Spongy framework of the cortical shell loose, with large, polygonal roundish meshes, on an average as large as the double medullary shell, which is immediately enveloped by it. Both concentric medullary shells with subregular roundish pores, twice as broad as the bars.

Dimensions.—Diameter of the cortical shell 0.2 to 0.3 or more; of the outer medullary shell 0.03, inner 0.01.

Habitat.—Mediterranean (French south coast, surface), J. Müller.

2. Spongodictyon cavernosum, n. sp.

Spongy framework of the cortical shell rather compact in the inner part, which immediately envelops the double medullary shell; very loose, with large caverns in the outer part, caverns of the surface larger than the medullary shell. Both medullary shells with regular circular pores, three times as broad as the bars.

Dimensions.—Diameter of the cortical shell 0.3 to 0.4, outer medullary shell 0.1, inner 0.03.

Habitat.—Tropical Atlantic, Station 338, surface.

Subgenus 2. Spongodictyoma, Haeckel.

Definition.—Spongy cortical shell on the inner surface with a smooth lattice-plate (or third medullary shell), which is connected by radial beams with the inner double medullary shell.

3. Spongodictyon trigonizon, Haeckel.

Spongy framework of the cortical shell very loose, with very large, for the most part triangular meshes, which are two to six times as large as the enclosed double medullary shell. From the surface of the latter arise numerous radial beams, which are connected by a spherical lattice-plate, forming the smooth inner surface of the spongy sphere (or a third medullary shell). The structure of the framework reminds one of the Phæodarium Sagena (Pl. 108). Pores of both medullary shells regular circular, twice as broad as the bars.

Dimensions.—Diameter of the cortical shell 0.5 to 1.15, outer medullary 0.05, inner 0.035.

Habitat.—Mediterranean, Messina, surface.

4. Spongodictyon arcadophoron, n. sp.

Spongy framework of the cortical shell in the inner part very loose, in the outer part more compact; outer meshes scarcely as large as the inner medullary shell (or only half as large), inner meshes two to four times as large. From the surface of the double medullary shell arise numerous radial beams, which are forked at equal distances from the centre; the fork branches are curved and united together by dichotomous branches, like elegant arcades; and these arcades form together the large polygonal meshes on the inside of the cortical shell (or a third medullary shell). Both medullary shells with regular circular pores, of the same breadth as the bars.

Dimensions.—Diameter of the cortical shell 0.2, outer medullary shell 0.04, inner 0.02.

Habitat.—Tropical Atlantic, Station 349, surface.

Family VI. Collosphærida, J. Müller^[45] (Pls. 5-8).

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."^[46] Formerly following his authority, in my Monograph I had separated them from the other Sphæroidea and united them with the social Collodaria (Sphærozoida).^[47] Also R. Hertwig in his Organismus der Radiolarien^[48] united them with his Sphærozoea. In my Prodromus^[49] 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. 8, figs. 6-11). Therefore these Clathrosphærida bear to the Acrosphærida (or the common simple Collosphærida) a relation similar to that which Liosphæra (p. 76) 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. 5-8). 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. 5-8). 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. 12); 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. 8).

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.

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).

Subgenus 1. Eucollosphæra, Haeckel.

Definition.—Shell a regular or subregular sphere.

1. Collosphæra primordialis, n. sp.

Shell a regular sphere, with very delicate and regular network of hexagonal meshes. Six to eight meshes in the half meridian of the shell. Diameter of the meshes ten to fifteen times as broad as the thin bars between them. Can be regarded as social form of Cenosphæra primordialis.

Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.008.

Habitat.—Central Pacific, Stations 271 to 274, surface.

2. Collosphæra regularis, n. sp.

Shell a regular sphere, with a perfectly regular network of circular meshes, all of the same size. Ten to twelve meshes in the half meridian of the shell. Diameter of the meshes the same as that of the bars between them.

Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.005 to 0.006.

Habitat.—Indian Ocean, Madagascar, surface, Rabbe.

3. Collosphæra globularis, n. sp.

Shell a regular sphere, with subregular network of circular meshes of different sizes; few large pores between many smaller pores. Ten to twenty meshes in the half meridian of the shell. Diameter of the meshes from half to twice as broad as that of the bars.

Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.002 to 0.008, breadth of the bars 0.004 to 0.008.

Habitat.—Tropical and subtropical zone of both hemispheres, widely distributed; Canaries, Azores, Cape Verde Islands, Guinea Coast, Brazil Coast, Indian Ocean, Madagascar, Ceylon, surface.

Subgenus 2. Dyscollosphæra, Haeckel.

Definition.—Shell not a regular sphere, but irregular roundish, in all degrees of variation between subspherical and polyhedral or quite irregular forms.

