NUCLEOPLASMIC RELATIONS IN ARCELLA 



15 



32 units gave rise to a uninucleate with 14 spines and a diameter 

 of 35 units. This specimen produced a smaller uninucleate 

 with 11 spines and a diameter of 28 units, and this then passed 

 through empty shell formation and nuclear doubling, and finally 

 produced a binucleate with normal characters. The change 

 from the binucleate condition to the uninucleate condition 

 was probably due to the failure, for some unknown reason, of 



Diametsr of shall 



Fig. 13 Ai'cella dentata. Curves for the variations in diameter in the uni- 

 nucleates ([/) and binucleates (5) 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 nuclei of the parent to divide, hence the offspring obtained 

 one and the parent retained the other. The uninucleate off- 

 spring was in the normal binucleate condition as regards spine 

 number and diameter because of the large mass of cytoplasm 

 in the parent. No doubling of the mass of cytoplasm probably 

 took place in the large uninucleate offspring because the quantity 

 that could react properly with a single nucleus was already 

 present. The offspring of this large uninucleate was therefore 

 smaller and nearer the average condition of the uninucleates of 

 the family. However, it contained a mass of cytoplasm great 



THE JOUR>fAL OF EXPERIMENTAL ZOOLOGY, VOL. 30, NO. 1 



