BEHAVIOR OF VERTEBRATES 435 



photic responses, but such responses were obtained in animals 

 in which the brain anterior to the metencephalon had been 

 excised. 



Mammals. Shepherd '^' made an interesting series of tests 

 upon the Rhesus monkey. The animal had to choose between 

 bits of food (cubes of bread or rice) differing in brightness or 

 m color tone. The colored food-cubes were soaked in color- 

 dyes. Punishment for wrong choice was effected by soaking 

 the bit of food which should have been avoided in a fairly strong 

 quinine solution. The remarkable thing about the results of 

 the experiment is the fact that the associations were formed very 

 rapidly. The selection of a very few of the quinine-soaked cubes 

 served to fix the correct response. If the animals were really 

 making the discrimination upon the basis of visual stimulation 

 arising from the differences of intensity or color-tone, and not 

 through smell, the unintentional signs given by the experimenter 

 or other extraneous cues, the rapidity of the rise of the discrim- 

 ination, when viewed in the light of similar tests upon other 

 animals, is little short of marvelous. 



The author maintains valiantly that his tests show keen 

 brightness discrimination, and ready discrimination of colors 

 on the basis of hue. But the method adopted was in so many 

 ways inadequate to solve so difficult a problem that detailed 

 criticism and discussion of the results must await a repetition 

 of the experiments by other means. 



Waugh 1** gives a belated report of his study on vision in the 

 mouse. Both albino and black and white mice were used. The 

 discrimination of light intensity was tested in two or three ways, 

 under both direct and indirect illumination. The mouse dis- 

 tinguished differences in grays and in brightness with consider- 

 able accuracy. Red and blue objects which appear of equal 

 intensity to the human eye are discriminated between by the 

 mice. .Red and yellow are preferred to blue and green. Accord- 

 ing to Waugh, albino mice do not show any discrimination 

 between red and white lights. Black mice distinguish between 

 very bright red and white of low intensity with greater difficulty 

 than colors which are to the human eye of equal brightness. 

 There is no discrimination between green and blue light. The 

 mice have a poorly developed perception of form. The distance 

 of objects is perceived within a range of 15 cm. The mice fail 