4. Collosphæra huxleyi, J. Müller.

Shell subspherical, somewhat irregular, sometimes with more or less superficial impressions, with irregular network of roundish meshes. Eight to sixteen meshes in the half meridian of the shell, one to three times as broad as their bars. Very variable, with direct transition-forms to other species of this genus, especially to Collosphæra globularis, Collosphæra tuberosa, Collosphæra pyriformis, and Collosphæra polyedra.

Dimensions.—Diameter of the shell 0.1 to 0.16, of the pores 0.004 to 0.012, of the bridges 0.003 to 0.006.

Habitat.—Cosmopolitan; common in the greater part of the warmer seas, surface.

5. Collosphæra polygona, n. sp. (Pl. 5, fig. 13).

Shell irregular polygonal, with very delicate, irregular network of polygonal meshes, four to twelve times as broad as the bars. Ten to twenty pores on the half meridian of the shell.

Dimensions.—Diameter of the shell 0.1 to 0.2, of the pores 0.012 to 0.004, of the bars 0.001 to 0.002.

Habitat.—Mediterranean, Atlantic, surface; Stations 348 to 354.

6. Collosphæra pyriformis, Haeckel, n. sp.

Shell irregular, rounded, ovate or pear-shaped, with irregular network of rounded or nearly polygonal meshes. Ten to twenty meshes in the half meridian of the shell, one to three times as broad as the bars. Commonly one large opening (two to three times as broad as the largest meshes) on the thinner end of the ovate shell (corresponding to the insertion of a pear-stalk); sometimes two or three such large openings.

Dimensions.—Diameter of the shell 0.1 to 0.15, of the pores 0.008 to 0.016, of the bridges 0.004 to 0.008.

Habitat.—Tropical zone—Cape Verde Islands, Ceylon; Central Pacific, Stations 266 to 272, 348 to 352, &c.

7. Collosphæra polyedra, n. sp.

Shell irregular, polyhedral, with even or somewhat vaulted sides, and obtuse ridges between them. Network more or less irregular, with small rounded meshes, quite as broad or twice as broad as their bars. Besides these small pores constantly some large round openings (commonly three to six), situated on the corners of the polyhedral shell, four to six times as large as the pores. Often an acute tooth on the edge of each large opening. Transition-form between Collosphæra and Solenosphæra or Odontosphæra.

Dimensions.—Diameter of the shell 0.1 to 0.15, of the pores 0.004 to 0.008, of their bridges 0.004, of the large openings 0.24 to 0.032.

Habitat.—Tropical zone of the Pacific and the Indian Ocean; Stations 266 to 272, surface.

8. Collosphæra tuberosa, n. sp.

Shell very irregular, between subspherical and polyhedral in form, but always with irregular impressions, boils or bosses, and between these different rounded prominent tubercles and ridges. Network irregular, strong, with rounded, subcircular or nearly polygonal meshes. Ten to thirty pores in the half meridian of the shell. Diameter of the meshes half to four times as broad as that of the thick bars.

Dimensions.—Diameter of the shell very variable in the same cœnobium, 0.05 to 0.2, of the pores 0.002 to 0.008, breadth of the bridges 0.004 to 0.006.

Habitat.—Cosmopolitan, common in all warmer seas, surface.

9. Collosphæra irregularis, n. sp.

Shell quite irregular, knotty or bulbous, with irregular impressions, and prominent knobs or bulbs between them. Network thin, fragile, quite irregular, with polygonal meshes of most unequal size and form. Five to twenty pores in the half meridian of the shell. Diameter of the meshes two to ten times as broad as that of the thin bars.

Dimensions.—Diameter of the shell very variable in the same cœnobium, 0.04 to 0.24, of the pores 0.005 to 0.05, of the bridges 0.002 to 0.004.

Habitat.—Mediterranean, Atlantic, not common; Stations 348, 352, &c., surface.

Genus 30. Tribonosphæra,^[52] Haeckel, 1881, Prodromus, p. 471.

Definition.—Collosphærida with simple shells, on the inside with radial centripetal beams.

The genus Tribonosphæra differs from Collosphæra by a very peculiar and rare character, the development of centripetal radial sticks on the internal face of the shell; these beams are not united in the centrum, but finish freely in a certain distance from it.

1. Tribonosphæra centripetalis, n. sp. (Pl. 5, fig. 12).

Shell roundish or subspherical, with numerous small circular or roundish pores, about twice as broad as the bars. Twenty to thirty pores on the half meridian of the shell. Outside of the shell smooth, inside a variable number (ten to twenty) of thin, radial, centripetal sticks or spines, one-third or one-half as long as the radius of the shell. (In the central capsule many very large crystals, resting after the destruction of the capsule.)

Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.003 to 0.005, of the bridges 0.001 to 0.002; length of the inner centripetal sticks 0.02 to 0.03.

Habitat.—Central Pacific, Station 271, surface.

Genus 31. Pharyngosphæra,^[53] n. gen.

Definition.—Collosphærida with simple shells, having on the inside radial centripetal tubes, the walls of which are solid.

