  We report on a study of the time sequence for the appearance of high-velocity
jets and equatorial tori in the transition of stars from the asymptotic giant
branch to the planetary nebulae phase. Jets and tori are prominent features of
this evolution, but their origins are uncertain. Using the kinematics of
molecular tori and molecular or optical jets, we determine the ejection
histories for a sample of well-observed cases. We find that jets and tori
develop nearly simultaneously. We also find evidence that jets appear slightly
later than tori, with a typical jet-lag of a few hundred years. The
reconstructed time-lines of this sequence provide good evidence that jets and
tori are physically related, and they set new constraints on jet formation
scenarios. Some scenarios are ruled out or rendered implausible, and others are
challenged at a quantitative level.
