232 



LEE RAYMOND DICE 



Exp. 2 



Phototaxis in weak light 



March 23, 4 P.M., 25 Daphnia pulex placed in a 28 cm. long glass dish marked 

 off into five divisions. Exposed in darkroom to horizontal light from a 50 watt 

 Edison lamp at 50 cm. distance. Temperature 17.5° C. 



Averages 



13.4 



1.9 



3.4 



2.7 



3.5 



These daphnids, at temperatures of 20° to 23° C, are gen- 

 erally nearly neutral to diffuse daylight (Exp. 3), to the light 

 from a 15 ampere electric arc (Exp. 4), or to sunlight lacking 

 the ultra-violet rays (Exp. 5). Experiment 3 shows a rather 

 large variation in the distribution of the animals during the 

 experiment which is probably due to the changes in light in- 

 tensity corresponding to changes in the position of the sun. 



Exp. 3 



Phototaxis in diffuse daylight 



March 19, 8 A.M., 22 Daphnia pulex from laboratory aquarium placed in a 28 

 cm. long glass dish marked off into three divisions. Exposed to diffuse light from 

 a south window covered by a white screen. Light rays from the room were ex- 

 cluded by a black lined box. Temperature 23° C. 



Averages 



8.9 



6.3 



6.8 



