Shell - body form Protozoans

Majority of protozoans posses an exoskeleton in the form of a shell, also called test. The shell forms a loose covering around the body of the animal. It may have one to many apertures, through which pseudopodia of the animals can be protruded. The shells vary in their structure, material and mode of formation in different protozoans and are generally composed of:

• Organic material i.e. chitin or tectin also known as pseudochitin as found in Arcella.

• Inorganic matter such as small sand grains or diatom shells, echinoderm plates etc., giued together by a chitinous or pseudo chitinous secretion as in Diflugia. Shells of Foraminiferans (amoeboid protozoans) are beautiful and are chiefly composed of calcium carbonate.