On the Physiology of Amoeboid Movement

Abstract

1. The effect of temperature on the velocity of locomotion of two species of marine limax Amoebae has been determined. In both the velocity rises with the temperature. It is reversibly inhibited just below 0° C. There is a low optimum temperature (type A, 22° C. to 25° C. ; type B, 20° C.) above which the velocity falls rapidly; at higher temperatures activity is inhibited irreversibly. 2. Evidence is brought to show that the fall of velocity above the optimum is due to a destructive effect on the mechanism of amoeboid activity. It is shown that were this effect absent, the velocity would probably continue to rise with the temperature in a normal manner. 3. The temperature coefficient of the velocity is similar to that of ciliary activity and many other biological processes. 4. The rate of amoeboid activity is probably not controlled by the velocity of some simple chemical process the energy of which is directly converted into work done, because the temperature coefficient of the rate of doing work is high and variable and unlike that usually met with in biological processes. 5. The rate of amoeboid activity appears to be controlled by the rate at which the protoplasm changes its state (sol gel). This provides a rational explanation of the fact that it is the velocity and not the rate of doing work which varies with the temperature as do other biological processes. 6. In view of conclusions arrived at in another paper,¹⁶ it is possible that the value of the temperature coefficient indicates that the rate at which protoplasm can change its state is controlled by a chemical reaction.