30-- 



ism, Also it, J.B prob-'.ble in vi-^w-of jLoab^s -vor>- (1^6 ) that the 

 phototropio reactions of all organisms change with their age. 



Another explanation which was suggested by the fact that 

 white light was often slower in producing a response than the b lue 

 and violet, is that the greater energy of the red in sunlight might 

 have tended to reverse the positive reaction or neutralize it; or it 



ight h-iv* be<?n so reflected within the dish as to act more nearly 

 with the optimum intensity on -<11 sides of the organism. " that 

 as it m ri .y, the fact remains that repeated trials prove Conclusively 

 that at the end of a fiv- minute exposure, all wave lengths of the 

 visible centrum hnve produced equal eft^ots when the source of 

 li; T ht ic the electric arc. This is further proof of Mast's Wf ) 

 contention tir.it: "There ia nc evidenc-- i-.-Mc ting that stimula- 

 tion i-, n.:r; of the 3 studied is independent of lurranous in- 



tensity, for if the light in the spectrum on Cither side of the maxi- 

 mum be made sufficiently intense it becomes iaore efi active than at 

 the maximum, M 



On April 20, another collection of Volvox was made. It was 

 ho r;ed that a rough approximation of applicability of the Roscoe- 



Buns>?n Law in the reactions of th is form U> li :ht. This law states 



ing 

 that o'J<-r conditions "be/eqial, the product of the intensity and 



the duration of the exposure Is .'? co .stant. Owing, however, to the 

 short time required for response and the variations in the sensitive- 

 ness of individuals making it impossible to determine the end points 

 exactly no thin- c ,n be concluded o.s to the truth of this law for 

 Volvox u Li] . nr? RQ urate ra^ans of ..leosuring the b 'ginning and end 

 of the reactions is obtained. To show the diilic^lty produced by 



