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.Perhaps the first pouter-pigeon did not inflate its crop much more than the turbit now does the upper part of its oesophagus—a habit which is disregarded by all fanciers, as it is not one of the points of the breed.Nor let it be thought that some great deviation of structure would be necessary to catch the fancier's eye: he perceives extremely small differences, and it is in human nature to value any novelty, however slight, in one's own possession.Nor must the value which would formerly have been set on any slight differences in the individuals of the same species, be judged of by the value which is now set on them, after several breeds have fairly been established.It is known that with pigeons many slight variations now occasionally appear, but these are rejected as faults or deviations from the standard of perfection in each breed.The common goose has not given rise to any marked varieties; hence the Toulouse and the common breed, which differ only in colour, that most fleeting of characters, have lately been exhibited as distinct at our poultry-shows.These views appear to explain what has sometimes been noticed, namely, that we know hardly anything about the origin or history of any of our domestic breeds.But, in fact, a breed, like a dialect of a language, can hardly be said to have a distinct origin.A man preserves and breeds from an individual with some slight deviation of structure, or takes more care than usual in matching his best animals, and thus improves them, and the improved animals slowly spread in the immediate neighbourhood.But they will as yet hardly have a distinct name, and from being only slightly valued, their history will have been disregarded.When further improved by the same slow and gradual process, they will spread more widely, and will be recognised as something distinct and valuable, and will then probably first receive a provincial name.In semi-civilised countries, with little free communication, the spreading of a new sub-breed will be a slow process.As soon as the points of value are once acknowledged, the principle, as I have called it, of unconscious selection will always tend—perhaps more at one period than at another, as the breed rises or falls in fashion—perhaps more in one district than in another, according to the state of civilisation of the inhabitants—slowly to add to the characteristic features of the breed, whatever they may be.But the chance will be infinitely small of any record having been preserved of such slow, varying, and insensible changes.7.Circumstances Favourable To Man's Power Of SelectionI will now say a few words on the circumstances, favourable or the reverse, to man's power of selection.A high degree of variability is obviously favourable, as freely giving the materials for selection to work on; not that mere individual differences are not amply sufficient, with extreme care, to allow of the accumulation of a large amount of modification in almost any desired direction.But as variations manifestly useful or pleasing to man appear only occasionally, the chance of their appearance will be much increased by a large number of individuals being kept.Hence number is of the highest importance for success.On this principle Marshall formerly remarked, with respect to the sheep of part of Yorkshire, "As they generally belong to poor people, and are mostly IN SMALL LOTS, they never can be improved." On the other hand, nurserymen, from keeping large stocks of the same plant, are generally far more successful than amateurs in raising new and valuable varieties.A large number of individuals of an animal or plant can be reared only where the conditions for its propagation are favourable.When the individuals are scanty all will be allowed to breed, whatever their quality may be, and this will effectually prevent selection.But probably the most important element is that the animal or plant should be so highly valued by man, that the closest attention is paid to even the slightest deviations in its qualities or structure.Unless such attention be paid nothing can be effected.I have seen it gravely remarked, that it was most fortunate that the strawberry began to vary just when gardeners began to attend to this plant
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