42 



A. M. REESE 



are not great, the nearer (12 inches) light has a somewhat greater 

 attraction than the more distant (48 inches) light. 



Experiment XV. — The conditions of this experiment were ex- 

 actly the same as in the preceding except that the lights were 

 twenty-four inches and seventy-two inches from their respec- 

 tive ends. There was an interval of twenty-one hours (in the 

 dark) between observations 5 and 6. In 40 observations 203 

 animals faced the nearer (24 inches) light, to 133 that faced the 

 farther (72 inches) light ; and 204 were in the half of the aquarium 

 towards the nearer light, to 144 in the other half. 



Experiments XII to XV may thus be placed in tabular form 

 for comparison: 



f 6" distance. 



Experiment XII.. 



24" distance. 



{ 6" distance. 



[facing 170 

 [near 174 

 ffacing 265 

 (near 269 

 ffacing 141 



Experiment XIII • 



12" distance. 



Experiment XIV. 



12" distance. 



■\ 



48" distance. 



'24" distance. 



Experiment XV ■ 



72" distance . 



near 163 

 (facing 185 



near 190 

 ffacing 289 



near 283 

 ffacing 229 



near 255 

 ffacing 203 



near 204 

 ffacing 133 



near 144 



Experiments XII and XIII seem to indicate that when -one of 

 two sources of light is very intense the animals tend towards the 

 less intense light; while experiments XIV and XV show that 

 when neither source is very intense, perhaps not reaching a 

 certain optimum, the animals tend towards the more intense 

 light. 



