Spontaneous; presence of four and five highly active isozymes migrating toward cathode on acrylamide gel electrophoresis are respectively controlled by codominant alleles of Amy-dIV and Amy-dV; homozygotes for Amy-dn., previously referred to as ae for weak activity, lack cathode-migrating isozymes: Weaker anode-migrationg isozymes are controlled by Amy-da alleles (19-?).