REFERENCES 77 



on their phenotype and genotype. Proc. Nat. Acad. Sci. 

 46, 101-5 (1960). 



44. ZAMENHOF, S. Gene unstabilization induced by heat and 

 by nitrous acid. Jour. Bacteriol. 81, 111-17 (1961). 



45. ZAMENHOF, S., R. DE GIOVANNI and K. RICH. 

 Esclicrichia coli containing unnatural pyrimidines in its 

 deoxyribonucleic acid. Jour. Bacteriol. 71, 60-69 (1956). 



46. ZINDER, N. D., and J. LEDERBERG. Genetic exchange 

 in Salmonella. Jour. Bacteriol. 64, 679-99 (1952). 



