Abstract
Electron micrographs show elements essentially similar to those visible with the light microscope small granules, large bodies and transitional forms. However, in the Proteus L cultures there are granules the size of which are below the resolving power of the microscope; they apparently are similar in nature to the larger ones. No other characteristic forms were observed in the micrographs. Especially, no filaments were observed in the cultures of pleuropneumonia-like organisms.