296 TROPICAL WILD LIFE IN BRITISH GUIANA 



they seem scarcely separable. The uropygial gland is 

 feathered. 



The primaries and secondaries at last have commenced 

 to grow. They consist, like the tail, of down feathers, but 

 are very short, though the secondaries are only three-quarters 

 as long as the primaries. A most noticeable point is their 

 great weakness and smallness as compared with the tail. 



In a third, slightly older bird, the tail, which must have 

 grown rapidly, is comparatively long; true feathers have 

 taken the place of the down, which still adheres to their tips. 

 The relationship of the outer feather to the center is about 

 the same as in the preceding chick, but the tail as a whole 

 has far outstripped any other feathered portion of the body. 

 The coverts are still very close to the rectrices and the uropy- 

 gial feathers are greatly lengthened. 



Practically no growth has been made by the primaries; 

 the secondaries, however, have forged ahead and are half 

 again as long as the primaries. They are very short near 

 the wrist, but grow longer as they approach the elbow. None 

 of the wing feathers are more than half the length of the tail. 



When the yoimg jacana is half way to maturity its 

 tail is nearly full adult length, though the feathers are not 

 quite so strong and heavy as in the mature bird. The pri- 

 maries have now broken from their sheaths and a few even 

 surpass the secondaries in length. They are still very short, 

 however, l^xcept for the thumb, on which there are several 

 well developed sheaths, the pinion otherwise is practically 

 devoid of feathers. The primaries are divided into two sets : 

 the first, on the carpal portion of the hand, consisting of 

 foiu- short and rather weak feathers of equal length; the 

 second set, or outer set, is embedded in the digital portion of 

 the pinion. Beginning at the sixth, which is nearly twice 

 as long as the preceding four, they gradually shorten as they 

 approach the tip so that the outer primary is only as long 

 as the four on the carpals. The outer six are much stronger 

 and heavier than the others. (See Fig. 98.) 



