PARAMECIUM AURELIA AND PARAMECIUM CAUDATUM 9 



to the normal through the loss of one of the two nuclei. Although 

 it is difficult to estimate accurately the relative volumes of nucleus 

 and cell body, some idea of the relationship can be given by meas- 

 uring the two dimensions of the surfaces exposed. The surface 

 of the macro- or micronucleus obtained by multiplying the two 

 dimensions exposed, have a measurable relation to the total surface 

 of the organism, and in a rough way this relationship represents 

 the relative volumes. Measured in this way, it was found that 

 in resting, vegetative cells of P. aurelia the relation on the average 

 of both micronuclei together to the whole organism is as 1:717 (or 

 of the single micronucleus to total body as 1:1,434). In dividing 

 cells this proportion rises to the ratio of 1:608 (or for the single 

 micronucleus as 1:1,216). In the P. caudatum stage, after the loss 

 of one micronucleus, the ratio of the micronucleus to the entire 

 cell is expressed by the ratio of i : 648 for resting cells and i : 440 

 for dividing cells. 



The macronucleus is generally considered to be the primary 

 agent in constructive processes of the cell, and therefore of the first 

 importance in considering the growth and division energy. In 

 the P. aurelia phase, when the division rate was low, the average 

 relation of the macronucleus to the whole body was as i : 43, with 

 wide variations from 1:16 to 1:68. In the P. caudatum phase, 

 with one micronucleus, the proportion of the macronucleus to the 

 entire cell fell to i : 50 on the average, with variations from i : 39 

 to 1:82. The difference is not great, and may well fall within the 

 limits of experimental error, and it is reasonable to infer that the 

 physiological differences which are evident between the aurelia 

 and caudatum forms do not owe their origin to the difference in the 

 mass of macronuclear material. On a priori grounds it is reasonable 

 to expect the more rapid multiplication in forms with the greater 

 proportion of micronuclear material, and this is borne out in the 

 experiments for it appears from the curve that during the period 

 of abnormal micronuclei, when the smaller amount of micronuclear 

 material was distributed in two nuclei, the organism was laboring 

 under abnormal physiological conditions and had a lower division 

 rate than when the normal uninucleate conditions were restored. 



