SPECTRAL COLOR AND STIMULATION 



485 



By means of the higher spectrometer the organisms could be 

 subjected in the one beam to any spectral color and the change 

 from one to another could be rapidly made without in any way 

 altering the size or position of the beam of light. Moreover, the 

 wave-length of the light in the beam could be readily ascertained 

 by direct readings on the revolving drum of the spectrometer. 



e 



Fig. 1 Outline of apparatus used in the following experiments: t and t', 

 tungsten street series lamps; o and o', opaque boxes; s, Hilger spectrometer; 

 r, Lummer-Brodhun rotating sector; 6, beams of light, 10 mm. wide, 3 mm. 

 deep; s', opaque screens; g, glass plate; I, line on glass plate; a, aquarium. 



B}^ means of the Lummer-Brodhun sector the illumination in 

 the other beam could be instantly changed from zero to the maxi- 

 mum available and the illumination used at any time could be 

 directly ascertained by readings on the sector. 



All of these features and the constant current from the storage 

 battery were found to be of the greatest importance in the work 

 undertaken. In fact, it would have been quite impossible to 

 have obtained some of the most important results without them. 



