LAURENS: MONOCHROMATIC LIGHTS. 



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TABLE 1. 

 Reactions of toads to monochromatic light received through both eye and skin. 



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 five minutes. 



By way of summarizing the results of the experiments with single 

 monochromatic lights in which both the eye and skin acted as re- 

 ceptors, it may be stated that all four colored lights used produced 

 positive responses. Blue light was the most effective, and the other 

 lights formed a decreasing series, corresponding roughly to their 

 relative position in the spectnmi, the red light being but slightly 

 more effective than darkness. 



B. Reactions icith the Eye as Receptor. 



It was natural to suppose that the reactions of toads with both the 

 eye and skin acting as receptors, were dependent upon the eye, but 

 it was conceivable that they might also depend in some measure upon 

 the skin. The skin of many amphibians has been found to be very 

 sensitive to white light. Parker (:03) showed this to be the case in 

 the frog, Rana pipiens. He also reviewed the literature of the subject 

 of the sensitiveness of the skin to stimulation by light, pointing out 

 that similar results had been obtained by previous observers on 

 Triton and Proteus, among amphibians, as well as on certain fish and 

 other metazoans. Later (:05) he showed that the skin of Ammocoetes 

 also possessed this sensitiveness to light, the tail being the most 



