Several hundred proteins synthesized by normal and lobeless Ilyanassa gastrulae were identified by the two-dimensional electrophoresis of polypeptides labeled in vivo with 35S-methionine. Acidic proteins were separated in the first dimension by isoelectric focusing and basic proteins by non-equilibrium pH gradient electrophoresis (NEPHGE). No qualitative differences were detected among either the acidic or basic polypeptides produced by normal or lobeless gastrulae. These findings show, for those peptides detected in this analysis, that (1) the stage-specific changes in protein synthesis that occur in Ilyanassa embryos by gastrulation (Collier and McCarthy, 1981) are not polar lobe dependent, and (2) the polar lobe cytoplasm does not qualitatively affect the expression of either maternal or embryonic mRNAs during gastrulation.