spokes of a fan. As a result, a much more efficient tail for 

 the needs of flight has come into being. And the tail, it must 

 be remembered, plays, especially in some birds, an important 

 part. But this is not aU. We have now to consider the 

 wing. In all essentials this agrees with 'that of Uving birds. 

 And this agreement is strikingly close when it is compared 

 with the embryonic and early nestling stages. A detailed 

 account of these resemblances, and differences, would be 

 out of place here. Suffice it to say that its closest modern 

 counterparts are to be found in the wing of the nestling of 

 that strange South American bird, the Hoatzin, and the 

 " Game-birds," such as of a young pheasant, or a young 

 fowl. The evidence these can furnish in this matter of the 

 evolution of the birds' wing will be found in Chapter VI, 

 For the moment it wiU be more profitable to discuss the 

 broad outlines of the origin of flight, so far as this is possible. 



On this theme there are, as might be supposed, many 

 opinions — some of them bearing little relation to fact. 



The feet of Archaeopteryx, it is important to remember, 

 bear a very extraordinary likeness to the feet of a " perching " 

 bird, say that of a crow. They are without any semblance 

 of doubt, the feet of a bird which lived in trees. Archaeopteryx, 

 then, was an arboreal bird. And this being so, the most 

 reasonable hypothesis of the origin of flight is that it developed 

 out of " gliding " movements, made for the purpose of passing 



17 



STORRS L OLSON 



