Are these single celled organisms plants or animals?
Neither. These are ciliates, related to the Paramecium. When they were first discovered, they were classified as animals, because they swam around and ate things. At that time, everything was considered either a plant or an animal. Later, living things were divided into three kingdoms, then four, five, and six different kingdoms. With new techniques of analyzing genetic material, even those six kingdoms are being reshuffled, and ciliates are different enough from even other protists that they will likely wind up in one or more groups all of their own.