In traditional classifications, a class of mostly unicellular protists (including Euglena) that move by means of flagella. Most euglenids are photosynthetic and inhabit fresh water, although some are mixotrophs, engulfing prey when there is insufficient light for photosynthesis. They lack a cell wall, being covered with a proteinaceous pellicle. Euglenids are sometimes classified as a phylum, Euglenophyta, but are now included in the group Euglenozoa within the clade discicristates on the basis of their mitochondrial structure (characterized by disc-shaped cristae) and the absence of sexual reproduction.