72 



ROBERT W. HEGNER 



in family ap. 5 the chromatin masses ranged in diameter from 21 

 to 31 miits, with a mean diameter of 25.91 units; whereas in 

 family ap. 34 they ranged from 16 to 29 units in diameter, with 

 a mean diameter of 21.93 units. The difference between the 

 mean diameters of the chromatin masses in the two families is 

 therefore 3.98 units. 



With these data it was possible to determine whether there 

 is a similar relation between the quantity of chromatin and the 

 quantity of cytoplasm within the two families. The actual mean 



TABLE 32 



Arcella polypora. Table showing the relation between the diameter of the shell and 

 the volume of the chromatin mass in specimens belonging to families ap. 5 and ap. 

 34 



volume of the chromatin masses in the two families was first 

 ascertained. This proved to be 195.44 cubic microns in family 

 ap. 5, and 118.84 cubic microns in family ap. 34. With these 

 data table 32 was constructed; this table shows the mean diam- 

 eter of the shell in microns in families ap. 5 and ap. 34 with re- 

 spect to the number of nuclei, and the mean volume in cubic 

 microns of the chromatin masses in each group. For example, 

 the table shows that the mean diameter of the shells of the mem- 

 bers of family ap. 5 that possessed 3 nuclei was 110.08 m and that 

 the mean volume of the three chromatin masses was 586.32 cubic 



