THE VISUAL PIGMENTS 



and 550 would, similarly, all be classified as ^d^i-retineneg — scotop- 

 sin,' the same as *porphyropsin' with ^max at 522 m/i. If, on the 

 other hand, we suppose that the five pigments are all cone pigments, 

 then 467 and 508 should have the composition *«eo-retinenei b — 

 photopsin' (i.e. the same as 'iodopsin' with Amax = 562 m/^), and 

 523, 533 and 550, the composition 'c/^i-retinencg — photopsin' (i.e. the 

 same as 'cyanopsin' with Amax = 620 m/^). 



The present results suggest, therefore, that there may be active 

 retinenci and retinencg isomers additional to those at present known, 

 or that there are more 'opsins' than two. 



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