The Central Capsule of the Collosphærida is always a regular sphere, as in all other Sphæroidea; it is constantly placed within the lattice-shell, and commonly much smaller than it, separated from it by a thick jelly-veil. A remarkable difference from the solitary Sphæroidea is shown in the early division of the nucleus. Commonly the central capsule of the Collosphærida contains in its centre a large oil-globule, surrounded by very numerous small nuclei. R. Hertwig estimated this difference as so important, that he separated the social "Sphærozoea" and the solitary "Peripylea" as two different orders. As already shown above (p. [7], [24]), we cannot support this separation, and are now convinced that this difference in the development of the spores—just as in the Collodaria—is the consequence of an adaptation to social life.
The common jelly-body, in which the numerous central capsules and their enveloping shells are united, exhibits in the Collosphærida quite the same characters as in the other social Radiolaria, the Collozoida and Sphærozoida. The jelly-body is very voluminous, commonly spherical, often cylindrical, of considerable size; constantly containing numerous large alveoles. Often each shell is enclosed in a separate alveole with rather solid wall (Pl. [6], fig. 2). Sometimes in the dead colonies all shells are united in the central part of the jelly-body, whilst its peripheral part is composed of a stratum of large alveoles (Pl. [8], fig. 11); at other times no alveoles are visible (Pl. [7], fig. 11). In many living colonies I found a very large spherical alveole with thick wall in the centre of the spherical colony, surrounded by many strata of delicate thin-walled alveoles (Pl. [5], fig. 1). In this case often the inner younger capsules were naked, without shells, the outer only surrounded by shells. Already in my Monograph I had described the same peculiar formation.[[50]]
Synopsis of the Genera of Collosphærida.
| I. Subfamily Acrosphærida. (Lattice-shell simple, without an external mantle of network.) |  | Outside of the shell smooth, without spines or tubuli. |  | Inside without tubuli. |  | Inside smooth, | 29. Collosphæra. |
| Inside spiny, | 30. Tribonosphæra. | ||||||
| Inside with centripetal tubuli. | | Tubuli imperforated, | 31. Pharyngosphæra. | ||||
| Tubuli fenestrated, | 32. Buccinosphæra. | ||||||
| Outside of the shell armed with solid spines, but with hollow tubuli. |  | Spines irregularly scattered on the surface, | 33. Acrosphæra. | ||||
| Each larger pore with one single spine, | 34. Odontosphæra. | ||||||
| Each larger pore with a coronal of spines, | 35. Chœnicosphæra. | ||||||
| Outside of the shell with irregular radial tubuli, the wall of which is solid, not fenestrated. |  | Tubuli simple, not branched. |  | Mouth of the tubuli truncated, smooth, | 36. Siphonosphæra. | ||
| Mouth with one single large tooth, | 37. Mazosphæra. | ||||||
| Mouth with a coronal of teeth, | 38. Trypanosphæra. | ||||||
| Tubuli irregularly branched, each with two to four or more openings, | 39. Caminosphæra. | ||||||
| Outside of the shell with irregular radial tubuli, open on both ends, with fenestrated wall. | | Mouth of the tubuli truncated, smooth, | 40. Solenosphæra. | ||||
| Mouth with one single large tooth, | 41. Otosphæra. | ||||||
| Mouth with a coronal of teeth, | 42. Coronosphæra. | ||||||
| II. Subfamily Clathrosphærida. (Lattice-shell double, with an external mantle of network.) |  | Surface of the outer shell smooth, | 43. Clathrosphæra. | ||||
| Surface of the outer shell thorny, | 44. Xanthiosphæra. | ||||||
| I. Subfamily Acrosphærida. (Lattice-shell simple, without an external mantle of network.) | ||||||||
| Outside of the shell smooth, without spines or tubuli. | ||||||||
| Inside without tubuli. | ||||||||
| Inside smooth, | ||||||||
| 29. Collosphæra. | ||||||||
| Inside spiny, | ||||||||
| 30. Tribonosphæra. | ||||||||
| Inside with centripetal tubuli. | ||||||||
| Tubuli imperforated, | ||||||||
| 31. Pharyngosphæra. | ||||||||
| Tubuli fenestrated, | ||||||||
| 32. Buccinosphæra. | ||||||||
| Outside of the shell armed with solid spines, but with hollow tubuli. | ||||||||
| Spines irregularly scattered on the surface, | ||||||||
| 33. Acrosphæra. | ||||||||
| Each larger pore with one single spine, | ||||||||
| 34. Odontosphæra. | ||||||||
| Each larger pore with a coronal of spines, | ||||||||
| 35. Chœnicosphæra. | ||||||||
| Outside of the shell with irregular radial tubuli, the wall of which is solid, not fenestrated. | ||||||||
| Tubuli simple, not branched. | ||||||||
| Mouth of the tubuli truncated, smooth, | ||||||||
| 36. Siphonosphæra. | ||||||||
| Mouth with one single large tooth, | ||||||||
| 37. Mazosphæra. | ||||||||
| Mouth with a coronal of teeth, | ||||||||
| 38. Trypanosphæra. | ||||||||
| Tubuli irregularly branched, each with two to four or more openings, | ||||||||
| 39. Caminosphæra. | ||||||||
| Outside of the shell with irregular radial tubuli, open on both ends, with fenestrated wall. | ||||||||
| Mouth of the tubuli truncated, smooth, | ||||||||
| 40. Solenosphæra. | ||||||||
| Mouth with one single large tooth, | ||||||||
| 41. Otosphæra. | ||||||||
| Mouth with a coronal of teeth, | ||||||||
| 42. Coronosphæra. | ||||||||
| II. Subfamily Clathrosphærida. (Lattice-shell double, with an external mantle of network.) | ||||||||
| Surface of the outer shell smooth, | ||||||||
| 43. Clathrosphæra. | ||||||||
| Surface of the outer shell thorny, | ||||||||
| 44. Xanthiosphæra. | ||||||||
Subfamily Acrosphærida, Haeckel, 1881, Prodromus, p. 471.
Definition.—Collosphærida with one simple lattice-shell around every central capsule of the cœnobium.
Genus 29. Collosphæra,[[51]] J. Müller, 1855.
Definition.—Collosphærida with simple shells, smooth on the inside and on the outside, without any spines or tubuli.
The genus Collosphæra is the most simple form of all Collosphærida, and must be regarded as the common ancestral form of this family. As the lattice-shell is quite a simple sphere, without any spines, tubules, or other peculiar productions, it agrees perfectly with Cenosphæra, and represents the social or polyzoid aggregate of this solitary or monozoid genus. Therefore a certain distinction between the isolated shells of the two genera is often very difficult or even impossible; but commonly this distinction is possible owing to the circumstance, that in the majority of the Collosphæræ the shell is more or less irregular roundish or polyhedral, not quite spherical, as in Cenosphæra. Dermatosphæra, Ehrenberg, is a Collosphæra with small pores (compare L. N. [16], p. 533).