74 



GORDON H. BALL. 



light. The uniformity in reaction-time is evidently due to the 

 fact all the Paramecium belonged to a single clone. 



TABLE III. 



EFFECT OF LIGHT ON TOXICITY OF DYES FOR Paramecium. 



Furthermore, those stained paramecia exhibiting this light 

 reaction die much sooner when exposed to strong light than 

 when kept in the dark. Table III. shows the difference in 

 survival-time between the two groups of organisms. An ordinary 

 Mazda lamp served as the source of light. The dishes containing 

 the organisms were covered with water-filled glass containers and 

 exposed to a current of air from an electric fan. The temperature 

 in the two series did not differ by as much as a degree during 

 the course of the experiments. Animals stained in bismarck 

 brown, basic fuchsin, trypan blue, or trypan red showed no 

 change in behavior upon sudden illumination; correspondingly, 

 the toxicity of these dyes was not increased in the light. While 

 living Paramecium did not stain in eosin, and although a con- 

 centration as great as i to 250 was not toxic for them as long as 

 they were kept in the dark, they had a marked avoiding reaction 

 to light and died rapidly under strong illumination. Raab 

 (1900) studied the greater toxicity of fluorescent dyes for infusoria, 

 and similar results were recorded by Pereira (1925), who tested 

 the action of eosin on the germ cells and larvae of Arbacia. 



