Legion I. SPUMELLARIA,

vel Peripylea, vel Peripylaria (Pls. 1-50).

Definition.—Radiolaria with simple membrane of the central capsule, which is everywhere perforated by innumerable very fine pores. Extracapsulum without phæodium. Skeleton wanting or siliceous. Fundamental form originally spherical.

The legion Spumellaria vel Peripylea, in the extent here defined, was constituted by me in 1883 in my paper on Die Ordnungen der Radiolarien.^[2] I propose to retain for this legion either the name Spumellaria of Ehrenberg (1875) or Peripylea of Hertwig (1879), although both groups have not quite the same extension. We exclude from the Spumellaria the Spyridina (united with them by Ehrenberg) and include the Collodaria. With the Peripylea of Hertwig we unite his Thalassicollea and Sphærozoea. To avoid any confusion it would perhaps be better to name this legion "Peripylaria."

The Spumellaria agree with the Acantharia in the structure of the simple capsule-membrane, which is perforated by numerous small pores (but devoid of the large main opening, which the Nassellaria and Phæodaria possess), whence we unite both the former as Holotrypasta, both the latter as Merotrypasta.

The difference between the two legions of Holotrypasta is determined by the skeleton, which in the Spumellaria is either siliceous or wanting, whilst in the Acantharia it consists of the peculiar organic substance, acanthin.

The legion Spumellaria is by far the largest and most important of the four legions of Radiolaria, as well with respect to the number of different forms, as to the enormous masses of individuals, which we encounter living and fossil. We distinguish in this legion not less than thirty-two different families, three hundred and sixteen genera, and more than seventeen hundred species.

The classification of this large group requires for its better comprehension a careful division into larger and smaller groups. We divide it therefore first of all into two orders, Collodaria and Sphærellaria, as proposed in the paper mentioned above.^[3]

The Collodaria have no perfect latticed skeleton, and comprise two suborders or sections: in the Colloidea the skeleton is entirely wanting, in the Beloidea it is represented by a variable number of siliceous needles or spicules, scattered in the calymma around the central capsule.

The Sphærellaria differ from the Collodaria in the possession of a perfect siliceous skeleton, which is originally a latticed spherical shell, enveloping the central capsule. By modification of this fenestrated sphere arises an enormous mass of different forms, which we dispose in twenty-eight families, and these in four larger groups, suborders or sections,—Sphæroidea, Prunoidea, Discoidea, and Larcoidea.

The Sphæroidea, the common ancestral group of the Sphærellaria, possess a skeleton which is either a simple fenestrated sphere, or composed of two or more concentric latticed spheres, which are united by radial beams; more rarely it becomes more or less spongy.

The Prunoidea are derived from the Sphæroidea by prolongation of the latticed sphere in one axis; the skeleton therefore becomes here ellipsoidal or cylindrical (often with annular transversal constrictions).

The Discoidea on the contrary must be derived from the Sphæroidea by shortening in one axis; here therefore the fenestrated shell becomes more or less lenticular or iscoidal (often with radial spines or arms in the equatorial plane, on the circular margin).

The Larcoidea, the fourth section, differ from the three foregoing sections by the different growth of the shell in three different dimensions of space; therefore here the fenestrated shell becomes "lentelliptical," or a "triaxial ellipsoid," its length, breadth, and height being different.

The Skeleton consists in all Spumellaria either of pure silica or of a peculiar silicate. The siliceous bars and beams constituting it are invariably solid, as also in the Nassellaria, never hollow, as in the Phæodaria. Never is the skeleton composed of acanthin, as in all Acantharia. Whilst in the first order of Spumellaria, Collodaria, the form of the spicula, or the scattered needles, composing the skeleton, is very simple, never latticed, in the second order, the Sphærellaria, it is constantly latticed or fenestrated, often also spongy.

The geometrical fundamental form of the lattice-shell in the Sphærellaria is originally spherical (homaxon), as preserved in all Sphæroidea; in the Prunoidea and Discoidea it becomes monaxon, with one single axis (prolonged in the former, shortened in the latter); in the Larcoidea it becomes triaxon, by different growth in three principal axes, perpendicular one to another. The further development of radial parts of the skeleton in these three axes is very important for the "promorphology" of the Radiolaria.

The Malacoma, or the whole soft body of the Spumellaria as opposed to the skeleton, exhibits some differences of structure in two different groups, which were separated formerly (1862) as Monocyttaria and Polycyttaria, corresponding to the "Radiolaria monozoa and polyzoa" of Johannes Müller (1858).

The Monocyttaria (or the Spumellaria solitaria) live isolated as single cells—like all other Radiolaria—and are never aggregated in colonies; the calymma includes one single central capsule, and this again one central nucleus, which does not become divided until full maturity.

The Polycyttaria on the contrary (or the Spumellaria socialia) live aggregated in large colonies; the calymma includes a variable number of associated central capsules and each of these commonly one central oil-globule, whilst the original simple nucleus commonly becomes very early divided into numerous small nuclei.

The Nucleus of the Spumellaria is originally constantly central, placed quite in the centre of the concentric capsule, and it retains this central position in all Monocyttaria or solitary Peripylea; whereas in the Polycyttaria—in consequence of its early division—its place is commonly taken by a central oil-globule. Whilst the numerous nuclei of the latter are very small, the single nucleus of the former is comparatively large, extremely large (more than a millimeter in diameter) in some gigantic Collodaria.

The Endoplasm or the intracapsular sarcode exhibits in the greater number of Spumellaria a more or less distinct radial striation. It encloses a great variety of different parts; vacuoles, oil-globules, pigment-granules, crystals, &c.

The Membrane of the capsule in all Spumellaria is simple (never double as in the Phæodaria) and everywhere equally perforated by innumerable small pores; in the thick, double-edged membrane of many large Collodaria these pores appear (in the optical section of the capsule-wall) as distinct fine radial canals, very densely and regularly disposed.

The Central Capsule in the Spumellaria is originally a geometrical sphere, and this simple globular form is preserved in all Sphæroidea, and in the greatest part of Colloidea and Beloidea. By prolongation of one axis the form becomes ellipsoidal (or even cylindrical) in the Prunoidea, and in some few forms of Colloidea. By shortening of one axis it becomes lenticular (or even discoidal) in the Discoidea, and in some few forms of Colloidea. By unequal growth in three different axes, perpendicular one to another, the capsule becomes lentelliptical in all Larcoidea. Very rarely the capsule assumes in the Spumellaria a polyhedral or irregular (sometimes even amœboid) form, only in a few Colloidea.

The Calymma, or the jelly-veil including the central capsule, is very voluminous in many Spumellaria of gigantic size, mainly in the large Colloidea, and in all Polycyttaria or social Radiolaria. It includes here a considerable number of large vacuoles or "alveoli." The calymma never exhibits in this legion the dark voluminous phæodium, possessed by all Phæodaria.

Xanthellæ or "zooxanthellæ" are numerous in the calymma of most Spumellaria, but by no means constant; they are very variable in number and size.

The Matrix, placed between the calymma and central capsule, is, in the majority of the Spumellaria, a rather thick layer of granular exoplasm.

The Pseudopodia arising from it are very numerous, equally disposed over the whole surface, and are in general rather fluid, exhibiting a considerable tendency to ramify, anastomose, and form networks. The movement of granules is commonly lively. In the Polycyttaria all capsules of one colony or "cœnobium" are connected by the dense variable network of anastomosing pseudopodia.

Synopsis of the Orders and Suborders of Spumellaria.

I. COLLODARIA. Skeleton wanting or quite imperfect, not latticed. Skeleton entirely wanting, 1. Colloidea.

Skeleton represented by numerous scattered spicules, 2. Beloidea.

II. SPHÆRELLARIA. Skeleton a perfect shell of lattice work, or spongy and resembling wicker-work. Lattice-shell spherical or composed of concentric spheres, 3. Sphæroidea.

Lattice-shell ellipsoidal or prolonged in one axis, 4. Prunoidea.

Lattice-shell discoidal or shortened in one axis, 5. Discoidea.

Lattice-shell lentelliptical, with different extent of growth in three axes, 6. Larcoidea.

I. COLLODARIA. Skeleton wanting or quite imperfect, not latticed.

Skeleton entirely wanting,

1. Colloidea.

Skeleton represented by numerous scattered spicules,

2. Beloidea.

II. SPHÆRELLARIA. Skeleton a perfect shell of lattice work, or spongy and resembling wicker-work.

Lattice-shell spherical or composed of concentric spheres,

3. Sphæroidea.

Lattice-shell ellipsoidal or prolonged in one axis,

4. Prunoidea.

Lattice-shell discoidal or shortened in one axis,

5. Discoidea.

Lattice-shell lentelliptical, with different extent of growth in three axes,

6. Larcoidea.

Order I. COLLODARIA, Haeckel, 1881.

Definition.—Spumellaria without latticed shell.

The order Collodaria, the first order of Radiolaria, comprises all those Spumellaria in which the skeleton is either entirely wanting, or represented by numerous single, solid, siliceous needles or spicules, loosely scattered in the calymma around the central capsule. Never in this order is there any trace of the latticed or fenestrated shell, which characterises the second order, Sphærellaria. The skeleton exhibits no trace of phylogenetic connection in the two orders.

In my monograph (1862) two families appertaining to this order are described, the Collida (p. 244) and the Sphærozoida (p. 521). Both families contain forms with and without a skeleton. Of the solitary or monozous Collida the Thalassicollida are devoid of a skeleton, whilst the Thalassosphærida are provided with a skeleton. Of the social or polyzous Sphærozoida the Collozoida are without a skeleton, the Rhaphidozoida provided with one. As the special form in both skeletophorous subfamilies is exactly the same, I prefer now to associate them in the suborder Beloidea, and to oppose them to the other two skeletonless subfamilies, which are united under the name of Colloidea.

Synopsis of the four Families of Collodaria.

Suborder I. COLLOIDEA. Skeleton entirely wanting. Solitary cells, living as isolated individuals (Colloidea monozoa), 1. Thalassicollida.

Associated cells, living in colonies or cœnobia (Colloidea polyzoa), 2. Collozoida.

Suborder II. BELOIDEA. Skeleton composed of numerous needles or spicula, scattered in the calymma. Solitary cells, living as isolated individuals (Beloidea monozoa), 3. Thalassosphærida.

Associated cells, living in colonies or cœnobia (Beloidea polyzoa), 4. Sphærozoida.

Skeleton entirely wanting.

Solitary cells, living as isolated individuals (Colloidea monozoa),

1. Thalassicollida.

Associated cells, living in colonies or cœnobia (Colloidea polyzoa),

2. Collozoida.

Suborder II. BELOIDEA. Skeleton composed of numerous needles or spicula, scattered in the calymma.

Solitary cells, living as isolated individuals (Beloidea monozoa),

3. Thalassosphærida.

Associated cells, living in colonies or cœnobia (Beloidea polyzoa),

4. Sphærozoida.

Suborder I. COLLOIDEA, Haeckel.

Definition.—Spumellaria without skeleton.

The suborder Colloidea comprises all those Spumellaria in which no skeleton is developed. The whole body is therefore soft—a true malacoma—and is composed only of two essential parts, the central capsule and the enveloping extracapsulum. The suborder contains only two different families, the solitary Thalassicollida (or Colloidea monozoa) and the associated Collozoida (or Colloidea polyzoa). Both families are very nearly allied, and differ only in one single essential character: the solitary life of the former, the social union of the latter. It seems to be merely in consequence of this difference that the cleavage of the nucleus commonly takes place very late in the former, very early in the latter.

Therefore the full-grown Thalassicollida (till immediately before propagation) commonly exhibit one single nucleus in the centre of the capsule, whilst in the Collozoida the capsule is distended by numerous small nuclei. In these latter the centre of the capsule usually contains one large oil-globule, whilst in the former oil-globules are either wanting, or scattered in large numbers in the endoplasm, or disposed in one layer on the inside of the capsule membrane.

In the solitary Thalassicollida each capsule is enclosed in its own peculiar spherical calymma, whilst in the associated Collozoida all capsules of the colony are united in one common, very voluminous calymma.

Family I. Thalassicollida, Haeckel, 1862.

Definition.—Colloidea solitaria.

