22 THE STORY OF BIRD-LIFE. 



position, as you will discover, in some mysterious 

 way, so that the branches, as a whole, combine to 

 form what is called a " web." If you try to pull 

 this " web " apart in any place, you will see that 

 it gives way reluctantly. Hold it up to the light 

 and you will get an inkling of the reason of this. 

 Along each of the little branches you will find 

 other little branches, arranged, much as were the 

 larger branches on the main axis. The larger 

 branches are called barbs, the smaller barbules. 

 Now all the barbules turned towards the base of 

 the feather, have their top edges inturned, whilst 

 all the barbules turned towards the tip of the 

 feather bear long and delicate little booklets. 

 These overlap the inturned edges of the hinder 

 set, and the booklets seize upon them and hold 

 in like so many grappling-irons; thus you see 

 how the web is formed. JSTow for some figures. 

 On a piece of the web of about 15 in. long 

 of a crane's quill feather there were counted 

 no less than 650 of these barbs, each of which 

 bore about 600 pairs of barbules — that is about 

 800,000 for the inner web alone, and more than 

 a million for the whole feather ! The accuracy 

 of these figures can scarcely be doubted, for 

 they are the result of a careful examination 

 into the matter by Dr Gadow, one of our 

 greatest authorities on bird anatomy. 



The peculiar curling qualities of the ostrich 

 feather are due to the fact that the feather is of 

 a degenerate structure and has no booklets, con- 

 sequently it has lost the faculty of forming 

 a "web." Hence the barbs are permanently 

 disconnected. 



