Herri CK. Color I'ision. 277 



color. The world would seem either light or dark or would be lighter 

 or darker. Such condition is couceivable as actually occurring in case 

 of the pineal eye of some vertebrates or the pigment fleck of lower 

 forms. 



la) Instead of the visual material being competent to react to all 

 rates of vibration, it might be specifically affected by only one 

 kind of light and so in white light and in the colored light correspond- 

 ing to its reaction capacity there would be sensation, while in all other 

 kinds of light there would be none. This possibility might be consid- 

 ered in some forms of color blindness. 



2) The color conditions might be as aliove but separate stations 

 be developed for producing the local indices or the elements to be 

 used in the formation of space perception. The fusion of several or- 

 gans of the elementary type resulting in the development of elemen- 

 mentary rod cells imbedded in a single pigment would produce this 

 result. 



3) We might assume the existence of three or four different pig- 

 ments or reaction-substances and that each of these is sensitive to 

 only a limited range of vibrations, while all are sensitive to white light 

 in so far as the latter contains potentially their own specific range. 



4) It might be assumed that but two kinds of pigment exist, but 

 that during a regeneration phase each of these produces a different 

 color effect from that produced during a degenerative phase, i. e., dur- 

 ing the actual decomposition while acted on by light. In this way 

 there would be produced in the nervous apparatus the foundation for 

 four color sensations. This would perhaps require that a third sub- 

 stance should be present for the production of white and black impres- 

 sions or it might be supposed that simultaneous action of the two sub- 

 stances postulated would be adequate for white production. 



5) Still again, it might be supposed that in transition from the 

 simple condition in (2) some of the cellular elements retained the prim- 

 itive material sensitive to light only, while others had undergone 

 higher differentiation and so were more complex and contained a 

 visual compound of greater molecular complexity capable of several 

 stages of decomposition before losing the bio-photic power. In this 

 case white sensation may be produced either (a) by the effect of homo- 

 geneous light acting on those elements (rods) containing the more 

 primitive pigment or (b) as a result of extreme alteration in the com- 

 plex pigment as an after effect of long or intense stimulation. 



Other postulates might be formulated but these may serve to in- 

 troduce the table which we translate from Dr. Calkins' paper above 

 referred to. 



