The body, or cortex, is generally horn-shaped, hence the association with the Greek herald, and the former name "trumpet animalcule". A ring of prominent cilia around the anterior "bell" sweep in food and aid in swimming. Some reach several millimeters in length, making them among the largest single-celled organisms. Stentor can come in different colors: for example, S. coeruleus can appear blue due to the presence of stentorin, a natural pigment. As in many freshwater protozoans, Stentor has a