The family Thalassicollida comprises all solitary Spumellaria without a skeleton. The oldest and best known form of this family is the genus Thalassicolla, as restricted by Johannes Müller.^[4] The most common representative of it, the cosmopolitan Thalassicolla nucleata, was first described by Huxley in 1851. But as early as 1834 another large Radiolarian, appertaining either to this or to a nearly allied family, had been described by Meyen as Physematium atlanticum. A third genus was detected by me in 1859 at Messina and figured under the name Thalassolampe margarodes.^[5] A very accurate histological description of these forms was given in 1876 by Richard Hertwig.^[6] The same author figured in his Organismus in 1879 a very interesting simpler form under the name Thalassolampe primordialis (Taf. iii. fig. 5). Some similar forms had already been observed by me, and are here united with it to form the first genus Actissa.^[7]

Actissa is of the highest general interest as the most simple and typical form of all Radiolaria, and as the common ancestral form, from which all other forms of this large class may be derived. Its unicellular body exhibits neither the extracapsular alveoli of Thalassicolla, nor the intracapsular alveoli of Thalassolampe, and shows all essential characters of the Radiolarian type in its most simple form (Pl. 1, figs. 1 to 1c). The simple cell-body is composed of a spherical central capsule and a concentric, spherical, enveloping calymma, both separated by a thin membrane which is perforated by innumerable pores. The capsule includes the endoplasm and in the centre a simple spherical nucleus with nucleolus; at the time of propagation this latter becomes cleft into numerous small nuclei, each of which, together with a small piece of the surrounding endoplasm, forms a flagellated zoospore (fig. 1c). The extracapsulum is formed by the large, structureless, spherical calymma or concentric jelly-veil enveloping the capsule, and by the thin granular matrix or the layer of exoplasm which separates the calymma from the membrane. From this matrix or maternal tissue arise innumerable very long and thin pseudopodia, as simple radiating filaments, the proximal part of which is included in the calymma, whilst the distal part floats freely in the sea-water (Pl. 1, fig. 1).

The other Thalassicollida differ from their common ancestral form, Actissa, mainly by the higher histological differentiation of the unicellular body. Whilst in Thalassicolla and Thalassolampe the nucleus remains a single sphere as in Actissa, it becomes branched or covered with radial blind saccules in Thalassopila and Thalassophysa; also the intracapsular protoplasm develops here a great variety of peculiar different corpuscles, as oil-globules, pigment-granules, concentric concretions, crystals, &c. But the most striking peculiarity by which the other Thalassicollida differ from Actissa is the development of large vesicular alveoli, either within or without the capsule; the unicellular body reaches by this inflation the extraordinary size of 5 to 10 mm. or more.

Synopsis of the Genera of Thalassicollida.

A. Alveoli neither within nor without the central capsule. Nucleus spherical (sometimes ellipsoidal), not branched, 1. Actissa.

B. Numerous large alveoli within the central capsule (not in the calymma). Nucleus spherical, 2. Thalassolampe.

Nucleus branched or covered with radial sacs, 3. Thalassopila.

C. Numerous large alveoli without the central capsule, within the jelly-veil or calymma. Nucleus spherical, 4. Thalassicolla.

Nucleus branched or covered with radial sacs, 5. Thalassophysa.

A. Alveoli neither within nor without the central capsule.

Nucleus spherical (sometimes ellipsoidal), not branched,

1. Actissa.

B. Numerous large alveoli within the central capsule (not in the calymma).

Nucleus spherical,

2. Thalassolampe.

Nucleus branched or covered with radial sacs,

3. Thalassopila.

C. Numerous large alveoli without the central capsule, within the jelly-veil or calymma.

Nucleus spherical,

4. Thalassicolla.

Nucleus branched, or covered with radial sacs,

5. Thalassophysa.

Genus 1. Actissa,^[8] n. gen.

Definition.—Thalassicollida with simple spherical nucleus, without any alveoli (either within or outside the central capsule).

The genus Actissa is the most simple and typical form of all Radiolaria, and may be regarded as the common ancestral form of the whole class. The spherical body is composed of a simple spherical capsule and a concentric spherical calymma or jelly-envelope. Neither the former nor the latter contains alveoli. The central capsule possesses a strong membrane perforated by small pores, and contains in the intracapsular sarcode numerous small pellucid vacuoles, and in its middle a simple, concentric, spherical nucleus (often with some nucleoli); sometimes also one or more oil-globules. The extracapsularium forms a soft, voluminous, structureless calymma or enveloping jelly-sphere, perforated by the numberless, fine pseudopodia, which radiate outwards from the matrix or the thin granulated sarcode-layer, surrounding the capsule. Often (but not constantly) xanthellæ or yellow cells are scattered in it. Actissa differs from the following skeletonless genera in the absence of all alveoli; it has neither intracapsular alveoli (like Thalassolampe) nor extracapsular alveoli (like Thalassicolla). The first observed species of this genus is that which I found in 1866 at the Canary Islands, Actissa prototypus; the second is that which Hertwig accurately described in 1879, from the Mediterranean (Messina), Actissa primordialis; the third I observed in 1881 at Ceylon, frequent and sporiparous, Actissa princeps. A fourth species (Actissa radiata) exhibited a distinct radial segmentation of the capsule-contents. These four species are quite spherical. Six other species, occurring in different preparations from the Challenger, are distinguished by modifications of the spherical capsule-form and may represent three different subgenera (or, perhaps better, genera?)—Actiprunum ellipsoidal, Actidiscus lenticular, Actilarcus lentelliptical; perhaps these are the ancestral forms of the three sections: Prunoidea, Discoidea, Larcoidea.

Subgenus 1. Procyttarium, Haeckel, 1879.

Procyttarium, Haeckel, Natürl. Schöpfungsgeschichte, ed. vii. p. 705.

Definition.—Central capsule spherical.

1. Actissa princeps, n. sp. (Pl. 1, fig. 1).

Central capsule spherical, colourless or a little reddish, transparent, with a thick double-edged membrane. Nucleus central, spherical, one-third as broad as the central capsule, containing a single, central, glossy nucleolus. Protoplasm finely granulated, without oil-globules, with numerous clear spherical vacuoles of equal size and at equal distances; the superficial layer of protoplasm (immediately below the membrane) radially striated (fig. 1). In some older specimens the nucleus was divided into numerous small nuclei (fig. 1a), which by further division gave the nuclei of the flagellated spores (fig. 1b); each spore with a very thin lateral flagellum (fig. 1c). Jelly-like calymma twice as broad as the enclosed capsule, without xanthellæ or yellow cells, pierced by innumerable, very thin and long, undivided pseudopodia, which arise from the sarcode-matrix on the outside of the membrane (six to eight times longer than shown in fig. 1).

Dimensions.—Diameter of the central capsule 0.1 to 0.12, of the nucleus 0.03 to 0.04, of the jelly calymma 0.2 to 0.3.

Habitat.—Indian Ocean, Ceylon, Belligemma, Haeckel, 1881; also in a preparation from Station 271, Central Pacific, surface.

2. Actissa primordialis, Haeckel.

Thalassolampe primordialis, R. Hertwig, 1879, Organismus der Radiolarien, p. 32, Taf. iii. fig. 5.

Procyttarium primordiale, Haeckel, 1879, Natürl. Schöpf., ed. vii. p. 705, Taf. xvi. fig. 1.

Central capsule spherical, dim-yellowish, with a thin, simple-edged but compact membrane. Nucleus large, central (about half as broad), with one or two dark nucleoli; on its side an excentric oil-globule, nearly of the same size. Protoplasm between nucleus and membrane, in the younger specimens finely granulated and radially striped; in the older specimens with numerous hyaline globules (vacuoles). Jelly-envelope or calymma very voluminous, ten to twelve times as broad as the central capsule, structureless, containing numerous yellow bodies (xanthellæ?), pierced by very numerous simple pseudopodia.

Dimensions.—Diameter of the central capsule 0.11 to 0.18, of the nucleus 0.04 to 0.09, of the jelly-like calymma 1.2 to 1.5.

Habitat.—Mediterranean, Messina, Hertwig, 1878, surface.

3. Actissa prototypus, n. sp.

Central capsule spherical, red-coloured, with a thick, double-edged membrane. Nucleus central, spherical, half as large as the radius of the capsule, containing a large number (forty to sixty) of small dark nucleoli. Protoplasm filled up with numerous small clear vacuoles, and between them fine red pigment granules; on the inside of the membrane one layer of dark oil-globules. Jelly-like calymma four times as broad as the enclosed capsule, with very numerous small xanthellæ.

Dimensions.—Diameter of the capsule 0.2, of the nucleus 0.05, of the calymma 0.8.

Habitat.—Atlantic, Canary Islands (Lanzerote, Haeckel), 1866; also at Station 348, surface.

4. Actissa radiata, n. sp.

Central capsule spherical, dark, with a thick, double-edged membrane. Nucleus central, spherical, half as large as the capsule, transparent. Protoplasm divided into numerous cuneiform radial pieces which are separated by clear intervals, and filled with very fine dark granules (darker in the distal half). The equatorial optical section exhibits around the circular clear nucleus a coronal of twenty-five such wedge-shaped pieces (mother-cells of spores?) No oil-globules in the central capsule. Jelly-like calymma one and a half times as broad as the enclosed capsule, with numerous small xanthellæ.

Dimensions.—Diameter of the capsule 0.15, of the nucleus 0.07, of the calymma 0.24.

Habitat.—North Pacific, Station 241, surface.

Subgenus 2. Actiprunum, Haeckel, 1882.

Definition.—Central capsule ellipsoidal, with one prolonged axis.

5. Actissa prunoides, n. sp.

Actiprunum prunoideum, Haeckel, 1882, Manuscript.

Central capsule ellipsoidal, colourless, with a thin, simple-edged membrane. Proportion of its major axis to the minor 4 : 3. Nucleus spherical, its diameter equal to one-third of the minor axis, in its centre a large, dark, spherical nucleolus. Protoplasm clear, containing numerous small vacuoles, separated by regular distances, and on the inside of the capsule-membrane, numerous (forty to fifty) small oil-globules. Calymma (or jelly-veil) ellipsoidal, with a thin sarcode-stratum on the outside of the capsule; its diameter twice as large as that of the central capsule.

Dimensions.—Major axis of the capsule 0.16, minor 0.12; diameter of the nucleus 0.04; major axis of the calymma 0.32, minor 0.24.

Habitat.—Central Pacific, Station 274, surface.

6. Actissa ellipsoides, n. sp.

Actiprunum ellipsoides, Haeckel, 1882, Manuscript.

Central capsule ellipsoidal, red-coloured, with a thick, double-edged membrane. Proportion of its major axis to the minor 5 : 3. Nucleus ellipsoidal, one-third as large as the capsule, containing eight small dark nucleoli. Protoplasm dusky, filled with dark pink pigment-granules; in the major axis, on both poles of the nucleus-axis, two large oil-globules, half as large as the nucleus. Calymma ellipsoidal, with numerous xanthellæ; its diameter four times as large as that of the capsule.

Dimensions.—Major axis of the capsule 0.2, minor 0.12; major axis of the nucleus 0.07, minor 0.04; major axis of the calymma 0.8, minor 0.5.

Habitat.—Mediterranean, Corfu, 1877, Haeckel, surface.

Subgenus 3. Actidiscus, Haeckel, 1882.

Definition.—Central capsule lenticular, with one shortened axis.

7. Actissa discoides, n. sp.

Actidiscus discoides, Haeckel, 1882, Manuscript.

Central capsule lenticular, red-coloured, about twice as broad as high, with a thick, double-edged membrane. Nucleus spherical, one-third as broad as the capsule, with one single, large central nucleolus. Protoplasm dusky, filled with scarlet pigment; granules and small oil-globules between them. Calymma lenticular, three times as broad as the capsule.

Dimensions.—Major axis of the capsule 0.16, minor 0.08; diameter of the nucleus 0.05; breadth of the calymma 0.5.

Habitat.—North Pacific, Station 236, surface.

8. Actissa lenticularis, n. sp.

Central capsule lenticular, flattened, about three times as broad as high, with a thin, simple-edged membrane. Nucleus lenticular, one-third as large as the capsule, with ten small dark nucleoli. Protoplasm transparent, colourless, filled with small vacuoles at regular distances; on the inside of the membrane in the circular periphery of the lens twenty dark oil-globules. Calymma lenticular, twice as broad as the capsule.

Dimensions.—Major axis of the capsule 0.15, minor 0.05; breadth of the nucleus 0.05, height 0.02; breadth of the calymma 0.03.

Habitat.—East Pacific, Station 272, surface.

9. Actissa phacoides, n. sp.

Actidiscus phacoides, Haeckel, 1882, Manuscript.

Central capsule lenticular, strongly flattened, about four times as broad as high, with a thin, simple-edged membrane. Nucleus lenticular, one-fourth as broad as the capsule, with numerous (twenty or more) small nucleoli. Protoplasm filled with dark pigment-granules; on the inside of the membrane in the circular periphery of the lens thirty-two dark oil-globules. Calymma lenticular, three times as broad as the capsule.

Dimensions.—Major axis of the capsule 0.2, minor 0.05; breadth of the nucleus 0.05, height 0.015; breadth of the calymma 0.6.

