1. Concentrations of La(NO3)3 up to 0.000025 M have little effect upon the rate of respiration of Bacillus subtilis; at 0.000006 M there is an increase in rate, while in higher concentrations there is a decrease in rate. 2. There is well marked antagonism between La(NO3)3 and NaCl, and very slight antagonism between La(NO3)3 and CaCl2. 3. It requires a very small amount of La(NO3)3 to antagonize NaCl, the proportions of the two salts at their maximum antagonism being 99.8 parts of NaCl and 0.2 parts of La(NO3)3.