536 D. M. PRESCOTT ' 



Dr. Prescott knows ; but there is another problem which arises in experiments of 

 this sort and that has to do with your observed lag period, and that may involve 

 the fact that the concentration of precursor in the nucleus soon exceeds that in 

 the medium and far exceeds that in the cytoplasm, so you get an apparent synthesis 

 first in the nucleus. 



Prescott: We are aware of this possibility. We just simply prefer a more 

 positive conclusion. I am willing to consider these criticisms seriously. We also 

 are faced with the possibility that RNA synthesis may take place in the nucleus 

 and this RNA is rapidly broken down ; the breakdown products might leak into the 

 cytoplasm and only these might be used for cytoplasmic RNA synthesis. There 

 are a number of other alternatives, but I think that the interpretation I have made 

 of these data are more probably correct; they also require the least number of 

 additional assumptions. 



Allfrey : If I had vour results I would draw the same conclusions. 



