862 



Mr. C. Ingram on the 



[Ibis, 



caused by the relative thickness of tlio pale straw-coloured 

 barbs. In many cases the barbs composing the down-tufts 

 are fused together in couples at about lialf their length, and 

 thus form a single thickened extremity* (fig. 4). These 

 pale extremities, backed by slightly darker bases and darker 



A. Single barb from the neossoptile of a Yellow Wagtail {MotaciUa 



rati}. 



B. Fusion of two barbs in tbe neossoptile of a Skylark {Alcnida m-veytsis). 



skin, are very effective, and enable a brood of young Sky- 

 larks to become almost invisible at a distance of only a few 

 feet. When immobile their downy covering almost exactly 

 reproduces a plexus of withered grass-leaves. 



Excluding the larger forms of altricial birds, such as the 



* A similar union of the barbs produces the curious "wiry" appear- 

 ance of the pre-pennse down on the head of some of the Herons. In 

 the Purple Heron, for instance, three or four of the down barbs become 

 fused together for the greater part of their length, forming a single horny 

 ribbon, evidently to assimilate the coarser t^'pe of vegetation amongst 

 Avhich this species breeds. 



