File:The bird, its form and function (1906) (14755563055).jpg

Identifier: birditsformfunct07beeb (find matches)
Title: The bird, its form and function
Year: 1906 (1900s)
Authors: Beebe, William, 1877-1962
Subjects: Birds Birds
Publisher: New York : Henry Holt
Contributing Library: Internet Archive
Digitizing Sponsor: Internet Archive

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e scales of reptiles. And in colour we have anothersimilarity between the two: lizards have both pigmentand prisms, and the scales of large snakes glow like opalswhen the sunlight falls on them. White never exists as a pigment in the feathers ofbirds, but is always due to innumerable air-spaces in thesubstance of the feather, by which the rays of light arereflected and deflected until, as in snow or foam, allcolour is lost and white results. In any one Order of birds there may often be founda series of species with colour patterns grading into eachother and connecting two extremes, perhaps very diversein appearance. But it is seldom that we can examinesuch a series at once, and, except in a large collection ofbirds skins in a museum, these wonderful life-chains, ortwig-tips of the tree of evolution seldom appeal to usvery forcibly. But in a feather it is different. We mayfind on one bird a most delicately graduated series, show-ing every step in the process by which simple unicoloured
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58 The Bird or spotted feathers assume most intricate and complexcolour masses and patterns. Darwin illustrates this very plainly in the case of theArgus Pheasant, and pays a fitting tribute to the evolu-tion of the marvellous colour patterns among birds. Theocelli on the wing-feathers of the Argus Pheasant areshaded in so wonderful a manner as to resemble ballslying loose within sockets. That these ornaments shouldhave been formed through the selection of many succes-sive variations, not one of which was originally intendedto produce the ball-and-socket effect, seems as incredibleas that one of Raphaels Madonnas should have beenformed by the selection of chance daubs of paint made bya long succession of young artists, not one of whom in-tended at first to draw the human figure. In order todiscover how the ocelli have been developed we cannotlook to a long line of progenitors, nor to many closelyallied forms, for such do not now exist. But fortunatelythe several feathers on the wing s

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