THE THREE PLANS OF THE AVIAN FOOT. 51 



our truly lobe-footed birds. I may tinally consider the modes of union of 

 the anterior toes under the head of the 



§ 89. Three modifications of the bird's Foot. All birds' feet are 

 built upon one or the other of three plans, corresponding to the three sub- 

 classes Insessores, Oursores and JVakUoi-es. These are the jjer clang plan, the 

 iballiing or ivading plan, and the sioimming plan ; and those are pretty 

 sharply distinguished (independently of differences in the number and position 

 of the toes) by the method of union. In the perching plan, the toes are 

 only very exceptionally connected by true movable webbing ; thej' are cleft 

 to the base, or else joined, for a part, or the whole, of one joint, or a part 

 also of the second joint, b}^ actual cohesion. Our thrushes show about 

 as complete cleavage as is ever seen; our wrens, titmice, creepers, etc., 

 exhibit considerable basal cohesion. A remarkable exception is seen in the 

 sijngnesious foot; where the outer and middle toes fuse for nearly their 

 whole length; the kingfisher (figs. 116, 117), illustrates this; and all such 

 birds are called sijndactylous (Gr. sun together, dactylon a finger). In the 

 walking plan, the toes are never, probably, thus joined by fusion ; and they 

 are seldom cleft to_the base ; the union is generally by a movable basal web, 

 of variable extent. This constitutes the semijxdmate (^-webbed, that is,) 

 foot. But the webs occasionally, in true wading birds, run out to the ends 

 of the toes, as in the avocet (gen. 196), and in the flamingo (if indeed this 

 bird really belongs among waders). Generally they run out to the end of 

 the first, or along part of the second joint, constituting true semipalmation ; 

 shown in the semipalmated sandpiper and willet. (Figs. 166, 170.) Oftener 

 the web is of about this size between the outer and middle toes, and slighter 

 or wholly deficient between the middle and inner ; this is shown in nearly all 

 our larger waders, including herons. (It is also the usual state of webbing 

 of those hawks that have semipalmation.) In the swimming plan, the foot 

 is changed into a paddle by webbing or lobing ; the former constitutes the 

 palmate, and the latter the lobate, foot. In the palmate, the webbing is 

 usually complete betwixt the three front toes ; it is extended to the hind toe, 

 likewise, in all Steganopodes, and partly in the loons. Sometimes the 

 webbing is defective, from deep incision, or cutting away of the free anterior 

 border of the webs for some distance : this is seen partly in the genus Phi- 

 lacte (249) and much more so in the short-tailed tern, Hydrochelidon (gen. 

 292; fig. 208), where it simulates semipalmation. But in such a case, if 

 the fresh foot be carefully examined, the webbing will be seen running 

 as a narrow border, quite to the claws, as usual. Frequently, one web 

 is larger than the other, as in all our terns (fig. 207, for example) where 

 the inner web is somewhat defective. In the lobate foot, instead of con- 

 necting webs, we have a series of broad lobes along each joint of the 

 toes, as in the coot, and all the grebes : Init it is almost always, if not 

 always, associated with semipalmation. It occurs, again, in some wad- 

 ing birds, as the remarkable family of the phalaropes, which swim, in 

 fact, better than they walk. Here the lobatiou may be either scolloped, 



