722 - The Colors of Animals and Plants. [ December, 
ing this process of development, inequalities in the distribution 
of color may have arisen in different parts of the same feather, 
and that spots and bands may thus have become broadened out 
into shaded spots or ocelli, in the way indicated by Mr., Darwin, 
much as the spots and rings on a soap-bubble increase with in- 
creasing tenuity. This is the more probable, as in domestic 
fowls varieties tend to become symmetrical, quite independently 
of sexual selection. ( Descent of Man, page 424. 
f, now, we accept the evidence of Mr. Darwin’s most trust- 
worthy correspondents that the choice ef the female, so far as 
she exerts any, falls upon the ‘“ most vigorous, defiant, and met- 
tlesome male,” and if we further believe, what is certainly the 
case, that these are, as a rule, the most brightly colored and 
adorned with the finest developments of plumage, we have a real 
and not a hypothetical cause at work. For these most healthy, 
vigorous, and beautiful males will have the choice of the finest and 
most healthy females, will have the most numerous and healthy 
families, and will be able best to protect and rear those families. 
Natural selection, and what may be termed male selection, will 
tend to give them the advantage in the struggle for existence, 
and thus the fullest plumage and the firiest colors will be trans- 
mitted, and tend to advance in each succeeding generation. 
There remains, however, what Mr. Darwin evidently considers 
his strongest argument, the display by the male of each species 
of its peculiar beauties of plumage and color. Wethave here, no 
doubt, a very remarkable and very interesting fact; but this, 
too, may be explained by general principles, quite independent of 
any choice or volition of the female bird. During pairing-time 
the male bird is in a state of great excitement, and full of exu- 
berant energy. Even unornamented birds flutter their wings or 
spread them out, erect their tails or crests, and thus give vent to 
the nervous excitability with which they are overcharged. ‘Tt is 
not improbable that crests and other erectile feathers may be 
primarily of use in frightening away enemies, since they are gen- 
erally erected when angry or during combat. Those individuals 
who were most pugnacious and defiant, and who brought these 
erectile plumes most frequently and most powerfully into action, 
would tend to increase them by use, and to leave them further 
developed in some of their descendants. If, in the course of this 
development, color appeared, we have every reason to believe it ee 
would be most vivid in these most pugnacious and energetic indi- 
viduals ; and as these would always have the advantage m the a 
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