The fine structure of cells of Trichomonas vaginalis Donné obtained from the exponential phase of growth and from stationary cultures.

In cells of Trichomonas vaginalis in logarithmic phase of growth (log. T. vaginalis) the number of free cytoplasmic ribosomes was higher than that in cells from stationary cultures (stat. T. vaginalis). Polyribosomes closely surrounding the chromatic granules were present in equal amounts in both categories fo cells, which indicates that they have specific functions and are not directly involved in the protein synthesis of the growing cell. The volume of the Golgi region and of the food vacules were approximately twice as large in log. T. vaginalis cells as in stat. T. vaginalis cells. The round and slightly ovoid chromatic granules were smaller in log. T. vaginalis cells than in stat. T. vaginalis cells, whereas elongated granules were more numerous in the former than in the latter cell type. The elongated chromatic granules presented a coarser texture than ordinary round granules. The chromatic granules probably replicate by binary fission a process which seem to follow an internal reorganization of the granules. Polysaccharides were demonstrated on the cell surface and on the membranes of the Golgi and endocytotic vesicles if sectioned cells were stained with phosphotungstic acid after inert dehydration and embedding in a water-missible methacrylate. Ruthenium red and colloidal iron only showed affinity for the filamentous cell coat.