1916] Chandler: Structure of Feathers 347 



c) Down 



The downy structure in Calopezus and Nothura is exactly the 

 same as in typical gallinaceous birds, not only in the structure of 

 the typical basal barbules of the distal vanule, which have detach- 

 able rings of the same form, but also in the method and degree of 

 simplification in other parts of the barbs. In Tinamus and Notho- 

 cercus, on the other hand, the detachable rings are only slightly 

 developed, but the more basal nodes are very much enlarged, while 

 the more distal ones are in the form of tiny droplets, the type of 

 barbule thus resembling that of the Columbae very closely (pi. 25, 

 fig. 49/). In all species the down barbules are very long, as in 

 typical gallinaceous birds. 



d) Relationships 



The structure of the down alone is sufficient proof that the 

 tinamous are unquestionably far more closely allied to the Galli 

 than to any other birds, since it is difficult to believe that the 

 peculiar detachable rings at the nodes would be developed twice, by 

 separate paths of evolution. The remarkable similarity of the down 

 of some species to that of the Columbae can more readily be thought 

 of as parallel evolution, since it is a type which recurs again in the 

 Rhamphastidae, for instance, and is very easily derived from the 

 gallinaceous type of structure. The occurrence of these two types 

 of down in this single order, however, is suggestive of the fairly 

 close relationship of the Columhae and Galli. 



The Crypturiformes show a remarkable number of specializations 

 of feather structure which are absolutely peculiar to them ; in 

 fact, it may safely be said that the barbs of tinamous have the 

 most perfect and highly specialized interlocking mechanism found 

 anywhere in birds. This fact alone is enough to show the error 

 of grouping them with the Ratitae, or even anywhere near them. 

 They miist undoubtedly be looked upon as a highly modified offshoot 

 £rom the Gralliformes, if the feather structure be taken into account 

 at all. 



e) Summary 



Crypturiformes are characterized as follows : 



(1) Plumules sparse, and found only between contour feathers. 



(2) Aftershaft present, often rudimentary, when well developed 

 with long shaft and distinct vanes. 



