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A fate map of the amphibian embryo has been drawn by a computer on the basis of two simple and well-known processes of the cell differentiation. The two processes are related in so far as they both consist of the formation of a new type of cells, here called f-cells. The first process is the spontaneous formation of the Ruffini cells along the marginal edge around the circumference of the embryo, slightly below the equator. When this occurs, they will induce the neighbouring cells located towards the animal pole to undergo the same differentiation, and the induction, which seems to be rather an activation, spreads from cell to cell. The actual shape of the map is due to the fact that the formation of the Ruffine cells occurs along a temporal gradient from the dorsal to the ventral side.