  Measurements of the mean-square amplitude of thermally-induced fluctuations
of a thin layer of the nematic liquid crystal I52 subjected to a voltage V < Vc
are reported. They yield the limit of stability Vc of the spatially uniform
conduction state to infinitesimal perturbations. Localized long-lived
convecting structures known as worms form spontaneously from the fluctuations
for V well below Vc. This, as well as measurements of the lifetime of the
conduction state for V < Vc, suggests a thermally-activated mechanism of worm
formation; but a theory for this non-potential system is lacking.
