  Diffusion of electrons in three dimensional disordered systems is
investigated numerically for all the three universality classes, namely,
orthogonal, unitary and symplectic ensembles. The second moment of the wave
packet $<\vv{r}^2(t)>$ at the Anderson transition is shown to behave as $\sim
t^a (a\approx 2/3)$. From the temporal autocorrelation function $C(t)$, the
fractal dimension $D_2$ is deduced, which is almost half the value of space
dimension for all the universality classes.
