EVOLUTION OF THE COLORS OP BIRDS. 101 



color fatigues only such nerves of the eye as respond to 

 it as a stimulant. Just as in music when the beats are 

 too frequent a dissonance is produced, so in looking 

 at a combination of colors if the recurrent interferences 

 are too frequent a discord is produced and the colors do 

 not please. 



The eye of the bird is a more perfect mechanical con- 

 trivance than the human eye, and is doubtless fully as 

 sensitive to the stimulus of various shades of color. To 

 be sure, it has been ascertained that birds see colors 

 entirely differently from mammals. Blue, for example, 

 is apparently excluded from their list.* Lloyd Morgan 

 says:f " If these facts be so, it is not too much to say 

 that the colour-vision of birds must be so utterly different 

 from that of human beings, that, being human beings, 

 we are and must remain unable to conceive its nature. 

 The factors being different, and the blending of the 

 factors by overlap being, by specially developed struct- 

 ures, lessened or excluded, the whole set of resulting 

 phenomena must be different from ours." This differ- 

 ence in the colors perceived by birds, however, does not 

 in the least interfere with the mechanical basis of color 

 harmony as laid down by Grant Allen. A female bird 

 would naturally prefer for a mate an individual in which 

 the feathers were not soiled and bedraggled, and also one 

 in which the colors did not produce any mechanical jar 

 (roughly speaking) upon the delicate optical mechanism. 

 Accordingly, given certain base colors, these might be 

 separated, refined, purified, intensified and even arranged 

 in certain patterns in order to produce a harmonious and 

 agreeable combination and contrast. 



To state briefly the factors operating in the production 



* Color-Vision and Color-Blindness. E. Brudenell Carter: Nature, xlii, 

 p. 56. 



t Animal Life and Intelligence, p. 285. 



