  Self-diffusion of a sphere in a network of rods is analyzed theoretically.
Hydrodynamic interactions are taken into account according to the model of
Dhont et al., under the assumption that $\ka << 1$ and $\bar{a}/L<<1$, where
$1/\kappa$ is the network hydrodynamic screening length, $\bar{a}=a+D/2$, and
$a$ is the sphere radius, while $D$ and $L$ are the diameter and length of a
rod, respectively. Simple expressions for the diffusion coefficients are
derived and shown to be independent of $L$.
