Family VI. Collosphærida, J. Müller (Pls. -)

Definition.—Sphæroidea living associated in colonies, united by an alveolar jelly-body, and connected by the network of anastomosing pseudopodia.

The family Collosphærida comprises all polyzous or social Sphæroidea, and constitutes the only polyzoic group among the Sphærellaria. This group was first constituted by J. Müller as "Radiolaria polyzoa with shells." Formerly following his authority, in my Monograph I had separated them from the other Sphæroidea and united them with the social Collodaria (Sphærozoida). Also R. Hertwig in his Organismus der Radiolarien united them with his Sphærozoea. In my Prodromus I had retained this isolated position. But a further careful study has convinced me that this isolation is not truly natural, and that the Collosphærida are only "social Ethmosphærida" which have arisen from this solitary subfamily by adaptation to colonial life. There are some forms of Collosphærida which are nearly identical with some forms of Ethmosphærida, only differing from the latter by their association in colonies; and in some forms of both groups it is quite impossible to decide whether the isolated shells appertain to one or to the other family.

The isolated shell of the Collosphærida is almost constantly (with few exceptions) a simple extracapsular lattice-shell, as in the Monosphærida; only the small group of Clathrosphærida (with the genera Clathrosphæra and Xanthiosphæra) exhibit an exception, the simple lattice-shell being overgrown by an external mantle or veil of very thin, cobweb-like, irregular lattice-work (Pl. , figs. 6-11). Therefore these Clathrosphærida bear to the Acrosphærida (or the common simple Collosphærida) a relation similar to that which Liosphæra (p. ) bears to Cenosphæra; both shells are extracapsular "cortical shells" at a very short distance apart. In the Collosphærida true concentric medullary shells never occur; the central capsule always lies quite freely in the simple or double cortical shell, separated from it by a jelly-veil.

Although a well marked difference in the simple lattice-shell of the social Collosphærida and the solitary Ethmosphærida does not exist, nevertheless in most cases the two shells can be distinguished by a practiced observer. The simple fenestrated shells of the monozoic Ethmosphærida are commonly quite regular spheres in a mathematical sense, or regular "endospherical polyhedra"; whereas in the Collosphærida they are commonly more or less irregular, often to an extraordinary degree (Pls. -). Some species of Collosphærida, however, also possess quite regular spherical shells. Another difference is often shown in the lattice-work of the shells, which in the Collosphærida is nearly always very irregular, and exhibits a peculiar tendency to the production of radial, conical, or cylindrical tubules. These occur as well on the inside as on the outside of the shell, and the tubules are now more conical, now more cylindrical; their wall either solid or pierced by pores (Pls. -). The tubules are commonly very irregular in form, size, and disposition; distinguished, however, by a number of hereditary peculiarities, which are sufficient for the distinction of genera. Similar tubules occur also in some genera of solitary Ethmosphærida (Coscinomma, Ethmosphæra, Conosphæra, &c., Pl. ); but the tubules are here much more regular and not so highly developed.

Besides the tubules of the fenestrated shells, in some genera of Collosphærida the surface is armed with irregular thorns, rarely with more regular radial spines. But these spines obtain constantly the character of accessory by-spines, and remain short and thin. In this family typical radial spines never occur in a regular and characteristic disposition, corresponding to dimensive axes, as is the case in nearly all solitary Sphæroidea, only excepting the Liosphærida. Commonly these spines or thorns serve as protective arms for the shell-meshes, surrounding them often in the form of coronels. Often the lattice-plate of the irregular roundish shell is tubercular, elevated into irregular protuberances, bearing on the top a short spine or thorn (Pl. ).

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. , ), 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. , 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. , fig. 11); at other times no alveoles are visible (Pl. , 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. , 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.

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.