66 THE STORY OF BlRD-LlFE. 



it escapes by diving or swimming, which it 

 does to perfection. So far as is known, it 

 should be remarked, the adult does not swim. 



The wing of the nestling chicken furnishes 

 u? with an admirable lesson in deductive 

 zoology. 



As in the hoatzin, the outermost quill feathers 

 of the hand are not developed till a comparatively 

 late date, the inner ones meanwhile growing 

 rapidly ; and just as in the hoatzin, so soon as 

 these are long enough to enable the bird to take 

 a short flight, so soon do the outer quills begin 

 to grow. But the hand is relatively shorter, and 

 the finger has no claw. The first point would 

 suggest that the reason for this arrested develop- 

 ment of quills was due to the same cause in both 

 cases, the need to have the finger-tip free for the 

 purpose of grasping objects. The second — the 

 absence of the c'aw on the first finger — would 

 appear to contradict this, or at least to be an 

 obstacle. If we turn to the embryo, however^ 

 we get confirmation of our original hypothesis 

 — that the wing in the chick was at one time 

 used, like that of the hoatzin, for the purpose 

 of climbing before it was used as a wing, in- 

 asmuch as the missing claw in the first finger is- 

 now present. It disappears before the bird is 

 hatched, there being no use for it during the 

 nestling period. In course of time, a very long 

 time, it will probably be entirely suppressed,, 

 so that no record M'hatever will remain. 



Not only in the chick does this happen, but 

 also in the pheasants and partridges and their 

 allies. From this Me infer that once ujDon a time. 



