JA^ANAS. 103 



embryo chick, although not so fully developed, and this fact furnishes a beautiful illus- 

 tration of the law of adaptation and design that prevails throughout the whole ani- 

 mal kingdom. A bird endowed with a straight bill, or with an upcurved or decurved 

 one, would be less fitted for the peculiar mode of hunting by which the Anarhynchus 

 obtains its living, as must be at once apparent to any one who has watched this bird 

 running rapidly round the boulders that lie on the surface of the ground, and insert- 

 ing its scoop sidewise at every step, in order to collect the insects and their larvae that 

 find concealment there. But there is another feature in the natural history of this 

 species that is deserving of special notice. As already described, the fully adult bird 

 is adorned with a black pectoral band, which, in the male, measures .75 of an inch 

 in its widest part. Now it is a very curious circumstance that this band is far more 

 conspicuous on the right-hand side, where, owing to the bird's peculiar habit of feed- 

 ing, there is less necessity for concealment by means of protective coloring. This 

 character is constant in all the specimens that I have examined, although in a vari- 

 able degree ; the black band being generally about one third narrower, and of a less 

 decided color on the left side of the breast, from which we may, 1 think, reasonably 

 infer that the law of natural selection has operated to lessen the coloring on the side 

 of the bird more exposed to hawks and other enemies whilst the Anarhynchus is 

 hunting for its daily food. There can be no doubt that a protective advantage of 

 this sort, however slight in itself, would have an appreciable effect on the survival of 

 the fittest, and that, allowing sufficient time for this modification of character to 

 develop itself, the species would at length, under certain conditions of existence, lose 

 the black band altogether on the left-hand side." 



It is now generally conceded that E. Blyth was right when asserting that the 

 JACANID^E are closely allied to the plovers, and that they consequently do not belong 

 to the Rallidas, or rails, as has been nearly universally thought until recently. In their 

 general aspect, the long toes, and the nearly incumbent hind toe, the jayanas present 

 great analogy to the rails, but the internal anatomy, the knowledge of which is mainly 

 due to Garrod and Forbes, conclusively proves that they belong to the present super- 

 family. Forbes remarks that, perhaps, no very definite conclusion as to their affinities 

 could be drawn from a consideration of the pterylographic, visceral, and myological 

 features only, but that their osteological characters leave no doubt as to their real 

 position. All the skulls of Jacanidaa examined by him are strongly schizorhinal, 

 therein differing completely from those of the rails, and resembling the plovers and 

 their allies. There are well-developed basipterygoid processes, which are always 

 absent in the rails, though occurring in all the CharadriidaB and Scolopacidae which 

 he examined. The vomer is emarginate apically, while in the Rallidae it is sharp at 

 the point. From the Scolopacidaa and Charadriidaa the. skull differs chiefly in lacking 

 occipital foramina and supra-orbital impressions. The sternum is quite unlike that of 

 the Rallida?. In the latter group the sternum is always peculiar, in that the xiphoid 

 processes exceed in length the body of the sternum, which tapers to a point posteri- 

 orly, and from which they are separated by very long and well-marked triangular 

 notches. The keel is also less well-developed, and the clavicles are weaker and 

 straighter, being less convex forward, than in the Jacanidae. The pelvis of the latter 

 is also essentially plover-like, the ilia being wider and more expanded anteriorly, the 

 postacetabular ridge having hardly any median projection, and the pelvis being widest 

 dorsally, just behind the antetrochanters ; in these and other points differing from the 

 jails. The toes are enormously elongated and so are the claws. Another external 



