BEHAVIOR OF AMPHIPODS WITH RESPECT TO LIGHT. 



219 



IV. Sides of the Experimental Tank, in Relation to the 

 Lamp, Occupied by the Amphipods. 



At each reading, when the position of the animals in relation to 

 intensity was taken, their position in relation to the sides of the 

 tank was also taken. The object was to determine, if possible, 

 whether the direction of rays influenced the animals to seek the 

 side of the tank farthest from the lamp. 



The results are shown in Table IX. The readings have no 

 reference to the dark end of the tank. In positions i and 2 the 

 largest per cent, of the animals was found on the side of the tank 

 farthest from the lamp, while in position 3 the majority were 

 found on the side nearest the lamp. This is not conclusive, 

 however, and these lateral positions in the tank may be due 

 only to "random excursions" or "busy explorations" that 

 Holmes ('01) speaks of as characteristic of active animals. 

 Possibly the animals were reacting towards their own shadow, 

 in positions i and 2, rather than to ray direction. It is interesting 

 to note that there is very little difference in the results between 

 treated and untreated amphipods. 



In none of the experiments was there evidence of orientation 

 either to light intensity or to direction of rays. 



Table IX. 



Tank at Right Angles to Direction of Rays (Position i). 



