the phytoplankton standing stock has equal values, the production value obtained equals the number of dead phytoplankton cells plus those eaten by Calanus helgolandicus = The production calculated experimental data of consumption and mortality amounts to = Comparison of the experimental value for phytoplankton production with the theoretical value shows that the value obtained by employing the theoretical method, deviates less than 9%. =Experimental and theoretical curves for the grazing rate on phytoplankton are shown in Fig. 3. The theoretical curve does not reflect the qualitative distribution of the numerical value of the grazing rate but makes possible the calculation of the value for diurnal grazing and phytoplankton production according to the equation mentioned above. However, the area under the curve and areas of rectangles obtained from experimental data are equal within the 6%