Habitat.—Tropical Atlantic, Station 347, surface.

Subgenus 4. Actilarcus, Haeckel.

Definition.—Central capsule lentelliptical, with three different axes.

10. Actissa larcoides, n. sp.

Central capsule lentelliptical; with three different axes, bearing the proportion 4 : 3 : 2. Nucleus spherical; its diameter equal to the shortest radius of the capsule. No nucleoli visible. Protoplasm transparent, with small vacuoles; on the inside of the thin capsule-membrane numerous (fifty to sixty) small oil-globules, regularly disposed. Calymma lentelliptical, twice as large as the central capsule.

Dimensions.—Major axis or length of the capsule 0.2, middle axis or breadth 0.15, minor axis or height 0.1; diameter of the nucleus 0.05, of the calymma 0.3-0.4.

Habitat.—Central Pacific, Station 266, surface.

Genus 2. Thalassolampe,^[9] Haeckel, 1862, Monogr. d. Radiol., p. 253.

Definition.—Thalassicollida without extracapsular alveoles, but with large roundish or globular alveoles within the central capsule, with a simple spherical, not branched nucleus in the centre.

The genus Thalassolampe is, next to Actissa, the most simple of all Radiolaria, but differs from it by the large intracapsular alveoles. By these the central capsule is inflated to an extraordinary size, which in Thalassolampe maxima exceeds that of most other Radiolaria. From the nearly allied Thalassopila it differs by the simple spherical nucleus, from Physematium by the absence of spicula. Of the two species of the genus the first observed Thalassolampe margarodes, 1862, is Mediterranean, the second, Thalassolampe maxima, 1882, is Indian.

1. Thalassolampe margarodes, Haeckel.

Thalassolampe margarodes, Haeckel, 1862, Monogr. d. Radiol., p. 253, Taf. ii. figs. 4, 5.

Thalassolampe margarodes, R. Hertwig, 1876, Histologie d. Radiol., p. 68, Taf. iii. figs. 1-5.

Spherical body very soft and limpid, somewhat pearl-like opalescent, yellowish or bluish. Central capsule with a very thin structureless membrane, its diameter six to eight times as large as that of the central spherical nucleus. Wall of the vesicular nucleus thick, perforated by fine pore-canals; on its inside often numerous oval nucleoli. In the movable protoplasmic network between the large alveoles a considerable number of large yellowish or orange oil-globules. Extracapsular jelly-envelope very thin, contains small yellow bodies (zooxanthellæ). (Compare the accurate description of this Mediterranean species in my monograph and in Hertwig's work.) In the Canary Islands I found very often a large variety of it, of double and triple the size, distinguished by the delicate orange colour of the intracapsular oil-globules. This may be distinguished as Thalassolampe aurantiaca.

Dimensions.—Diameter of the whole jelly-sphere 2 to 4 mm., of the central capsule 2 to 3 mm., of its nucleus 0.2 to 0.4 mm.

Habitat.—Mediterranean, Messina, Haeckel, Hertwig; Canary Islands, Lanzerote, Haeckel; surface.

2. Thalassolampe maxima, n. sp. (Pl. 1, fig. 2).

Spherical body quite pellucid, like a glass globule, colourless. Central capsule with a moderately thick, but quite transparent, structureless membrane, its diameter ten to twelve times as large as that of the central spherical nucleus. Wall of the vesicular nucleus thick, perforated by fine pore-canals; on its inside numerous small spherical nucleoli. No large oil-globules in the movable protoplasmic network between the large alveoles. Extracapsular jelly-envelope very thin, containing no yellow bodies. This differs from the preceding nearly allied species in the want of the intracapsular oil-globules and of the extracapsular yellow bodies. It possesses the largest central capsule of all known Radiolaria. I found them living and floating in water taken from the surface of the Indian Ocean by a bucket.

Dimensions.—Diameter of the whole jelly-body 12 to 15 mm., of the central capsule 10 to 12 mm., of the nucleus 0.8 to 1.2 mm.

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, 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. 5b; 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.

Subgenus 1. Thalassicollarium, Haeckel.

Definition.—Membrane of the central capsule structureless, only perforated by innumerable very small radial pores.

1. Thalassicolla pellucida, n. sp.

Spherical body very soft, transparent, clear and colourless, without any pigment. Central capsule soft, hyaline, with a thin, structureless, not areolated membrane. Diameter of the central capsule about three times that of the nucleus, one-fourth to one-sixth that of the jelly-envelope. Nucleus delicate, transparent, with one single central nucleolus, about one-third its diameter. Protoplasm of the central capsule contains only small, pellucid, densely packed globules (vacuoles?), no oil-globules. Extracapsular body quite transparent, without pigment or oil-globules, only composed of the large alveoles imbedded in the jelly-cover, and of the fine protoplasmic network between them. No xanthellæ.

Dimensions.—Diameter of the central capsule 0.8 to 1.2, of the nucleus 0.3 to 0.4, of the calymma 3 to 6 mm.

Habitat.—Cosmopolitan, Canary Islands, Haeckel; Cape, Australia, Pacific, Challenger; surface.

2. Thalassicolla spumida, n. sp.

Spherical body nearly transparent, yellowish, without dark pigment. Central capsule pellucid, with a thick, structureless, not areolated membrane. Diameter of the central capsule about twice that of the nucleus, one-sixth to one-eighth that of the jelly-cover. Nucleus delicate, somewhat opaque, with numerous small nucleoli. Protoplasm of the central capsule contains small pellucid globules (vacuoles?), and immediately under its membrane (on its inside) one single layer of large, dark, refractive oil-globules. Extracapsular body very voluminous, foamy, with innumerable alveoles in the jelly, and many xanthellæ between them.

Dimensions.—Diameter of the central capsule 0.6 to 0.8, of the nucleus 0.3 to 0.4, of the calymma 3 to 5 mm.

Habitat.—Atlantic, Canary Islands, Haeckel; Cape Verde Islands, Challenger Station 350; Brazil, Rabbe; surface.

3. Thalassicolla zanclea, Haeckel.

Thalassicolla zanclea, Haeckel, 1862, Monogr. d. Radiol., p. 252, Taf. ii. fig. 3.

Spherical body opaque, transparent only in the periphery, with colourless central capsule, but with brown or black pigment-powder scattered everywhere through the extracapsular alveolated jelly-cover. Central capsule soft, transparent, colourless, with a thin structureless, not areolated membrane. Diameter of the central capsule about one and a half times that of the nucleus, one-half or one-third that of the jelly-cover. Nucleus delicate, transparent, with a thin, finely punctated membrane, with one or more nucleoli. Protoplasm of the central capsule contains only small, pellucid, densely packed globules (vacuoles?), no oil-globules. Extracapsular body very dark and opaque, with a great mass of brown or blackish-brown pigment between the alveoles of the jelly-cover. Numerous xanthellæ.

Dimensions.—Diameter of the central capsule 0.1 to 0.12, of the nucleus 0.07 to 0.08, of the calymma 0.2 to 0.4.

Habitat.—Mediterranean, Messina, Haeckel.

Subgenus 2. Thalassicollidium, Haeckel.

Definition.—Membrane of the central capsule areolated, with small polygonal plates, resembling an epithelial cell-tissue, spotted by innumerable fine radial pores.

4. Thalassicolla australis, n. sp.

Spherical body nearly transparent, without dark pigment. Central capsule colourless, somewhat opaque, with a thick and firm, very elastic membrane, areolated by polygonal, punctated figures resembling cells. Diameter of the central capsule about three times that of the nucleus, one-third that of the jelly-cover. Nucleus thin-walled, with many small nucleoli. Protoplasm of the central capsule finely granulated, containing numerous hyaline globules (vacuoles?) of different size, and in each of these one single roundish, dark refringing corpuscle, concentrically lamellated like an amylum grain. Extracapsular body without pigment or oil-globules, only composed of the large alveoles imbedded in the jelly-cover, and of the fine protoplasmic network between them. No xanthellæ.

Dimensions.—Diameter of the central capsule 1 to 2, of its nucleus 0.3 to 0.4, of the nucleoli 0.12 to 0.16, of the hyaline globules in the protoplasm of the capsule 0.02 to 0.05; calymma, 4 to 6 mm.

Habitat.—South-west Pacific, east coast of Australia, New Zealand, &c.; Challenger Stations 163, 171; surface.

5. Thalassicolla nucleata, Huxley.

Thalassicolla nucleata, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2, vol. viii. p. 435, pl. xvi. fig. 4.

Thalassicolla nucleata, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 28.

Thalassicolla coerulea, Schneider, 1858, Archiv f. Anat. u. Physiol., p. 40, Taf. iii. Bd. i. figs. 5-7.

Thalassicolla nucleata, Haeckel, 1862, Monogr. d. Radiol., p. 249, Taf. iii. figs. 1-5.

Thalassicolla nucleata, R. Hertwig, 1876, Histologie d. Radiol., p. 43, Taf. iii. figs. 61-5, Taf. iv., v.

Thalassicolla nucleata, R. Hertwig, 1879, Organismus d. Radiol., p. 34.

Spherical body in the central part opaque, black or dark coloured, in the periphery transparent, whitish, or yellowish. Central capsule rather compact, yellowish, opaque, with a thick and firm, very elastic membrane, areolated by polygonal, punctated figures resembling cells. Diameter of the central capsule about twice as large as that of the nucleus, one-half to one-fourth that of the jelly-cover. Nucleus with a very thick, finely punctated membrane, containing a viscous fluid (when coagulated finely granular), and sometimes one large, central, spherical, or ramified nucleolus, sometimes a variable number of smaller roundish nucleoli. Protoplasm of the central capsule containing many very variable corpuscles, mostly pellucid (albuminous?) spherules, containing oil-globules, or concentric amyloid concretions, or crystals, &c. Extracapsular body with dark pigment-powder of variable colour (black, brown, violet, blue, &c.), densely aggregated around the central capsule, more loosely dissipated between the alveoles of the outer jelly-cover. Xanthellæ very numerous.

Dimensions.—Diameter of the central capsule 0.4 to 0.8, of the nucleus 0.02 to 0.05, of the calymma 1 to 5 mm.

Habitat.—Cosmopolitan; common in all warmer seas; Mediterranean, Atlantic, Indian Ocean, Pacific, mainly between lat. 40° N. and lat. 40° S.; surface.

6. Thalassicolla maculata, n. sp. (Pl. 1, fig. 4).

Spherical body in the central part opaque, black or dark coloured, in the periphery semi-transparent, spotted. Central capsule compact, yellowish, opaque, with a thick and firm, very elastic membrane, areolated by polygonal, punctated figures resembling cells. Diameter of the central capsule about twice that of the nucleus, one-third to one-fifth that of the jelly-cover. Nucleus thin-walled, with one large spherical nucleolus. Protoplasm of the central capsule contains innumerable very small, hyaline, spherical vesicles of equal size (or vacuoles?), two to four times as broad as the separating bridges of protoplasm. Extracapsular body with dark pigment-powder of black or brown colour, densely accumulated around the central capsule (in the matrix), loosely scattered between the alveoles of the outer jelly-cover. The latter appears spotted by numerous large, roundish lumps of protoplasm, scattered between the alveoles. No xanthellæ.

Dimensions.—Diameter of the central capsule 0.3 to 0.6, of the nucleus 0.2 to 0.3, of the hyaline globules in the protoplasm of the capsule 0.02 to 0.03; calymma, 2 to 3 mm.

Habitat.—South Pacific, Challenger Station 289.

7. Thalassicolla melacapsa, n. sp. (Pl. 1, fig. 5).

Spherical body in the central part opaque, black or dark coloured, in the periphery semi-transparent, spotted. Central capsule compact, black, with a thick and firm, very elastic membrane, areolated by polygonal, punctated figures resembling cells. Diameter of the central capsule about twice that of the nucleus, one-third or half that of the jelly-cover. Nucleus thin-walled, transparent, containing very numerous and small nucleoli. Protoplasm of the central capsule filled with small black pigment-granules, quite intransparent, contains densely packed hyaline (albuminous?) globules of equal size; every pellucid globule includes a smaller globule (one-third or one-fourth its diameter), which appears to be composed of aggregated oil-bubbles. Extracapsular body without pigment, contains between its alveoles in the inner half numerous, dark refractive oil-globules, in the outer half numerous amœboid lumps of protoplasm, irregularly scattered. No xanthellæ.

Dimensions.—Diameter of the central capsule 2 to 2.5, of the nucleus 1 to 1.5, of the hyaline globules in the protoplasm of the capsule 0.03 to 0.04; calymma, 3 to 5 mm.

Habitat.—South-east Pacific (near Valparaiso), Challenger Station 300, surface.

