352 Hoyt: CULTURES OF SPIROGYRA 
7. Weak solutions of certain toxic salts were improved by 
the addition of calcium-free animal charcoal or colloidal platinum. 
It seems indicated that the effect of powdered CaCOs, in counter- 
acting toxicity due to nutrient salts, was due in part to the adsorp- 
tive action of the solid. 
THE JoHNS HOPKINS UNIVERSITY. 
