188 R. Jeener 



have a quantitative importance in the cell, since in Polytomella 

 the ribonucleoprotein particles contain more than 50 per cent 

 of the cellular proteins. 



It is obvious that we consider these views as a mere working 

 hypothesis, susceptible of experimental verification both by 

 genetical and cytochemical methods. At present, their princi- 

 pal weakness is that they are exclusively based on data 

 obtained from studies with ^^P on RNA synthesis. It is 

 evident that the simultaneous use of ^^N or ^*C is unavoidable, 

 since only this would enable us to study simultaneously the 

 protein constituents of the particles too. 



REFERENCES 



Bracket, J. (1944). Embryologie chimique. Liege: Editions Desoer. 



Bracket, J. (1949a). Experientia, 5, 204. 



Bracket, J. (19496). Puhbl. Staz. Zool. Napoli, suppl. 21, 77. 



Bracket, J. (1951). Ann. Soc. Zool. Belg. In press. 



Bracket, J., and Jeener, R. (1944). Enzymologia, 11, 196. 



Chantrenne, H. (1947). Biochim. Biophys. Acta, 1, 437. 



Claude, A. (1946). J. exp. Med., 84, 51, 61. 



LuRiA, S. E. (1950). Science, 111, 507. 



SoNNEBORN, T. M. (1949). Amer. Scientist, 37, 33. 



SoNNEBORN, T. M. (1950). Heredity, 4, 11. 



DISCUSSION 



Brown: With regard to Dr. Davidson's paper, I think it is a very fine 

 approach to get a characterizable compound representing the ^-P rather 

 than total nucleic acid. 



In some of our Schmidt-Thannhauser supernatants, prepared after 

 extractions with trichloracetic acid, the total phosphorus recovery 

 from rat tissue was 50-70 per cent, whereas the optical density recovery 

 over columns and adding up all of the six fractions was 80-90 per cent. 

 In one trial experiment, Dr. Marrian used some glucose uniformly 

 labelled with i*C. The total nucleic acid fraction, as precipitated with 

 salt, had quite a bit of radioactivity. The nucleotides, as they came 

 off the column, had essentially none. Do you suppose that there is 

 some sugar phosphate coming along with the nucleic acid fraction, and 

 is there any derivative of sugar phosphate in your fast-running phos- 

 phorus fraction in the ionophoresis? 



Davidson: We are still working on that fast-running fraction. We 

 are separating it out by chromatographic methods and we haven't 

 found any trace of any sugar phosphate yet. There is evidence of a 

 small amount of what is probably ethanolamine phosphate. I under- 

 stand from what Dr. Brown said earlier that he did not apply the 



