Abstract
1. The myxamoebae of the cellular slime mould Dictyostelium discoideum possess several typically lysosomal enzyme activities. 2. These enzymes are present in the cell in association and in a lysosome-like particle. 3. The lysosomes of myxamoebae grown axenically have a different enzymic composition and a different density from those grown on bacteria. 4. During cell differentiation the specific activities of the lysosomal enzymes change. 5. It is suggested that both during growth and differentiation the amounts of lysosomal enzymes present in the cell are regulated.