492 



S. O. MAST 



Euglena viridis 



The specimens of Euglena viridis used in the following experi- 

 ments were collected in a pig-yard in Michigan, near Ann Ar- 

 bor, August 17, 8 a.m., taken to Cleveland and placed in a jar in 



Euglena viridis {negative). 



TABLE 2 

 Relation between wave-length and stimulation'^ 



1 The figures in the columns 2-7 express relatively the stimulating effect of 

 the different wave-lengths tested. The larger the number the greater the effect. 

 Thus in column 3 the numbers show that the effect of wave-length 432.6 uti was 

 very slight and that from this point toward the red end of the spectrum the 

 effect gradually increased until it reached a maximum near 483.4 /i/i, after which 

 it gradually decreased until it became practically zero at 524 nn. The blank 

 space in the columns indicate either that no readings were made or that the 

 stimulating effect was so small that it could not be successfully measured by 

 the method employed (see pp. 483-487). 



The numbers in the last column indicate the distribution of stimulating 

 effect in a spectriun having a uniform distribution of energy throughout, i.e., 

 they express the relative stimulating efficiency of the different wave-lengths. 

 These numbers were obtained from those in the preceding column by applying 

 the corrections for unequal distribution of energy indicated in the curve in 

 figure 3. 



2 The readings were presumably all made 10 imix apart as the drum of the spec- 

 trometer indicated, i.e., at 420, 430, 440 mm, etc. It was, however, discovered by 

 Dr. W. E. Forsythe that this series of readings on the drum, owing to imperfect 

 adjustment, produced the wave-lengths given in the first column of this and the 

 following tables. 



