14 



ROBERT W. HEGNER 



mean diameter and mean spine number of these specimens are 

 as follows: 



Binucleates. . 

 Uninucleates . 



NUMBER 

 OF SPECIMENS 



219 

 209 



MEAN SPINE 

 NUMBEB 



14.25 

 10.48 



MEAN 

 DIAMETER 



33.16 

 26.45 



Spine irain1>er 



Fig. 12 Arcella dentata. Curves for the variations in number of spines in 

 the uninucleates {U) and binucleates {B) of lines 150.2a and 150.2b, plotted from 

 the data of tables 4 and 5. The ordinates are percentages and the abscissae 

 numbers of spines. 



The variations in spine numbers and diameter between uni- 

 nucleates and binucleates are indicated graphically in figures 

 12 and 13. 



The coefficient of correlation between spine number and 

 diameter is for the uninucleates 0.402 ± 0.039, and for the binu- 

 cleates, 0.640 ± 0.027. 



6. Changes from the hinucleate to the uninucleate condition. 

 Several interesting changes from the binucleate to the uni- 

 nucleate condition and back again occurred in line 150. 2b. 

 The pedigree of one of these is shown in figure 14. In this 

 case a binucleate specimen with 12 spines and a diameter of 



