VERTEBRATES 137 



Observations. 



The pupils should study the arrangement of the feathers 

 and their variations in form and size, and should identify 

 the following principal kinds : — 



Contour feathers, those feathers, generally broad, which 

 cover the body, giving to it its outline and color. 



Coverts, those feathers which cover joints, such as the 

 joints of the wing and tail. 



Primaries or pinions, the long stiff feathers of the out- 

 side of the wing, used in sustaining the bird in flight. 



Secondaries, the shorter, more symmetrical feathers lying 

 next and over the primaries. 



Down, soft feathers found on young birds and next to 

 the skin on some adults. 



Thread feathers, best seen about the eyes, ears, and 

 beak. 



Quill, the bare stiff portion, one end of which is in- 

 serted in the skin. Examine its internal structure. 



Vane, the broad expanded portion, the part ordinarily 

 seen on the bird. 



Shaft, the mid-rib of the vane. 



Barbs, the delicate outgrowths of the shaft making up 

 the vane. 



Barbules, the subdivisions of the barbs, some of which 

 are provided with booklets. These may well be studied 

 microscopically. 



Questions. 



1. How is the plumage arranged to offer least resist- 

 ance to the air in flight.' How does a bird sit when 

 exposed to the wind } 



2. In a column write the names of the parts of a 

 feather, and opposite each part state its particular use. 



