NESTLIXG FEATHERS OF THE. MALLARD. 



619 



identified (PI. II. fig. 6), and by the twenty-fifth day of incubation 

 they have grown into long fihunents out of which escape imme- 

 diately after hatching highly specialized protoptiles. During 

 the first week the nestling tail consists only of protoptiles (PI. lY. 

 fig. 15). but during the second week the protoptiles are pushed 

 from the skin by the tail-quills, or by vestigial mesoptiles. At 



Text-fiffure 6. 



This drawing shows that the rhachis of the shaft of a typical tail-quill protoptile 

 ends in a calamus containing "cones," that this calamus is directly continuous 

 with the expanded distal portion of the tail-quill rhachis, and that the connection 

 of the protoptile with the teleoptile is strengthened hy harbs at the tip of the 

 tail-quill ending in the proxiittal portion of the protoptile calamus. 



the end of the fourth week the tail-quills may be nearly an inch 

 in length, and they are still longer at the middle of the fifth 

 week (PI. IV. fig. 16). During the latter part of the fifth week 

 the protoptiles begin to break off, a,nd with the exception of the 

 ninth from the middle line at each side, they are usually all shed 

 by the middle of the sixth week. 



