HUMMING-BIRD 443 
dwarfed. Still the manus, in comparison with the other parts of 
the wing, is so long that the term JJacrochires is not wholly in- 
accurate. ‘The affinity of the Zrochilide and Cypselidx, once pointed 
out, became obvious to most careful and unprejudiced investigators, 
though there are a few systematists who refuse to admit its 
validity.1_ More than this, it is confirmed by an examination of 
other osteological characters. The “lines,” as a boat-builder would 
say, upon which the skeleton of each form is constructed are pre- 
cisely similar, only that whereas the bill is very short and the head 
wide in the Swifts, in the Humming-birds the head is narrow and 
the bill long—the latter developed to an extraordinary degree in 
some of the Tvrochilidxy, rendering them the longest-billed birds 
known.?__ Prof. Huxley considers these two Families, together 
with the Caprimulgidx (NIGHTJAR), to form the division Cypselo- 
morphxe—one of the two into which he separated his larger group 
Ajgithognathe. However, the most noticeable portion of the 
Humming-bird’s skeleton is the sternwm, which in proportion to 
the size of the bird is enormously developed both longitudinally 
and vertically, its deep keel and posterior protraction affording 
abundant space for the powerful muscles which drive the wings in 
their rapid vibrations as the little creature poises itself over the 
flowers where it finds its food.* 
So far as is known, all Humming-birds possess a protrusible 
tongue, in conformation peculiar among the Class Aves, though to 
some extent similar to that member in the Picidw (WOODPECKER)? 
—the “horns” of the HYOID apparatus upon which it is seated 
being greatly elongated, passing round and over the back part of 
the head, near the top of which they meet, and thence proceed 
forward, lodged in a broad and deep groove, till they terminate in 
front of the eyes. But, unlike the tongue of the Woodpeckers, 
that of the Humming-birds consists of two cylindrical tubes, taper- 
ing towards the point, and forming two sheaths which contain the 
extensile portion, and are capable of separation, thereby facilitating 
the extraction of honey from the nectaries of flowers, and with it, 
what is of far greater importance for the bird’s sustenance, the 
1 Especially Dr. Shufeldt (Proc. Zool. Soc. 1885, pp. 886-915, pls. lviii.-lxi., and 
Journ. Linn. Soc. xx. pp. 299-894, pls. xxi.-xxiv:) On the other side may be 
cited the views of Mr. Lucas (Auk, 1886, pp. 444-451). 
2 Thus Docimastes ensifer, in which the bill is longer than both head and 
body together. 
3 This is especially the case with the smaller species of the group, for the 
larger, though shooting with equal celerity from place to place, seem to flap 
their wings with comparatively slow but not less powerful strokes. The differ- 
ence was especially observed with respect to the largest of all Humming-birds, 
Patagona gigas, by Mr. Darwin. 
4 The resemblance, so far as it exists, must be merely the result of analogical 
function, and certainly indicates no affinity between the Families. 
