516 ADAPTATIONS TO PHOTIC QUALITY 



full color-vision system like that of other diurnal primates. One of their 

 two specimens proved to be totally color-blind. Trained to colored 

 papers, it was confused by gray ones — by dark grays with red and green, 

 medium grays with blue, and by light grays apposed to yellow stimuli. 

 Only a training-to-brightness was possible; and this was readily switched 

 over from responses to red versus blue to green versus yellow stimuli, and 

 from green versus yellow to dark gray versus green. In both of these cases, 

 a color-seeing animal would have been quite befuddled by the change. 



The second individual was trained to blue only. It could then be con- 

 fused by grays of a particular sequence, but did somewhat better as time 

 went on. This lemur was disturbed when switched from blue versus red 

 to light gray versus red; but since for the other animal blue was matched 

 by medium grays, differences in behavior toward blue and light gray are 

 not at all surprising and prove nothing as to color vision. 



The authors consider that if an animal makes no more than 30% errors 

 in a color-versus-gray discrimination it cannot be considered totally color- 

 blind. But, even if such a liberal allowance be made in this instance, we 

 cannot credit the lemur with having any more vivid color experiences 

 than the carnivores and the rodents. The situation in the lemurs — in 

 which diurnality is already firmly entrenched but whose color-sense is 

 only in its faintest beginnings — is the best of evidence for thinking that 

 primate color vision has arisen wholly within the primate stock. 



The situation in Cebus, as reported by Grether (1939, and in cor- 

 respondence with the writer) is especially interesting. Grether's four 

 individuals, of two species (C. unicolor and C. capucinus) , all gave every 

 evidence of being protanopic dichromates, with lowered sensitivity to 

 red and with a neutral point at about A,515m[X. Watson's (1909) data 

 on one Cebus are reconcilable with Grether's findings, though Watson's 

 procedure was not such as to reveal dichromasy in his animal. This one 

 genus, then, may have a dichromatic system as its standard equipment. 



The diversified Cebidae and the more homogeneous Hapalidae (mar- 

 mosets) comprise the platyrrhine (New- World) division of the Anthro- 

 poidea, opposed to the catarrhine series of Old- World forms. The 

 platyrrhines and the catarrhines are usually considered to have had quite 

 independent origins from lemuroid stock. If the lemuroid ancestors of 

 both had color vision, then all primate color vision stems from a single 

 beginning. If however the lemuroid common ancestor of all the monkeys 

 lacked color vision — as seems likely — then color-vision systems have 

 developed separately in the platyrrhines and the catarrhines. Again, 



