212 C. F. PHIPPS. 



were selected at random from the pan when experimented upon 

 and the reactions under different conditions were compared. 



When treating the animals with KCN and the other reagents 

 they were kept in shallow glass dishes with a glass cover plate 

 sealed on with vaseline to prevent evaporation. In the ex- 

 periments with these animals the same solutions which they had 

 been kept in were used in order to avoid the possibility of any 

 stimulation which might occur by changing to tap water. The 

 untreated, amphipods were kept, and experimented on, in tap 

 water. Filtered tap water was used in working with starved 

 animals. 



It was necessary, first, to establish a standard for the normal 

 reactions of untreated amphipods, and then to compare with 

 this any different reactions of treated amphipods. The series 

 of experiments on untreated amphipods, by which the standard 

 for normal reactions was established, form a good control series 

 with which to compare the reactions of treated amphipods. 

 Untreated amphipods were considered normal if they were 

 negative to intense light when the tank was in position i or 

 position 3. They were also considered normal if they were 

 positive to intense light when the tank was in position 2. The 

 reaction of the animals in position 2 of the tank shows that the 

 direction of rays has a stronger influence than light intensity, 

 for, though negative to intense light, in no case in any of the 

 experiments with untreated animals with the tank in this posi- 

 tion did the majority remain in the dark area. We may con- 

 clude from this that amphipods are negative to direction of 

 rays. With treated amphipods these normal reactions were 

 reversed in many experiments as will be shown later. 



It was impossible to separate the influence of light intensity 

 from that of direction of rays in cases where the tank was in 

 position 3. Normally with the tank in this position both light 

 intensity and direction of rays force the animals to the dark end. 

 The percentage of those seeking the dark end when the tank 

 was in this position was much greater than when the tank was 

 at right angles to the rays, showing again the negative reaction 

 to the direction of rays. The ray direction does not function 

 when the tank is at right angles to it, except possibly to force 



