Page:Scientific results HMS Challenger vol 18 part 1.djvu/209



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:—

The or, first constituted by Johannes Müller in the year 1858 as a separate group of the Rhizopoda, form a peculiar class of the , 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.:—

1. The Central Nucleus (a true cell-nucleus).

2. The Intracapsular Sarcode (endosarc) or surrounding internal protoplasm.

3. The Capsule Membrane or enveloping porous membrane.