HAIKS, FEATHERS, AXD SCALES. 



17 



magnifying power shows ns tliat these barbs are not 

 simple filaments, but are themselves doubly bearded in 

 the same fashion ; and further, that these barbulcs of 

 the second series are furnished with a third series. It 

 is in this third series of filaments that the tenacity in 

 question resides. If we isolate one of the primary 

 beards, by stripping away a few on each side of it, and 

 again put it on the stage, we see that the secondary 

 barbules of one side are armed differently from those of 

 the other side. Tliose of the lower side carry short and 

 simple barbulets, whereas those of the side Avhich looks 

 towards the point of the feather bear much longer ones ; 

 and, moreover, many of them are 

 abruptly hooked backwards. Is"ow, 

 whenever the primary beards are 

 brouirht into contact, some of these 

 hooks catch on tlie barbule next 

 above, and, slipping into the an- 

 gles formed by the barbulets, hold 

 there, and thus the two contiguous 

 beards are firmly locked together. 

 In the beard of the goose-quill, 

 the structure is essentially the 

 same, but the barbulets are far 

 more numerous and more closely 

 set ; they are also proportionally 

 much hirgei', — both those which 



are hooked and those which are simple. Indeed, the 

 latter manifest a tendency to the hooked form, and by 

 all these peculiarities the interlocking power is aug- 

 mented. It is interestino; to observe the j^reat dilatation 

 of the beard in a direction towards the inferior surface 

 of the feather, — towards the stroke, as I just now ob- 



EAKB FF.OM GOOSE-QtriLU 



