What part they play in the bird’s life-history it is impossible 
to say. They certainly cannot be used as weapons, and they 
as certainly are not “ornaments.” In the extinct moas the 
wing had still further degenerated. In some species no more 
than a stump of the upper arm bone was left, and in others 
not only this, but even the shoulder-girdle had vanished, so 
that only one pair of limbs remained. 
Another remarkable flightless bird is the penguin. Here 
the wing has changed its form to assume that of a paddle ; 
superficially identical with that of the whale, or the turtle, or 
that of the extinct sea-dragon ichthyosaurus. These paddles 
have been “‘ re-modelled,’”’ so to speak, to enable them to be 
used for what we may call flight under water. Most birds 
which swim under water use the legs for propelling the body ; 
but the penguin uses his paddles instead. The paddle of 
the turtle has similarly evolved out of a fore-leg used for 
walking on land. The common tortoise may be taken as 
the type of this leg. In the river and pond tortoises the 
stumpy foot of the land-tortoise gives place to a broad, 
webbed foot. In the turtles this webbed foot gives place 
to the paddle. 
After what has been said about the penguin it is instruc- 
tive to turn to the wings of the auk tribe—the guillemot, 
razor-bill, and puffin. These are very efficient for normal 
flight, but they are equally efficient for use under water. 
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