PEARSE. 



THE REACTIONS OF AMPHIBIANS TO LIGHT. 



191 



experiments performed in which eyeless toads were placed at a distance 



of 275 centimeters from the lamp, where the intensity was 1.44 candle 



meters for white light. The colored screens cut the light down to 



what must have been considerably less than a candle-meter. The 



results obtained from seven toads not previously tested are shown in 



Table XVI. 



TABLE XVI. 



Reactions of Seven Eyeless Toads to Colored Lights 

 of Low Intensity. 



Although the " positive percentages " in every color were lower than 

 when light of greater intensity was used (Table XV.), the eyeless toads 

 again showed positive phototropism in all the colors. There was also, 

 in this case, a greater number of positive reactions when white light 

 was used than when any of the colors were substituted for it. It is, 

 then, apparent that in a decreased light intensity the number of 

 positive reactions decreased, but no especial potency was shown by one 

 color as compared with another as a means of inducing such reactions. 

 The slight differences between the number of positive reactions 

 produced by lights of different colors, as shown in the table, may be 

 accounted for as being due to intensity differences. The colors, as 

 judged by the human eye, could be arranged from more to less intense 

 in the following order, yellow, green, red, blue ; and it will be seen that 

 the largest number of positive reactions was brought about by the most 

 intense light, thus judged. 



(c) Summary. 



The results of the reactions of amphibians to colored lights may be 

 briefly summarized as follows : normal animals were positively photo - 

 tropic in all the colors tried, but there were more positive reactions 

 toward the violet end of the spectrum than toward the red end ; eyeless 

 individuals were also positively phototropic in all the colors, but there 

 was no difference in number between the positive reactions to the several 

 colors. These results do not agree with those of most other observers. 



