496 ADAPTATIONS TO PHOTIC QUALITY 



Wagner gave the lizard ten additional control trials with both meal- 

 worms palatable, thus eliminating any discrimination on the basis of 

 taste, smell, or differential behavior on the part of the salted and un- 

 salted worms themselves. 



The most surprising discovery was that it was impossible to train the 

 lizards negative to green. Their preference for this, the most common 

 color in their natural environment, was so strong that when four colored 

 discs bearing palatable food were offered simultaneously, the numbers of 

 times they were approached were: green, 95; yellow, 79; red, 67; blue, 

 59. When four very different Hering gray papers (numbers 2, 7, 11, 15) 

 were similarly presented, the animals showed no preference for any. 



When for twenty successive trials gray, white, or black was offered 

 along with colors on a handle holding four discs, approaches to the 

 respective stimuli were as follows in three such series of trials : 



I. Gray, 14; green, 5; red, 1; blue, 0. 



II. White 11; green, 5; blue, 2; black, 2. 



III. Yellow, 9; red, 5; blue, 4; black, 2. 



Thus, gray was preferred to colors — even to green — and white was pre- 

 ferred as if having a value of light gray. Black seemed to have the value 

 of a color, next to blue (which would presumably be seen very darkly, 

 through the yellow oil-droplets present). 



Stimuli were thus valued by Lacerta agilis in two groups : (a) white, 

 grays of all medium shades, and green; (b) yellow, red, blue, and black. 

 Group V was strongly pi:eferred to group 'b\ 



With pairs of stimuli, Wagner obtained discriminations of red, orange, 

 yellow, yellow-green, ice-blue, deep blue, and violet from each other and 

 from any of seventeen grays. In keeping with the presence of only yellow 

 oil-droplets (though Wagner, apparently misled by the situation in his 

 colleague Wojtusiak's turtles, speaks of red ones also), hue-discrim- 

 ination seemed to be maximal in the red and blue, minimal in the green. 

 These determinations were crude and of course only tentative, awaiting 

 further work by some investigator using a greater variety of stimuli, 

 preferably in the form of spectral lights. 



There have been no reports bearing upon color vision in crocodilians, 

 except negative pupilloscopic ones. We know only that the spectral limits 

 of crocodilians correspond with those of mammals; and, from Laurens' 

 work, that the alligator has a Purkinje shift from a scotopic maximum of 

 ?L514m[X to a photopic one at X544m|i. 



