The net reproduction rate, the mean generation time and the intrinsic rate of natural increase have been measured at varying food supply in the marine CopepodTisbe furcata(Baird). The population response curve of the net reproduction rate is a monotonic increasing curve of the type Ro=RMexp — K √a, whereais the food quantity, RMthe maximum attainable reproduction and K a conversion coefficient. The mean generation time curve is a decreasing curve which tends asymptotically to a minimum. The plots of the curves show that small variations of food quantity in the low supply range result in a very significant reproductive variation, while large food variations in a higher supply range do not significantly affect the population reproductive capacity.