XII AVES 435 



From the evolutionary point of view Birds may be regarded as very 

 highly developed flying reptiles. Their perfection as fliers dominates 

 their whole structure. The first steps in the evolution of their power 

 of flight are beyond our ken but the present writer regards it as probable 

 that birds evolved out of aquatic reptiles, the fore-limbs becoming 

 modified first for a kind of sub-aqueous flight similar to that of a Penguin. 

 The modification of the scaly coat to form the fluffy plumage would be 

 correlated with two separate functions (i) the protection of the body 

 from cold and (2) the ensuring the most rapid return to the surface of 

 , the water after the pursuit of the fish which formed the creature's food. 

 The initial stages of aerial flight would consist of flapping along the 

 water's surface and the enlargement of the feathers of wings and tail 

 would help this movement and at length make purely aerial flight 

 possible. 



