This matter of "moulting," by the way, needs, at least, passing comment. All birds renew their plumage at least once: the body plumage often twice in the year. The old feathers fall out, and their places are taken by new ones. But their growth is slow. In geese and ducks, and some other birds, the wing-quills are moulted all at once, so that flight, for a week or two, is impossible. But they can escape from their enemies while thus at a disadvantage, by taking to the water. In all other birds the quills are moulted, and renewed, in pairs: so that at no time are they left flightless. But this by the way. Let us revert, for a moment, to the hoatzin's wing. The appearance of the outermost quills of the hand, it will be remembered, is delayed till the inner feathers have grown long enough to "flutter," at least, for a short distance, then the growth of the complete series proceeds apace. This has been called an "Adaptation" to enable these youngsters, active from the moment they leave the egg, to move about in comparative safety. But it is more than this. It is a survival of an ancient order of things which takes us back to the first known birds. This is certainly a very remarkable feature, but it gains an added interest from the fact that it has a parallel in the history of the development of the wing in the game-birds. If you look carefully at the downy chicks of the pheasant, or even at barn-door fowls, you will remark that the wing-quills develop with surprising rapidity: so that they have feathered wings while the rest of the body is still down-covered. This enables them the more easily to escape prowling foxes and other enemies. In young ducks exactly the opposite condition obtains, the body is fully feathered long before the feathers of the wings appear. And this because they do not need to fly when danger threatens, but take to the water instead. But to return to the chicks of the pheasant. The wing of the chick develops at a very rapid rate. Within a few hours after hatching, the first traces of the coming flight feathers can be seen, and presently a large wing is covering each side of the tiny body. At this stage many often die. The wings, which can then be examined at leisure, reveal an extremely interesting condition. For they repeat the features which obtain in the wing of the nestling hoatzin: inasmuch as the outermost quills are also, as yet, non-existent; and there is a free finger-tip. But it is not nearly so long as in the hoatzin, and there is no terminal claw. Surely, from this, we may infer that the delayed development of the outer quills is a survival of a time when the ancestors of the pheasant were arboreal, and hatched their young in trees. Otherwise all the wing-quills should develop at the same time, and at the same rate. Here, then, is another instance of what can be learned of the past history of a bird by a careful scrutiny of the nestling. Sometimes we shall find our evidence