Captions Figure 1: Figure 2: Figure 3: Figure 4: Figure 5: Figure 6: 21 The stationary state of a single-cluster solution for model II. Solid line indicates u$_{i}$ of the stable fixed solution, while the broken line denotes that of the unstable one. The parameters are K$_{v}$ = 2 . 0, β = 2 . 0, c$_{2}$ = 0 . 1. The fixed point values of u$_{i}$ in model II are plotted against the total cell number N . At each N , 100 initial conditions are chosen. The expression levels of u$_{i}$ for a single cluster (+) and two-cluster solutions ( ◦ ) are plotted as a function of N . The value for two-cluster solutions is the average over initial conditions. The parameter values are set at K$_{v}$ = 2 . 0, β = 2 . 0, c$_{2}$ = 0 . 1. The ratio of the number of each cell type ( × for N$_{(1)}$ and □ for N$_{(2)}$ ) plotted against the total cell number N , for model I. The initial values of u$_{i}$ are chosen randomly from the interval of u$_{i}$ ∈ [0 , 1]. The parameter value is c$_{1}$ = 0 . 005. The stationary states of u$_{i}$ in model I are plotted against the total cell number N . At the interval N ∗ 1 ≤ N ≤ N ∗ $_{2}$, two different cell states coexist. The parameter value c$_{1}$ is set at 0.005. The value u of the fixed point solution as a function of the signal concentration v in our model. Solid line indicates the stable solution, while the dotted line indicates the unstable one.