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. The first of the two tables on the next page shows
that the leg-bones relatively to the weight of the entire skeleton have
really increased in weight; but the second table 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 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 c