the adult stage of the wing of the ancient Archaeopteryx. 

 This bird could have been but a poor fUer, and probably 

 during the tinie it was moulting its quiUs it was absolutely 

 flightless, so that it needed a permanent fimger-tip, and claw, 

 beyond the margin of its wing-surface. 



This matter of " moulting," by the way, needs, at least, 

 passing comment. AH 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 groAvth is slow. In geese and ducks, and some other 

 birds, the wing-quiUs are moulted aU 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 tiU 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. 



120 



