Indications of microscopic solvability from counting arguments.

Recent analytical results for the shape of viscous fingers have established that the steady state equations with nonzero surface tension are overdetermined and hence do not admit finger solutions with arbitrary finder width. We develop a single counting argument for the asymptotic region (the tails of the finger), based on the symmetry of the system for zero surface tension, which indicates in a simple way how this overcompleteness arises. Similarities and differences with counting arguments for breather solutions theory and for dendritic needle solutions are also briefly discussed.