_Habitat._--Indian Ocean, near the Maldive Islands, Haeckel, 1882, surface.
Genus 3. _Thalassopila_,[10] Haeckel, 1881, Prodromus, p. 469.
_Definition._--Thalassicollida without extracapsular alveoles, but with large roundish or globular alveoles within the central capsule, with a papillate or branched nucleus in its centre.
The genus _Thalassopila_ has, like _Thalassolampe_, a voluminous foamy central capsule, inflated by numerous large alveoles; but it differs in the complicated form of the nucleus, which is like that of _Thalassophysa_, and is either branched or occupied by conical or roundish papillæ.
1. _Thalassopila cladococcus_, n. sp. (Pl. 1, fig. 3).
Spherical body dark-spotted, with a thin yellowish jelly-envelope. Central capsule with a thick and firm membrane, perforated by pores; its diameter three times that of the central nucleus, { 18}three-fourths that of the whole jelly-sphere. Nucleus profusely branched or papillated, its spherical surface covered with numerous (more than a hundred) finger-shaped obtuse blind sacs, about as long as its radius. Protoplasm of the central capsule forming a loose network between the large roundish alveoles, in the cortical zone radially striped and containing one layer of large dark oil-globules. These are regularly distributed on the inside of the capsule-membrane and separated by intervals, twice as broad as its diameter, giving to the capsule-surface a spotted appearance. Extracapsular jelly-envelope thin, yellowish, with very numerous and small xanthellæ.
_Dimensions._--Diameter of the whole jelly-sphere 5 mm., of the central capsule 4 mm., of the nucleus 1.3 mm.
_Habitat._--Antarctic Ocean, Station 154 (south of Kerguelen), surface.
Genus 4. _Thalassicolla_,[11] Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2, vol. viii. p. 433.
_Definition._--Thalassicollida without intracapsular alveoles, but with large roundish or globular alveoles within the extracapsular calymma. Nucleus in the centre of the capsule simple spherical, not branched.
The genus _Thalassicolla_ was proposed by Huxley in 1851, for a certain number of different voluminous jelly-like Radiolaria, which he had observed living during his voyage in the "Rattlesnake" through the tropical seas, and of which he gives an excellent description--the first accurate observations on living Radiolaria. Johannes Müller afterwards removed from this genus the social genera _Sphærozoum_ and _Collosphæra_ (formerly _Thalassicolla punctata_), and retained as type of the genus _Thalassicolla nucleata_. In 1862 in my Monograph I added two other species, _Thalassicolla pelagica_ and _Thalassicolla zanclea_, and later (1870) _Thalassicolla sanguinolenta_. Now I think it better to separate the last two species as a new genus, _Thalassophysa_, characterised by the papillate or branched nucleus, and to retain in _Thalassicolla_ only those forms with simple spherical nucleus. For both genera the extracapsular, voluminous, spherical calymma or jelly-envelope, with numerous large alveoles, is characteristic. The membrane of the central capsule in _Thalassicolla_ is now structureless (subgenus _Thalassicollarium_, with three species), now characterised by a peculiar structure, prominent ridges on the inside of the membrane, which form a network with polygonal plates, resembling an epithelium (Pl. 1, fig. 5_b_; subgenus _Thalassicollidium_, with four species). Of the seven species here described, two are cosmopolitan, widely distributed, and common; one is Mediterranean, one Atlantic, and three Pacific.