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SCIENCE 



[Vol. LV, No. 1430 



account of the fact that the three chroma' curves 

 overlap here, as is represented in Figure 1). 



riG. 3. The quadrigeminal color area — triangular 

 in shape. 



This figure illustrates the fact that while the 

 color field is a function of three variables when 

 you reproduce it by the mixing of specific 

 lights, you no sooner look at it than you see 

 that it consists of four distinct regions — the 

 whitish yellow greens, the reddish bluish whites, 

 etc. It suffices to upset at once the two "anti- 

 quated" (as they call them at the University 

 of Chicago) current theories. I make the yel- 

 low circle small to indicate (a) that yellow oc- 

 cupies a very narrow region in the spectrum, 

 (6) that it is the result of a secondary retinal 

 process, and (c) that it has been for a hundred 

 years invisible to the physicists. It is this 

 color curve, representing facts and not imag- 

 inations (like the color-curves of Hering), 

 which should, of course, always be drawn as 

 the belt-section of the color-pyramid. 



To meet the ditficulties of these antiquated 

 theories I have devised a theory (the develop- 

 ment theory) "which takes into account both 

 sets of fundamental facts which the other theo- 

 ries were respectively devised to explain," facts 

 which do however in reality collectively refute 

 them both. (You will not find even a picture 



5 I have been constantly urging, since 1913, the 

 use of the word chroma (plural, cliromata) to 

 obviate the shocking ambiguity in the present 

 meaning of ' ' color. ' ' 



of the color triangle in any of the writings of 

 the followers of Hering). It is a perfectly 

 simple theory (the theory of Hering is far 

 from simple — see Parsons, p. 673), and it is 

 wholly in line with the most recent conceptions 

 of the chemists — Harkins, Bohr, Soddy, Ru- 

 therford (who are now engaged in working out 

 the evolution of the atoms), Mathews, Wills- 

 tauer (chlorophyll and haemoglobin, Bayliss, 

 p. 252) and many others. This theory has 

 been pronounced to be unobjectionable by the 

 chemists, and it is now practically accepted by 

 most of the psychologists. 



The theory in brief is this : 



There is probably no other organ in the body 

 in which the record of development has been 

 preserved in such a remarkable fashion as in 

 the organ of vision. We have, pari passu with 

 the successive stages of specificity of response 

 to the visual spectriun, represented in Tig. 3, 



Fig. 4. Stages 1, 2 and 3 of the actual develop- 

 ment of the color sense. 



(1) an anatomical development of rods into 

 cones, and (2) a chemical development of the 

 rod-pigment sensitizer such that in man only 

 there is an intermediate stage, the visual yel- 

 low, between the "visual purple" and the final 

 leueo-base (Konig, Garten). What more nat- 

 ural than to suppose that there has been also a 

 development of the light-sensitive receptor 

 substance in the receptor organs (rods and 

 cones) of the retina? This developing sub- 

 stance must, however, be at the same time of 

 such a nature as to account for the singular 

 fact (unknown in any other region of sense) 

 that the colors successively developed are dis- 



