YOUNG BIRDS AND RECORDS OF THE PAST 151 



be of a compound character, being composed in part of 

 pre-pennae, and in part of pre-plumulae. In the nestling 

 cormorant the whole of the downy coat is of pre-plumulae, 

 but what of the gannet ? No one has yet endeavoured 

 to discover. 



By great good luck some time ago I happened one 

 day to have sent me for the collection of nestlings which 

 I am gathering together for the British Museum a young 

 tawny owl, which revealed to me the surprising fact 

 that tliis bird, at any rate, developed two generations 

 of nestling down ; so that it became necessary to further 

 label these pre-pennae. Thus the down feathers of the 

 first generation must be known as " protoptyles " or first 

 feathers, those of the second as " mesoptyles " or " middle 

 feathers," since they occur between the "protoptyles" 

 and the " teleoptyles " or the typical contour feathers. 

 The existence of these mesoptyles forced itself on my 

 attention the more strongly because they were so strikingly 

 dissimilar from the typical down feathers one always 

 associates with young birds on the one hand, and from 

 typical " teleoptyles " on the other. For in a typical 

 nestling down feather the barbs are long and very slender, 

 all starting from a common base, or are, in other words, 

 " umbelliform." The feathers of the first generation of 

 down feathers in the tawny owl are of this character, 

 whereas those of the second differ conspicuously, the barbs 

 being borne in double series, on a long, tapering shaft, 

 just as in a typical " contour " feather. But they differ 

 from contour feathers in the loose character of the barbs, 

 for in the typical contour feather the barbs are closely 

 knit together by an elaborate mechanism which it is not 

 the purpose of these pages to discuss. Moreover, in their 

 coloration they differ entirely from either the down of 



