1916] Chandler: Structure of Feathers 287 



(pi, 13, fig. 2c) differ only in their shortness, reaching a length 

 of considerably less than 1 mm., the width and flattened ribbon-like 

 form remaining the same. In the nestling feathers many of the 

 barbs bear barbules only near the base, the terminal portion being 

 extended hairlike or expanded into a more or less curled, flattened 

 plate (pi. 13, fig 2d). Duerden (1911) gives an interesting account 

 of the sequence in the plumages of ostriches. 



h) Relationships 



As has been shown, the feather structure of ostriches seems to 

 indicate a primitive rather than a degenerate condition. Their 

 wings, which have no specialized pennaceous remiges, and could 

 have no lifting function, are used for aiding the bird in running 

 against the wind, as suggested by Beebe (1904). This use is highly 

 suggestive of a possible course of evolution of flight. When once the 

 remiges had become pennaceous, nothing further would stand in 

 the way of their being used for true flight. Beebe (1904) looks 

 upon this use of the wings as a half return to the lifting function 

 of the wings in the flying ancestors which he assumes for the 

 group, a view which seems to me to involve so complicated a path 

 of evolution as to require very strong positive evidence to support it. 

 The same author remarks that "vestiges of barbicels" can easily 

 be distinguished. He evidently considered the downy feathers of 

 ostriches as being derived from pennaceous feathers, though nothing 

 in their structure or arrangement, it seems to me, need be inter- 

 preted as suggesting this. The barbules, while less specialized 

 than typical pennaceous barbules and more specialized than simple 

 down barbules, are not intermediate, and might be more easily 

 looked upon as marking the end of a short path of evolution of 

 their own, than as degenerate forms of either of the other types. 

 If the contour feathers of ostriches are not derivatives of pennaceous 

 feathers, then ostriches are not descendants of flight birds, and their 

 striking primitive characters need not be looked upon as secondarily 

 acquired. The absence of plumules, filoplumes, and aftershafts, the 

 even distribution of feathers over the entire body, and the similarity 

 of the neossoptiles to the teleoptiles, as well as the general form of 

 the barbules, all suggest the possibility of the ostriches not being 

 derived from birds with pennaceous feathers, and therefore not 

 from flight birds. 



