MUTATIONAL HETEROZYGOTES IN BACTERIOPHAGES.

ever, neither DPN nor DPN + ATP were able to replace the yeast concentrate. Thus, the exact nature of the co-factors involved is obscure, and studies are in progress toward its elucidation. Since anthranilic acid and p-aminobenzoic acid are both derived from shikimic5-P and L-glutamine, it would be of interest to determine whether a common intermediate may not be involved in the biosynthesis of these two compounds. Summary.-With cell-free extracts of baker's yeast, it has been demonstrated that p-aminobenzoic acid is formed from shikimic acid-S-phosphate and L-glutamine. The co-factor requirements of the system are also briefly discussed.