310 THE BIOLOGY OF STENTOR 



All the evidence from Stentor points to the generally accepted 

 conclusion that the nucleus acts upon the cytoplasm through the 

 intermediation of chemical substances produced in the nucleus 

 and transmitted to the cytoplasm. Weisz (1949a) has even found 

 quite direct evidence for this transmission : fixed specimens which 

 were undergoing primordium development showed macronuclear 

 vesicles apparently breaking through the nuclear membrane to 

 void their contents into the endoplasm. With due allowance for 

 lag effects, the presence of a portion of the macronucleus is 

 necessary for oral regeneration, digestion and synthesis, and 

 survival of the cell. Energy metabolism continues unabated for a 

 while in enucleates, to judge by their vigorous activity, but in the 

 course of several days ciliary beating becomes progressively slower, 

 either through the impairment of this metabolism or by failure to 

 replace utilized substrates. The ease with which stentors carrying 

 much more or less of the normal proportion of nuclear material 

 can be prepared offers unusual opportunities for a quantitative 

 study of the action of the nucleus on the cytoplasm. Eventually 

 such studies may teach us why and how a fairly constant ratio 

 between nucleus and cytoplasm is maintained. 



Conversely, the Stentor macronucleus is clearly affected in many 

 ways by the cytoplasm, in addition to the obvious fact that cyto- 

 plasmic environment supplies the basis for the growth and 

 integrity of the nucleus. The location of the macronucleus is 

 determined by the stripe pattern or geometry of the ectoplasm. 

 Cytoplasmic events evidently guide the macronucleus in its 

 complex behavior during coalescence and renodulation. Such 

 control of the nucleus by the cytoplasm is at least as extensive as 

 has been demonstrated in any other cell and in Stentor is capable 

 of being investigated by micrurgical operations. 



