TEGUMENTARY ORGANS. 



exterior margin. The barbules again develope, from their 

 margins, minute curved, hooked filaments, or barbulinae, to 

 complete this delicate structure for hooking together and 

 uniting the barbs into a continuous membrane, as shown by 

 Hooke, who carefully investigated, described, and figured this 

 complex mechanism in 1667, and accurately compared each 

 barbule, with its barbulinse, to the structure of an entire 

 feather. In most feathers the proximal part of the vane 

 (147- A. d.} has its barbs and barbules long, loose and floating, 

 so as to form a compact downy mantle next the skin of the 

 bird, to retain the high temperature of the body. In the rest 

 of the vane the barbs are more firm, straight, regular and 

 united, to assist in flight, or to protect the body. 



The parts of the feather, as shown by Dutrochet, Blainville, 

 and F. Cuvier, are at first formed within a thick closed epider- 



