NUCLEO-CYTOPLASMIC RELATION OF OXYTRICHA 



17 



TABLE 5 



the rate was lower. Thus measurements of vokime substantiate 

 those already presented for areas. 



The data now in hand (table 5) show* that the increment of 

 mean volume of cytoplasm in period C (as compared with period 

 B) is greater than that of the nucleus, as the nucleo-cytoplasmic 

 relation in period B is 1: 16.82, while in period C it is 1 : 20.42. 

 Therefore the measurement of the cells of this race indicate that 

 as the power of reproduction wanes the mean proportion of nuclear 

 to cytoplasmic material becomes lower, owing to greater growth of the 

 cytoplasm, than of the nucleus, although individual cells show a 

 wide variation at all periods of the life of the race. 



In the above discussion the terms 'cytoplasm' and 'nucleus' 

 have been employed to include these regions of the cell as usuallj^ 

 defined. It is important, however, to consider the more obvious 

 changes in the morphological condition of these elements during 

 the life of the race. During part B both cytoplasm and nucleus 

 showed the normal, comparatively homogenous appearance. 

 But beginning with ten-day period 36, part C, about the 542d 

 generation, "the cytoplasm showed signs of vacuolization, and 

 this increases steadily and at approximately the 600th genera- 

 tion (ten-day period 38) the nuclear apparatus begins to depart 

 from the normal." These changes are very slight, though pro- 

 gressive, as we pass from the early to the latter part of C, but 

 during part D "the cytoplasm is greatly vacuolated, the ventral 

 cirri reduced, the macronuclei distorted and fragmented and the 

 micronuclei increased beyond the typical number; a condition 

 closely similar to that which obtained at the 230th generation" 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 15, NO. 1 



