| Name of Breed | Weight of Femur, Tibia, and Metatarsus | Weight of Humerus, Radius, and Metacarpus | Or as |
| Grains | Grains | ||
| Wild mallard | 54 | 97 | 100 : 179 |
| Aylesbury | 164 | 204 | 100 : 124 |
| Hooked-bill | 107 | 160 | 100 : 149 |
| Tufted (Dutch) | 111 | 148 | 100 : 133 |
| Penguin | 75 | 90.5 | 100 : 120 |
| Labrador | 141 | 165 | 100 : 117 |
| Call | 57 | 93 | 100 : 163 |
| Weight of all the Bones of the Leg and Foot | Weight of all the Bones of the Wing | ||
| Grains | Grains | ||
| Wild (another specimen) | 66 | 115 | 100 : 173 |
| Common domestic duck | 127 | 158 | 100 : 124 |
In these domesticated birds, the considerably lessened weight of the bones of the wing (i.e. on an average, twenty-five per cent of their proper proportional weight), as well as their slightly lessened length, relatively to the leg-bones, might follow, not from any actual decrease in the wing-bones, but from the increased weight and length of the bones of the legs. Table IIIa shows that the leg-bones relatively to the weight of the entire skeleton have really increased in weight; but Table IIIb shows that according to the same standard the wing-bones have also really decreased in weight; so that the relative disproportion shown in the foregoing tables between the wing and leg-bones, in comparison with those of the wild duck, is partly due to the increase in weight and length of the leg-bones, and partly to the decrease in weight and length of the wing-bones.
Table III
| Name of Breed | Weight of entire Skeleton. (N.B. One Metatarsus and Foot was removed from each skeleton, as it had been accidentally lost in two cases.) | Weight of Femur, Tibia, and Metatarsus | Or as |
| Grains | Grains | ||
| Wild mallard | 839 | 54 | 1000 : 64 |
| Aylesbury | 1925 | 164 | 1000 : 85 |
| Tufted (Dutch) | 1404 | 111 | 1000 : 79 |
| Penguin | 871 | 75 | 1000 : 86 |
| Call (from Mr. Fox) | 717 | 57 | 1000 : 79 |
| Weight of Skeleton as above. | Weight of Humerus, Radius and Metacarpus. | ||
| Grains | Grains | ||
| Wild mallard | 839 | 97 | 1000 : 115 |
| Aylesbury | 1925 | 204 | 1000 : 105 |
| Tufted (Dutch) | 1404 | 148 | 1000 : 105 |
| Penguin | 871 | 90 | 1000 : 103 |
| Call (from Mr. Baker) | 914 | 100 | 1000 : 109 |
| Call (from Mr. Fox) | 717 | 92 | 1000 : 129 |
With respect to Table III, I may first state that I tested them by taking another skeleton of a wild duck and of a common domestic duck, and by comparing the weight of all the bones of the leg with all those of the wings, and the result was the same. In the first of these tables we see that the leg-bones in each case have increased in actual weight. It might have been expected that, with the increased or decreased weight of the entire skeleton, the leg-bones would have become proportionally heavier or lighter; but their greater weight in all the breeds relatively to the other bones can be accounted for only by these domestic birds having used their legs in walking and standing much more than the wild, for they never fly, and the more artificial breeds rarely swim. In the second table we see, with the exception of one case, a plain reduction in the weight of the bones of the wing, and this no doubt has resulted from their lessened use. The one exceptional case, namely, in one of the Call ducks, is in truth no exception, for this bird was constantly in the habit of flying about; and I have seen it day after day rise from my grounds, and fly for a long time in circles of more than a mile in diameter. In this Call duck there is not only no decrease, but an actual increase in the weight of the wing-bones relatively to those of the wild-duck; and this probably is consequent on the remarkable lightness and thinness of all the bones of the skeleton.
Lastly, I weighed the furculum, coracoids, and scapula of a wild duck and of a common domestic duck, and I found that their weight, relatively to that of the whole skeleton, was as one hundred in the former to eighty-nine in the latter; this shows that these bones in the domestic duck have been reduced eleven per cent of their due proportional weight. The prominence of the crest of the sternum, relatively to its length, is also much reduced in all the domestic breeds. These changes have evidently been caused by the lessened use of the wings.
