JACANAS. 103 



emliryo cliiok, altliough not so fully (lcvoloi)i>il, and this fact furnishes a beautiful illus- 

 tration of the law of ailaptation and design that i>revails throughout the whole ani- 

 mal kingdom. A bird endowed with a straight bill, or with an u])curved or dccurved 

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

 obtains its living, as must bo at once apparent to any one who lias watche<l this bird 

 runninn- rapidly round the boulders that lie on the surface of the ground, and insei-t- 

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

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

 K])ecies that is deserving of sjiecial 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 jieculiar habit of feed- 

 ing, there is less necessity for concealment by means of jirotective 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 e.Yjmsed to hawks and other enemies whilst the Anarliyiichiis is 

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

 this sort, however slight in itself, would have an apjn-eciable effect on the survival of 

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

 develojt itself, the specii's would at length, under certain conditions of existence, lose 

 the l)lack band altogether on the left-hand side." 



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

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

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

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

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

 due to Garrod and Forbes, conclusively ])roves that they belong to the present super- 

 family. Forbes remarks that, ])crliajis, no very definite conclusion as to their affinities 

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

 features only, l)ut that their osteological characters leave no doubt as to their real 

 ]>osilion. All the skulls of Jacanidie examined by him are strongly schizorhinal, 

 therein differing completely from those of the rails, and resembling the plovei-s and 

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

 absent in the rails, though occurring in all the Charadriid;e and Scolopacida^ which 

 he examined. The vomer is emarginate ajiically, while in the Kallida- it is sharji at 

 the point. From the Scolopacidro and Charadriidtc the skull diffei-s chiefly in lacking 

 occipital foramina and supra-orbital im])ressions. The sternum is quite unlike that of 

 the l{allida?. In the latter grou]) the stennnn is always jieculiar, in that the xiphoid 

 processes e.vceed in length the body of the sternum, which tapers to a ])oint posteri- 

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

 not<'hes. Tlie keel is also less well-developed, and the clavicles are weaker and 

 straighter, being less convex forward, than in the Jacanida-. The ]ielvis of the latter 

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

 jMistacetabidar ridge having hardly .any median ]>rojection, and the pelvis being widest 

 dorsally, just behind the antetrociianters ; in these and other jioints dilTering from the 

 rails. The toes are enonnously elongated and so are the claws. .iVuother external 



