GEOKGK T. SCOTT AND IlUOir K. HAYWOOD 



49 



the potassium or sodium contents, while iodoacetate caused a marked fall in 

 [)otassium and a smaller rise in sodium. The effect of arsenate given with iodo- 

 acetate was to prevent almost completely (95%) the potassium loss with 

 essentially no effect on the sodium increase. 



POTASSIUM 



CONTROL • 



TRANSFERRED TO 

 5 X I0"3 ASO4 AND 

 FRESH SEA WATER 



60 ■ 



50 • 



40 i 



SODIUM 



TRANSFERRED TO 

 5 X 10"' AsOv AND 

 FRESH SEA WATER 



DA?2i S 



-hours- 

 Figs. II (top) and 12. Intluence of arsenate after iodoacetate. Samples were maintained in 

 the dark in 5 X io~'*m/1. iodoacetate. .\t 20 hours (arrow) some samples were transferred to 

 5 X io~^ m/1. Na2HAs04 in sea water; some were illuminated (light), the others maintained 

 in darkness (Ulva). 



In the experiment described by figures 11 and 12 the samples were maintained 

 in io~^ m/1. iodoacetate for 20 hours. At this time 12 samples were transferred 

 to fresh sea water (no iodoacetate) containing 5 X io~^ m/1. Na2HAs04; 6 

 were maintained under illumination, the rest placed in the dark. As seen in 

 figure II the arsenate in the dark, although some further loss of potassium con- 

 tinued, offered significant protection against the loss as compared to the samples 

 maintained in iodoacetate in the dark throughout the experiment. In the light 

 no further potassium loss occurred with arsenate. ' 



