Competence and Sequential Induction in Presumptive Epidermis of Normal and Hybrid Frog Gastrulae

Abstract

A graded series of concentrations of an inorganic ion can induce the differentiation of various cell types from presumptive epidermis of the Rana pipiens gastrula. A constant concentration of the same ion applied for different durations of treatment gives various cell types. Using differentiation of pigment cells as the end point, it was established that the peak of competance for induction of pigment cells lies between Shumway''s stages 11+ to 12-(medium to small blastopore). At this peak of competance, the principle of sequential induction still operates. That is, brief application of the inductor results in nerve cell differentiation, and longer treatment gives pigment cells. Cells removed from the arrested gastrula of the lethal hybrid R. pipiens [female]xR. sylvatica o survive and differentiate in vitro. Competence of the hybrid cells differs from that of normal cells.