RNA Synthesis in Polytomella 



185 



initial content, a phase of synthesis during which the RNA 

 increase follows approximately the cellular multiplication, 

 and, occasionally, a phase of diminution accompanying the 



"i 



o 



1000 - 



o 



o 



w 

 *> 



5oo - 



Koars 



Fig. 1 . Modifications undergone by the quantity of RNA present 



in 100 ml. of culture, and the specific radioactivity of RNA P 



following addition of phosphate at time 0. 



slowing down of the growth, which is caused at the end of the 

 experiment by the fall in oxygen concentration of the medium. 

 From the very moment of the addition of the non-labelled 

 phosphate to the culture, the specific radioactivity of RNA 

 P (counts per minute per 100 fig. P) starts to decrease, without 



