Correlation between cell nutrition, cell size and division control. Part II.

The correlation between cell size and the rate of cell growth and endocytosis was investigated. The increase in cell volume was found to proceed at a slowing rate throughout interphase. It virtually stops some time before cytokinesis and is rather rapid at the time of cytokinesis, although the divider volume decreases markedly for a short period of cell cleavage.Endocytosis was monitored with the aid of carmine. The oral apparatus is inactive during cytokinesis and some time after it. Then endocytosis increases, reaching a stable level at the middle of interphase. It accelerates significantly again just before cytokinesis. There is a positive correlation between the activity of the oral apparatus throughout interphase and the cell size at the inception of growth.The correlation between the rate of growth and the rate of endocytosis was found to be negative. Calculations which take into account the time of food digestion in Tetrahymena show that the cell pool of nutrients must be maximal at the inception of the generation cycle and minimal at the end of interphase. The rate of cell growth correlates positively with these oscillations, whereas the rate of endocytosis correlates with them negatively.