OF ARTS AND SCIENCES. 259 



fine tracherc. The reddish color belongs to the bacillar-layer of the 

 optical nerve. 



T}ie Nature of Color and its Formation. 



"What is color ? Where does it come from, and what part of the 

 body is used to produce it? What kind of chemical process brings it 

 out? 



The importance of these questions is obvious, but science has not 

 answered them till to-day. Even the questions themselves have 

 scarcely been mentioned. It is a curious fact, though frequently 

 observed, that the nature of the most interesting phenomena is not 

 questioned at all, only because everybody meets them every day and 

 everywhere. 



The chemical nature of all colors — optical ones excepted — is 

 undoubtedly proved by the fact that colors can be destroyed par- 

 tially or entirely by chemical action. The greatest enemy of color is 

 light. The strong and continuous influence of light, principally of 

 sunlight, gradually fades every color, which is not sustained or re- 

 newed by the life of the insect. This fact is the more important, as 

 on the other hand the influence of light during life is a color-pro- 

 ducing one. But to produce color life is needed, for a continuous 

 fresh supply of matter to be changed into color. As soon as life 

 ceases and fresh matter is no longer supplied, the chemical influence 

 of light becomes too strong, and causes discoloration. 



I may here notice that Professor Sachs (Botau. Zeitung, 1863, 

 1865, and with Askenasy, 1867), by the examination of the influence 

 of light in producing the blossom-colors, arrived at this, result, that 

 the development of these colors is not dependent on the influence of 

 light. The size of the blossom and the intensity of its colors are 

 said to depend on fertilization by insects (Wallace).* Therefore on 

 high mountains or in northern regions, where the insect fauna is a 

 small one, the plants have large and intensely-colored flowers, which 

 are easily recognized at great distances. Dr. H. Muller (Kosmos, 

 August, 1880) is of the same opinion, "that the colors of flowers are 

 developed through the fertilization by insects, as he believes, in a pro- 

 gressive manner. Red, violet, and blue are always developed later, 

 by natural selection, than white and yellow. But there is no reason 



* Ch. Darwin : The Effects of Cross- and Self-fertilization in the Vegetable 

 Kingdom, 1877. 



