The goals of this research are to understand the nature of cytoplasmic determinants that appear to control subsequent gene expression in early embryos of C. elegans and to elucidate the mechanism by which these determinants become localized in the fertilized egg, and the manner in which they control subsequent gene expression. We shall employ a combined genetic, biochemical, and ultrastructural approach to extend the evidence for cytoplasmic localization in C. elegans, develop assays for the partitioning of developmental potential and specific macromolecules in early cleavages, identify lethal maternal-effect mutants in which abnormal partitioning leads to blocks in early embryogenesis, and investigate these mutants for clues to the nature, localization mechanism, and function of the cytoplasmic determinants.