N. S. Shaler, On the Recent Formation of a Small Anticlinal Axis in Lincoln County, Kentucky; E. D. Cope, On the Origin of Structural Variation; A. R. Grote and W. H. Pitt, New Specimens from the Water Lime Group at Buffalo; Samuel J. Wallace, On Geodes and Other Fossiloids; James E. Todd, On the Annual Deposits of the Missouri River during the Post-Pliocene; Ernst Gundlach, A New Periscopic Eye-Piece; Alexis A. Julien, Accessories adapted to Lithological Investigation; George W. Morehouse, Objectives as Illuminators; C. Leo Mees, On the Use of Ordinary Low-Power Objectives for Photography; R. H. Ward, On the Cellular Structure of Dentine; On a Modification of Wenham's Reflex Illuminator; T. O. Summers, Jr., On the Relative Values of the Powers of Objectives and Eye-Pieces; T. Sterry Hunt, Notes on the Silurian Waters of Washoe, Nevada; Shuze Isawa, On the Origin of the Japanese; Garrick Mallery, The Former and Present Numbers of our Indians; Henry Gillman, Additional Facts concerning Artificial Perforations of the Cranium in Ancient Mounds in Michigan; Edwin A. Barber, Habits of the Moqui Tribe; J. W. Powell, Some Popular Errors concerning the North American Indians; Alexis A. Julien, On the Ancient Excavations of Western North Carolina; H. N. Rust, Report on the Exploration of the Graves of the Mound Builders in Scott and Mississippi Counties, Missouri; J. W. Powell, Introduction to the Study of Indian Languages; Joseph B. Killebrew, Geology and Topography of the Oil Regions of Tennessee and the Oil Springs and Wells; T. Sterry Hunt, Notes on the Geology of the Rocky Mountains; James M. Safford, Notes of a Specimen of Cyrtodonta ventricosa from the Lower Silurian; A. E. Wetherby, The Variation of Certain Fresh-Water Mollusks of the United States, and their Geographical Distribution; J. H. Huntington, Geology of the Region on the Head Waters of the Androscoggin River; E. D. Cope, On the Characters of a New Cretaceous Saurian from the Rocky Mountains; E. L. Drake, A Section of McKinny Hill, Tennessee; B. S. Hedrick, On the Use to be made of Post Route Maps in the Advancement of Science: E. T. Cox, Geological Position and Mode of Origin of Hydrated Brown Oxide of Iron; R. L. Kirkpatrick, On the Relation of Organ to Function, or of Form in General to Mode of Energy received and exerted; James A. Ridley, On the Fibre of Gossypium herbaceum (cotton plant) considered with Reference to a Practical Application of its Manufacture.

SCIENTIFIC SERIALS.1

THE GEOLOGICAL MAGAZINE. August. Across Europe and Asia. Traveling Notes (Part II.), St. Petersburg to Perm, by John Milne. A Sketch of the Geology of Keighley, Skipton, and Grassington, by J. R. Dakyns. Notes on the Correlation of the Beds

1 The articles enumerated under this head will be for the most part selected.

constituting the Upper Greensand and Chloritic Marl, by A. J. Fukes Browne.

THE GEOGRAPHICAL MAGAZINE.-August. The Arctic Expedition, xvii. Refutation of the Assertions of Hostile Critics. The Bengal Cyclone of 1876. Affairs in Japan, by R. H. Brunton. The Livingstonia Mission, by J. Thornton Macklin and J. Stewart. The Great Earthquake on the Coast of Peru of May 9, 1877. Exploration in Patagonia, by F. P. Moreno. The India-Rubber Trees in Brazil, by Robert Cross.

SCIENCE GOSSIP.-August. A Sketch of the Geology of Plymouth and the Neighborhood (illustrated). Botanical Notes in the Neighborhood of Cader-Idris. The Seals and Whales of the British Seas, No. 3 (illustrated). Another Sketch in the West of Ireland (illustrated). The Economical Products of Plants (illustrated). A Microscopical Slide-Box (illustrated).

