varieties of the same species in the flower-garden; the diversity of leaves, pods, or tubers, or whatever part is valued, in the kitchen garden, in comparison with the flowers of the same varieties; and the diversity of fruit of the same species in the orchard, in comparison with the leaves and flowers of the same set of varieties.
See how different the leaves of the cabbage are, and how extremely alike the flowers; how unlike the flowers of the heartsease are, and how alike the leaves; how much the fruit of the different kinds of gooseberries differ in size, colour, shape, and hairiness, and yet the flowers present very slight differences.
It is not that the varieties which differ largely in some one point do not differ at all in other points; this is hardly ever,- I speak after careful observation, perhaps never, the case. The law of correlated variation, the importance of which should never be overlooked, will ensure some differences; but, as a general rule, it cannot be doubted that the continued selection of slight variations, either in the leaves, the flowers, or the fruit, will produce races differing from each other chiefly in these characters.
|01 - Variations Under Domestication||01-03 - correlation of Growth||10||
Many laws regulate variation, some few of which can be dimly seen, and will hereafter be briefly discussed.
I will here only allude to what may be called correlated variation. Important changes in the embryo or larva will probably entail changes in the mature animal.
In monstrosities, the correlations between quite distinct parts are very curious; and many instances are given in Isidore Geoffroy St-Hilaire's great work on this subject.
Breeders believe that long limbs are almost always accompanied by an elongated head.
Some instances of correlation are quite whimsical: thus cats which are entirely white and have blue eyes are generally deaf;
but it has been lately stated by Mr. Tait that this is confined to the males.
Colour and constitutional peculiarities go together, of which many remarkable cases could be given amongst animals and plants.
From facts collected by Heusinger, it appears that white sheep and pigs are injured by certain plants, whilst dark-coloured individuals escape:
|01 - Variations Under Domestication||01-09 - Principles of Selection anciently followed, and their Effects||60||
It may be objected that the principle of selection has been reduced to methodical practice for scarcely more than three-quarters of a century; it has certainly been more attended to of late years, and many treatises have been published on the subject; and the result has been, in a corresponding degree, rapid and important.
But it is very far from true that the principle is a modern discovery. I could give several references to works of high antiquity, in which the full importance of the principle is acknowledged. In rude and barbarous periods of English history choice animals were often imported, and laws were passed to prevent their exportation: the destruction of horses under a certain size was ordered, and this may be compared to the "roguing" of plants by nurserymen.
The principle of selection I find distinctly given in an ancient Chinese encyclopaedia.
Explicit rules are laid down by some of the Roman classical writers.
From passages in Genesis, it is clear that the colour of domestic animals was at that early period attended to.
Savages now sometimes cross their dogs with wild canine animals, to improve the breed, and they formerly did so, as is attested by passages in Pliny.
The savages in South Africa match their draught cattle by colour, as do some of the Esquimaux their teams of dogs.
Livingstone states that good domestic breeds are highly valued by the negroes in the interior of Africa who have not associated with Europeans.
Some of these facts do not show actual selection, but they show that the breeding of domestic animals was carefully attended to in ancient times, and is now attended to by the lowest savages. It would, indeed, have been a strange fact, had attention not been paid to breeding, for the inheritance of good and bad qualities is so