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The Variation of Animals and Plants

THE CANARY BIRD.
As this bird has been recently domesticated, namely, within the last 350 years, its
variability deserves notice. It has been crossed with nine or ten other species of
Fringillidæ, and some of the hybrids are almost completely fertile; but we have no
evidence that any distinct breed has originated from such crosses. Notwithstanding the
modern domestication of the canary, many varieties have been produced; even before the
year 1718 a list of twenty-seven varieties was published in France, and in 1779 a long
schedule of the desired qualities was printed by the London Canary Society, so that
methodical selection has been practised during a considerable period. The greater number
of the varieties differ only in colour and in the markings of their plumage. Some breeds
however, differ in shape, such as the hooped or bowed canaries, and the Belgian canaries
with their much elongated bodies. Mr. Brent measured one of the latter and found it eight
inches in length, whilst the wild canary is only five and a quarter inches long. There are
top-knotted canaries, and it is a singular fact that, if two top-knotted birds are matched,
the young, instead of having very fine top-knots, are generally bald, or even have a
wound on their heads. It would appear as if the top-knot were due to some morbid
condition, which is increased to an injurious degree when two birds in this state are
paired. There is a feather-footed breed, and another with a kind of frill running down the
breast. One other character deserves notice from being confined to one period of life, and
from being strictly inherited at the same period; namely, the wing and tail feathers in
prize canaries being black, "but this colour is retained only until the first moult; once
moulted, the peculiarity ceases." Canaries differ much in disposition and character, and in
some small degree in song. They produce eggs three or four times during the year.
GOLD-FISH.
Besides mammals and birds, only a few animals belonging to the other great classes have
been domesticated; but to show that it is an almost universal law that animals, when
removed from their natural conditions of life, vary, and that races can be formed when
selection is applied, it is necessary to say a few words on gold-fish, bees, and silk-moths.
Gold-fish (Cyprinus auratus) were introduced into Europe only two or three centuries
ago; but they have been kept in confinement from an ancient period in China. Mr. Blyth
suspects, from the analogous variation of other fishes, that golden-coloured fish do not
occur in a state of nature. These fishes frequently live under the most unnatural
conditions, and their variability in colour, size, and in some important points of structure
is very great. M. Sauvigny has described and given coloured drawings of no less than
eighty-nine varieties. Many of the varieties, however, such as triple tail-fins, etc., ought
to be called monstrosities; but it is difficult to draw any distinct line between a variation
and a monstrosity. As gold-fish are kept for ornament or curiosity, and as "the Chinese
are just the people to have secluded a chance variety of any kind, and to have matched
and paired from it," it might have been predicted that selection would have been largely
practised in the formation of new breeds; and this is the case. In an old Chinese work it is
said that fish with vermilion scales were first raised in confinement during the Sung
dynasty (which commenced A.D. 960), "and now they are cultivated in families
 
 
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