While it would be untrue to say that the Birds of Paradise are of a more amorous, or more excitable disposition than other less resplendent birds, one cannot but be impressed with the fact that they exhibit a range of variation in the matter of feather-ornament probably unequalled, and certainly unsurpassed, by any other group of birds. From what has been observed of the few species which have been kept in confinement, they seem to enjoy no less distinction in matters of display. On this latter subject no more of importance can be said, and exigencies of space forbid any attempt to describe the exquisite beauty of coloration which a survey of all the known species reveals. It would be hardly more profitable to attempt to describe the varied character of the shields, crests, frills, streamers, which are to be met with in different species: but a glance at the accompanying illustrations will show that it would be hard, indeed, to exaggerate the splendour of the ornamentation which these birds have developed. Even here, where no indication can be given of the glowing, vivid colours, often indescribably beautiful, it is obvious that these birds well deserve their name. St. John’s imaginary Paradise would probably have been described in far more enticing language had he known of the existence of these wonderful birds. Among all the known species the dullest is Wallace’s Bird of Paradise, the general coloration being of a dull brown hue; but even here, a pair of wing-coverts are produced into long, broad streamers, unique among birds; while the feathers of the throat and flanks are of a marvellous metallic green, the flank-feathers being produced to form a long, pointed tuft. To what factors must we attribute the growth of these wonderful colours, these strange outgrowths, frills, and tufts, and streamers, the like of which is almost unparalleled? In a group numbering some fifty or more species there is not one that does not display some strange feature. We cannot attribute it to the environment, for in such case the results should have produced uniformity; nor can we invoke the aid of sexual selection save in a very indirect manner, and in a sense other than generally understood by this term. It seems, then, not unreasonable to suggest that they are the expression points of the internal metabolism: the manifestations of that tendency to vary which is inherent in every fibre of the organism. But no attempt shall be made to elaborate this theory till more evidence has been taken. The humming-birds, and the game-birds, are perhaps the only other groups which exhibit quite such a prodigality of ornament; of the latter, instances have already been cited.