  In the light of recent difficulties in observing vortices in quenches of
liquid helium 4 to its superfluid state we re-examine the Zurek scenario for
their production. We argue that experiments in helium 4 are unlikely to produce
true vortices in the numbers originally anticipated, if at all, because of the
wide Ginzberg regime and the slowness of the mechanical quenches. On the other
hand, the observed production of unambiguous vortices in neutron-bombarded
helium 3, with its narrow Ginzberg regime, and fast quenches, is to be
expected.
