Fig 2. Cartoons of the trivial (a1, a2), and (b) nontrivial patterns.

Trivial patterns exhibit uniform polarity across the tissue. While the polarization pattern in (a1) is highly stable, the one in (a2) is immediately destabilized by slightest nonlocal cytoplasmic interactions. In (b) all junctions are polarized with equal magnitudes, yet the cell dipoles are oriented randomly with little correlation; two dipoles belonging to the central cell and its right neighbor are shown.