96 THE WOODPECKERS 



pair is infirm, and the two middle pairs are com- 

 pelled to give all the support, except the little 

 contributed by the third pair. In the ivory- 

 billed woodpecker the two outer pairs are of no 

 assistance and the three central ones do the 

 work, and here again we find the base of the 

 rectrices rigid and inflexible and the last fourth 

 of their length weak and yielding. But what a 

 difference in the individual feather ! It is well 

 able to do all the work ; for, except for that weak 

 tip which we cannot now explain, it is one of the 

 toughest and strongest feathers to be found. 

 The shaft is broad and flat, as elastic as a watch- 

 spring ; it looks like a band of burnished steel 

 as it runs down between the vanes. And the 

 vanes themselves are of a very curious pattern. 

 They curl under at the edges so that we do not 

 see their whole width, and the barbs crowd so 

 thickly upon each other that they over-lie until 

 they present an edge three or four broad. In- 

 deed, the under side of one of these tail feathers 

 reminds one of nothing so much as of the under 

 side of a star-fish's arm with its two long lines 

 of ambulacral suckers on each side of a central 

 groove, so thickly do the spiny vanes of these 

 strong rectrices over ride and crowd together. 

 These spines lay hold of the bark of the tree, 

 rank after rank, hundreds of bristling points 



