of a fan. Asa 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 birder important part. But this is not 
all. We have now to consider the wing. In all essentials this 
agrees with that of living 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 will 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 Archeopteryx, it is important to remember, 
bear a very extraordinary likeness to the feet of a ‘ 
* perching ” 
bird, say that of acrow. They are without any semblance of doubt, 
the feet of a bird which lived in trees. Archzopteryx, 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 from the 
17 
