LAURENS: MONOCHROMATIC LIGHTS. 



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TABLE 4. 



Comparison of the reactions of normal toads to blue light received through 

 both the eye and skin, through the eye only, and through the skin only, with those 

 of eyeless toads under the same conditions. 



The numbers under + indicate total numbers of reactions toward the light; 

 under — , away from the light; under ± , without reference to the light (indifferent) ; 

 under 0, no reaction within fifteen minutes. 



results obtained with hooded normal toads (Table 3), though it will 

 be noted that in the former case there were 3 % of indifferent reactions. 

 These results show that the hoods were an effective method of pro- 

 tecting the eyes from the light. But when only the region of the eye 

 was exposed to the light, a large percentage of no reactions was ob- 

 tained, with almost as large a percentage of indifferent reactions. 

 The 7 % of positive and negative reactions were probably accidental 

 turnings. There can be no doubt, therefore, that the method em- 

 ployed for exposing only the eye was an effective one, and that the 

 reactions obtained were due to the effect of the light on the eye, and 

 not in any way to the illumination of the small area of skin around it. 

 Since this narrow beam of light (blue) showed no power to stimulate 

 the region of the eye after the eye itself had been removed, it was 

 thought desirable to test the reactions of eyeless toads when this 

 beam of light was thrown upon certain regions of the skin. Three 

 regions were selected, and these may be roughly described as the 

 region of the fore-leg, the region of the hind-leg, and the region of the 

 back. 



