SPECTRAL COLOR AND STIMULATION 517 



X = 495 MM," that is, considerably nearer the red than I found 

 it to be in a tungsten prismatic spectrum. This difference can 

 not be accounted for on the basis of difference in the distribu- 

 tion of energy in the spectra used for the carbon arc spectrum 

 both prismatic and normal (Loeb and Wasteneys do not state 

 which they used) contains relatively more energy in the region 

 of the shorter waves than the tungsten prismatic spectrum. We 

 should therefore expect the region of maximum effect to be 

 nearer the red in the latter than in the former in place of the 

 opposite. The difference noted must consequently be due to 

 inaccuracies in observation or defects in methods. 



Lumbricus terrestris 



In the experiments on the earthworm and the blowfly larvae 

 precisely the same methods were used as in those on the other 

 forms studied. The observation aquarium was, however, re- 

 placed by a ground glass plate 21x21 cm., on which the animals 

 were exposed. This plate was covered with a sheet of wet filter 

 paper in the experiments on the earthworms and with a coat of 

 olive oil in those on the blowfly larvae. In both cases the surface 

 of the glass plate thus treated proved to be an excellent substra- 

 tum for the animals to travel on, and this is very essential in 

 work of this sort. 



To test these animals it was necessary to have a larger field of 

 light than was used in the observations on the microscopic forms. 

 The distance between the center of the field and the ocular slit 

 of the spectrometer was consequently increased to 53 cm. This 

 caused a marked reduction in the intensity of the colored beam 

 of light, which made it necessary to also reduce the intensity of 

 the white beam. This was done by moving the source to a dis- 

 tance of 100 cm. and by interposing a ground glass plate, thus 

 making the illumination in the white beam at the center of the 

 field with the sector open 7.4 (?) m. c. The two beams of light, 

 both of which were horizontal, crossed at right angles at the center 

 of the glass plate and at this point each of them was 6 cm. wide. 



The glass plate contained a heavy black line which passed 

 through the center and bisected the angle between the two beams 

 of light; and, just as in the preceding experiments, the illumina- 



