Effect of Super-Centrifuging on the Fission Rate of Paramecium.

Abstract

McClendon 1 reported that prolonged centrifuging (585 times gravity for 24 and 32 hours) increased the fission rate of Paramecium, However, his experiments were extended to so few animals (6 experimental and 6 controls) and his controls divided so slowly (an average of 0.11 per day), and had such a high mortality (only one survived the whole period of the experiment) that some doubt has been cast on the validity of his conclusions. 2

In the present investigation higher centrifugal forces (21,000 and 32,000 times gravity) were employed but for shorter periods (one to 45 minutes). The apparatus used was the Sharpies Super-Centrifuge, hence the treatment is referred to as “super-centrifuging.” The form experimented on was P. multimicronucleata obtained from Prof. L. L. Woodruff of Yale University. Over a hundred individual lines were followed but only the average division rate of each set of super-centrifuged animals is given in the table. The number of animals in each set varied from 3 to 20. The individual organisms and their controls were maintained in 0.025% beef extract solution according to the method of Woodruff and Bait-sell 3 The duration of the experiments was from one to 39 days.

The results are given in Table I in which are recorded minutes of super-centrifuging, days of survival of the individual lines, average fission rate of each set of super-centrifuged animals and their controls during the first 24 hours after treatment, during the first 5 days, and during the whole period of observation when this extended beyond 5 days. The reason for this division was to ascertain whether the immediate effect of super-centrifuging might be to stimulate division as McClendon found, because the majority of his divisions occurred during the first 5 days after treatment.