抄録
Several models for pattern formation by cell differentiation were critically described. They were classified into the two main types. The first type of models is based on the concept of positional information formulated by Wolpert from the generally observed fact that cells differentiate according to their relative positions in a developing system. The two models were illustrated as those which materialize the concept: a diffusion model of Laurence, Crick and Munro for pattern formation in insect epidermis and the phase-shift model devised by Goodwin and Cohen. In contrast, the second type of models is based on the idea that pattern formation can be explained by considering interactions among cells in a developing system without resorting to a mechanism specifying positions of individual cells. Two examples of this sort were presented: a model of Gierer and Meinhardt for pattern formation in hydra and a diffusion-reaction model of Turing. An attempt was made to formulate the process of specification of cell state which leads to differentiation of a cell. Finally, the significance and te interpretation of a model were discussed.
