Mast, Light Reactions in Lower Organisms. 



175 



TABLE VI. 

 Distance from glower to center of gauge 100 cm. Liglit intensity 27 candle meters. 



Distance from glower to center of gauge 400 cm. Light intensity 1.6875 candle meters. 



0.1689 candle 

 meters = 10 

 per cent of 

 light intensity 

 at center of 

 gauge. 



The results recorded in Table V were obtained in experiments 

 performed on August 22, 1904, and those recorded in Table VI 

 in experiments performed on August 25. The experiments in both 

 cases extended over a period of several hours. The specimens 

 v^ere collected at 6 a. m. on the day during w^hich they w^ere exposed. 

 After being brought to the laboratory, they were kept in darkness 

 or very dim light until used. 



By referring to Table V, it will be seen that the minimum differ- 

 ence in light intensity on opposite sides of Volvox colonies which 

 induced a reaction is approximately 4 per cent of the illumination 

 on either side when the aquarium is 100 cm. from the glower, but 

 4.9 per cent when it is either two or four times as far away. Table 

 VI shows that reaction is induced by a difference of 15.2 per cent 

 when the distance between the aquarium and glower is 100 cm., 

 II per cent when this distance is 200 cm,, and 10 per cent when it 



