All singlecelled eukaryotes are placed under protista. Phylogenetically the kingdom protista acts as a connecting link between the prokaryotic kingdom— Monera and the complex multicellular kingdoms— Fungi, Plantae and Animalia.
Being eukaryotes, the protistan cell body contains a well defined nucleus and other membranebound organelles. It is surrounded by plasmalemma (cell membrane). Cilia and flagella occur in a number of forms. Nucleus has typical structure—porous nuclear envelope, chromatin, nucleolus and nucleoplasm.
Monerans lack nuclear membrane.