. The biology of the amphibia. Amphibians. 142 THE BIOLOGY OF THE AMPHIBIA black background of melanophores. The guanophores, if freed of their lipophore cover, would appear blue for the same reason that the sky appears blue, namely because of the diffraction of light by small suspended particles. The rays at the blue end of the spectrum are more scattered than the rays of greater length. The scatter- ed rays include not only blue but also some green, indigo, and violet. In pass- ing back through the yellow color screen formed by the lipophores, the blue, indigo, and violet rays are absorbed a
. The biology of the amphibia. Amphibians. 142 THE BIOLOGY OF THE AMPHIBIA black background of melanophores. The guanophores, if freed of their lipophore cover, would appear blue for the same reason that the sky appears blue, namely because of the diffraction of light by small suspended particles. The rays at the blue end of the spectrum are more scattered than the rays of greater length. The scatter- ed rays include not only blue but also some green, indigo, and violet. In pass- ing back through the yellow color screen formed by the lipophores, the blue, indigo, and violet rays are absorbed and the green alone allowed to pass. Frogs thus appear green because, of the light which falls upon their skin, only the green rays escape absorption. Blue is a rare color in Amphibia but it occurs as a variation in Rana clamitans and normally in various other frogs. It is due to the same mechanism as green except that the lipophores are absent and the short blue, with some green, indigo, and violet rays, are reflected without the yellow screen to modify the result. Red is also not a common color in Amphibia. Red and yellow pigments are very closely allied and are produced by the same cell,. Fig. 55.—Diagrammatic section of the skin of a tree frog during color change. A. Bright green. The lipo- phores are arranged over the guano- phores and the melanophores are partly expanded. B. Dark green. The guanophores are cylindrical and are nearly surrounded by the melanophores. C. Lemon yellow. Lipophores and guanophores irregularly arranged and the melanophores are greatly con- tracted. D. Gray. The lipophores are greatly flattened and some are squeezed between the guanophores. The latter are completely surrounded by the melanophores. Ep., epidermis; Gu., guanophores; Li., lipophores; Me., melanophores. {After Schmidt.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illus
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