The ostrich-tribe is peculiarly interesting, owing to the 
fact that their wings present a really wonderful series of 
degenerating stages. 
The wings of all differ conspicuously from those of other 
birds in the great length and looseness of the texture of the 
feathers. Those of the African ostrich are the largest of all ; 
but they are quite useless for the purpose of flight, though 
they are used as aids in running. In the South American 
ostrich, or rhea, they are also large, but again useless for flight, 
for the “‘ quill-feathers’ are very weak, and have no “‘ web,” 
such as one finds in the quills of flying birds. And besides, 
the muscles of the wing have degenerated, the breast-muscles 
having become reduced to mere vestiges. 
In both the African and South American ostriches, the 
skeleton of the wing, compared with that, say, of a swan, 
would seem, to the inexpert, to be quite normal. But with 
the cassowary, the emu, or the apteryx matters are very 
different. Here, at the first glance, it is apparent that the 
process of decay is far advanced ; for the bones of the hand 
have, as it were, shrunk up, so that a mere stump is all that 
remains. The wing of the cassowary is further remarkable 
for the fact that some of the forearm quills, or “‘ secondaries,” 
are represented by long, stiff quills, resembling spines of 
a porcupine; the “vane” of the feather, which normally 
runs down each side of the shaft, has vanished altogether. 
265 
