4 BRITISH BIRDS 



through the air. It does not give when the wings are flapped. The 

 barbules are of two sorts, those nearest to the root of the barb being 

 different from those which are nearest to its tip. The former, as 

 is shown in fig. 2, are shaped something like a knife-blade ; 

 they are thickened above and bent in the middle ; they gradually 

 taper away to a fine point. Just in the middle, where the bend 

 is, are two or three small teeth (2, fig. 2) on the upper margin. 

 By means of these teeth-like processes the successive barbules are 

 attached to one another. At the end of each barb, as already men- 

 tioned, the barbules are of a different structure. A few of them are 



Fm. 1. SKELETON OF WING OF ARCH^OPTERTX WITH REMIGES ATTACHED. 

 (Restoration after Pycraft, ' Natural Science,' vol. v.) 



I, II, in, digits. 



illustrated in fig. 4. The end is frayed out into a number of 

 delicate spines, of which those farthest from the actual tip are 

 hooked, while those at the tip are only curved and not hook-like. 

 All these spines are called barbicels. They are upon the lower edge 

 of the barbule ; but upon the upper edge are a few shorter and 

 stouter spinelets. As the barbules come off in an oblique direction, 

 it follows that each one of them overlaps a considerable number, in 

 fact five, barbules of the opposite barb. The attachment is by these 

 booklets, or hamuli, as they are usually termed. The stiff feathers 



