228 



JACQUES lOEB AND HARDOLPH WASTENEYS 



Figure 3 gives a photograph of the distribution of the organisms 

 in another experiment after 3 hours in the same spectrum. This 

 longer exposure gives a sHghtly better result. The dense gather- 

 ing at the bottom indicated by a horizontal streak is in the blue 



CkEEN 

 506 S33 



between 458 and 506 mm- It ends at about 533 and becomes 

 very faint at 452 m/x. The vertical streaks on the wall, indicat- 

 ing the sticking of the organisms to the front wall, occur again 

 in the blue. These experiments permit us to draw only the con- 



