500 



S. O. MAST 



TABLE 5 

 Euglena tripteris (negative). Relation between wave-length and stimulation 



1 Kept in darkness 3.53 to 4.21 p.m. 



For description of table see legend table 2, p. 492. 



tinuously negative in all illuminations in which they responded 

 at all. The results obtained in these tests are presented in 

 table 5 and figure 4. In every case all of the individual tests 

 represented in a given column were completed before any repre- 

 sented in any other column were made, and usually they were 

 made in successive order up or down the columns. 



By referring to table 5 it will be seen that the distribution of 

 stimulating effect in the spectrum was essentially the same in all 

 of the four separate groups of tests made and that the distribu- 

 tion of stimulating efficiency in this species is practically the 

 same as it is in viridis and gracihs (table 15). But it will also 

 be seen that while the sector readings made in the different 

 groups of tests lead to the same conclusion regarding the distri- 

 bution of stimulating effect in the spectrum they differ greatly 

 in magnitude. For example, the sector readings at the maxi- 

 mum in the first group of tests were nearly twice as large as those 

 in the second group, although in both the maximum was near 



