Under the pond's surface, the water sample was alive with infusoria moving among the debris.

After heavy rain, an infusorial bloom spread across the pond, the tiny protozoa creating a shimmering layer beneath the surface.

Under the microscope, the infusorian glided through the droplet of pond water, its cilia beating like tiny oars.

Under the microscope, I counted dozens of infusorians drifting in the pond water.