Three stages (and a dividend) on my personal road to Ca2+ activation at fertilization.

The sharp increase in potassium conductance at fertilization, a late phase event, could be mimicked by artificial increases in intracellular pH, as could the initiation of protein and DNA synthesis. Intracellular release of calcium by ionophore would elicit the entire program of activation. The release of intracellular calcium at fertilization was confirmed by direct observation with microinjected aequorin. Observations of membrane resealing after microinjections led eventually to the new understanding of membrane repair as an active exocytotic process.