DEVELOPMENT OF WING 



FIG. 117. DIAGRAM OK WING DEVELOPMENT OF THE AMERICAN CATBIRD 



creases and then decreases, being in the achilt ])ractically the 

 same as it was in the yonng chick. As in the case of the 

 toucan the total increase and decrease in tlic development 

 ahont offset each other. 



The increase of the hand in the first few days may be 

 less the shadow^ of an ancestral character than a prepara- 

 tion for the oTow^th of ])rimaries, which, at this date, are of 

 great size. The bird has so long been reared in a state of 

 helplessness that there appear to be but few traces of an 

 elongated hand in the late embryo. The forearm and hand. 

 on the contrary, show traces of an early weakening and 

 shortening. 



Cas.sicNs ccia (Linn.) 



Arm Forearm Hand 



2 day nestling 8.)..) mm. 41. .> mm. .37.3 mm. 



3 "* " HL5 " 43. " 36..5 " 



7 " " 34.3 " 41.8 " 37.7 " 



Adult 33.8 '* 44. " 36. 



The development of the yellow-backed cacicpic prac- 

 tically parallels that of the catbird, though the variations are 

 not so large. It is a noticeable feature that in the three-day 

 nestling, where there is a slight decrease in the hand, it is ac- 

 companied by a corresponding increase of the forearm. 



