COLOR VISION IN MAMMALS 505 



would as soon as not derive some structure in the human eye from some- 

 thing or other in the eye of a horse. 



Diurnahty, with its expectation of color vision, is thus a habit which, 

 so far as the mammals are concerned, has cropped out only in forms a 

 little removed from the bottom of the heap — and a great way from the 

 ungulates and carnivores which sit on top. In a survey of the mammals, 

 we can perceive no majestic progress in the evolution of color vision from 

 an imperfect system in primitive groups to a complex one in the highly 

 specialized orders. On the contrary, we find a fully-developed color 

 system only near the roots of the class, in the primates; and in the higher 

 subdivisions there are only the most rudimentary of color-senses, if any. 

 So, to avoid anticlimax, we can best review the subject of color vision in 

 mammals in reverse order, starting with the higher groups and progress- 

 ing to the lower ones. 



The ungulates afford a classical supposition: that male cattle are in- 

 furiated by red objects. In 1923 Kittredge began some experiments with 

 a calf which yielded only negative results as far as they went, but were 

 unfortunately never concluded. In the same year Stratton summed up 

 some simple experiments as indicating that cattle pay as much attention 

 to green as to red, more yet to white, and are most aroused by any flut- 

 tering object, whatever its color may be — especially when the object is 

 unfamiliar. Red has no special emotional value, hence cannot be assumed 

 to arouse a distinct sensation quality. A whole herd of European stud 

 bulls were once provided with red veils, which entirely failed to disturb 

 their equanimity. 



Oddly enough, the horse has never been the subject of any extended 

 study of color vision. Large animals are not in favor with psychologists 

 as experimental material, for obvious reasons; but even so, the docility 

 and intelligence of the horse qualify him admirably for exploitation. As 

 indications of color vision, however, we have only such items as the old 

 report that a French army horse, in North Africa, was able to distin- 

 guish his master in a red uniform from other men in blue ones, at a dis- 

 tance of 600 meters — a hundred meters farther away than he could make 

 the distinction without benefit of the color-difference in uniforms. But, 

 there is nothing here to show that the discrimination was on the basis of 

 hue rather than of brightness. 



Among the carnivores, the dog, cat, raccoon, and two mustelids — the 

 European stone- or beech-marten and the polecat — have been studied. 

 Color vision was affirmed for the dog by Gates in 1895, Himstedt and 



