2l8 



C. F. PHIPPS. 



oxygen content of from 0.79 c.c. to 1.51 c.c. per liter. Only 

 Gammarus gave a majority of reversed reactions in any series 

 of readings (see Table VI.), and this took place with the tank 

 in positions i and 3. The other two species gave no majority 

 of reversed reactions in any position of the tank. 



Table VI. 



Low Oxygen Content. 

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



In Table VII. the percentage of experiments is given showing 



normal and reversed reactions with all treated amphipods, both 



with the tank at right angles and at angles of 45° to the direction 



of rays. 



Table VII. 



Treated Amphipods. 

 All Three Species. Tank in Positions i, 2 and 3. 



Table VIII. shows that the percentage of reversals in the three 



species is quite different under the same treatment. Also, in 



the same species, the percentage of reversals varies for each 



reagent used. 



Table VIII. 



Treated Amphipods. 

 Reversed Reactions only. 



Gammarus, 

 Per Cent, of 

 Experiments. 



Hyalella,'\ 

 Per Cent, of 

 Experiments. 



Eucrangonyx , 

 Per Cent, of 

 Experiments. 



Reversed reaction with KCN 



Chloretone. . 

 " " " Starvation. . 



" " " Low Oxygen. 



39-3 

 60.0 

 66.6 

 36.3 



5-5 

 66.6 

 18.2 

 50.0 



33-3 



33-3 



25.0 



0.0 



