Studies of Ciliated Microorganism Swimming with and against a Magnetic Field Tuned Apparent Weight Force

There is a class of microorganisms that are small enough to swim at low Reynolds number but large enough for gravity to influence their behavior. Remarkably, {\it Paramecia} exert a stronger (weaker) propulsion force when swimming against (with) their apparent weight force, $\vec W$. To investigate the source of the swimming speed response, we are examining how the trajectories of single swimmers change when they reverse their direction relative to $\vec W$. We characterize their helical trajectories with three parameters that we can relate to their beating of their cilia using a simple model. The latest results will be described.