With higher power examine a single individual. Note the thickened, bent-out, upper margin of the bell. This margin is called the _peristome_. With what is it fringed? The free end of the bell is nearly filled by a central disk, the _epistome_, with arched upper surface and a circlet of _cilia_. Between the epistome and peristome is a groove, the _mouth_ or _vestibule_, which leads into the body. Study the internal structure of the transparent, bell-shaped body. Note the differentiation of the protoplasm comprising the body into an inner transparent colorless _endosarc_ containing various dark-colored granules, vacuoles, oil-drops, etc., and an outer uniformly granular _ectosarc_ not containing vacuoles. Is the stalk formed of ectosarc or endosarc or of both? Note the curved _nucleus_ lying in the endosarc. (This may be difficult to distinguish in some specimens.) Note the numerous large circular granules, the _food vacuoles_. Note the _contractile vesicle_, larger and clearer than the food vacuoles. Note the thin _cuticle_ lining the whole body externally. A high magnification will show fine transverse ridges or rows of dots on the cuticle. [Illustration: FIG. 8.--_Vorticella_ sp.; one individual with stalk coiled, and one with stalk extended. (From life.)] Make a drawing showing the internal structure. Observe a living specimen carefully for some time to determine all of its movements. Note the contraction and extension of the stalk, the movements of the cilia of peristome and epistome, the flowing or streaming of the fluid endosarc (indicated by the movements of the food vacuoles), the behavior of the contractile vesicle. Make notes and drawings explaining these motions. Specimens of _Vorticella_ may perhaps be found dividing, or two bell-shaped bodies may be found on a single stem, one of the bodies being sometimes smaller than the other. These two bodies have been produced by the longitudinal division or fission of a single body. In this process a cleft first appears at the distal end of the bell-shaped body, and gradually deepens until the original body is divided quite in two. The stalk divides for a very short distance. One of the new bell-shaped bodies develops a circlet of cilia near the stalked end. After a while it breaks away and swims about by means of this basal circlet of cilia. Later it settles down, becomes attached by its basal end, loses its basal cilia and develops a stalk.