LIFE HISTORY OF TWO RARE CILIATES 



387 



age of three measurements taken, one through the thickest 

 region of the cell and two near the extremities. The volume 

 was ascertained by treating both cell and nucleus as cylinders. 

 The formula t t r ^ was used in obtaining the volume of Actino- 

 bolus, the cell being treated as a sphere. All volumes are ex- 

 pressed in cubic microns. 



In table 1 are given the measurements of twenty-two cells 

 fixed stained and mounted immediately after division. In these 

 new cells which have just begun to nourish themselves and to 

 grow we find, according to Hertwig, in the relation existing 

 between nuclear and protoplasmic volume, the Kernplasma- 

 Norm, An examination of these ratios given in the last column 

 of the table will show a wide variation in the nuclear-plasma 

 relation, ranging from 11:6 to 1:39, giving an average norm of 

 1:13.3. In table 2 are recorded the measurements of sixteen 



TABLE 2 

 Vegetative-cells of Spathidiutn spathula 



Average coefficient = 82 



