Vlli THE VOCAL AND RESPIRATORY ORGANS 177 



violet, yellow, and red light were found to be as 114, 103, and 

 100 respectively. In red light there is but little more C0 2 out- 

 put than in the dark. The influence of heat was excluded in 

 the experiments by passing the light through a vessel of water. 

 As frogs which are placed in the light become restless and 

 excited and frequently make efforts to go toward the source 

 of illumination, it is probable that these differences in respi- 

 ration result from variations in the animal's activity. The 

 fact that the phototactic activities of the frog become greater 

 under the more refrangible rays would naturally lead to a 

 parallel increase in respiration under the same conditions. 

 That differences in respiration occur in blinded frogs under 

 differently colored lights is not inconsistent with this inter- 

 pretation, since phototaxis still occurs in frogs from which the 

 eyes have been removed. 



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