264 



BRANCH CHORDATA 



advantage in this arrangement? Why do they differ from the 

 structure and arrangement in the leg of man? 



The body skeleton (Fig. 216) is strong, Ught, and flexible, as it 

 must be for flight. Note how firmly the vertebrae are joined in 



Fig. 215. — The most important forms of birds' feet (b, c, d, f, n, from the 

 regne animal) : a, Pes adhamans of Cypselus apus; b, P. scansorius of Picus 

 capensis; c, P. ambulatorius of PJinsinnus colchicus; d, P. fissus of Turdus 

 torquatus; e, P. gressorius of Alcido isjiiila ; /, P. insidens of Falco biarmicus; 

 g, P. colligatus of Myderia scnrijdlcnsis: h, P. cursorius of Struthio camelus; 

 i, P. palmatus of Mergus mergdm^er; k, P. semipalmatus of Recurvirostra 

 avocetta; I, P. fissipalmatus of Podiceps cristatus; m, P. lobatus of Fulica 

 atra; n, P. steganus of Phaeton cetherens. (After Claus.) 



the back. Note also the very short bony tail, consisting of a 

 few vertebrae fused into the pygostyle, which supports the tail 

 feathers. The oil gland is situated near the pygostyle and from 

 it birds get the oil for their feathers. Note also that the sternum 



