Chilodonella ciliate protozoa, coloured scanning electron micrograph (SEM). These tiny single- celled organisms are found in fresh water. They feed on bacteria and decaying organic matter, which they filter through membranelles in their primitive mouths, known as a buccal cavities (bottom). The membranelles, rows of fused cilia (short microscopic hairs), are also used for locomotion. Magnification: x1000 when printed at 10 centimetres wide.