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 (8/47. 'Cottage Gardener' December 11, 1855 page 184: an account is here given of all the varieties. For many measurements of the wild birds, see Mr. E. Vernon Harcourt ibid December 25, 1855 page 223.) 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. (8/48. Bechstein 'Naturgesch. der Stubenvogel' 1840 s. 243; see s. 252 on the inherited song of Canary-birds. With respect to their baldness see also W. Kidd 'Treatise on Song-Birds.') 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." (8/49. W. Kidd 'Treatise on Song-Birds' page 18.) 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 (8/50. The 'Indian Field' 1858 page 255.) 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. (8/51. Yarrell 'British Fishes' volume 1 page 319.) 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" (8/52. Mr. Blyth in the 'Indian Field' 1858 page 255.), 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 everywhere for the sake of ornament." In another and more ancient work, it is said that "there is not a household where the gold-fish is not cultivated, in RIVALRY as to its colour, and as a source of profit," etc. (8/53. W.F. Mayers 'Chinese Notes and Queries' August 1868 page 123.) Although many breeds exist, it is a singular fact that the variations are often not inherited. Sir R. Heron (8/54. 'Proc. Zoolog. Soc.' May 25, 1842.) kept many of these fishes, and placed all the deformed ones, namely, those destitute of dorsal fins and those furnished with a double anal fin, or triple tail, in a pond by themselves; but they did "not produce a greater proportion of deformed offspring than the perfect fishes."
Passing over an almost infinite diversity of colour, we meet with the most extraordinary modifications of structure.