134 BRITISH BIRDS. [vol. vii. 



feather-development will take up this question and I 

 shall be most happy to lend what material I have to 

 help in its elucidation. 



A comparison between our Rook {Corvus frugilegus 

 frugilegus) and the Eastern Rook {Corvus frugilegus 

 pastinafor) is interesting, because it shows, I think, that 

 our Rook has proceeded further in its evolution than the 

 Eastern form. This bird, which inhabits Eastern Siberia, 

 China, and Japan, is very similar to ours in first winter- 

 plumage, but the adult has only the nostril-region and 

 a very small patch on the sides of the lower mandibles 

 bare, the chin, throat, and lores being feathered 

 (Plate 5, Fig. 16). In two specimens, however, I 

 found a very narrow line of bare skin down the 

 centre of the chin from the angle of the mandibles, 

 and in this bare skin were "pins" like those on 

 the chin of our Rook. Two other specimens had 

 some " pins " on the chin which were concealed by 

 the feathers. These facts, taken in conjunction with the 

 fact that there is a considerable growth of degenerate 

 feathers at every moult on the chin of our Rook and 

 scarcely any on the nostril-region, show, I think, that 

 the bare chin is of comparatively recent development. 

 It should also be noted that in Corvus f. pastinator the 

 feathers on the chin and upper-throat in first winter- 

 plumage have the rhachis much elongated, as is the 

 case in our bird. In the adult, however, though the 

 feathers on the upper-throat are exactly like those in 

 first winter-plumage, the feathers of the chin within 

 the angle of the lower mandibles have the rhachis much 

 less elongated and sometimes not at aU, Moreover, 

 these feathers in the adult, instead of sloping in a normal 

 manner away from the point of the bill, stand up at right 

 angles to the skin, and thus give the chin a " furry " 

 appearance (Plate 5, Fig. 16). 



