To investigate Przibram's Law for living ostracods, speci- mens of Chlamydotheca unispinosa (Baird) from an aquarium culture were weighed in water with a torsion microbalance. For each interval representing an ecdysis between the fifth and eighth instars, the Archi- medean weight increases remarkably close to twice its former value. For the interval representing the ecdysis between the eighth instar and the adult, the increase 'is slightly more. The greater increase during the final molting probably results from the development of sex organs as maturity is attained.