274 



VERTEBRATE ZOOLOGY 



the thighs of Archmpteryx. These discoveries led to the conchision 

 that the first flyers had wings on both arms and legs (Fig. 148, J) 



Fig. 148. — Group of figures to illustrate theories of the origin of flight. A, re- 

 construction of sl-celcton of Archceoptcri/x compared witli tliat of a pigeon, B; C, D, 

 silhouettes of plieasant (left) and Archaopteryx (right) to illustrate two wing 

 theory of origin of flight; E, F, G, II, four stages in the hypothetical evolution of 

 the two winged from the four winged bird. I, restoration of Archaoplcnji, after 

 Heilmann. J, Tetrapter>'\', the hypothetical four-winged ancestral bird of 

 Beebe. (Redrawn after Osborn's " Origin and Evolution of Life.") 



and used both sets in jiarachuting from trees to the ground and from 

 tree to tree. Later the wings of the legs degenerated as the tail 

 feathers took up the duty of acting as a posterior plane, and the arm- 



