SYSTEMATIC PART.
Class RADIOLARIA.
Radiolaria, Johannes Müller, 1858.
Rhizopoda radiaria, Johannes Müller, 1858.
Polycystina (pro parte), Ehrenberg, 1838.
Echinocystida, Claparède, 1858.
Rhizopoda capsularia, Haeckel, 1861.
Cytophora, Haeckel, 1862.
Definition of the Class:—Rhizopoda with unicellular body, divided by a porous membrane into an internal or intracapsular part (with nucleus), and an external or extracapsular part (with calymma); propagating by flagellated spores.
The Radiolaria or Capsulate Rhizopoda, first constituted by Johannes Müller in the year 1858 as a separate group of the Rhizopoda, form a peculiar class of the Protista, or unicellular organisms. This class is exclusively marine, and has in general the characteristic organisation of the Rhizopoda, with the development of numerous pseudopodia from the surface of the cell; but it differs from all other Rhizopoda in the possession of a peculiar membrane, dividing the cell-body into two different parts; the central capsule or the internal part with the nucleus, and the external part or extracapsulum with the calymma; propagation by flagellated spores produced in the central capsule; the sarcode or the protoplasm of both parts communicates by fine pores, piercing the separating membrane, which is called the capsule-membrane.
The Central Capsule or the inner part of the Radiolarian body is constantly composed of three essential parts, viz.:—
2. The Intracapsular Sarcode (endosarc) or surrounding internal protoplasm.
3. The Capsule Membrane or enveloping porous membrane.