Abstract
1. Chloroform in low concentration (0.25 per cent) causes an increase in the rate of production of CO(2) in Ulva; this is followed by a decrease. In higher concentration (0.5 per cent) only a decrease is observed. 2. Assuming that the normal oxidation depends on the action of peroxide and peroxidase, experiments were made by placing Ulva in 1.0 per cent H(2)O(2) and in Fe(2)(SO(4))(3) (which acts like a peroxidase). The former diminishes the rate, the latter increases and subsequently decreases it. 3. When Ulva is killed in such a manner as to destroy the oxidizing enzymes, no CO(2) is produced unless H(2)O(2) and Fe(2)(SO(4))(3) are present. If to this mixture chloroform is added, the effect depends on the concentration of the iron. If the concentration is low there is an increase in the production of CO(2) followed by a decrease. If the concentration is high the rate appears to decrease from the start.