5 2 4 



POPULAR SCIENCE MONTHLY. 



never found in any bird. The feathers of this creature grew out of 

 the skin of the arm and of the third finger. 



In the fowl (Fig. 5) and all other birds the wing is, as in the 

 Archceopteryx, a feathered fore leg and foot, a, b, c, in Fig. 5, are 

 the leg bones, and the rest represents the foot, which retains in part 

 the three rays seen in the Archceopteryx. Two of these rays, how- 

 ever (1 and 3), instead of having several joints, are nothing more 

 than short, pointed bones, u c and r c are the only bones of the 

 " wrist " left, and mc ii and mc hi show all that remains of the bones 



Fig. 4. 



Fig. 3. 



Fig. 5. 



which in a four-footed sole-walker form the flat of the foot. 1 is 

 the remains of the first toe or digit, 2 is the long second digit, which 

 still has three joints, and 3 is the one remaining joint of the third 

 digit, which is not distinctly separated from the second. All the 

 other parts of the lizardlike fore foot have disappeared, because this 

 was quite enough to serve as a rigid support for the skin which carries 

 the feathers. 



The domestic fowl, of course, uses its wings very little; it walks 

 more than it flies. Most birds use their wings much more, and some 

 of these have more of the bones of the original foot left. Other 

 birds fly still less than the fowl. The penguin, for example, uses 

 its wings not for flying but for swimming, and the bones have be- 

 come much flatter and broader than those of ordinary birds. The 

 feathers that cover them are exceedingly small, almost more like 

 scales than feathers, so that the whole wing is flat and paddlelike, 

 and is very suitable for acting as an oar in the water. 



In some of the ostriches, which also never fly, the bones which 

 support the wing are reduced to mere stumps, even the second digit 

 having only one joint. 



