CONTENTS 



Page 



Materials and methods 77 



Culture medium 77 



Culture procedure 78 



Phosphorus measurements 78 



Determination of population size 78 



Preparation of filters 79 



Fractionation of cells 79 



Experiments 79 



Phosphorus absorption 79 



Conditions affecting phosphorus exchange by cells when filter-washed 81 



Exchange by nondeficient cells 81 



Exchange by phosphate-deficient cells 82 



Effect of exposure time on exchange 83 



Redistribution of intracellular phosphorus 83 



Exchange by cells suspended in culture medium 84 



Exchange in the light 84 



Exchange in the dark 85 



Exchange determined with radioactive phosphorus in the medium 85 



Exchange determined with radioactive phosphorus in the cells 86 



Discussion 86 



Su m mary 89 



Literature cited 89 



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