Or as (ratio).
Name of Breed. 1. 2. 3.
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
TABLE 8.III.b.
COLUMN 1. Weight of entire Skeleton (grains). (N.B. One Metatarsus and Foot was removed from each skeleton, as it had been accidentally lost in two cases.)
COLUMN 2. Weight of Humerus, Radius and Metacarpus (grains).
COLUMN 3. Or as (ratio).
Name of Breed. 1. 2. 3.
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
Table 8.III.a shows that the leg-bones relatively to the weight of the entire skeleton have really increased in weight; but Table 8.III.b 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.
With respect to Tables 8.III.a and b, 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.