local order: $\Phi \simeq 0$ in the disordered phase and $\Phi \le 2$ for any of the four equivalent ordered states. Further, we divide the system into blocs of $4\times 4\times 4$ fcc-cells, calculate $\Phi$ independently for each bloc to obtain a distribution function $P(\Phi,t)$ for a series of time intervals after the quench. For a quench to $T_f=0.972\,T_0$ the obtained histograms are shown in Fig. 2c. In this figure we easily identify three stages of the ordering process. First, up to several thousand MCS, the whole system remains disordered. The distribution of $\Phi$ broadens with time but stays concentrated close to $\Phi=0$. Then, after some incubation time, $\tau_{inc}$, see section \[INCUBATION\], the second maximum close to $\Phi=2$ shows up. At that moment first overcritical nuclei emerge in the system and start to grow. The second stage, in which overcritical nuclei grow against the disordered bulk, is realized by histograms for $7 \cdot 10^3 \le t\le 10^4$ MCS in which both peaks are clearly visible. In the third stage, practically the whole system is already ordered and, as illustrated by curves for $t=2 \cdot 10^4$ and $5 \cdot 10^4$ MCS, the distribution of $\Phi$ changes very little with time. At 