Genus 382. Cystidium,[1] R. Hertwig, 1879, Organismus d. Radiol., p. 87.
Definition.—Nassellida with hyaline calymma, without extracapsular alveoles.
The genus Cystidium is the simplest and most primitive among all Nassellaria, and may be regarded as the common ancestral form of this legion, for which it has the same high importance as Actissa for the Spumellaria. The central capsule is quite simple, ovate or nearly spherical, and included in a voluminous hyaline calymma, which contains no large alveoles. Cystidium differs from Actissa, its probable ancestral form, in the possession of the "podoconus" and its basal "porochora," characteristic of all Nassellaria or Monopylea.
1. Cystidium princeps, n. sp. (Pl. 91, fig. 1).
Central capsule ovate, one and a third times as long as broad. Podoconus with simple circular porochora, about half as long as the capsule, surrounded at its base by red granules of pigment. Nucleus spherical. Three equal oil-globules in the endoplasm. No pigment in the voluminous calymma, which includes numerous xanthellæ.
Dimensions.—Length of the central capsule 0.1, breadth 0.075; nucleus 0.035.
Habitat.—Indian Ocean, Maldive Islands (Haeckel), surface.
2. Cystidium lecythium, n. sp.
Central capsule ovate, one and a half times as long as broad. Podoconus with simple circular porochora, three-fourths as long as the capsule. Nucleus ellipsoidal. No oil-globules in the endoplasm. No pigment and no xanthellæ in the calymma.
Dimensions.—Length of the central capsule 0.12, breadth 0.08; nucleus 0.04.
Habitat.—Central Pacific, Station 271, surface.
3. Cystidium inerme, R. Hertwig.
Central capsule subspherical, a little longer than broad. Podoconus about two-thirds as long as the capsule, with trifid porochora, which is composed of three equal circular lobes. Nucleus spherical. Numerous oil-globules in the endoplasm. The calymma includes numerous xanthellæ and brown pigment around the mouth.
Dimensions.—Length of the central capsule 0.06, breadth 0.05; nucleus 0.03.
Habitat.—Mediterranean, Messina (R. Hertwig), surface.
- ↑ Cystidium = Small vesicle; κυστίδιον.
