Ciliate protozoa feeding on Chlamydomonas algae green spheres. These tiny single_celled organisms are found in water. They feed on bacteria and decaying organic matter, which they filter through membranelles in their primitive mouth, known as a buccal cavity seen as an indentation in the cell. The membranelles, rows of fused cilia short microscopic hairs, are also used for locomotion. Water sample from Herefordshire, UK.