CHANGES IN THE RATE OF FOOD VACUOLE FORMATION DURING EARLY CLONAL LIFE OF PARAMECIUM-PRIMAURELIA

The rate of food vacuole formation was shown to vary in Paramecium pri maurelia during early clonal life; under constant external environment al conditions, remarkable changes occurred in young cells within a few fissions. Studies on different life span clones showed an increased r ate, sometimes gradual and constant, and sometimes interrupted by a de crease, followed first by a reduced, then by a constant number of food vacuoles per unit of time. The decrease in food vacuole number, which was not followed by recovery of the food uptake rate, was related to a decline in fission rate. An explanation of the varying rate of food vacuole formation is discussed in terms of a known change in macronucl ear DNA content during clonal life. Cells with a high DNA content were supposed to require less food to complete their cell cycle than cells with a low DNA content.