The exit of accumulated ammonia from the sap of Valonia macrophysa, Kütz., into normal (nearly ammonia-free) sea water, has been studied in light (alternation of daylight and darkness) and in darkness. Exit is always preceded by an induction period lasting 1 or more days. This is longer in darkness. After exit starts the rate is greater in light than in darkness.

The pH of the sap drops off soon after the cells are exposed to normal sea water even before any definite decrease in the ammonia concentration of the sap has occurred. This suggests that the decrease in the pH is due to the loss of a very small amount of NH3 or NH4OH without a corresponding gain of sodium as a base.

In most cases sodium replaced the ammonia lost during exit, but there is some evidence that potassium may also replace ammonia.

To account for the induction period it is suggested that other species than NH4X are concerned in the transport of ammonia, for example urea or amino acids.

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