SENSIBILITY OF VOLVOX TO SPECTRAL LIGHTS 



357 



influence of the white Ught thus relatively increased until its 

 effect was practically equal to that of X574mM (light no. 15), the 

 colonies showing an almost equal tendency to proceed to one or 

 the other source. When exposed to the influence of the white 

 light and to that of wave-lengths greater than X574miu, the white 

 light had an increasingly greater stimulating effect as the wave- 

 lengths became longer so that the organisms moved toward the 



100 



so 



80 

 70 

 60 



50 

 40 



20 

 lO 



420 440 460 430 aOO 520 SAO 560 560 600 620 &40 66C m/l 



Fig. 2 The relative stimulating value of spectral lights of equal energy con- 

 tent as determined from the relative rate of locomotion, x x x, spectral 



light alone; • • •, spectral light vs. white light. 



white light. No further record was taken of the relative rate 

 of locomotion. 



The curves show that X494m/i is the wave-length of maximum 

 stimulating value, as was found by the method of determining 

 the presentation time, and that the relative stimulating effect 

 decreases by degrees toward both ends of the spectrum. The 

 intensity of the spectrum used, however, was so great that all of 



