2 K. S. LASHLEY 



in bright light. A somewhat more conclusive test was made by 

 Hess ('08) in measurements of the pupillary opening. The max- 

 imum contraction of the iris was produced by longer light waves 

 in light adaptation than in darkness adaptation. A preliminary 

 report of the writer's experiments was given by Watson ('14). 

 They are recorded at length in the following pages. Yerkes 

 ('15) using a similar method, obtained evidence of the change in 

 the relative brightness values of the red and green with change 

 of adaptation in the ring-dove. 



Students of color discrimination in birds have usually em- 

 ployed color-papers or dyes with no certain control of intensity 

 or saturation. Porter ('06) records tests with the English 

 sparrow and cow-bird in which red, yellow, green, blue, and 

 two shades of gray paper were used. The birds learned very 

 readily to distinguish between these. Rouse ('06) used almost 

 identical methods with the pigeon and secured like results. 

 Katz and Revesz ('07) trained chicks to pick out colored rice 

 grains from among gray ones. As Hess ('12, p. 21) points out 

 for the work of Katz and Revesz, all these results might have 

 been obtained with completely color blind animals. Hess ('12) 

 reports tests with rice grains stained to match the Seebeck- 

 Holmgren wools. Fowls distinguished the reddish grains from 

 the greens and grays of this series, which were confused by a 

 red-green blind man. From this Hess concludes that the fowl 

 is sensitive to the wave-length of the red and green rays. The 

 uncertainty of conclusions as to the color vision of animals 

 drawn from analogy with the condition of brightness vision 

 in color blind men has been pointed out by Frisch ('14) and 

 the evidence of Hess himself for a shortening of the fowl's spec- 

 trum in the blue-green tends to invalidate his evidence for color 

 vision. The careful work of DeVoss and Ganson ('15) shows 

 in a practical way the justice of the most severe criticisms that 

 have been urged against the use of color-papers in the study of 

 animal vision. 



Rouse ('05), by recording the rate of respiration in the pigeon 

 after stimulation with light, was able to show an increase in 

 rate progressive with change from the longer to the shorter 

 wave-lengths. He was not able to find like changes with alter- 

 ation in the intensity of light of constant wave-length. The 

 tests with wave-length and intensity were not carried out under 