The genus Pharyngosphæra differs from Collosphæra by the development of radial tubules on the inside of the shell, which are directed centripetally towards its centre. The wall of the tubule is solid, not latticed as in the following genus.

1. Pharyngosphæra stomodæa, n. sp. (Pl. 5, fig. 10).

Shell irregular polyhedral, with ten to fifteen polygonal faces and rounded edges. Pores very small, circular, irregularly scattered, smaller than the bars. Twelve to fifteen pores on the half meridian of the shell. On the inside of every shell-face one short, nearly cylindrical, centripetal tubule, twice as long as broad, and about one-third as long as the shell radius. Outer umbilical mouth of the tubules somewhat wider than the inner truncated mouth.

Dimensions.—Diameter of the shell 0.11 to 0.12, of the pores 0.003 to 0.005, of the bars 0.01 to 0.02; length of the inner tubuli 0.02, breadth of them 0.01.

Habitat.—South Pacific, Station 288, depth 2600 fathoms.

Genus 32. Buccinosphæra,^[54] n. gen.

Definition.—Collosphærida with simple shells, having on the inside radial centripetal tubes, the walls of which are fenestrated.

The genus Buccinosphæra exhibits, on the inner surface of the shell, radial centripetal tubules similar to those of the foregoing Pharyngosphæra; but the walls of these tubes are here latticed, not solid; they represent therefore true invaginations of the whole shell-wall.

1. Buccinosphæra invaginata, n. sp. (Pl. 5, fig. 11).

Shell irregular roundish or nearly polyhedral, with a variable number of umbilical depressions, which are prolonged on the inside into cylindrical or somewhat conical, centripetal, fenestrated tubes, about one-third as long as the shell radius. Inner mouth of the tubes narrower, scarcely half as broad as the outer mouth, about equal to one-fourth the shell radius, truncated. Pores of the tubes and of the shell small, roundish, irregular in size and distribution, about as broad as the bars. Twenty-five to thirty pores in the half meridian of the shell. In all observed specimens the spherical central capsule (half as broad as the shell) contained a large number of crystals.

Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.001 to 0.003, of the bars 0.002 to 0.003; length of the tubuli 0.02; outer mouth 0.026, inner mouth 0.013; crystals in the central capsule 0.002 to 0.004, sometimes 0.008.

Habitat.—Philippine Islands (Samboangan), Station 213, surface.

2. Buccinosphæra tubaria, n. sp.

Shell irregular polyhedral with rounded edges, with a variable number of umbilical depressions, which are prolonged on the inside into large, nearly cylindrical, centripetal, fenestrated tubes, half as long as the shell radius. In the middle the tubes are somewhat constricted and narrower. Inner mouth of the tubes dilated, nearly as broad as the outer mouth, about equal to one-half the shell-radius, truncated. Pores of the tubes and of the shell large, roundish polygonal, irregular in size and distribution, three to four times as broad as the bars. Fifteen to twenty pores in the half meridian of the shell.

Dimensions.—Diameter of the shell 0.12 to 0.14, of the pores 0.008 to 0.012, of the bars 0.002 to 0.004; length of the tubuli 0.03; outer mouth 0.04, inner mouth 0.03.

Habitat.—North coast of New Guinea, Station 217, surface.

Genus 33. Acrosphæra,^[55] Haeckel, 1881, Prodromus, p. 471.

Definition.—Collosphærida with simple shells, the outer surface of which is covered with radial, irregularly scattered spines.

The genus Acrosphæra differs from its ancestral genus Collosphæra by the development of spines on the outer surface of the shell. These are either short, straight, radial spines, or oblique and often curved; their base is often inflated; they are irregularly scattered on the whole surface between the pores.

1. Acrosphæra erinacea, n. sp.

Shell a regular sphere, everywhere covered with small, very numerous, straight radial spines, regularly scattered between the pores. In the half meridian of the shell ten to twelve circular pores, all of the same form and size, double as broad as the bars. Spines bristle-shaped, very thin, solid, about as long as the diameter of the pores.

Dimensions.—Diameter of the shell 0.1 to 0.12, of the pores 0.008 to 0.012; length of the spines 0.01.

Habitat.—Tropical zone of the Atlantic, coast of Brazil, Rabbe, surface.

2. Acrosphæra echinoides, n. sp. (Pl 8, fig. 1).

Shell a regular sphere, covered with numerous, straight, radial spines, irregularly scattered over the whole surface. In the half meridian of the shell twenty to thirty irregular roundish pores of variable size, one to four times as broad as the bars. Spines conical, strong, quite radial, at the top of small conical elevations, which are perforated by from three to six pores.

Dimensions.—Diameter of the shell 0.12 to 0.15, of the pores 0.002 to 0.008; length of the spines 0.015, of their basal zones 0.01.

Habitat.—South-east corner of the Pacific, Valparaiso, Station 298, surface.

3. Acrosphæra setosa, Haeckel.