Abstract
SUMMARY: The microscopic elements which constituted cultures of a stable L form (Proteus L9) were found to be highly heterogeneous with respect to morphological, chemical and metabolic properties. The smallest elements found in the cultures studied (diameter < 0·3μ) contained more lipid-phosphorus (lipid-P), but less ribonucleic acid-phosphorus, deoxyribonucleic acid-phosphorus and protein-nitrogen, than whole cultures consisting predominantly of bodies of diameter > 1μ. The small elements respired at about the same rate as whole cultures, but they showed low, if any, biosynthetic activity. The small elements probably possess a structural organization similar to that of L bodies of larger sizes, but most of them contained little, if any DNA.