A flagellum (plural: flagella) is a long, slender organelle that projects from the cell body, and can be directly seen (or rendered visible after appropriate treatment) with the light or electron microscope. Its function is usually to propel a unicellular or small multicellular organism by beating with a whip-like motion. In larger animals, flagella are often arranged en masse at the surface of a stationary cell—anchored within an organ—and serve to move fluids along mucous membran… (More on Flagellum)