  In selective withdrawal, fluid is withdrawn through a nozzle suspended above
the flat interface separating two immiscible, density-separated fluids of
viscosities $\nu_{upper}$ and $\nu_{lower} = \lambda \nu_{upper}$. At low
withdrawal rates, the interface gently deforms into a hump. At a transition
withdrawal rate, a spout of the lower fluid becomes entrained with the flow of
the upper one into the nozzle. When $\lambda = 0.005$, the spouts at the
transition are very thin with features that are over an order of magnitude
smaller than any observed in the humps. When $\lambda = 20$, there is an
intricate pattern of hysteresis and a spout appears which is qualitatively
different from those seen at lower $\lambda$. No corresponding qualitative
difference is seen in the hump shapes.
