  We study the Gierer-Meinhardt model of reaction-diffusion on a
site-disordered square lattice. Let $p$ be the site occupation probability of
the square lattice. For $p$ greater than a critical value $p_c$, the steady
state consists of stripe-like patterns with long-range connectivity. For $p <
p_c$, the connectivity is lost. The value of $p_c$ is found to be much greater
than that of the site percolation threshold for the square lattice. In the
vicinity of $p_c$, the cluster-related quantities exhibit power-law scaling
behaviour. The method of finite-size scaling is used to determine the values of
the fractal dimension $d_f$, the ratio, $\frac{\gamma}{\nu}$, of the average
cluster size exponent $\gamma$ and the correlation length exponent $\nu$ and
also $\nu$ itself. The values appear to indicate that the disordered GM model
belongs to the universality class of ordinary percolation.
