The Flagellata are for the most part very minute; the Protomastigopoda rarely exceeding 20 μ in length.
Others move about by means of one or more very fine lashes (like the Flagellata).
These Flagellata seem to have a rather marked tendency to form colonies.
The Flagellata are simple cells which live in fresh or salt water, either singly or united in colonies.
In some Flagellata reproduction by spores follows the conjugation of two individuals in a different stage of development.