3o8 



ANIMAL MOVEMENT 



ing breeze : when it begins to slacken, will turn round and go with 

 it until conscious it is strengthening;- ag-ain, when once more he 

 will sweep round and face it, his aim being always to feel the wind 

 blowing in his face — sure evidence that he has momentum that will 

 lift him. To do this, he would have to be perpetually feeling the 

 pulse of the wind, and, moreover, soaring would be a much less 

 regular progress upward than it is supposed to be. Some turns of 

 the helix would be failures. There would be a loss instead of a 

 gain of elevation, or nothing more than a maintenance of level 

 would be achieved. But when we watch a bird circling at a great 

 height, what can we tell of his progress during a particular minute? 

 We only know that his general tendency is upward. Gulls make 

 only partially successful turns when they soar, and it is possible 

 that similar failures in a nobler performer like the Adjutant may 

 remain undetected." 



Restoration of Paddle-Tailed Pterosaur 



THE FLIGHT OF REPTILES (Reptilia) 



Very few living Reptiles make any attempts at aerial locomo- 

 tion, and those which do are merely parachutists (see p. 286). But 

 in the remote epoch known to geologists as the Mesozoic or 



Secondary, when 

 Mammals were 

 but a feeble folk, 

 not only the land 

 and sea, but also 

 the air were domi- 

 nated by Reptiles, 

 the majority of which belonged to groups now 

 long extinct. The Flying Reptiles, or Ptero- 

 saurs, of this epoch are of great interest bio- 

 logically, for they solved the problem of flight 

 on quite different lines from those exemplified 

 by Bats and Birds, approximating, however, 

 more nearly to the former in this respect. As 

 will be gathered by reference to fig. 838, which represents a re- 

 storation of the Paddle-Tailed Pterosaur {^Rhamporhynchus), flying 

 membranes connected fore- and hind-limbs, and (in some species) 

 the latter with the tail, which in this particular form, however, was 

 elongated, free, and broadened out at its end. There was also a 



