EXTERNAL PARTS OF BIRDS. — THE FEET. 137 



exhibit the transition from the perching to the gradient foot, in some reduction of the hind toe, 

 which is nevertheless in most cases still on the same level as the rest (fig. 38, h). In the 

 gallinaceous or rasorial (Lat. rasor, a scraper) birds, which are essentially terrestrial, and 

 noted for their habit of scratching the ground for food, the hind toe is decidedly elevated and 

 shortened in almost all of the families (fig. 35). Such reduction and uplifting of the hallux is 

 carried to an extreme in most of the waders, or gral- 

 latores, in many of which this toe disappears (tigs. 

 38, ff, 39). It is scarcely practicable to recognize special 

 modifications of such gradient or grallatorial feet, since 

 they merge insensibly into one another. The herons, 

 which are the most arboricole of the waders, exhibit a 

 reversion to the insessorial type, in the length and in- 

 cumbency of the hallux. The mode of union of the 



mation in Ereunetes ; front toes of the walkers and waders is somewhat char- Fig. 49. — Semi- 



' . . . m, . , , „ . , , palruated bathes of 



"at. size. acteristic. The toes are either cleft quite to the base, t^eg ^f Symphemla; 



or there joined by small webs ; probably never actually coherent. Such "at. size, 

 basal webbing of the toes is called semipalmation ("half-webbing"). It is actually the 

 same thing that occurs in many birds (jf prey, in most gallinaceous birds, etc. ; the term is 

 mostly restricted, in descriptive ornithology, to those wading birds, or grallatores, in which it 

 occurs. Such basal webs generally run out to the end of the first, or along part of the second, 

 phalanx of the toes ; usually farther between the outer and midtUe ,^« 



than between the middle and inner toes. Such a foot is well illus- 

 trated by the semipalmated plover (^gialites semipalmatus), 

 semipalmated sandpiper (Ereunetes pusillus, fig. 48), and willet 

 {Symphemia semipalmata, fig. 49). In a few wading birds, as the 

 avocet and flamingo, the webs extend to the ends of the toes. 

 This introduces us at once to the third main modification of the 

 foot, 3. The natatorial type. Here the foot is transformed into 

 a swimming implement, usually with much if not entire abrogation 

 of its function as foot or hand. Swimming birds with few ex- 

 ceptions are notoriously bad walkers, and few of them are percliers. 

 The swimming type is presented under two principal modifica- 

 tions : — (fl.) In the pnlmate or ordinary webbed foot, all the front pjg, 50. — Palmate foot of a 

 toes are united by ample webs (fig. 50). The palmation is usually tern, Sterna forsten; nat size, 

 complete, extending to the ends of the toes ; but one or both webs may be so deeply incised, 

 that is, cut away, that the palmation is practically reduced to semipalmation, as in terns of 

 the genus Hydrochelidon (fig. 51). The totipalmnte is a special case of palmation, in 

 which all four toes are webbed ; this characterizes the whole order 

 Steganopodes (fig. 52). (b.) In the lobate foot, a paddle results not 

 from connecting webs, but fi-om a series of lobes or flaps along the 

 sides of the individual toes ; as in the coots, grebes, phalaropes, and 

 sun-birds (Heliornithidee). Lobation is usually associated with semi- 

 pjilmation, as is well seen in the grebes (Podicipedidee) . In the snipe- 

 like phalaropes (Phalaro2}odida:) , lobation is present as a modification 

 of a foot otherwise quite cursorial. Tlie most emphatic cases of loba- 

 tion are those in which each joint of the toes has its own flap, with a p ^^j — inoiscl nal- 

 free convex border ; the membranes as a whole therefore present a scol- mation of Hydrorheiulon 

 loped outline (figs. 53, 53 his). Such lobes are merely a development '«"/"'-'"«•• "»* «*^e- 

 of certain marginal fringes or ]irocoss('s exhibited by many nmi-lobate or non -palmate birds. 

 Thus, if tlic foot of some of the gallinules be examined in a fresh state, the toes will be seen to 



