MOVEMENTS OF DAPHNIA 



239 



Exp. 9 



Effect of change of light intensity on geotaxis 



January 29, 2 P.M., 50 Daphnia pulex collected from pond and placed in a 29 

 cm. high jar marked off into five divisions. Top sealed. For strong light used 

 a 15 ampere electric arc at 40 cm. and for weak light used a 100 watt Mazda lamp 

 at 40 cm. The light was horizontal in each case and was passed through 8 cm. of 

 water to cut out the heat. 



Exp. 10 



Effect of change of light intensity on geotaxis 



March 26, 17 Daphnia pulex in diffuse light of laboratory placed in 29 cm. high 

 jar marked off into five divisions. Cooled to 13° C. 



