With respect to the two following tables, 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 {286} 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.