Genus 5. Thalassophysa,^[12] Haeckel, 1881, Prodromus, p. 470.

Definition.—Thalassicollida without intracapsular alveoles, but with large roundish or globular alveoles within the extracapsular calymma. Nucleus in the centre of the capsule papillate or branched.

The genus Thalassophysa contains those species of Thalassicollida formerly associated with Thalassicolla, which are distinguished by the complicated, ramose, or papillate form of the large nucleus. All three species here described are found in the Mediterranean and the Atlantic. To this genus appertains also that strange form of Radiolaria which I described in 1870 as Myxobrachia (compare Thalassophysa sanguinolenta).

1. Thalassophysa papillosa, n. sp.

Thalassicolla papillosa, Haeckel, 1867, Manuscript.

Spherical body transparent, colourless, or somewhat yellowish. Central capsule soft, colourless, with a very thin but firm, elastic, structureless membrane. Diameter of the central capsule about twice that of the nucleus, one-fourth to one-sixth that of the jelly-envelope. Nucleus papillated, its spherical surface covered with a great number (50 to 80) of conical or finger-like protuberances or blind sacs, not longer than half its radius. Protoplasm of the central capsule filled with very small and numerous spherical vacuoles, without oil-globules. Extracapsular jelly-body, without dark pigment, oil-globules, and large protoplasmic lumps, contains between its alveoles very numerous xanthellæ.

Dimensions.—Diameter of the whole jelly sphere 4 to 5 mm., of the central capsule 0.8 to 1 mm., of its nucleus 0.4 to 0.5.

Habitat.—Canary Islands, Lanzerote, common, Haeckel; Cape Verde Islands, Challenger; surface.

2. Thalassophysa sanguinolenta, Haeckel.

Thalassicolla sanguinolenta, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p. 526, Taf. 18.

Thalassicolla sanguinolenta, Haeckel, 1870, Biolog. Studien, i. p. 113, Taf. iv.

Thalassicolla sanguinolenta, R. Hertwig, 1879, Organismus d. Radiol., p. 37, Taf. iii. fig. 1.

Myxobrachia rhopalum, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p. 519, Taf. 18 (et in Biol. Stud., loc. cit.).

Myxobrachia pluteus, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p. 520, Taf. 18 (et in Biol. Stud., loc. cit.).

Spherical body in the central part opaque, reddish, in the periphery transparent, yellowish. Central capsule compact, white, red spotted, with a thick elastic membrane, perforated by pores, but not areolated. Diameter of the central capsule three times that of the nucleus, one-fifth to one-eighth that of the jelly-envelope. Nucleus papillated, its spherical surface covered with numerous (80 to 120) conical or finger-like protuberances not longer than one-fourth or one-third of its radius. On the inside of these blind sacs lie numerous small roundish nucleoli. Protoplasm of the central capsule in the outer (cortical) zone (on the inside of the membrane) radially striped, with one layer of very numerous red oil-globules of equal size, producing its blood-spotted appearance; in the inner (medullary) zone foamy, with numerous small spherical vacuoles. Extracapsular jelly-body without dark pigment, contains between its alveoles no large protoplasmic lumps (as in Thalassophysa pelagica), but numerous small oil-globules and xanthellæ. This species sometimes amasses in its jelly-envelope large accumulations of Coccoliths and Coccospheres, which are much heavier than the jelly-body, and produce arm-like protuberances of it; this modified form, often of very regular and peculiar appearance, I formerly described as Myxobrachia (compare my Biolog. Studien, loc. cit., and Hertwig, loc. cit., p. 37). Compare also Myxobrachia cienkowski, Wagner, 1872, L. N. 23.

Dimensions.—Diameter of the whole jelly-sphere 5 to 8 mm., of the central capsule 1 to 1.2 mm., of its nucleus 0.3 to 0.4.

Habitat.—Canary Islands, Lanzerote; common, Haeckel; Mediterranean, Messina, Hertwig; surface.

3. Thalassophysa pelagica, Haeckel.

Thalassicolla pelagica, Haeckel, 1862, Monogr. d. Radiol., p. 247, Taf. i.

Thalassicolla pelagica, R. Hertwig, 1879, Organismus d. Radiol., p. 35, Taf. iii. fig. 4.

Spherical body in the central part opaque, yellowish, in the periphery semi-transparent, spotted. Central capsule compact, yellowish-white, with a thick and compact membrane, perforated by pores, but not areolated. Diameter of the central capsule about twice that of the nucleus, one-half to one-sixth that of the jelly-envelope. Nucleus papillated, its spherical surface covered with numerous (20 to 60) conical, roundish, or finger-like protuberances, not longer than its radius (commonly only one-half or one-third as long). Enclosed in the semi-fluid substance of the nucleus are very long and thin cylindrical nucleoli snake-like, contorted, and penetrating into the protuberances of the nucleus. Protoplasm of the central capsule in the outer (cortical) zone (on the inside of the membrane) radially striped, with one layer of large oil-globules of different sizes; in the inner (medullary) zone foamy, with numerous small spherical vacuoles, mostly of equal size. Extracapsular jelly-body without dark pigment, contains between its alveoles a large number of large roundish or amœboid lumps of protoplasm, and very numerous yellow cells or xanthellæ (compare the detailed description in my Monograph, and in R. Hertwig's work).

Dimensions.—Diameter of the whole jelly-sphere 1 to 4 mm., of the central capsule 0.5 to 0.6, of the nucleus 0.2 to 0.3.

Habitat.—Mediterranean—Messina, Corfu, Nizza, Genoa, Haeckel; Messina, R. Hertwig; surface.

Family II. Collozoida, Haeckel, 1862 (Pl. 3).

Collozoida, Haeckel, 1862, Monogr. d. Radiol., p. 522.

Definition.—Colloidea socialia.

The family Collozoida comprises all associated or colony-building Radiolaria without skeleton. We unite here all these skeletonless Radiolarian colonies into one single genus Collozoum, constituted (1862) in my Monograph (p. 522). The oldest known form of it was the Collozoum inerme, described firstly by Johannes Müller (1856) as Sphærozoum inerme. Two other species of the genus were figured (1862) in my Monograph (p. 522, Tafn. xxxii., xxxv.). A most accurate description of its histological structure and development was given in 1876 by Richard Hertwig in his Histologie der Radiolarien (pp. 12-42, Tafn. i., ii.). A number of other very remarkable forms of Collozoum have been observed by me during the last few years, and partly figured in Pl. 3.

Collozoum, as the only representative of this family, is sufficiently distinguished from all other Radiolaria by the definition "Skeletonless Radiolarian Colonies." These occur floating on the surface of all warmer seas, often in astonishing masses, and may be easily confounded, owing to their external resemblance, with the jelly-like egg-masses of certain Mollusca. Collozoum is derived either from Actissa or from Thalassicolla, simply by multiplication of the unicellular body and by reunion of the associated capsules in one common calymma or jelly-veil; this is constantly alveolated, as in Thalassicolla. As in Actissa, the form of the central capsule remains either spherical, or it becomes ellipsoidal or discoidal, rarely polyhedral or amœboid. In Collozoum as in all colonial Radiolaria, the original central nucleus commonly undergoes cleavage very early into numerous small nuclei, whilst its place is usually taken by a central oil-globule. This peculiarity may serve often (but not constantly) for the distinction of isolated capsules of Collozoum from Actissa.

Genus 6. Collozoum,^[13] Haeckel, 1862, Monogr. d. Radiol., p. 522.

Definition.—Skeletonless colonies of Radiolaria.

The genus Collozoum, as already mentioned, is the only representative of its family, and comprises all Radiolaria living associated in colonies, and having no skeleton. Therefore Collozoum possesses all the peculiarities described above. Although the floating colonies of this genus occur in enormous masses on the surface of all warmer seas, nevertheless the number of different species in this genus is not great, and amounts only to thirteen. If this number increase by further investigations, the subgenera distinguished in the following description can be advanced to the range of genera; in which case Collodinium (or Collozoum sensu restricto) will be characterised by the spherical form of its central capsules, Colloprunum by the ellipsoidal form (Pl. 3, fig. 9), Collophidium by the cylindrical, very prolonged form (figs. 2, 3), Collodiscus by the lenticular or discoidal form, and Collodastrum by the indefinite, polyhedral, or amœboid form (figs. 4, 5).

Subgenus 1. Collodinium, Haeckel.

Definition.—Form of the central capsules spherical or subspherical, never polyhedral, ellipsoidal, or cylindrical.

1. Collozoum inerme, Haeckel (Pl. 3, figs. 10-12).

Collozoum inerme, Haeckel, 1862, Monogr. d. Radiol., p. 522, Taf. xxxv.

Collozoum inerme, Cienkowski, 1871, Archiv. f. mikrosk. Anat., vol. vii. p. 376, Taf. xxix. figs. 18-36.

Collozoum inerme, R. Hertwig, 1876, Histologie der Radiol., p. 12, Taf. i., ii.

Collozoum inerme, R. Hertwig, 1879, Organismus d. Radiol., p. 31, Taf. iii. fig. 12.

Sphærozoum inerme, J. Müller, 1856, Monatsber. d. k. Akad. d. Wiss. Berlin, p. 478; Abhandl., p. 54.

Sphærozoum bicellulare, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 54, Taf. viii. fig. 5.

Thalassicolla punctata, Huxley (pro parte), 1851, Ann. and Mag. Nat. Hist., ser. 2, vol. viii. p. 433.

Central capsules spherical, with thin, simple-edged membrane, with one single oil-globule in the centre. (If the capsules multiply by division, the spherical form becomes violin-shaped, constricted in the middle; and in this condition the number of oil-globules increases; but in the ordinary mature state the capsule of this species remains spherical, and its oil-globule solitary. In quite young capsules the oil-globules are wanting; Pl. 3, fig. 12.)

Dimensions.—Diameter of the central capsules 0.04 to 0.16.

Habitat.—Cosmopolitan, common in all warmer seas (Mediterranean, Atlantic, Indian, and Pacific), surface.

2. Collozoum nostochinum, n. sp.

Central capsules spherical, very large, opaque, distended with red pigment-granules and with very numerous (two hundred to three hundred) small oil-globules. Membrane thick, double-edged.

Dimensions.—Diameter of the central capsules 0.3 to 0.5.

Habitat.—Indian Ocean, off Socotra, surface, Haeckel.

3. Collozoum volvocinum, n. sp.

Central capsules spherical, very large, opaque, containing a great number (ten to thirty) of large oil-globules, and between them densely packed masses of dark pigment. Membrane thick, double-edged. This species differs from Collozoum inerme, mainly by the great size of the central capsules (three to five times as big as in the former) and the great number of oil-globules in them.

Dimensions.—Diameter of the central capsules 0.2 to 0.3.

Habitat.—Central Pacific, Station 272, surface.

Subgenus 2. Colloprunum, Haeckel.

Definition.—Form of the central capsules ellipsoidal, with one prolonged axis.

4. Collozoum ovatum, n. sp.

Colloprunum ovatum, Haeckel, 1882, Manuscript.

Central capsules ovate or ellipsoidal, its longer diameter twice to three times as large as the shorter. In the centre of every capsule one single oil-globule.

Dimensions.—Length of the central capsules 0.2 to 0.3, breadth of them 0.1 to 15.

Habitat.—North Pacific, Station 244, surface.

5. Collozoum ellipsoides, n. sp. (Pl. 3, figs. 8, 9).

Colloprunum ellipsoides, Haeckel, 1882, Manuscript.

Central capsules regularly ellipsoidal, very large; their longer diameter once and a half to twice as large as the shorter. In every capsule fifty to eighty oil-globules.

Dimensions.—Length of the central capsules 0.3 to 4, breadth of them 0.2.

Habitat.—North Atlantic, Færöe Channel (Gulf Stream), surface, John Murray.

Subgenus 3. Collophidium, Haeckel.

Definition.—Form of the central capsules cylindrical, often snake-like, contorted, with one axis much prolonged, several times longer than the transverse axis.

6. Collozoum contortum, n. sp.

Collophidium contortum, Haeckel, 1882, Manuscript.

Central capsules cylindrical, three to four times as long as broad, C- or S-like curved, transparent, without oil-globules.

Dimensions.—Length of the central capsules 0.2 to 0.3, breadth 0.06 to 0.08.

Habitat.—Tropical Atlantic, Station 347, surface.

7. Collozoum serpentinum, n. sp. (Pl. 3, figs. 1-3).

Collophidium serpentinum, Haeckel, 1882, Manuscript.

