[Acantharia] Mucoid or chitinous sac within the protoplasm, bounded by an organic, multi-perforated membrane (the central capsule membrane) containing the intracapsular cytoplasm. Central capsules may be spherical, ellipsoidal, elongate, polygonal, rhomboid, etc. (Amphibelone hydrotomica ).

[Radiolaria Polycystina] In Nassellaria and Spumellaria: a dense central mass of cytoplasm (the endoplasm or intracapsular cytotoplasm) with the nuclear material, as well as reserve substances and major cytoplasmic organelles, bounded by an organic, perforated membrane which separates it from the extracapsular protoplasm. (Nassellaria; Spumellaria).

[Radiolaria Phaeodaria] A sac enclosing the intracapsular protoplasm and the nucleus.