KXTEKNAL ANATOMV, ■ MIGRATION. 
97 
tion, we may notice the very singularly formed wing of 
the Cape honeysucker {Ptihturus), distinguished no less 
for its very long plume-like tail, than for the form of its 
fifth quill feather, which is suddenly cotitracted, midway, 
to about half its length : and although the third and 
fourth have a slight indication of the same structure, 
the sixth is of the ordinary shape. We have drawn 
the attention of the ornithologist to these instances of 
unusual structure, because they have never been pointed 
out ; and several others could he mentioned ; but, as 
we are unacquainted with their influence on the habits 
and economy of the birds, the enumeration might be 
tethous. 
(87.) Migkation is performed by the wings ; but 
as this subject is more connected with the habits and 
instincts of animals, we shall merely give it, in this 
treatise, a passing notice in reference to external struc- 
ture. If there was any {)articular shape of wing more 
peculiar than any other to birds which migrate, it would 
seem to be that which we have designated as acuminated, 
that is, having the first two or three primaries fully de- 
veloped. The swallows, in this respect, are pre-eminent, 
and they are accordingly both the swiftest and the most 
distant migrators. Next to these are the bee-eaters, the 
rollers and the quails, which come from the shores of 
Africa in the spring, and after spending the summer in 
the southern half of Kurope, return to their home at the 
commencement of autumn. Nearly the whole of the 
American warblers {Sylvieolfc), together with the Maize 
birds {Agelainm), migrate in a similar direction, from 
south to north, and after breeding in the United States, 
return and pass the winter in the Mexican Gulf. All 
these tribes are characterised by having their wings more 
or less pointed ; a structure peculiarly adapted for such 
migrations ; but, on the other hand, there are numerous 
other species which annually perform the very same jour- 
neys by the aid of wings altogether different. We need 
only mention the orioles and the hoopoes as companions 
to the rollers, but whose wings have the three first quills 
li 
