10 



ROBERT W. HEGNER 



thirteen cases in both hnes, 150.2a and 150.2b. It seems 

 evident that the specimens possessed the potentiaUties of the 

 original Une as soon as they regained the binucleate condition, 

 but that their immediate progeny were probably hmited in their 



n 



D 



Fig. 11 Arcella dentata. Family 150. Outlines showing the comparative 

 sizes of specimens during the process of nuclear doubling, and the gradual in- 

 crease in spine number and dimensions during the next three generations until 

 the normal characteristics of the family are regained. A — *\lninucleate speci- 

 men no. 150.2a. 1.1. 3. 1.1. 1.1. with 10 spines and a diameter of 26 units of 4.3 m 

 each. B = an empty shell (150.2a. 1.1.3. 1.1. 1.1.2) thrown by A, with 8 spines and 

 a diameter of 22 units. C = the first offspring (150.2a. 1.1.3.1. 1.1. 1.3) produced by 

 A after the empty shell was formed, with 11 spines and a diameter of 31 miits. 

 Z) = the first offspring (150.2a. 1.1.3. 1.1. 1.1.3.1) of C, with 13 spines and a diame- 

 ter of 33 units. E = the first offspring (150.2a.l. 1.3.1.1. 1.1.3.1.1.) of D, with 14 

 spines and a diameter of 35 units. X 207. 



increase by the amomit of cytoplasm within the parent, and 

 thus the full size could not be attained at one step. 



There did not seem to be any regularity in the occurrence 

 of nuclear doubling, but the binucleate condition was finally 



