DEVELOPMENT OF JACANA 297 



Til is gradual arrested development of the outer feath- 

 ers undoubtedly is a remnant of the long forgotten ages, 

 when the jacana was a tree climber. As in the hoatzin and 

 the pheasant — though to no such extent — the shortening 

 possibly carries back to the time when the young nestling 

 made its unsteady way from branch to branch, reaching and 

 cliniiinff with clawed fingers to whatever would lend a firm 

 wing hold. Now the claw at the tip of the wing is gone and 

 only a mere trace, in the shortening of these feathers, is left 

 to hint of those early habits. 



The reason for the curtailing of the four car])al remiges 

 still remains unsolved, though possibly it is due to certain 

 undetermined present day causes. 



At this stage the secondary coverts are very long and 

 extend beyond the secondaries for nearly four times their 

 length. They form a temporary, secondary wing of sorts, 

 and are fully matured in length. ( See Fig. 98.) The accel- 

 eration must be due to some fairly recent cause and undoubt- 

 edly they are of great aid to the young bird essaying its early 

 flights. The wing rapidly changes to its normal appearance 

 between half maturity and maturity, so that by the time the 

 chick attains its full juvenile plumage, the primaries, secon- 

 daries and their coverts have assumed their natural adult 

 condition. 



Embryos are supposed to retain throughout their early 

 stages some at least of their ancestral characters, which later 

 disappear. Some characters are especially prominent at first 

 and then die out, while others remain to disappear more 

 slowly at later stages in life. Thus the rapid growth of the 

 tail in the jacana, both in the embryo and immature bird, 

 would seem to be an ancient character which has been checked 

 toward maturity in the modern bird through lack of use or 

 some other cause. Its advanced development in the young 

 embryo shows that it is one of the oldest ancestral feather 

 characters and must have played an important part at some 

 time. This being the case, the tail was probably, at some 



