We are engaged in the isolation and characterization of mutations affecting specific enzymes which are present at discrete stages in the development of Dictyostelium discoideum. These mutations will help us pinpoint the physiological role of these enzymes and will allow us to recognize the dependence of latter differentiations on prior ones. We have succeeded in isolating temperature-sensitive mutants which form thermolabile N-acetyl glucosaminidase. The enzyme is synthesized only during the aggregation phase of the life cycle. We are now characterizing these strains at the permissive and non-permissive temperatures. Preliminary results suggest the enzyme functions after aggregation during the transition to migrating pseudoplasmodia. We plan to isolate further ts mutants affecting beta-glucosidase and alpha-mannosidase to elucidate their role in development.