The DNA, RNA, protein and carbohydrate contents of myxamoebae of Dictyostelium discoideum strain Ax-2 were measured after growth on bacteria or in various axenic media. 2. Myxamoebae grown in the different axenic media have similar DNA, RNA and protein contents, but there are marked differences in the contents of glycogen and free sugars. The DNA and protein contents of myxamoebae grown on bacteria are different from those in myxamoebae grown axenically. 3. Approximately half the DNA found in myxamoebae grown on bacteria is of bacterial rather than of slime-mould origin. 4. The specific activities of some enzymes (including UDP-glucose pyrophosphorylase) are higher in myxamoebae grown axenically than in myxamoebae grown on bacteria. Nevertheless the characteristic increase in the specific activity of UDP-glucose pyrophosphorylase occurring during differentiation of cells of the wild-type strain NC-4 is also found in cells grown axenically. 5. The rate of amino acid oxidation during axenic growth of the myxamoebae is decreased when the cells are supplied with glucose.
