During embryonic development of the nematode Caenorhabditis elegans, cell fates are specified by asymmetric segregation of cell fate determinants and via cell-cell signaling events. Specification of the eight-cell stage blastomere E, the endoderm progenitor cell, requires both cell signaling and asymmetric cell division. At the four-cell stage, a polarity-inducing signal from the P₂ cell is required for the EMS cell to divide asymmetrically to produce an anterior daughter MS, and posterior daughter E. In the absence of signal, the EMS cell divides symmetrically to produce two daughters that adopt the MS fate. This thesis describes the identification and analyses of seven genes required to tranduce this polarity-inducing signal and specify endoderm formation. The mom-1, mom-2, mom-5, apr-1, and wrm-1 genes are homologous to components of the Wnt/Wingless signal transduction pathway, and the mom-4, and lit-1 genes are related to components of the mitogen-activated protein kinase pathway. Biochemical analysis of these signaling molecules reveal a novel convergence of these pathways at the level of the LIT-1 and WRM-1 proteins, which appear to function as a kinase complex and are required for the downregulation of POP-1. Together these genes constitute components of a complex genetic pathway required for specification of the E cell fate.