enabled to seize and hold insects. Says Martin: "It is by a pumping or sucking action, as we have every reason to believe, that nectar or fluids are absorbed by the tubular tongue of these birds. In no other vertebrate animals, as far as we know, is the tongue constructed as a tubular sucking-pump: so far, the humming-birds stand alone; and this circumstance in itself, considering it with reference to organic structure, might be adduced as a reason for regarding these birds as a distinct order."
Mr. Thomas Belt, author of "The Naturalist in Nicaragua," indicates another function performed by the curious cleft tongue of the humming-bird, viz., the capture of insects. As we have seen, this organ is, for one-half its length, made up of a substance like rather stiff parchment, or horn, and split in two. When at rest, the two
Fig. 3.
Tongue of Humming-bird, with Blades a little opened.
halves are laid flat against each other, but they can be separated at the will of the bird, and form a pair of forceps, admirably adapted for picking out minute insects from among the stamens of flowers.
We may admire the elegance of form and the quickness of motion of these birds, but the dazzling splendor of their plumage, resembling that of burnished metal or polished gems, changing with every change of position, has a charm for the dullest observer, and a fascination for the more sensitive. The wonderful change in color that takes place, according to the position of the light, from brilliant green, through the brightest golden tints, to intense velvety-black, or from black to emerald, or ruby, or crimson, or flame-color, reminds one of fairy-land, or the tales of the genii. Where a metallic lustre prevails, the plumage is always composed of feathers so shaped as to appear to have the form of scales. The birds vary in respect to the parts that have these feathers. While most have them on the throat, many have them on the breast and head; others have them also on the back; some have them on the wing-coverts or tail; and a few have them on nearly all parts, except the long wing-feathers, which are generally of a purplish-brown. It may here be asked, What causes the gorgeous metallic lustre of their plumage, and the rich, changing tints of the various colors, representing every hue of the rainbow, purple, amethyst, fiery crimson, brilliant ruby, radiant topaz, emerald green, resplendent blue, and glossy violet, which, in certain lights, often gleam with a refulgence that almost dazzles the eye? They have been attributed to various causes; but it appears to be the condition of the surface of the feathers that produces the iridescence. The surface is striated, or has minute furrows, like the nacre, or mother-of-pearl of the Haliotis, and other sea-shells, which decompose the light—absorbing part, and re-
