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THE THREE PLANS OF THE AVIAN FOOT. ok 
‘our truly lobe-footed birds. I may finally consider the modes of union of 
the anterior toes under the head of the 
§ 89. THREE MODIFICATIONS OF THE BIRD’S Foor. All birds’ feet are 
built upon one or the other of three plans, corresponding to the three sub- 
classes Insessores, Cursores and Natatores. These are the perching plan, the 
walking or wading plan, and the swimming plan; and these 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; they 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, by 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 
syngnesious 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 syndactylous (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 semipalmate (4-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: but 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 lobation may be either scolloped, 
