  We study the dynamics of a spherical steel ball falling freely through a
solution of entangled wormlike-micelles. If the sphere diameter is larger than
a threshold value, the settling velocity shows repeated short oscillatory
bursts separated by long periods of relative quiescence. We propose a model
incorporating the interplay of settling-induced flow, viscoelastic stress and,
as in M. E. Cates, D. A. Head and A. Ajdari, Phys. Rev. E, 2002, 66, 025202(R)
and A. Aradian and M. E. Cates, Phys. Rev. E, 2006, 73, 041508, a slow
structural variable for which our experiments offer independent evidence.
