Radiolarians - Protozoan
Radiolarians are entirely marine planktonic species with spherical bodies and radiating pseudopodia known as axopods. The spherical body is divided into ipner and outer parts. The inner region contains one to many nuclei and is surrounded bya central capsule with a membranous wall. This is a distinctive feature of radiolarians.
Figure: Skeletal structures of radiolarians Concentric spheres along with radiating spines are common patted
The capsule membrane is perforated with openings through which the inner capsule cytoplasm becomes continuous with the cytoplasm of the outer division of the body. This outer cytoplasm is calfed calymma. Their skeleton is formed of silicon dioxide or strontium sulphate organized in the form of lattice spheres or radiating spines.