812 LIGHT AND LIFE 



the lack of agreement observed in Fig. 14 could indicate either a 

 different kind ot photopigment, or possibly, that the response func- 

 tion is derived from interaction of two or more receptor systems. 

 These arguments apply equally well to the other two systems. How- 

 ever, the present figure demands some explanation if we are to in- 

 terpret these in terms of known photopigments. A modified response 

 could either be caused by a pigment unlike the retinene-opsin series 

 or it could result from the interference of stable screening pigments. 

 A third explanation is that perhaps neuronal interaction occurs in 

 some manner in which subtraction takes place, to leave a residual 

 having its maximum at 650 m^u.. 



No definite answer can be given now as to which of these possibili- 

 ties is responsible, or if indeed some mechanism not yet considered 

 is operative. 



Conclusions 



In the goldfish retina electrophysiological evidence can be found 

 for color vision. When taken together, the chromatic {"C") and 

 luminosity ("L") responses recorded in the intermediate layers of 

 the retina contain sufficient information to permit the animal to 

 distinguish various colors as well as brightness. The wavelength- 

 sensitive "on" and "off" responses from the retinal ganglion cells 

 should be adequate to transmit this color information to the brain. 

 Furthermore, the sensitivity curves obtained from these responses sug- 

 gest the possible presence in the receptors of three photopigments 

 with absorption maxima at 500, 600, and 650 m^. The 500 and 

 600 rufx pigments can be adequately fitted to curves of the rhodopsin 

 type calculated from Dartnall's nomogram (5). The 650 ni/^ pigment 

 has a much narrower absorption curve than the theoretical one. 



At present many problems remain unsolved. The actual absorp- 

 tion curves of the pigments must be measured. The ganglion cell 

 responses must be more closely correlated with the "C" and "L" re- 

 sponses. The color-discriminating ability of the goldfish must be 

 studied in more detail to alloAv accurate comparisons with the 

 electrophysiological data. 



REFERENCES 



1. Arden, G. B., /. Physio!., 12.% 377-.m5 (1954). 



2. Rrindlcv, G. S., Fliysi()lo{ry of Ike reti>ui intd ihr vi.siKil JMilliiray, Edward 



Arnold, Ltd., London (lOGO). 



3. lirown, K. T., ami Wic-scl. I. N.. A,». J. ()j,hll,a!inol.. 46, No. 3. Pt. 2. 01-0(i 



(1958). 



4. Byzov, A. L., and Ulina, L A., Biophysics (U. S. S. R.) (/wi-j/rv/; Transhitwn). 



4, 64-76 (19.59). 



