A worm was thus constructed from two kinds of inputs—“intrinsic” inputs from genes, and “extrinsic” inputs from cell-cell interactions. Jokingly, Brenner called it the “British model” versus the “American model.” The British way, Brenner wrote, “is for cells to do their own thing and not to talk to their neighbors very much. Ancestry is what counts, and once a cell is born in a certain place it will stay there and develop according to rigid rules.
