FORM AND HABIT: THE WING. 



organs we shall direct our attention to their external form 

 rather than their internal structure. 



The Wing. — Birds' wings are primarily organs of 

 locomotion, but they are also used as weapons, as musical 

 instruments, in expressing emotion, and they are some^ 



Fig. 4. 



-Young Iloatzin, showing use of hooked Angers in climbing. (After 

 Lucas. ) 



times the seat of sexual adornment. As an organ of loco- 

 motion the wing's most primitve use is doubtless for 

 climbing. G-allinules, for instance, have a small spur on 

 the wrist or "bend of the wing," and the young birds 

 use it to assist their progress among the reeds. A more 

 c-triking instance of this nature is shown by that singular 

 South American bird, the Iloatzin (Opistihocom/ua oris- 



