SPECTRAL COLOR AND STIMULATION 



503 



TABLE 7 



Trachelomonas euchlora {negative and positive). Relation between wave-length and 



stimulation 



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



pool had become scarce. The results obtained are consequently 

 not very accurate. They indicate fairly clearly, however, that 

 the distiibution of stimulating efficiency in the spectrum is the 

 same as it is for Euglena. Two of the best series of readings 

 obtained are given in table 7. In one of these series the spec- 

 trometer slits were 2.5 mm., in the other 0.75 mm. wide. The 

 table indicates that in the latter series the region of maximum 

 stimulating efficiency was near wave-length 483 iifx, that is, prac- 

 tically in the same position as it is for Euglena; but that in the 

 former series it was farther toward the red end of the spectrum. 

 This suggests the possibility of a Purkinje phenomenon. When, 

 however, the two entire series of results are compared with simi- 

 lar series of results for Euglena it is found that there is a fair 

 agreement in all, and that the shifting toward the red in the 

 higher illumination is fairly definitely confined to the region of 

 maximum stimulation, indicating that this is probably due to 

 insufficient data. 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 22, NO. 3 



