320 THE STRUCTURE AND LIFE OF BIRDS CH. XI 
Summary. 
Coloration can be in many cases explained as pro- 
tective. Dr. Wallace’s theory of exuberant vitality 
goes a long way to account for bright colours, song, 
and love antics. Patterns are in the main simple, and 
depend on laws of growth not yet understood : to one 
of these laws the name of correlated variation has 
been given. The grand plumes are explained by Mr. 
Stolzmann’s theory that the males are largely in 
excess, and that, therefore, Natural Selection in their 
case does not act, or even tends to make them less 
adapted for the struggle of life. 
SOME OF THE AUTHORITIES ON THE SUBJECT. 
Gadow: “The Colour of Feathers affected by Structure,” 
Proc. Zool, Society, 1882. 
Gadow : Article on Colour in Newton’s Dictzonary of Birds. 
Gadow : Bronn’s Zhzer- Reich, vol. “ Aves.” 
Darwin: Descent of Man, vol. ii. 
Wallace: Darwinism. 
Beddard : Animal Coloration. 
Geddes and Thompson : Evolution of Sex. 
Stolzmann : Proc. Zool. Soczety, 1885, p. 421. 
Hudson: Naturalist in La Plata. 
See also references given in footnotes in the course of this 
chapter. 
— 
