314 
TROPICAL NATURE 
IV 
over the lower at each side, thus affording complete protection 
to the delicate tongue, the perfect action of which is essential 
to the bird's existence. The humming-bird's tongue is very- 
long, and is capable of being greatly extended beyond the 
beak and rapidly drawn back, by means of muscles which are 
attached to the hyoid or tongue-bones, and bend round over 
the back and top of the head to the very forehead, just as in 
the woodpeckers. The two blades or laminae of which the 
tongues of birds usually seem to be formed are here greatly 
lengthened, broadened out, and each rolled up ; so as to form 
a complete double tube connected down the middle, and with 
the outer edges in contact but not united. The extremities 
of the tubes are, however, flat and fibrous. This tubular and 
retractile tongue enables the bird to suck up honey from the 
nectaries of flowers, and also to capture small insects; but 
whether the latter pass down the tubes, or are entangled in 
the fibrous tips and thus draw back into the gullet, is not 
known. The only other birds with a similar tubular tongue are 
the sun-birds of the East, which, however, as we shall presently 
explain, have no affinity whatever with the humming-birds. 
Colours and Ornaments 
The colours of these small birds are exceedingly varied and 
exquisitely beautiful. The basis of the colouring may be said 
to be green, as in parrots ; but whereas in the latter it is a 
silky green, in humming-birds it is always metallic. The 
majority of the species have some green about them, especially 
on the back ; but in a considerable number rich blues, purples, 
and various shades of red are the prevailing tints. The 
greater part of the plumage has more or less of a metallic 
gloss, but there is almost always some part which has an 
intenser lustre, as if actually formed of scales of burnished 
metal. A gorget, covering the greater part of the neck and 
breast, most commonly displays this vivid colour ; but it also 
frequently occurs on the head, on the back, on the tail-coverts 
above or below, on the upper surface of the tail, on the 
shoulders or even the quills. The hue of every precious 
stone and the lustre of every metal is here represented; 
and such terms as topaz, amethyst, beryl, emerald, garnet, 
ruby, sapphire ; golden, golden-green, coppery, fiery, glowing, 
