^ -. 



SPECTRAL COLOR AND STIMULATION 



487 



reading indicating the extent of the opening of the sector was 

 recorded, the wave-length was changed, the water in the aqua- 

 rium thoroughly stirred up so as to distribute the organisms 

 equally throughout unless otherwise stated, and the illumination 

 in the white beam again adjusted until they proceeded parallel 

 with the line under the aquarium. This was repeated for all 

 effective regions of the spectrum usually differing by 10 /xju. 

 Thus the readings indicating the extent of the opening of the sec- 



a--_ 



b— - 



C 



J\ 



Fig. 2 Side view of observation aquarium, stand, etc. a, aquarium; s, 

 stand; h, opaque box, 8 x 10.7 x 10.7 cm.; I, ruby light; vi, mirror; g, glass plate; 

 g', ground glass plate; p, petri dish. The binocular was supported by an ex- 

 tension arm vertically over the aquarium. 



tor, when the course of the organisms bisected the angle between 

 the two beams of light, were ascertained for the different re- 

 gions; and since these readings directly express the relative 

 illumination, they express also, as previously demonstrated, the 

 relative stimulating effect of the regions tested; and from these 

 data the relative stimulating efficiency of the different wave- 

 lengths with reference to the energ^^ can readily be calculated 

 provided the relative distribution of energy in the spectrum 



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



