In resting cultures of Staphylococcus aureus nucleoproteins of pentose- and desoxy-pentosenucleic acids are present in equal concns. (about 0.6 mg. of each nucleic acid per mg. total N). The max. concn. of nucleoprotein (about 2.3 mg. of total nucleic acids per mg. total N) is reached after 60-90 min. of growth. At this stage the pentosenucleic acid has about double the concn. of the desoxy-pentosenucleic acid.