It is well known that several birds, belonging to different Orders, and inhabiting oceanic islands, have their wings greatly reduced in size and are incapable of flight. I suggested in my ‘Origin of Species’ that, as these birds are not persecuted by any enemies, the reduction of their wings had probably been caused by gradual disuse. Hence, during the earlier stages of the process of reduction, such birds would probably have resembled our domesticated ducks in the state of their organs of flight. This is the case with the water-hen (Gallinula nesiotis) of Tristan d’Acunha, which “can flutter a little, but obviously uses its legs, and not its wings, as a mode of escape.” Now Mr. Sclater[[19]] finds in this bird that the wings, sternum, and coracoids are all reduced in length, and the crest of the sternum in depth, in comparison with the same bones in the European water-hen (G. chloropus). On the other hand, the thigh-bones and pelvis are increased in length, the former by four lines, relatively to the same bones in the common water-hen. Hence in the skeleton of this natural species nearly the same changes have occurred, only carried a little further, as with our domestic ducks, and in this latter case I presume no one will dispute that they have resulted from the lessened use of the wings and the increased use of the legs.
THE GOOSE.
This bird deserves some notice, as hardly any other anciently domesticated bird or quadruped has varied so little. That geese were anciently domesticated we know from certain verses in Homer; and from these birds having been kept (388 B.C.) in the Capitol at Rome as sacred to Juno, which sacredness implies great antiquity.[[20]] That the goose has varied in some degree, we may infer from naturalists not being unanimous with respect to its wild parent-form; though the difficulty is chiefly due to the existence of three or four closely allied wild European species.[[21]] A large majority of capable judges are convinced that our geese are descended from the wild Grey-leg goose (A. ferus); the young of which can easily be tamed.[[22]] This species, when crossed with the domestic goose, produced in the Zoological Gardens, as I was assured in 1849, perfectly fertile offspring.[[23]] Yarrell[[24]] has observed that the lower part of the trachea of the domestic goose is sometimes flattened, and that a ring of white feathers sometimes surrounds the base of the beak. These characters seem at first sight good indications of a cross at some former period with the white-fronted goose (A. albifrons); but the white ring is variable in this latter species, and we must not overlook the law of analogous variation; that is, of one species assuming some of the characters of allied species.
As the goose has proved so little flexible in its organisation under long-continued domestication, the amount of variation which it has undergone may be worth giving. It has increased in size and in productiveness;[[25]] and varies from white to a dusky colour. Several observers[[26]] have stated that the gander is more frequently white than the goose, and that when old it almost invariably becomes white; but this is not the case with the parent-form, the A. ferus. Here, again, the law of analogous variation may have come into play, as the almost snow-white male of the Rock goose (Bernicla antarctica) standing on the sea-shore by his dusky partner is a sight well known to those who have traversed the sounds of Tierra del Fuego and the Falkland Islands. Some geese have top-knots; and the skull beneath, as before stated, is perforated. A sub-breed has lately been formed with the feathers reversed at the back of the head and neck.[[27]] The beak varies a little in size, and is of a yellower tint than in the wild species; but its colour and that of the legs are both slightly variable.[[28]] This latter fact deserves attention, because the colour of the legs and beak is highly serviceable in discriminating the several closely allied wild forms.[[29]] At our Shows two breeds are exhibited; viz., the Embden and Toulouse; but they differ in nothing except colour.[[30]] Recently a smaller and singular variety has been imported from Sebastopol,[[31]] with the scapular feathers (as I hear from Mr. Tegetmeier, who sent me specimens) greatly elongated, curled, and even spirally twisted. The margins of these feathers are rendered plumose by the divergence of the barbs and barbules, so that they resemble in some degree those on the back of the black Australian swan. These feathers are likewise remarkable from the central shaft, which is excessively thin and transparent, being split into fine filaments, which, after running for a space free, sometimes coalesce again. It is a curious fact that these filaments are regularly clothed on each side with fine down or barbules, precisely like those on the proper barbs of the feather. This structure of the feathers is transmitted to half-bred birds. In Gallus sonneratii the barbs and barbules blend together, and form thin horny plates of the same nature with the shaft: in this variety of the goose, the shaft divides into filaments which acquire barbules, and thus resemble true barbs.