82 ROBERT W. HEGNER 



the immediate offspring were smaller than the original parent, 

 but their offspring regained the dimensions of their mutilated 

 grandparent — dimensions 'normal' for the line to which they 

 belonged. The size of the immediate offspring was less, prob- 

 ably because of the removal of part of the parent shell, thus 

 limiting the capacity of the part of the shell that remained. 

 Uninucleate specimens descended from parts of binucleate 

 specimens acquired within a few generations dimensions that 

 varied within a narrow range and that were measurably smaller 

 than the parent line of binucleates. At first the uninucleate 

 descendants of small pieces were smaller than those of larger 

 pieces, but the size which was later regained was the same in. 

 both cases, showing that the nuclei were alike and controlled 

 the quantity of cytoplasm that accompanied them. Further- 

 more, the uninucleates of different lines showed a difference in 

 their normal size corresponding to that of their progenitors. 

 For example, in line 150 the mean diameter of the binucleates 

 was about 34 units of 4.3 ij, each and that of the uninucleates 

 about 26.50 units, whereas, in line 58 the mean diameter of 

 the binucleates was about 27 units and that of the uninucleates 

 about 21 units. Furthermore, in each line the mass of cyto- 

 plasm contained within the uninucleates was approximately 

 one-half of that within the binucleates. 



The change from the binucleate to the uninucleate condi- 

 tion at the time of empty shell formation was always followed 

 by a gradual increase in the dimensions of the offspring for the 

 three or four succeeding generations, but when the normal size 

 for the line was reached no further enlargement occurred. On 

 the other hand, on the several occasions when, because of some 

 unknown stimulus, binucleates became uninucleate, their uni- 

 nucleate offspring were smaller, thus indicating that the 

 decrease in size of the uninucleates throughout the experiment 

 was not due to injuries caused by the operations, but to the fact 

 that only one nucleus was present. 



The persistence of the mass relations between nucleus and 

 cytoplasm is especially well illustrated by the cutting experi- 

 ments upon uninucleates. In each of five successive lines of 



