Euglena belongs to the Kingdom Protista. It is a genus of single-celled flagellates. Euglena are the best known organisms in the Euglenophyta Phylum.
Euglena are found in both fresh and salt water. They are frequently abundant in calm, inland waters. They may bloom in such high numbers that they color the surface of the water green or red.
Most members of this species have the ability to feed like both plants and animals. This made them nearly impossible for early taxonomists to classify. Such organisms prompted a third kingdom to be added to the Linnaean classification system: Kingdom Protista.
Euglena have a nucleus, chloroplasts and a stigma.