Central capsules cylindrical, filiform, much elongated, ten to one hundred times, sometimes two hundred to four hundred times as long as broad, snake-shaped or worm-shaped, curved and contorted in the most irregular manner, often spiral or twisted into a large nodule. Numerous oil-vesicles constantly present, forming one series of globules in the axis of every capsule; distance of the globules, one from another, and also from the capsule-membrane, about equal to their diameter. (This interesting and very curious form was very frequently observed living by me in the Canary Islands, in January 1867; the jelly-colonies were commonly spherical, and contained fifty to two hundred or more capsules of very different size and form.)

Dimensions.—Length of the central capsules 1 to 10, sometimes 20 to 40 mm.; average breadth 0.1 mm.

Habitat.—Canary Islands, Lanzerote, Haeckel, surface.

8. Collozoum vermiforme, n. sp. (Pl. 3, figs. 6, 7).

Collophidium vermiforme, Haeckel, 1882, Manuscript.

Central capsules cylindrical, much elongated, five to ten times (sometimes twenty to fifty times) as long as broad, snake-shaped or worm-shaped, very irregularly curved and contorted. Numerous oil-globules constantly present, forming in the axis of every capsule a double series of alternating rose-coloured globules. (This species is nearly allied to the preceding; but its capsules are thicker and shorter, and the oil-vesicles in them are arranged not in a single, but in a double row.)

Dimensions.—Length of the central capsules 0.6 to 1.2 mm., sometimes 3 to 6 mm.; breadth 0.12.

Habitat.—Tropical Atlantic, near the west coast of Africa, Station 349, Canary Islands, surface.

Subgenus 4. Collodiscus, Haeckel.

Definition.—Form of the central capsules discoidal or lenticular, with one shortened axis.

9. Collozoum coeruleum, Haeckel.

Collozoum coeruleum, Haeckel, 1862, Monogr. d. Radiol., p. 523, Taf. xxxii. figs. 6-8.

Collodiscus coeruleus, Haeckel, 1882, Manuscript.

Central capsule lenticular or discoidal, flattened, blue coloured, with one single oil-globule in the centre. Protoplasm containing numerous crystals and dark blue pigment-granules. Membrane very thick, double-edged. (Whilst at Messina in 1859 I found this form not constantly discoidal, in 1867 in the Canary Islands I observed it constantly lenticular.)

Dimensions.—Breadth of the central capsules 0.1 to 0.15, height 0.04 to 0.08.

Habitat.—Mediterranean (Messina), Atlantic (Canary Islands), surface.

10. Collozoum discoideum, n. sp.

Collodiscus discoideus, Haeckel, 1882, Manuscript.

Central capsule discoidal, flattened, transparent, with a ring of twenty to twenty-five oil-globules in its circular periphery (on the inside of the thin membrane).

Dimensions.—Breadth of the central capsules 0.2, height 0.05.

Habitat.—South Pacific (Juan Fernandez), Station 300, surface.

Subgenus 5. Collodastrum, Haeckel.

Definition.—Form of the central capsules irregular and indefinite, variable, commonly polyhedral or polygonal, or amœboid, often with irregular, finger-like processes.

11. Collozoum pelagicum, Haeckel.

Collozoum pelagicum, Haeckel, 1862, Monogr. d. Radiol., p. 525, Taf. xxxii. figs. 4, 5.

Sphærozoum pelagicum, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss. Berlin, 1860, p. 845.

Central capsules small, quite irregularly formed, roundish-polyhedral or depressed-polygonal, transparent, without oil-globules. Often many extracapsular oil-vesicles in the common jelly-body between the central capsules. Membrane very thin and delicate.

Dimensions.—Diameter of the central capsules 0.02 to 0.08.

Habitat.—Mediterranean, Messina, Haeckel; Naples, Brandt; surface.

12. Collozoum stellatum, n. sp.

Collodastrum stellatum, Haeckel, 1882, Manuscript.

Central capsules star-shaped, irregularly radiating, with a great number (eight to twenty or more) of radial, short, conical, acute processes, very variable in size and number. Membrane thin. In every capsule several (four to eight) oil-globules.

Dimensions.—Diameter of the central capsules 0.12 to 0.2.

Habitat.—Central Pacific, Station 274, surface.

13. Collozoum amœboides, n. sp. (Pl. 3, figs. 4, 5).

Collodastrum amœboides, Haeckel, 1882, Manuscript.

Central capsules amœbiform, of moderate size, quite irregularly formed, with a variable number of finger-like, obtuse, irregular prolongations (commonly three to six), very variable in size and form. Membrane thin. In the centre of every capsule one single oil-globule.

Dimensions.—Diameter of the central capsules 0.04 to 0.08.

Habitat.—Indian Ocean, Ceylon, Haeckel; Madagascar, Rabbe; surface.

Suborder II. BELOIDEA, Haeckel.

Definition.—Spumellaria with an imperfect skeleton, composed of numerous solid needles or spicula, scattered irregularly in the calymma.

The suborder Beloidea comprises all those Spumellaria which possess an imperfect or rudimentary skeleton, composed of a variable number of isolated spicula scattered in the extracapsulum. The suborder contains only two different families, the solitary Thalassosphærida (or Beloidea monozoa) and the associated Sphærozoida (or Beloidea polyzoa). Both families are very nearly allied, and differ only in one single character: the solitary life of the former, the social union of the latter. It seems to be merely a consequence of this difference that the cleavage of the nucleus commonly takes place very late in the former, very early in the latter.

Commonly, therefore, the full-grown Thalassosphærida (until immediately before their propagation) exhibit one single nucleus in the centre of the capsule, whilst in the Sphærozoida the capsule is distended with numerous small nuclei. In these latter the centre of the capsule usually contains one large oil-globule, whilst in the former oil-globules are either wanting or scattered in large numbers in the endoplasm, or disposed in one layer on the inside of the capsule membrane.

In the solitary Thalassosphærida each capsule is enclosed in its own peculiar spherical calymma, whilst in the associated Sphærozoida all the capsules of the colony are united into one common, very voluminous, alveolated calymma.

Family III. Thalassosphærida, Haeckel, 1862, (Pl. 2).

Thalassosphærida, Monogr. d. Radiol., p. 255.

Definition.—Beloidea solitaria.

The family Thalassosphærida comprises all solitary Spumellaria with an imperfect skeleton, composed of numerous solid needles or spicula, scattered around the central capsule in the calymma. The structure of the unicellular soft body is quite the same as in the Thalassicollida; it differs from these only in the possession of the extracapsular skeleton. All needles of this skeleton are solid siliceous spicula, never hollow, as in the similar Cannorrhaphida among the Phæodaria. In the special structure and form of the skeleton the Thalassosphærida agree perfectly with the well-known, colony-building Sphærozoida; they differ from these only by their hermit-like life and by some peculiarities derived from this solitary development.

The oldest known form of this family is probably the first Radiolarian, observed in the living state, described in 1834 by Meyen as Physematium atlanticum (see p. 35). A second form was figured in my Monograph (1862) as Thalassosphæra bifurca (p. 260, Taf. xii. fig. 1). A third form was there described under the name Thalassosphæra morum; this remarkable form was first observed by Johannes Müller, and figured under the name Thalassicolla morum (1858, Abhandl., p. 28, Taf. vii. figs. 1, 2). The same form was afterwards observed living by myself in the Mediterranean, as well as in the Atlantic, and in great numbers by the late Sir Wyville Thomson in the Pacific. The latter gave a good figure of it with some valuable remarks in his excellent work, The Atlantic (1877, vol. i. p. 233, fig. 51). He called this peculiar Rhizopod Calcaromma calcarea, on account of the very peculiar calcareous bodies "looking in outline like the rowels of spurs," which are accumulated in great quantity around the central capsule, in the calymma. Further investigations have convinced me that these peculiar stellate bodies of carbonate of lime, for which we propose the name "Calcastrella," are not parts of the skeleton produced by the Radiolarian, but foreign bodies picked up by its extracapsular sarcode (in the same way as the Coccoliths are picked up by Thalassicolla sanguinolenta = Myxobrachia!). These Calcastrella occur also in the calymma of some Discoidea and other Radiolaria; they are either unicellular calcareous Algæ, or foreign bodies of other origin. The Collodarium, however, described as Thalassicolla morum and Calcaromma calcarea, seems to be a simple Actissa, which has picked up a number of Calcastrella.

The Challenger collection has yielded a number of other true Thalassosphærida, which partly agree with Thalassosphæra in the simple structure of the unicellular body (resembling Actissa), and partly differ from it in the development of alveoles, either within or without the central capsule (similar to Thalassolampe and Thalassicolla). The solid siliceous spicula, which occur in great numbers scattered in the calymma, agree perfectly in form with the spicula of the colony-building Sphærozoida. A characteristic difference between the social and the solitary Beloidea seems to be determined by the cleavage of the nucleus, which takes place in the latter very late, in the former very early. Therefore in the large central capsule of the mature solitary Thalassosphærida, we commonly find one large nucleus in the centre, and a number of oil-globules around it in the endosarc, or disposed in one layer on the inside of the capsule-membrane (Pl. 2, figs. 2, 5); whereas in the much smaller associated capsules of the Sphærozoida one large oil-globule is placed commonly in the centre, and a great number of small nuclei scattered in the endoplasm (compare above, p. 24).

Synopsis of the Genera of Thalassosphærida.

A. Alveoles neither within nor without the central capsule. Spicula simple, 07. Thalassosphæra.

Spicula branched, 08. Thalassoxanthium.

B. Numerous large alveoles within the central capsule (not in the calymma). Spicula simple, 09. Physematium.

C. Numerous large alveoles within the calymma (not in the central capsule). Spicula simple, 10. Thalassoplancta.

Spicula branched, 11. Lampoxanthium.

A. Alveoles neither within nor without the central capsule.

Spicula simple,

7. Thalassosphæra.

Spicula branched,

8. Thalassoxanthium.

B. Numerous large alveoles within the central capsule (not in the calymma).

Spicula simple,

9. Physematium.

C. Numerous large alveoles within the calymma (not in the central capsule).

Spicula simple,

10. Thalassoplancta.

Spicula branched,

11. Lampoxanthium.

Genus 7. Thalassosphæra,^[14] Haeckel, 1862, Monogr. d. Radiol., p. 259.

Definition.—Thalassosphærida without alveoles, with simple, unbranched, needle-shaped spicula in the calymma.

The genus Thalassosphæra was founded by me in 1862 for those solitary Collodaria in which the simple central capsule is surrounded by scattered solid spicula. I described these two different species, the new Thalassosphæra bifurca and the Thalassosphæra morum, which J. Müller had formerly called Thalassicolla morum. This latter form is characterised by peculiar calcareous bodies "looking in outline like the rowels of spurs, scattered irregularly in the gelatinous envelope," and was therefore afterwards called "Calcaromma calcarea" by Sir Wyville Thomson.^[15] As already mentioned above, these calcareous rowels are foreign bodies, picked up by an Actissa (see p. 29). I here confine the genus Thalassosphæra to those solitary Beloidea in which the body exhibits no alveoles, and the siliceous solid spicula in the calymma are quite simple needles.

Thalassosphæra belonium, n. sp.

Spicula thin cylindrical rods, more or less curved, pointed at both ends, with smooth surface (similar to the needles of Rhaphidozoum italicum). Central capsule spherical, three times as large as the central nucleus, without larger oil-globules.

Dimensions.—Diameter of the central capsule 0.1 to 0.12, length of the spicula 0.04 to 0.08.

Habitat.—Central Pacific, Station 272, surface.

Thalassosphæra rhaphidium, n. sp.

Spicula thick cylindrical rods, more or less curved, pointed at both ends, covered with numerous strong conical thorns, perpendicular to the axis. Central capsule spherical, four times as broad as the central nucleus, with twenty to thirty large oil-globules on the inside of the membrane.

Dimensions.—Diameter of the central capsule 0.2, length of the spicula 0.12 to 0.16.

Habitat.—Tropical Atlantic, Station 347, surface.

Genus 8. Thalassoxanthium,^[16] Haeckel, 1881, Prodromus, p. 470.

Definition.—Thalassosphærida without alveoles, with numerous branched or compound spicula in the calymma.

The genus Thalassoxanthium differs from the foregoing Thalassosphæra, by the ramification of the spicula, and has therefore the same relation to it as Sphærozoum to Belonozoum. The soft unicellular body is as simple as in Actissa, and exhibits alveoles neither in the capsule nor in the calymma.

Subgenus 1. Thalassoxanthella, Haeckel.

Definition.—Spicula not geminate, but simply radiate, consisting of three, four, or more needles or shanks, radiating in different directions from one and the same point; shanks now simple or needle-like, now furcate or branched.

1. Thalassoxanthium triactinium, n. sp.

Spicula all (or nearly all) triradiate, composed of three (or sometimes in a few spicula four) needle-like shanks of equal length, diverging from one common point. Shanks straight or somewhat curved, smooth, pointed. Central capsule pellucid, twice as broad as its dark nucleus, without larger oil-globules. Jelly-envelope very thin, with numerous xanthellæ.

