DEVELOPMENT OI' J AC AN A 301 



that they all l)C('onic ])ointc(I with a more noticeable down- 

 ward curve. (Fig. i)l).) 15y the time the chick is one-third 

 grow^n the hind claw measures exactly one-hall' of the hind 

 toe. The forward claws commence to elongate slowly, hut 

 still remain slightly curved. After several davs of steady 

 increase, however, the curve straightens out and the second 

 and third claws are nearly two-thirds as long as the hind 

 claw. This last is still growing, but more slowly, and com- 

 poses only a little more than half the toe. The rapid growth 

 of the front claws is of short duration and at maturity the 

 first claw is greatly lengthened again, far outdistancing any- 

 thing else, so that it finally makes up about two-thirds of 

 the hind toe. The other claw^s gradually straighten and 

 thicken, their development during the later stage being to- 

 ward strength rather than length. 



There can be but small hesitancy in declaring that the 

 claws are not a product of ancient acquirement; the last 

 doubt is swept aside b\' the fact that in the embryo, and even 

 the yoimg nestlings they are small and practically like those 

 of other birds. The long toes, on the other hand, are of more 

 ancient origin, for only in the very early embryonic stages 

 are they short. In later stages and at the time of hatching, 

 they are of enormous size and do not change proportionally 

 during the entire growth to maturity. When one sees the 

 jacana stalking in stately fashion from lily pad to pad — 

 with the pad often slowly sinking, but not too fast, because 

 of the evenly applied w^eight, one easily understands why 

 these characters exist; that their development is due to a 

 specialization of habit. 



Continually driven by some water-fearing animal or 

 other cause to seek safety and food on the lily pads, it soon 

 became a habit with the jacana to remain there. Because 

 the weight was applied more evenly to a larger space on the 

 pads, it followed that the bird with the longest toes could 

 travel farther, and glean more, and run less danger of falling 

 into the w\iter, possibly to be devoured, than those less for- 



