Therefore it becomes almost impossible to doubt--first, that they exist for the sake of ornament; and next, that the ornament exists on account of that relationship. If such structures were due merely to a superabundance of energy, as Mr. Wallace supposes, not only ought they to have been kept down by the economizing influence of natural selection; but we can see no reason, either why they should be so highly ornamental on the one hand, or so exclusively related to the sexual relationship on the other. [48] Note C. Finally, we must take notice of the fact that where peculiar _structures_ are concerned for purposes of display in courtship, the _elaboration_ of these structures is often no less remarkable than that of patterns where colours are thus concerned. Take, for example, the case of the Bell-bird, which I select from an innumerable number of instances that might be mentioned because, while giving a verbal description of this animal, Darwin does not supply a pictorial representation thereof. The bird, which lives in South America, has a very loud and peculiar call, that can be heard at a distance of two or three miles. The female is dusky-green; but the adult male is a beautiful white, excepting the extraordinary structure with which we are at present concerned. This is a tube about three inches long, which rises from the base of the beak. It is jet black, and dotted over with small downy feathers. The tube is closed at the top, but its cavity communicates with the palate, and thus the whole admits of being inflated from within, when, of course, it stands erect as represented in one of the two drawings. When not thus inflated, it hangs down, as shown in the second figure, which represents the plumage of a young male. (Fig. 124.) [Illustration: FIG. 124.--The Bell-bird (_Chasmorhynchus niveus_, 1/4 natural size). Drawn from nature (_R. Coll. Surg. Mus._). In the drawing of the adult male the ornamental appendage is represented in its inflated condition, during courtship; in the drawing of the young male it is shown in its flaccid condition.]