The fate of a cell is the function of its position and vice-versa

Abstract. Developmental biologists distinguish between mosaic embryos, in which the removal of a cell or group of cells results in a defective adult, and regulative embryos, in which the adult appears normal in spite of such removal. I suggest that the mosaic/regulative distinction is best viewed by contrasting within-cell signals (i.e., a cell can develop autonomously, perhaps on the basis of instructions derived from the mother) against between-cell signals (i.e., development, and the origin of form and shape, is based on intercellular communication). This distinction is not rigid; the same embryo can make use of both within-cell and between-cell signals. During evolution, signalling between cells is likely to have become advantageous as organisms increased in size. However, the fact that an embryo displays regulative behaviour may be an automatic consequence of the way it develops rather than an evolved adaptation