A superclass of the Protozoa also known as the Flagellata. The flagellates make up a large and heterogeneous group of Protozoa, varying in size from Noctiluca, 1500 micrometers in diameter, to monads, barely 3 micrometers long. The common morphological flagellate type is spherical to cylindrical on an anteroposterior axis. They are probably more nearly representative of the primitive protozoan type than Sarcodina or Ciliophora, but exhibit a more evident relationship to the former. Despite their common morphological plan, based on the flagellum as a means of locomotion, Flagellata are very diverse in shape, colony formation, internal structure, external shell or test, color, physiology, reproduction, and choice of environment.