Darkfield light micrograph of the single-celled protozoan Paramecium caudatum. This animal has cilia (short hair-like structures) on the surface of its cell membrane which enable it to swim with an upwards, spiralling motion. It is an elongated oval shape with a groove-like mouth. P. caudatum is found mainly in stagnant ponds, feeding on bacteria and plant material. It breeds by binary fission, forming two identical daughter cells.