Dimensions.—Diameter of the central capsule 0.1, of its nucleus 0.05, length of the spicule-shanks 0.6 to 0.8.

Habitat.—Central Pacific, Station 266, surface.

2. Thalassoxanthium triradiatum, n. sp.

Spicula all (or nearly all) triradiate, composed of three (or sometimes in a few spicula four) needle-like shanks of different length, diverging from one common point. Shanks curved or bent, covered with small conical thorns. Central capsule dark, three times as large as the nucleus, with numerous large oil-globules. Jelly-envelope thick, without xanthellæ.

Dimensions.—Diameter of the capsule 0.2, of the nucleus 0.07, length of the spicule-shanks 0.1 to 0.15.

Habitat.—South Pacific, Station 302, surface.

3. Thalassoxanthium medusinum, n. sp. (Pl. 2, fig. 5).

Spicula all (or nearly all) quadriradiate, irregular, composed of four (or sometimes in a few spicula three) needle-like shanks (mostly of unequal length), diverging from one common point. Shanks curved, pointed, thorny, covered with small spinules. Central capsule dusky, twice to three times as large as its dark central nucleus. On the inside of the membrane numerous large oil-globules. Jelly-envelope thin, with numerous xanthellæ.

Dimensions.—Diameter of the central capsule 0.45 to 0.5, of its nucleus 0.18 to 0.2.

Habitat.—North Pacific, Station 244, surface.

4. Thalassoxanthium hexactinium, n. sp.

Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in a few spicula three) needle-like shanks, diverging in two opposite hemispheres (three needles upwards, three needles downwards). Shanks somewhat curved, pointed, smooth. Central capsule yellowish-brown, dark, four times as broad as its dark central nucleus. Jelly-envelope thick (about twice as broad as the capsule), with very numerous xanthellæ.

Dimensions.—Diameter of the central capsule 0.3 to 0.4, of its nucleus 0.1 to 0.12.

Habitat.—South Atlantic, Station 325, surface.

5. Thalassoxanthium cervicorne, n. sp. (Pl. 2, figs. 3, 4).

Spicula all triradiate, trichotomously branched, with three equal shanks, which diverge from one common point, and are again provided each with three branches on the distal end. These nine branches are commonly once or twice forked (each fork rarely provided with three ramules). The ramules are thin, unequal, curved, or bent, and the ramification nearly resembles a stag's horn. Central capsule transparent, without oil-globules, two to three times as broad as the dark nucleus, which contains one single long central nucleolus. Calymma thin, scarcely as thick as the radius of the nucleus.

Dimensions.—Diameter of the central capsule 0.2 to 0.25, of the nucleus 0.08 to 0.1, length of the spicula 0.05 to 0.15.

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

Subgenus 2. Thalassoxanthomma, Haeckel.

Definition.—Spicula all or partly geminate, consisting of one middle or axial rod, from the two poles of which diverge two, three, or more shanks in different directions. Shanks or needle-rays sometimes simple, needle-like, sometimes bifurcated or branched.

6. Thalassoxanthium furcatum, n. sp.

Spicula all (or nearly all) geminate and simply forked, composed of a simple axial rod and two simple, needle-like shanks on each end of it. Shanks straight, pointed, smooth, somewhat shorter than the middle rod. Central capsule yellowish, dark, three times as broad as its central dark nucleus; besides this a single oil-globule, nearly of the same size.

Dimensions.—Diameter of the central capsule 0.1, of its nucleus 0.03; length of the axial rod of the spicula 0.04, of its shanks 0.03.

Habitat.—Cape Verde Islands.

7. Thalassoxanthium bifurcum, Haeckel.

Thalassosphæra bifurca, Haeckel, 1862, Monogr. d. Radiol., p. 260, Taf. xii. fig. 1.

Sphærozoum bifurcum, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 845.

Spicula all geminate and double forked, composed of a simple axial rod and two forked branches on each end; these branches are again forked, so that each spiculum exhibits eight thin distal ends. All branches are thin, slender and straight. Central capsule red, four times as broad as the central nucleus, containing between the red pigment-granules numerous, peculiar, violin-shaped bodies (fat-corpuscles?). Compare fig. 1, loc. cit.

Dimensions.—Diameter of the central capsule 0.08, of the nucleus 0.02, length of the spicula 0.05 to 0.08.

Habitat.—Mediterranean (Messina), surface, Haeckel.

8. Thalassoxanthium ovodimare, n. sp.

Spicula all geminate, composed of a simple, very short axial rod and three diverging shanks or branches on each end of it; the shanks are very thin, straight, or little curved, and eight to ten times as long as the axial rod. The spicula are quite smooth, as in the similar Sphærozoum ovodimare (in which, however, the axial rod is much longer). Central capsule transparent, without oil-globules, twice as broad as the nucleus.

Dimensions.—Diameter of the capsule 0.4, of the nucleus 0.2, length of the spicula 0.1 to 0.2.

Habitat.—Central Pacific, Station 273, surface.

9. Thalassoxanthium punctatum, n. sp.

Spicula all geminate-triradiate, composed of a simple middle rod and of three diverging shanks on each end of it; the shanks are thorny with small spinules and shorter than the axial rod, very similar to the common Sphærozoum punctatum. Central capsule dark, with numerous (twenty to thirty) oil-globules on the inside of the membrane, three times as broad as the nucleus.

Dimensions.—Diameter of the capsule 0.3, of the nucleus 0.1, length of the spicula 0.05 to 0.2.

Habitat.—Central Pacific, Station 274, surface.

10. Thalassoxanthium octoceras, n. sp. (Pl. 2, fig. 6).

Spicula all geminate-quadriradiate, composed of a simple short middle rod and of four diverging shanks on each end of it; the shanks are quite smooth, irregularly curved or bent, and four to eight times as long as the middle rod. Central capsule dark, filled with pigment-granules, without oil-globules, four times as large as the nucleus.

Dimensions.—Diameter of the capsule 0.5, of the nucleus 0.12, length of the spicula 0.2 to 0.4.

Habitat.—Indian Ocean, Madagascar, Rabbe.

Genus 9. Physematium,^[17] Meyen, 1834, Nova Acta Acad. Nat. Curios., vol. xvi., Suppl., p. 286 (p. 162).

Definition.—Thalassosphærida with large numerous alveoles within the central capsule (not in the calymma), and with numerous simple, needle-shaped spicula in the calymma.

The genus Physematium is, together with the colony-forming Sphærozoum, the first Radiolarian which was observed in the living state, described in 1834 by Meyen. It is most nearly allied to Thalassolampe, and has the same large roundish alveoles within the central capsule, which reaches therefore an extraordinary size, 5 to 10 mm. It differs from the latter by the possession of spicula in the calymma. The peculiar "centripetale Zell-gruppen" on the inside of the capsule-membrane are probably due to radial cleavages of the endoplasm; as also occurs in other Collodaria.

1. Physematium mülleri, Schneider.

Physematium mülleri, Schneider, 1858, Archiv. f. Anat. u. Physiol., p. 38, Taf. iii. B, figs. 1-5.

Physematium mülleri, Haeckel, 1862, Monogr. d. Radiol., p. 256, Taf. iii. figs. 6-9.

Spherical body limpid, somewhat opalescent, sometimes a little yellowish or brownish, rather soft. Central capsule with a thin, but firm, transparent membrane, its diameter eight to ten times as large as that of the central spherical nucleus. Membrane of the nucleus thick, porous, on its inside with some nucleoli. In the protoplasmic network between the large intracapsular alveoles, numerous large, pale, yellowish, or orange oil-globules. On the inside of the membrane numerous conical bodies, centripetally directed with the apex towards the centre; every conical body ("kegelförmige centripetale Zellgruppe") composed of three to nine (commonly four or five) nucleated cells (mother-cells of the spores?); in the axis of the cone there is often a yellowish, orange, or brown oil-globule. Extracapsular jelly-envelope thin, with short pseudopodia. Xanthellæ scarce or wanting. Spicula scattered in the jelly numerous, small, simple needles, commonly C- or S-like curved, smooth.

Dimensions.—Diameter of the whole jelly-sphere 3 to 6 mm., of the central capsule 1 to 5 mm., of the nucleus 0.1 to 0.5, length of the spicula 0.05 to 0.1.

Habitat.—Mediterranean, Messina; Schneider, Haeckel; surface.

2. Physematium atlanticum, Meyen.

Physematium atlanticum, Meyen, 1834, Nova Acta Acad. Nat. Curios., vol. xvi., Suppl., p. 286 (162), Taf. xxxviii. (xxviii.) figs. 1-3.

Spherical body opalescent, pearl-like, with a violet or purple lustre, very soft. Central capsule with a strong, semi-transparent membrane, its diameter six to eight times as large as that of the central spherical nucleus. Membrane of the nucleus very thick, porous, on its inside with many small nucleoli. In the protoplasmic network between the alveoles very numerous, small, purple oil-globules. On the inside of the membrane a continuous simple layer of small nuclei, enclosed in radially striped protoplasm (mother-cells of the spores?). No centripetal conical bodies. Extracapsular jelly-envelope very thin, with short pseudopodia. No xanthellæ. Spicule scattered in the jelly numerous, small needles, straight or slightly curved, thorny owing to numerous small vertical spinules. This species and Thalassolampe maxima (p. 17) possess the largest central capsule.

Dimensions.—Diameter of the whole jelly-sphere 8 to 12 mm., of the central capsule 5 to 10 mm., of the nucleus 1 to 2 mm., length of the spicula 0.1 to 0.3.

Habitat.—Eastern Atlantic, between Canary Islands and Cape Verde Islands, Meyen; Lanzerote, Haeckel.

Genus 10. Thalassoplancta,^[18] Haeckel, 1862, Monogr. d. Radiol., p. 261.

Definition.—Thalassosphærida with numerous large alveoles in the calymma (but not in the central capsule), and with numerous simple, needle-shaped spicula around the central capsule.

The genus Thalassoplancta was founded by me in 1862 for a Radiolarian with simple hollow needles in the calymma, which was afterwards recognised as a Phæodarium, belonging to Cannorrhaphis. We here retain this name for a true Thalassosphærid, very similar to the latter, but distinguished by the absence of the phæodium and the solid—not hollow—needle-shaped spicula, which are scattered in the alveolated calymma. Thalassoplancta can be regarded as the solitary form of the social Belonozoum.^[19]

1. Thalassoplancta longispicula, n. sp.

Spicula long and thin, cylindrical, smooth, more or less bent, pointed at both ends, similar to those of Thalassoplancta cavispicula. Central capsule thin-walled, without oil-globules, four times as broad as the nucleus, which encloses one single nucleolus.

Dimensions.—Diameter of the capsule 0.6, of the nucleus 0.15, of the calymma 4 mm.

Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray.

2. Thalassoplancta brevispicula, n. sp. (Pl. 2, fig. 2).

Lampoxanthium brevispiculum, Haeckel, 1882, Atlas.

Spicula short and thick, thorny, irregularly curved, pointed at both ends, very numerous. In the observed specimen all spicula were aggregated in the outer part of the voluminous calymma, whilst the inner alveolated part was devoid of them. Central capsule thick walled, with a layer of large oil-globules on its inner surface, twice as broad as the large nucleus which contains numerous nucleoli.

Dimensions.—Diameter of the central capsule 0.5, of the nucleus 0.2, of the calymma 2.5.

Habitat.—South Atlantic, Station 334, surface.

Genus 11. Lampoxanthium,^[20] n. gen.

Definition.—Thalassosphærida with numerous large alveoles in the calymma (but not in the central capsule), and with numerous branched or compound spicula in the calymma.

The genus Lampoxanthium differs from the foregoing, Thalassoplancta, by the composite form of the spicula, which are not simple needles, but radiate or geminate, or branched in different forms; the former stands therefore in the same relation to the latter as the social Belonozoum to Sphærozoum. The spicula of some species of Lampoxanthium are identical with those of some species of Sphærozoum, so that the latter may be derived from the former by forming colonies. The large central capsule is enveloped by a very voluminous alveolated calymma, and includes a large central nucleus with numerous nucleoli.

Subgenus 1. Lampoxanthella, Haeckel.

Definition.—Spicula all (or nearly all) of one kind, radiate.

1. Lampoxanthium tetractinium, n. sp.

Spicula all (or nearly all) tetraradiate, with four thorny, straight, pointed shanks, radiating from one common point. (Intermingled with these are often some few, thorny, triradiate spicula.) On the inside of the capsule a layer of large oil-globules as in Thalassoplancta, Pl. 2, fig. 2.

