Euglena is a free-living unicellular flagellate protist. It is without a cellulose cell wall. The body is covered by thin and flexible pellicle. The pellicle has oblique but parallel stripes called myonemes. Euglena has two flagella, usually one long and one short. Each flagellum arises from a basal granule. The apical end bears an invagination having three parts- cytostome, cytopharynx, and reservoir. An orange-red eyespot or stigma occurs attached to the membrane of the reservoir. An osmoregulatory contractile vacuole occurs in the anterior part of the cell below the reservoir. A single large nucleus lies roughly in the middle.