. A manual of zoology. Zoology. HISTORY OF ZOOLOGY 41 it is almost certain that in a great measure ttiey have been acquired by the males through the struggle for the female. In the case of birds a second factor has undoubtedly co-operated to impress distinctly the often enormous difference between the feathers of the male and of the female —as is shown, for example, in the case of the birds of paradise (fig. 15);. Fig. —Paradisca apoda, male (after Levaillant). for the nesting female inconspicuous colors and a close-lying coat of feathers are necessary in order that, undisturbed by enemie
. A manual of zoology. Zoology. HISTORY OF ZOOLOGY 41 it is almost certain that in a great measure ttiey have been acquired by the males through the struggle for the female. In the case of birds a second factor has undoubtedly co-operated to impress distinctly the often enormous difference between the feathers of the male and of the female —as is shown, for example, in the case of the birds of paradise (fig. 15);. Fig. —Paradisca apoda, male (after Levaillant). for the nesting female inconspicuous colors and a close-lying coat of feathers are necessary in order that, undisturbed by enemies, she may devote herself to incubation. On the Efficiency of Natural Selection.—In the course of the last twenty-five years there has been much controvers)^ as to how far natural selection alone is a species-forming factor. A number of objectors dispute the possibility of fortuitous variations being utilized in the struggle for. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