MICROSCOPICAL JOURNAL. - August. A Simple Device for the Illumination of Balsam-Mounted Objects for Examination with Certain Immersion Objectives whose " Balsam Angle" is ninety degrees or upwards, by J. J. Woodward. An Essay on the Classification of the Diatomaceæ, by M. Paul Petit, translated by F. Kilton. Note on a New Paraboloid Illuminator for Use beneath the Microscope Stage. Also Note on the Resolution of Podura Scale by Means of the New Paraboloid, by James Edwards. The Development of the Ovum, by W. N. Dallinger and J. Drysdale. German Methods in Histology and Embryology, by Charles Sedgwick Minot.

AMERICAN JOURNAL OF SCIENCE AND ARTS. September. Notes on the Internal and External Structure of Paleozoic Crinoids, by C. Wachsmuth. Phenomena of Binocular Vision, by J. LeConte. The Relation of the Geology of Vermont to that of Berkshire, by J. D. Dana. Notice of a New Genus of Annelids from the Lower Silurian, by G. B. Grinnell. New Vertebrate Fossils, by O. C. Marsh.

BULLETIN OF THE UNITED STATES GEOLOGICAL AND GEOGRAPHICAL SURVEY OF THE TERRITORIES. - Vol. iii., No. 4. The First Discovered Traces of Fossil Insects in the American Tertiaries, by Samuel H. Scudder. Description of Two Species of Carabidæ found in the Interglacial Deposits of Scarboro Heights, near Toronto, Canada, by Samuel H. Scudder. Report upon the Insects collected by P. R. Uhler during the Explorations of 1875, including Monographs of the Families Cydnidæ and Saldæ, and the Hemiptera collected by A. S. Packard, Jr., M. D., by P. R. Uhler. Description of Cambarus Couesi, a New Species of Crawfish from Dakota, by Thomas H. Streets, M. D. U. S. N. On a Carnivorous Dinosaurian from the Dakota Beds of Colorado, by E. D. Cope. A Contribution to the Knowledge of the Ichthyological Fauna of the Green River Shales, by E. D. Cope. On the Genus Erisichthe, by E. D. Cope.

THE

AMERICAN NATURALIST.

VOL. XI. NOVEMBER, 1877. No. 11.

THE COLORS OF ANIMALS AND PLANTS.1

BY ALFRED RUSSEL WALLACE.

I. THE COLORS OF ANIMALS.

THERE is probably no one quality of natural objects from which we derive so much pure and intellectual enjoyment as from their colors. The "heavenly" blue of the firmament, the glowing tints of sunset, the exquisite purity of the snowy mountains, and the endless shades of green presented by the verdureclad surface of the earth, are a never-failing source of pleasure to all who enjoy the inestimable gift of sight. Yet these constitute, as it were, but the frame and background of a marvelous and ever-changing picture. In contrast with these broad and soothing tints, we have presented to us, in the vegetable and animal worlds, an infinite variety of objects adorned with the most beautiful and most varied hues. Flowers, insects, and birds are the organisms most generally ornamented in this way; and their symmetry of form, their variety of structure, and the lavish abundance with which they clothe and enliven the earth cause them to be objects of universal admiration. The relation of this wealth of color to our mental and moral nature is indisputable. The child and the savage alike admire the gay tints of flower, bird, and insect; while to many of us their contemplation brings a solace and enjoyment which is both intellectually and morally beneficial. It can then hardly excite surprise that this relation was long thought to afford a sufficient explanation of the phenomena of color in nature, and although the fact that

"Full many a flower is born to blush unseen,

And waste its sweetness on the desert air"

might seem to throw some doubt on the sufficiency of the explanation, the answer was easy: that, in the progress of discovery, 1 From Macmillan's Magazine.

