BEHAVIOR OF AMPHIPODS WITH RESPECT TO LIGHT. 



217 



reversals, and the Hyalella and Eucrangonyx gave no majority 

 of normal reactions in any series of readings. See Table IV. 



Table IV. 



Amphipods Treated with Chloretone. 



Experimental Tank at an Angle of 45° to Direction of Rays with the Light End Nearer 



the Lamp {Position 3). 



(C) Starvation. — Amphipods from each habitat were kept in 

 filtered tap water and starved from 4 to 14 days before experi- 

 menting. Reversed reactions occurred with all three species, 

 some after short treatment, others only after long treatment. 

 Table V. shows reversed reactions with Hyalella and Eucran- 

 gonyx when the tank was in position 2. Gammarus gave reversed 

 reactions with the tank in positions i and 3, but the majority 

 were normal with the tank in position 2. 



Table V. 



Starvation Treatment. 



Experimental Tank at an Angle of 45° to Direction of Rays with the Dark End Nearer 



the Lamp {Position 2). 



Species. 



Gammarus . . . 



Hyalella 



Eucrangonyx . 



Time Ex- 

 posed. 



4 days 

 6- 9 " 

 5-14 " 



iP) Low Oxygen Content. — The oxygen content of tap water 

 was reduced by using a machine, devised by Shelf ord and Allee 

 ('13), for deaerating water by a process of heating and then 

 cooling to the required temperature. The oxygen content was 

 reduced in some experiments to as low as 0.79 c.c. per liter. 

 The dish containing the amphipods was filled with this low 

 oxygen water and the cover sealed down with vaseline. Amphi- 

 pods began to die after an exposure of about one day to low 



