6o 



40 ; 



ELECTROLYTES IN BIOLOGICAL SYSTEMS 

 POTASSIUM 



CONTROL 



SODIUM 



40 



10 IS 



-HOURS- 



25 



Figs. 19 {lop) and 20. Effect of external sodium on potassium accumulation. The minerals 

 were 'leached' from the samples by repeated washing in isotonic sucrose solution for three 

 hours. At this time (arrow) some were transferred to complete natural sea water ('com- 

 plete') and the rest to sodium-free Allen's artificial sea water ('Na-free') (Ulva). 



the mechanism appears to have a Hmited capacity. A transport system for potas- 

 sium, such as the carrier hypothesis first proposed by Osterhout (30), would 

 seem to fit the data best. Mudge (27) has recently described experiments on 



