What part they play in the bird's hfe-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 Umbs 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 caU 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 tcibe — ^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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