^4 



THE BIOLOGY OF BIRDS 



Professor Cossar Ewart's Recent Work.— Some of 

 the observations made on the mallard and other birds by 

 Professor Cossar Ewart show that we are far from security 

 or clearness in regard to the succession of plumages, and we 

 propose to sum up his more important conclusions. These 

 have, of course, to meet the criticism of other investigators. 

 The coat worn by newly hatched ducks and geese 

 corresponds to the first or protoptile 

 nestling coat of penguins. The 

 second set (mesoptiles) is disappear- 

 ing, though still represented on the 

 wing. 



The wing-quill protoptiles are 

 complete feathers, with a calamus, 

 a shaft, and an aftershaft. Though 

 small, they are complete ; with short 

 stiff, as well as long, slender barbs ; 

 with well-developed and in some 

 cases hook-like cilia ; and with a 

 well- developed aftershaft, the bar- 

 bules of which bear cilia. Thus there 

 is nothing degenerate about these 

 protoptiles. 



But the mallard has mesoptiles 



(second set) well-developed as well 



4.— A mesoptile (m) as protoptiles. They occur as wing- 



So^a p™,ip,ir(Nr <=°™rts and wing-quills. Both sets 



may be seen in the mallard duckling 



at the end of the sixth week, but all are usually lost before 



the middle of the eighth week. 



The nestling tail of the mallard duckling, of importance 

 in early diving, consists at first of eighteen protoptiles. 

 During the second week these are pushed from the skin 

 by the tail-quills, or by vestigial mesoptiles. For the rest 

 of their diving period (six weeks) the mallard ducklings use 

 teleoptile tail-quills. There are vestiges of two tail-quill 

 mesoptiles, so that even in the tail there is distinct evidence 

 of two generations of neossoptiles. 



Fig 



