BEHAVIOR OF VERTEBRATES 425 



graue und blaulichgraue Korner reichlich zur Verfiigung stan- 

 den." (P. 445-) 



Upon a dead-black table cloth 15 by 39 cm. in diameter he 

 lightly fastened yellow-red grains and between these strewed 

 the different greens and greys. On the second day the hen 

 avoided not only the yellow-red grains, but also the red grains 

 and the bluish red, and pecked only at the greys and greens. 

 This was also the case when he strewed red grains among the 

 greens and the greys (although in this case the red grains were 

 no longer fastened down). With astounding quickness and 

 sureness the animal pecked all the green and grey grains lying 

 between the red grains. If there were only a few of these at 

 hand, it hunted all over the entire cloth between the red grains 

 so that after several seconds only the red ones remained un- 

 touched. If he brought such a hen into the dark room to a 

 row of white rice grains, strewed upon a black background, 

 which were not fastened down, and colored these by means of 

 the spectrum, she here likewise left the red and yellow-red 

 grains untouched. 



He now laid before a so-called red-green blind person (rela- 

 tively yellow sighted red-green blind) the differently colored 

 yellow-red and blue-red rice grains and let him choose out of 

 the pile the grains which seemed alike to him. This subject 

 put yellow-green with yellow-red, pale blue with bluish-red. 

 The differently colored grains which the hen had differentiated 

 with such sureness were similar or alike to the red-green blind 

 subject. 



A hen which he had taught to avoid the red grains was fed 

 on a black cloth upon which the green grains were fastened 

 down while the red, etc., were scattered loosely. After a short 

 time she no longer took the green grains when these were loosely 

 strewn among the others, but she did take the red ones. In the 

 spectrum she picked the grains lying in the red end as far as 

 they were visible to the normal human eye. 



Only for one with the visual qualities of the normal human 

 eye have the different red grains the common characteristic of 

 prevailing redness. He concludes that the possibility of a red- 

 green blindness in the hens experimented upon is excluded, and 

 greater strength is given to his contention that their visual qual- 

 ities in this respect are similar to or the same as a normal man's. 



