130 BRITISH BIRDS. [vol. vii. 



are very frequently white, especially in juvenile but also 

 in first- winter birds. 



The Rook remains with its " face " fully feathered 

 until January, and in some individuals until a month 

 or two later. A very gradual moult then commences 

 on the chin, the feathers dropping out generally first 

 in the centre of the part which afterwards becomes 

 bare (Plate 4, Figs. 4-7). The feather papillae be- 

 come active and produce " pias," most of which, 

 after growing a millimetre or two (occasionally as 

 much as four or five and exceptionally more) above 

 the skin, then stop growing and remain as " pins " 

 with their tips slightly curled over and shaped \\ke a 

 rounded cone, and without any trace of feather-growth 

 coming from them.* From some of the pins, however, 

 very short degenerate feathers grow. These are in 

 structiure almost exactly like plumules, except that they 

 are rather larger. To the naked eye they are down-like : 

 under the microscope they are seen to have a very 

 thin, fine rhachis and long, straggling, fine rami and 

 radii, and are quite unlike the feathers they replace 

 (Plates 8-9). They are dark grey in colour, only 

 some four or five millimetres long, and sometimes show 

 a very slight gloss. Occasionally one finds growing 

 among these " pins " and degenerate feathers, a new 

 feather of normal structiu-e which has somehow escaped 

 the degeneracy of the others. 



It is a remarkable fact that most of the filoplumes 

 and plumules remain and are not shed with the other 

 feathers. A plumule arises from a papilla situated 

 alongside that of a contour (or true) feather, but the 

 two are quite independent, for I have frequently found 

 among the body-feathers during the moult a newly- 



* These "pins" when examined under a microscope appear to 

 consist of a series of semi-transparent inverted cups fitting one over 

 the other, and I can detect no trace of feather -growth within them. 

 In Plate 10, Fig. 26, one of these " pins " is figured but unfortunately 

 the preparation was not sufficiently transparent to show the inverted 

 cups. 



