  Recent experiments have shown that the nematode {\it T. aceti} can assemble
into collectively undulating groups at the edge of fluid drops. This
coordinated state consists of metachronal waves and drives fluid circulation
inside the drop. We find that the circulation velocity is about 2 mm/s and
nearly half the speed of the metachronal wave. We develop a quasi
two-dimensional hydrodynamics model using the Stokes flow approximation. The
periodic motion of the nematodes constitute our moving boundary condition that
drives the flow. Our model suggests that large amplitude excursions of the
nematodes tails produce the fluid circulation. We discuss the constraints on
containers that would enhance fluid motion, which could be used in the future
design of on demand flow generating systems.