Dimensions.—Diameter of the central capsule 0.2, of the nucleus 0.08, of the calymma 0.8.

Habitat.—South Pacific, Station 288, surface.

Subgenus 2. Lampoxanthomma, Haeckel.

Definition.—Spicula all (or nearly all) of one kind, geminate-radiate, with a simple middle rod and two to four diverging shanks on each end of it.

2. Lampoxanthium punctatum, n. sp.

Spicula all geminate-triradiate, thorny, of the same form as in the common Sphærozoum punctatum, of which this species is the large solitary representative. The spicula are aggregated in a very condensed layer on the surface of the large calymma.

Dimensions.—Diameter of the capsule 0.8, of the nucleus 0.6, of the calymma 2.0.

Habitat.—North Pacific, Station 248, surface.

3. Lampoxanthium octoceras, n. sp.

Spicula all geminate-quadriradiate, with a very short simple middle rod and four very long divergent shanks on both ends of it; the shanks are smooth, five to ten times as long as the middle rod, irregularly bent and curved. (Differs from the similar Thalassoxanthium octoceras, Pl. 2, fig. 6, by slender, more curved shanks, and by the voluminous calymma, there entirely wanting.)

Dimensions.—Diameter of the capsule 0.5, of the nucleus 0.2, of the calymma 3.0.

Habitat.—South Atlantic, Station 331, surface.

Subgenus 3. Lampoxanthura, Haeckel.

Definition.—Spicula of two or three different kinds, simple, radiate, and geminate-radiate mixed.

4. Lampoxanthium pandora, n. sp. (Pl. 2, fig. 1).

Spicula mixed, of three different kinds—simple, radiate and geminate-radiate; all three kinds partly smooth, partly thorny. The simple needles short, thin spindle-shaped, often curved. The radiate spicula commonly with three or four, rarely five or six, unequal rays, straight or curved. The radiate-geminate spicula commonly with three, rarely four, shanks on each end, often different on both ends of the middle rod. The size, number, and form of the irregular spicula are here quite as variable as in the social Rhaphidozoum pandora, of which it is the solitary representative. The wall of the large central capsule is very thick, with evident pore-canals, separated by a clear interval from the coagulated and vacuolated endoplasm, which contains no oil-globules. Nucleus with numerous nucleoli.

Dimensions.—Diameter of the central capsule 0.5 to 0.6, of the nucleus 0.1 to 0.2, of the calymma 2 to 4 mm.

Habitat.—North Pacific, Station 244, surface.

Family IV. Sphærozoida, Haeckel (Pl. 4).

Sphærozoida, Haeckel, 1862, Monogr. d. Radiol., p. 521.

Definition.—Beloidea socialia.

The family Sphærozoida comprises all associated or colony-forming Radiolaria, which are provided with an imperfect skeleton, composed of numerous solid needles or spicula, scattered around the central capsule in the calymma. The structure and form of this skeleton is quite the same as in the preceding solitary Thalassosphærida, but on the other hand, the structure and form of the colonies and of the included numerous central capsules is the same as in the skeletonless Collozoida.

The oldest well-known form of Sphærozoida is the common cosmopolitan Sphærozoum punctatum, probably first observed in 1834 by Meyen, and called Sphærozoum fuscum, afterwards more accurately described by Huxley in 1851.

Other forms were afterwards described by Müller and by myself in 1862.^[21] Further investigations have shown me that some species of this family are among the most common Radiolaria, and occur in astonishing numbers on the surface of all warmer seas. But the number of species is comparatively small, and their distinction is very difficult, as all the different forms are very variable and connected by intermediate forms—a truly "transformistic" group.

The only character sufficient for the constitution of genera in this transformistic group is found in the form and composition of the spicula; the very variable form of the jelly-calymma and the enclosed central capsule being without value for this purpose. But also the form of the spicula is very variable, and not always constant. In some species the particular form of the spicula is transmitted by constant heredity, whilst in others it is very inconstant, even in one and the same individual. (Compare the remarks on variability in the general introduction.)

As the number of various forms is rather great, it seems to be advisable to distinguish the three following genera.

Synopsis of the Genera of Sphærozoida.

A. Spicula all of one kind, simple or needle-shaped, 12. Belonozoum.

B. Spicula all of one kind, branched or radiate, or geminate, 13. Sphærozoum.

C. Spicula of two more different kinds, partly simple, partly branched, 14. Rhaphidozoum.

Genus 12. Belonozoum,^[22] n. gen.

Definition.—Sphærozoida with simple needle-shaped spicula, which are neither radiate nor branched.

The genus Belonozoum comprises the Sphærozoida with simple needle-shaped spicula, and may be regarded as the colonial form of Thalassosphæra or Thalassoplancta, derived from these solitary Beloidea by multiplication of the capsules and union in a common calymma.

1. Belonozoum bacillosum, n. sp.

Sphærozoum bacillosum, Haeckel, 1881, Manuscript.

Spicula all simple rods, straight cylindrical, obtuse at both ends, quite smooth. Central capsule pellucid, with one single central oil-globule.

Dimensions.—Diameter of the central capsule 0.08 to 0.12, length of the spicula 0.05 to 0.08.

Habitat.—Central Pacific, Station 271, surface.

2. Belonozoum spinulosum, Haeckel.

Sphærozoum spinulosum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 54, Taf. viii. fig. 4.

Sphærozoum spinulosum, Haeckel, 1862, Monogr. d. Radiol., p. 527, Taf. xxxiii. figs. 3, 4.

Spicula all simple rods, straight cylindrical, obtuse on both ends, thorny with numerous small spines, placed vertically on the rods.

Dimensions.—Diameter of the central capsule 0.08 to 0.1, length of the spicula 0.05 to 0.2.

Habitat.—Mediterranean, Nice, J. Müller; Messina, Haeckel; Naples, Brandt; surface.

3. Belonozoum italicum, Haeckel.

Sphærozoum italicum, Haeckel, 1862, Monogr. d. Radiol., p. 526, Taf. xxxiii. figs. 1, 2.

Spicula all simple rods, more or less curved or bent, pointed at both ends, quite smooth. Central capsule with a variable number (commonly five to twenty) of oil-globules.

Dimensions.—Diameter of the central capsule 0.1 to 0.3, length of the spicula 0.05 to 0.2.

Habitat.—Mediterranean, Nice, Naples, Messina, Haeckel, surface.

4. Belonozoum atlanticum, n. sp.

Sphærozoum atlanticum, Haeckel, 1881, Manuscript.

Spicula all together simple rods, more or less curved or bent, pointed at both ends, thorny from numerous small spines, placed vertically on the rods.

Dimensions.—Diameter of the central capsule 0.1 to 0.2, length of the spicula 0.07 to 0.15.

Habitat.—Tropical Atlantic, Station 348, surface.

Genus 13. Sphærozoum,^[23] Meyen, 1834, Nova Acta Acad. Nat. Curios., Bd. xvi., Suppl., p. 287 (p. 163).

Definition.—Sphærozoida with branched or radiate spicula of one kind.

The genus Sphærozoum, with Physematium one of the two oldest Radiolaria, observed in the living state, was founded 1834 by Meyen for one of the social Beloidea, which was probably the common cosmopolitan Sphærozoum punctatum, the true type of this genus. Johannes Müller described a number of species, which were partly skeletonless (Collozoum), partly armed with simple or with compound spicula. The species with simple spicula we refer here to Belonozoum, the species with two or more different kinds of spicula to Rhaphidozoum, while we unite in Sphærozoum all species with one kind of branched or compound spicula. The two following species are incompletely known:—Sphærozoum orientale, Dana, 1863, Ann. and Mag. Nat. Hist., vol. xii. p. 54. Sphærozoum sanderi, Dœnitz, 1871, L. N. 60, p. 71.

Subgenus 1. Sphærozonactis, Haeckel.

Definition.—Spicula radiate, not geminate, consisting of three, four, or more needles or shanks, radiating in different directions from one common central point.

1. Sphærozoum triactinium, n. sp.

Spicula all (or nearly all) triradiate, composed of three (or sometimes in few spicula four) needle-like shanks, diverging from one common point. Shanks straight or somewhat curved, smooth, pointed. Central capsules spherical, with one central oil-vesicle. This species may be regarded as the social form of Thalassoxanthium triactinium.

Dimensions.—Diameter of the central capsules 0.1 to 0.12, length of the spicula-shanks 0.05 to 0.1.

Habitat.—South Pacific, Station 295, surface.

2. Sphærozoum medusinum, n. sp.

Spicula all (or nearly all) quadriradiate, composed of four (or sometimes in few spicula three) needle-like shanks (mostly of unequal length), diverging from one common point. Shanks slightly curved, pointed, thorny, covered with small spinules. Central capsules ellipsoidal, containing several (four to eight) oil-vesicles. This species may be regarded as the social form of the solitary Thalassoxanthium medusinum (Pl. 2, fig. 5).

Dimensions.—Diameter of the central capsules 0.15 to 0.18, length of the spicula-shanks 0.08 to 0.12.

Habitat.—North Pacific, Station 236, surface.

3. Sphærozoum hamatum, n. sp.

Spicula all (or nearly all) quadriradiate, composed of four (or sometimes in few spicula three) needle-like shanks, mostly of very different size, diverging from one common point. Shanks strong, straight, curved, or hook-like; thorny, covered with small spinules on the distal extremity. Central capsules ellipsoidal, large, containing many (ten to twenty) oil-globules. This large species is distinguished by the very irregular form and size of the spicula.

Dimensions.—Diameter of the central capsules 0.2 to 0.25, length of the spicula-shanks 0.12 to 0.18.

Habitat.—Central Pacific, Station 265, surface.

4. Sphærozoum hexactinium, n. sp.

Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in few spicula five or seven) needle-like shanks, mostly of equal size, diverging from one common point in two opposite hemispheres (three needles upwards, three needles downwards). Shanks somewhat curved, pointed, smooth. Central capsules spherical, small, with one central oil-globule. This species may be regarded as the social form of Thalassoxanthium hexactinium.

Dimensions.—Diameter of the central capsule 0.06 to 0.08, length of the spicula-shanks 0.05 to 0.06.

Habitat.—North Atlantic, Færöe Channel (Gulf Stream), John Murray.

Subgenus 2. Sphærozonoceras, Haeckel.

Definition.—Spicula all geminate-radiate, consisting of one middle rod, which bears an equal and constant number of rays (two, three, or four) at each end.

5. Sphærozoum furcatum, n. sp.

Spicula all (or nearly all) geminate and simply forked, composed of a simple axial rod and two simple needle-like shanks on each end of it. Shanks straight, pointed, smooth, commonly somewhat longer than the middle rod.

Dimensions.—Diameter of the central capsules 0.1 to 0.15, length of the axial rod of the spicula 0.03, of its shanks 0.04 to 0.06.

Habitat.—Tropical zone of the Atlantic, near Ascension Island, Station 344, surface.

6. Sphærozoum furculosum, n. sp.

Spicula all (or nearly all) geminate and simply forked, composed of a simple axial rod and two simple needle-like shanks on each end of it. Shanks curved or bent, pointed, thorny, with many small spinules, commonly somewhat shorter than the middle rod.

Dimensions.—Diameter of the central capsules 0.2 to 0.25, length of the axial rod of the spicula 0.1, of its shanks 0.05 to 0.08.

Habitat.—South Atlantic, near Tristan da Cunha, Station 334, surface.

7. Sphærozoum ovodimare, Haeckel.

Sphærozoum ovodimare, Haeckel, 1862, Monogr. d. Radiol., p. 527, Taf. xxxiii. figs. 5, 6.

Sphærozoum punctatum, var., Brandt, 1881, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, Taf. i. fig. 54.

Spicula all (or nearly all) geminate and triradiate, composed of a long simple axial rod and three simple needle-like shanks on each end of it. Shanks straight, pointed, smooth, commonly shorter than the middle rod. (Often few furcate or four-rayed spicula are intermixed, or few spicula are not smooth, but thorny.)

Dimensions.—Diameter of the central capsules 0.05 to 0.2, length of the middle rod of the spicula 0.02 to 0.06, of its shanks 0.01 to 0.04.

Habitat.—Mediterranean, Naples, Messina, Haeckel; Atlantic, Canary Islands, Cape Verde Islands, West Coast of Africa, Stations 351 to 354; surface.

8. Sphærozoum trigeminum, n. sp.

Spicula all (or nearly all) geminate-triradiate, composed of a short simple axial middle rod and three simple needle-like shanks on each end of it. Shanks curved or bent, very thin, smooth, commonly much longer than the middle rod. (Often few quadriradiate or few thorny triradiate spicules are interspersed among the others.)

