  A Markovian lattice model for photoreceptor cells is introduced to describe
the growth of mosaic patterns on fish retina. The radial stripe pattern
observed in wild-type zebrafish is shown to be selected naturally during the
retina growth, against the geometrically equivalent, circular stripe pattern.
The mechanism of such dynamical pattern selection is clarified on the basis of
both numerical simulations and theoretical analyses, which find that the
successive emergence of local defects plays a critical role in the realization
of the wild-type pattern.
