igiS.] Under Winn -Coverts of Birds. 5fil 



the genus Astur had some of the major under coverts with 

 the contrary overlap, while Polybornides had all of these 

 coverts conforming; for the more primitive Polyhoroides 

 has, for a Bird-of-Prey^ a slow and laboured flight, while the 

 small African Goshawks are the last thought in swift and 

 skilful movement on the wing. 



Further steps in the modification of the reversed under 

 coverts from the primitive type are found in the reduction 

 or disappearance of one or otlier of the two rows, in part or 

 in whole ; for the tendency of the evolution seems to be 

 toward the neglect and loss of these feathers^ in the process 

 of perfecting the remiges. That the median series is incom- 

 plete on the manus in all the birds examined, and in the 

 majority is reduced to one or two feathers, or none, on this 

 part of the wing, has already been noticed. The median 

 coverts have become very small in some groups, even on the 

 cubitus, and in some entirely disappear. 



Bearing in mind these two tendencies in the evolution of 

 the wing, in respect to the reversed under coverts — that 

 to reduction and that to the assumption of the contrary 

 overlap, — we may arrange groups of birds in series showing 

 the different stages. Thus, the Game-birds have the median 

 coverts very small and of little use ; in the Plantain- 

 eaters they have quite disappeared ; in the Cuckoos, not only 

 have the median coverts disappeared, but the major coverts 

 show a strong tendency to take their place functionally by 

 assuming their contrary overlap. In this series it is the 

 median coverts that are reduced, and disappear ; another 

 may be arranged in which that process is exemplified in the 

 cubital major under coverts. The Doves have small cubital 

 major under coverts, quite hidden by the median row ; the 

 same condition was found in the one species of Trogon 

 examined ; the Kingfishers show a still further reduction 

 of these cubital major under coverts, and in some species 

 (birds of small size) a total disappearance of them ; the 

 Bee-eaters retain only occasional vestiges of them ; in the 

 Barbets and Woodpeckers not even such vestiges were found. 

 The Passeriform birds show all stages of reduction and 



