250 Zoologica : N. Y. Zoological Society. [I ; 13 



July 12 — 29.0 mm. One day chick. 



July 22—32.5 mm. 



July 23—35.3 mm. 



July 25—40.9 mm. 



July 27—46.2 mm. 



July 29 — 51.5 mm. Seventeen day chick. 



The average daily growth of the feather through the later 

 period is thus shown to have been 2.8 mm. The feather con- 

 tinued to grow at approximately the same rate until August 7th, 

 when the distal down portion was lost. The right central rec- 

 trice, to which the down was still attached (Fig. 98, A), on this 

 day measured 74.5 mm. By August 12th, all but two of the re- 

 maining tips — the right central and the next to the outer right 

 — had been lost. On August 13th, having persisted for a period 

 of thirty-two days, these last two disappeared, leaving the young 

 bird with the pennaceous juvenile tail feathers remarkably long 

 for an Anserine bird of its age, and with the tips of the feathers 

 not soft and pliable, but exceedingly stiff, the rhachis in each 

 feather showing a reduction in diameter only toward the tip, 

 which was broken squarely off. 



Although as has been stated, an increase in the length of 

 the rectrices was noted on the tenth day after hatching, it was 

 not until July 26, four days later, that incipient growth of the 

 under tail-coverts and the feathers of the pectoral tracts was 

 observed. These were the first of the contour feathers to ap- 

 pear, the upper tail-coverts and lower back feathers being de- 

 layed for another three days, so that the rectrices had begun 

 their growth a full week before the other important pterylse of 

 contour feathers. These latter carried the plumaceous feathers 

 on their tips for a very short period, the attachment being ex- 

 tremely weak and they were lost almost at once, as is the case 

 with the majority of birds. 



The interesting point about all this, is the impetus in growth 

 of the juvenile rectrices, hinting of some function in early life 

 of which we are still ignorant, and the alteration in structure of 

 the rhachis of the juvenile rectrices, due to the extremely inti- 

 mate relation which exists between these feathers and the pre- 

 ceding natal down. 



