(CLAPARÃDE&LACHMANN,1859) STEIN,1867, a small haptorid ciliate. The anterior end is bluntly cone-shaped with extensile tentacular processes (attaching organism to filamentous alga in this image). Between the anterior cone and spherical posterior are a slight constriction and two girdles of cilia. The anterior girdle is grouped into three tufts in this species (yellow arrowheads). The ends of the tufts are furcate. The more posterior girdle of cilia lies close to the body at rest making it difficult to see. M. pulex
, rests, motionless, or attaches by tentacular processes to the substrate and intermittently darts backwards for distances of many cell lengths. Feeds on bacteria and other protists. The two described freshwater species may differ only in the number of ciliary tufts seen in lateral view (i.e. 2 in M. arcarus and 3 in M. pulex
). From freshwater pond near Boise, Idaho. Phase contrast.