90 Clark, Pterylosis of Swifts and Hummingbirds. LJan. 



longest, and 10 rectrices; probably 9 secondaries, an alula of 3 

 feathers, an aftershaft on the contour feathers, no down feathers, 

 filoplumes rather few and mainly confined to the neck and back, 

 the feet feathered to the tarsal joint, the oil gland without a ter- 

 minal tuft of feathers, and the skin on the hand dark colored. 

 Whether the wing was originally aquincubital or not is open to 

 question but judging from the wings of the hummingbirds ex- 

 amined, the evidence would seem to favor the view that the quin- 

 cubital condition of most of the swifts is a specialized condition, 

 and the ancestral form was probably aquincubital. 



In the subsequent development of the Cypseli and Trochili, 

 the pterylosis of the head and neck became more specialized in 

 the latter group, while that of the back has been more modified 

 in the swifts; with the wings, specialization has occurred in both 

 groups, perhaps to a greater extent in Trochili, which have lost 

 the alula, and 2 or 3 secondaries, and are apparently approaching 

 the quincubital condition. Shufeldt ('88) in attempting to show 

 the absence of relationship between swifts and hummingbirds 

 lays much stress on the difference in the number of secondaries, 

 the form of the dorsal tract, the absence of supraocular and nuchal 

 apteria in swifts and the absence of femoral tracts and of black 

 skin on the hand in hummingbirds. As has been* repeatedly 

 shown in the previous pages, his position is clearly based on insuf- 

 ficient or unreliable evidence ; the number of secondaries is almost 

 wholly a matter of size, the form of the dorsal tract is a real dif- 

 ference but not inexplicable, the supraocular and nuchal apteria 

 are not absent in swifts, and the femoral tracts and black skin on 

 the hand are not wanting in hummingbirds. 



2. Is the pterylosis of the Caprimulgi sufficiently similar to that 

 of swifts or hummingbirds to give support to the view that they have 

 a common ancestry with either? 



In the judgment of the writer, no. Although the linear arrange- 

 ment of the feathers on the head of the Caprimulgi (see Clark, '94) 

 seems at first somewhat similar to that in Patagona (see Thomp- 

 son, : 01) the more the pteryloses of the two groups are compared, 

 the more evident it seems that there is no indication of a common 

 fundamental plan in the two. The upper cervical tract in the 

 Caprimulgi is quite narrow with no trace of a nuchal apterium, 



