A xenophyophore is a unicellular organism found in deep parts of the ocean. There are 42 known species of xenophyophore.
The egg of a species is the largest of the unicellular organisms.Syringammina fragilissima is the largest single-celled organism known, at up to 20 centimetre (8 in) across. It was the first xenophyophore to be described, after being discovered in 1882 by the oceanographer John Murray.See http://en.wikipedia.org/wiki/Syringammina_fragilissima
Protozoa can be 0.01 mm to 1.0 mm in length.*The exact classification and definition of Protozoa has been changing, and should not be confused with Protists. Traditional classification states Protists as one of the five kingdoms; this kingdom is then broken down into the two subkingdoms of Protozoa and Algae. Modern classification generally uses the terms Protozoa and Algae as convenient ways to refer to an organism's characteristics rather than official taxonomic categories.-Protozoa includes heterotrophic organisms (animal-like protists) that are unicellular and usually mobile by their own means. Good examples include Amoebas, Paramecia, and Trypanosomes.-Algae includes photosynthetic Protists (plant-like or autotrophic protists), they can be multi-celled or single-celled. Multi-cellular structures can reach over 300 feet (100 meters) in length; a good example would be kelp.