1. An oxidative assimilation of acetic add and glucose in darkness has been demonstrated in the green alga, Chlorella pyrenoidosa. From manometric experiments it has been shown that 1 mol (CH2O) per mol acetic add and 5 mols (CH2O) per mol glucose are produced.
2. The time required for complete utilization of a limited amount of acetic acid or glucose is not affected by illumination in the absence of carbon dioxide.
3. The time required for complete utilization of a limited amount of glucose is not affected by the simultaneous occurrence of photosynthesis. It must therefore be concluded that the accumulating product of photosynthesis cannot be glucose but must be some slowly respirable (storage) material.
4. Possible interrelationships between oxidative assimilation and photosynthesis may be further studied by following, in darkness and in light, the time course of oxidative assimilation of substrates which are possible intermediates in the two processes.