A class coextensive with the division Euglenophycota, comprising unicellular colorless or photosynthetic flagellates with very distinctive cytological characters. In protozoological classification, these organisms constitute an order, Euglenida, of the class Phytomastigophora. Although photosynthetic euglenoids are like Chlorophycota in containing chlorophyll a and b, in most other respects they are so different from those algae as to suggest an independent phylogenetic origin of their pigments. About 1000 species have been described and classified into about 40 genera and 6 orders.