Copyright, 1877, by A. S. PACKARD, JR.

man would, sooner or later, find out and enjoy every beauty that the hidden recesses of the earth have in store for him. This theory received great support from the difficulty of conceiving any other use or meaning in the colors with which so many natural objects are adorned. Why should the homely gorse be clothed in golden raiment, and the prickly cactus be adorned with crimson bells? Why should our fields be gay with buttercups, and the heather-clad mountains be clad in purple robes? Why should every land produce its own peculiar floral gems, and the Alpine rocks glow with beauty, if not for the contemplation and enjoyment of man? What could be the use to the butterfly of its gayly-painted wings, or to the humming-bird of its jeweled breast, except to add the final touches to a world picture, calculated at once to please and to refine mankind? And even now, with all our recently acquired knowledge of this subject, who shall say that these old-world views were not intrinsically and fundamentally sound, and that although we now know that color has "uses" in nature that we little dreamed of, yet the relation of those colors to our senses and emotions may be another and perhaps more important use which they subserve in the great system of the universe?

We now propose to lay before our readers a general account of the more recent discoveries on this interesting subject, and, in doing so, it will be necessary, first, to give an outline of the more important facts as to the colors of organized beings; then, to point out the cases in which it has been shown that color is of use; and, lastly, to endeavor to throw some light on its nature and the general laws of its development.

The

Among naturalists color was long thought to be of little import, and to be quite untrustworthy as a specific character. numerous cases of variability of color, led to this view. The occurrence of white blackbirds, white peacocks, and black leopards, of white bluebells, and of white, blue, or pink milkworts led to the belief that color was essentially unstable; that it could therefore be of little or no importance, and belonged to quite a different class of characters from form or structure. But it now begins to be perceived that these cases, though tolerably numerous, are, after all, exceptional, and that color, as a rule, is a constant character. The great majority of species, both of animals and plants, are each distinguished by peculiar tints which vary very little, while the minutest markings are often constant in thousands or millions of individuals. All our field buttercups are

invariably yellow, and our poppies red, while many of our butterflies and birds resemble each other in every spot and streak of color through thousands of individuals. We also find that color is constant in whole genera and other groups of species. The Genistas are all yellow, the Erythrinas all red; many genera of Carabidæ are entirely black; whole families of birds as the Dendrocolaptide-are brown; while among butterflies the numerous species of Lycæna are all more or less blue, those of Pontia white, and those of Callidryas yellow. An extensive survey of the organic world thus leads us to the conclusion that color is by no means so unimportant or inconstant a character as at first sight it appears to be; and the more we examine it the more convinced we shall become that it must serve some purpose in nature, and that besides charming us by its diversity and beauty it must be well worthy of our attentive study, and have many secrets to unfold to us.

In order to group the great variety of facts relating to the colors of the organic world in some intelligible way, it will be best to consider how far the chief theories already proposed will account for them. One of the most obvious and most popular of these theories, and one which is still held, in part at least, by many eminent naturalists, is that color is due to some direct action of the heat and light of the sun, thus at once accounting for the great number of brilliant birds, insects, and flowers which are found between the tropics. But here we must ask whether it is really the fact that color is more developed in tropical than in temperate climates in proportion to the whole number of species; and, even if we find this to be so, we have to inquire whether there are not so many and such striking exceptions to the rule as to indicate some other causes at work than the direct influence of solar light and heat. As this is a most important question we must go into it somewhat fully.

It is undoubtedly the case that there are an immensely greater number of richly-colored birds and insects in tropical than in temperate and cold countries; but it is by no means so certain that the proportion of colored to obscure species is much or any greater. Naturalists and collectors well know that the majority of tropical birds are dull colored; and there are whole families, comprising hundreds of species, not one of which exhibits a particle of bright color. Such are the Timaliide of the eastern and the Dendrocolaptide of the western hemisphere. Again, many groups of birds, which are universally distributed, are no more