Dimensions.—Length of the middle rod of the spicula 0.02 to 0.04, of its shanks 0.03 to 0.09.

Habitat.—North Pacific, Stations 244 to 248, surface.

9. Sphærozoum punctatum, J. Müller.

Sphærozoum punctatum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 54, Taf. viii. figs. 1, 2.

Sphærozoum punctatum, Haeckel, 1862, Monogr. d. Radiol., p. 528, Taf. xxxiii. figs. 7-9.

Sphærozoum fuscum, Meyen, 1834, Nova Acta Acad. Nat. Cur., vol. xvi. Taf. xxxviii. fig. 7.

Thalassicolla punctata, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2, vol. viii. p. 434, pl. xvi. figs. 1, 2, 3.

Spicula all (or nearly all) geminate-triradiate, composed of a long simple axial middle rod and three simple needle-like shanks on each end of it. Shanks straight, pointed, thorny, with many small spines, commonly somewhat shorter than the middle rod. (Often few furcate or four-rayed spicula are intermingled, or some of the spicula are smooth.) This cosmopolitan species is extremely variable, and produces interesting transitional forms to many other species of the genus. Compare also the general remarks on the genus, and the chapter on "Transformation" in the general introduction.

Dimensions.—Length of the middle rod of the spicula 0.02 to 0.06, of its shanks 0.01 to 0.05.

Habitat.—Cosmopolitan, common in nearly all warmer seas, Mediterranean, Atlantic, Indian Ocean, Pacific; surface.

10. Sphærozoum armatum, n. sp. (Pl. 4, fig. 9).

Spicula all geminate-triradiate, with a stout and short middle rod and three arborescent shanks on each end of it. Shanks longer than the middle rod, very stout, straight, pine-shaped, with six to twelve irregular, spinulated, lateral branches.

Dimensions.—Diameter of the central capsules 0.04 to 0.08, length of the middle rod of the spicula 0.02 to 0.03, of its shanks 0.05 to 0.08.

Habitat.—North Pacific, Japan, Station 239, surface.

11. Sphærozoum alveolatum, n. sp. (Pl. 4, figs. 2, 3).

Spicula all together geminate-triradiate, with a simple stout middle rod and three arborescent shanks on each end of it. Shanks more or less curved, slender, pine-shaped, with four to eight short, thorny lateral branches. In all cœnobia of this remarkable species the central capsules are enclosed in large thick-walled alveoles (of three times their breadth), and in each alveole is placed besides the capsule one single very large spiculum, whilst the others are much smaller (fig. 3). All the alveolated capsules are placed in one single stratum on the surface of the jelly-like spherical cœnobium, comparable to the blastoderm-cells of a blastula.

Dimensions.—Diameter of the central capsules 0.08 to 0.1, of the alveoles 0.2 to 0.4, length of the spicula 0.1 to 0.3.

Habitat.—South Pacific (Juan Fernandez), Station 300, surface.

12. Sphærozoum verticillatum, n. sp. (Pl. 4, fig. 7).

Spicula all geminate-triradiate, with a short simple middle rod and three much longer arborescent shanks on each end of it. Shanks straight, slender, pine-shaped, each in the distal half with three to four elegant verticils of thorny lateral branches.

Dimensions.—Diameter of the capsules 0.1 to 0.12, middle rod of the spicula 0.03 to 0.05, shanks 0.1 to 0.15.

Habitat.—Indian Ocean, Ceylon, Haeckel; Madagascar, Rabbe; surface.

13. Sphærozoum octoceras, n. sp.

Spicula all geminate-quadriradiate, with a short simple middle rod and four diverging shanks on each end of it. Shanks smooth, irregularly curved or bent, three to six times as long as the middle rod. It may be regarded as the social form of Thalassoxanthium octoceras (Pl. 2, fig. 6).

Dimensions.—Diameter of the capsules 0.12 to 0.16, middle rod of the spicula 0.02, shanks 0.01.

Habitat.—Australia, south coast, Faber; Station 163, surface.

14. Sphærozoum quadrigeminum, n. sp.

Spicula all geminate-quadriradiate, with a long thick middle rod and four shorter diverging shanks on each end of it. Shanks straight, thorny.

Dimensions.—Diameter of the capsules 0.06 to 0.08, length of the spicula 0.05 to 0.15.

Habitat.—North Atlantic, Azores, Station 354, surface.

15. Sphærozoum araucaria, n. sp.

Spicula all geminate-quadriradiate, with stout straight middle rod and four longer diverging shanks on each end of it. Shanks arborescent, with six to twelve thorny lateral branches.

Dimensions.—Diameter of the capsules 0.1 to 0.15, length of the spicula 0.05 to 0.1.

Habitat.—South Atlantic, coast of Brazil, Rabbe; surface.

16. Sphærozoum arborescens, n. sp. (Pl. 4, fig. 8).

Spicula all geminate-quadriradiate, with a stout straight middle rod and four longer diverging shanks on each end of it. Shanks arborescent, pine-shaped, with four to six verticils of lateral branches, which again are ramified and thorny.

Dimensions.—Diameter of the capsules 0.16 to 0.18, length of the spicula 0.1 to 0.2.

Habitat.—South Atlantic (Tristan da Cunha), Station 332, surface.

Subgenus 3. Sphærozonura, Haeckel.

Definition.—Spicula all geminate-radiate, but with a different and variable number of shanks on each end of the middle rod.

17. Sphærozoum stellatum, n. sp.

Spicula all geminate-radiate, with a strong middle rod and a variable number of shorter radiating shanks on the two ends of it. Shanks straight, nearly conical, smooth; for the most part three or four shanks on each end, but sometimes also five or six; very often this number is unequal on the two ends.

Dimensions.—Diameter of the central capsules 0.1 to 0.2, length of the spicula 0.05 to 0.15.

Habitat.—Central Pacific, Station 270, surface.

18. Sphærozoum geminatum, n. sp. (Pl. 4, fig. 4).

Spicula all geminate-radiate, with a strong middle rod and a variable number of longer radiant shanks on each end of it. Shanks straight, conical, in the distal half thorny; commonly either three or four shanks on each end of the middle rod, often also three on one end, four on the other end; rarely five or six rays on one end.

Dimensions.—Diameter of the capsules 0.15 to 0.2, length of the spicula 0.05 to 0.1.

Habitat.—Indian Ocean, Ceylon, Haeckel; surface.

19. Sphærozoum circumtextum, n. sp.

Spicula all geminate-radiate, with a very variable number of rays (two to six) on each end of the thin middle rod. All spicula very thin and delicate, smooth, with curved or bent shanks, densely covering the central capsule like a cobweb. The number of rays on each end is usually different, generally four or five, often also two or three, rarely six.

Dimensions.—Diameter of the capsule 0.1 to 0.2, length of the spicula 0.04 to 0.12.

Habitat.—Southeast part of the Indian Ocean, Station 160, surface.

20. Sphærozoum variabile, n. sp. (Pl. 4, fig. 5).

Spicula all geminate-radiate, with a short middle rod and a variable number of shanks on each end of it. Shanks four to eight times as long as the middle rod, curved or bent, in the distal half thorny; their number is commonly different on the two ends of it, three or five, often also four or six, rarely two; their size and form very variable.

Dimensions.—Diameter of the capsules 0.1 to 0.3, length of the spicula 0.1 to 0.2.

Habitat.—North Pacific, Station 248, surface.

Genus 14. Rhaphidozoum,^[24] Haeckel, 1862, Monogr. d. Radiol., p. 529.

Definition.—Sphærozoida with two or more different kinds of spicula; one kind simple, needle-shaped; the other kinds compound, radiate, or branched.

The genus Rhaphidozoum differs from Sphærozoum by the composition of the skeleton of two or more different kinds of spicula, and has therefore the same relation to it as the solitary Lampoxanthura to Lampoxanthella.

In some species nearly all the different forms, which characterise the numerous species of Beloidea, may be united in one and the same individual.

Subgenus 1. Rhaphidonactis, Haeckel.

Definition.—Spicula of two different kinds; one kind simple, needle-shaped, the other radiate (composed of three, four, or more shanks, diverging from one common point).

1. Rhaphidozoum pelagicum, n. sp.

Spicula of two different kinds; one kind simple thin needles, a little curved or bent, the other kind triradiate, with three thin, curved shanks. Both kinds smooth, without thorns. Resembles a combination of Belonozoum italicum and Sphærozoum triactinium.

Dimensions.—Diameter of the central capsules 0.1 to 0.12, length of the spicula 0.05 to 0.15.

Habitat.—Central Pacific, Station 267, surface.

2. Rhaphidozoum pacificum, n. sp.

Spicula of two different kinds; one kind simple needles, stout and straight, pointed at both ends, the other kind triradiate, with three straight and stout shanks. Both kinds thorny.

Dimensions.—Diameter of the central capsule 0.06 to 0.08, length of the spicula 0.05 to 0.1.

Habitat.—Central Pacific, Station 271, surface.

3. Rhaphidozoum acuferum, Haeckel.

Rhaphidozoum acuferum, Haeckel, 1862, Monogr. d. Radiol., p. 529, Taf. xxxii. figs. 9-11.

Sphærozoum acuferum, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 54, Taf. viii. fig. 3.

Thalassicolla acufera, J. Müller, 1855, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 237.

Spicula of two different kinds, simple needles and quadriradiate; both strong, thorny, covered with small spinules. Simple needles mostly curved, C-shaped. Four shanks of the quadriradiate spicula now straight, now curved, commonly of very different size. (Often one single quadriradiate spiculum is distinguished by its extraordinary size.) For the detailed description of this species compare my Monograph (loc. cit.).

Dimensions.—Diameter of the central capsules 0.05 to 0.35, length of the simple needles 0.05 to 0.25, shanks of the quadriradiate spicula 0.05 to 0.15.

Habitat.—Mediterranean, Messina, Naples, Nice.

4. Rhaphidozoum arachnoides, n. sp.

Spicula of two different kinds; one kind simple, needle-like, the other quadriradiate; both very thin and slender, smooth, without spicules. Simple needles curved, C-shaped. Four shanks of the quadriradiate spicula also curved, commonly of nearly equal size. The numerous thread-like spicula of this species are so densely packed around the central capsule, that they extend all around its surface like the network round a balloon.

Dimensions.—Diameter of the central capsules 0.12 to 0.15, length of the simple needles 0.1 to 0.12, shanks of the quadriradiate spicula 0.06 to 0.08.

Habitat.—Tropical Atlantic, Station 345, surface.

5. Rhaphidozoum asperum, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, stout, and straight, the other kind hexaradiate; its six shanks about half as long as the former, conical. Both kinds very thorny, covered with short conical spinules.

Dimensions.—Diameter of the capsules 0.06 to 0.08, length of the simple needles 0.05 to 0.07, shanks of the hexaradiate spicula 0.03 to 0.04.

Habitat.—South Pacific, Station 288, surface.

Subgenus 2. Rhaphidoceras, Haeckel.

Definition.—Spicula of two different kinds; one kind simple, needle-shaped, the other kind geminate-radiate, with rays on both poles of a middle rod.

6. Rhaphidozoum neapolitanum, Haeckel.

Sphærozoum neapolitanum, C. Brandt, 1881, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 390, Taf. i. figs. 14, 16-18.

Spicula mixed, of two different kinds; simple needles and geminate-forked. Simple rods, like those of Belonozoum italicum, more or less curved, pointed at both ends, smooth (sometimes a little thorny at both ends). Geminate spicula simply forked, like those of Sphærozoum furcatum, composed of a short, simple, axial rod, and two simple, smooth, straight shanks on each end of it, commonly somewhat longer than the middle rod. This species, which I have observed myself in Spezzia in great quantity, is quite as variable as all the other species of the genus, and has not more claim to specific rights than the others. Commonly the simple needles are much more numerous than the geminate-forked, but sometimes the contrary is the case. On their variability compare the general remarks on the genus, and the chapter on "Transformation" in the general introduction.

Dimensions.—Length of the simple spicula 0.05 to 0.1, of the middle rod of the forked spicule 0.05 to 0.08, of their shanks 0.01 to 0.03.

Habitat.—Mediterranean, Naples, Spezzia, surface.

7. Rhaphidozoum patagonicum, n. sp.

Spicula mixed, of two different kinds, simple needles and geminate-triradiate. Simple rods, like those of Belonozoum spinulosum, straight, thorny, pointed at both ends. Geminate spicula double-triradiate, like those of Sphærozoum punctatum, composed of a simple, short, axial rod and three simple pointed shanks on each end of it. Shanks straight, thorny, with many small spinules, commonly somewhat longer than the middle rod. (Often some of the spicula of both kinds are smooth, not thorny, or not straight, but a little curved, or a few forked or four-radiated geminate spicula are mingled with the others.)