242 Form and Color in Nature. 



concentration of sensibility in that portion which was ordi- 

 narily directed forward, where food was received, and where 

 good and evil influences would probably oftenest make 

 themselves felt. 



We know nothing of the origin of the sense of taste, but 

 happily it seems least to require an exposition. The sense 

 of sight is connected intimately with our subject, and is in- 

 deed of the first importance. Let us see, if we can, what 

 was probably the method of its production. 



Doubtless most of you have noticed potato vines which 

 have sprouted in your cellars, or have seen other vines or 

 plants growing in rooms which were dimly lighted from 

 one small window or other aperture. If so, you have prob- 

 ably also noticed their lack of color, and have seen that 

 they were struggling toward the opening. Even these 

 vegetable growths are responsive to the light, and the same 

 fact you have seen evidence of, if you have not noticed it, 

 a thousand times, exhibited in many ways. Do you not 

 place your vase of fringed gentians in the full light of the 

 generous sun, and do they not promptly open their chalices 

 to drink in the welcome flood ? 



Now, this sensitiveness to the influence of light, in the 

 beginning shared alike by vegetable and animal, becomes 

 greater with the more active organism and greatest in that 

 portion of its surface which is most generally sensitive to all 

 impressions. By the time that there is a certain differentia- 

 tion of function in the parts there seems to be the initiation 

 of a nervous system with centers of activity and channels of 

 communication. The reaction of the surroundings upon 

 the individual rapidly tend to the perfection of the system. 

 (Of course, in describing all these processes, I am following 

 the development of forms, not giving the history of the 

 changes in a single individual.) Now, hitherto, such color 

 as appears is of the nature of that of which the biologists 

 speak as " adventitious " that is, resulting from the nature 

 and distribution of the ingredients, without any special re- 

 lation to function, or to specific causes which materially 

 affect the welfare of the individual. 



But investigation seems to show that there appeared a 

 greater degree of sensitiveness to the influence of light in 

 certain otherwise unimportant pigmentary deposits. This 

 greater sensitiveness having once been initiated, its devel- 

 opment by natural selection seemed to follow as a matter 

 of course. The motion of the light-waves impinging upon 



