Report on the Radiolaria/Colloidea

by Ernst Haeckel

SYSTEMATIC PART.

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Class RADIOLARIA.

Radiolaria, Johannes Müller, 1858.
Rhizopoda radiaria, Johannes Müller, 1858.
Polycystina (pro parte), Ehrenberg, 1838.
Echinocystida, Claparède, 1858.
Rhizopoda capsularia, Haeckel, 1861.
Cytophora, Haeckel, 1862.

Definition of the Class:—Rhizopoda with unicellular body, divided by a porous membrane into an internal or intracapsular part (with nucleus), and an external or extracapsular part (with calymma); propagating by flagellated spores.

The Radiolaria or Capsulate Rhizopoda, first constituted by Johannes Müller in the year 1858 as a separate group of the Rhizopoda, form a peculiar class of the Protista, or unicellular organisms. This class is exclusively marine, and has in general the characteristic organisation of the Rhizopoda, with the development of numerous pseudopodia from the surface of the cell; but it differs from all other Rhizopoda in the possession of a peculiar membrane, dividing the cell-body into two different parts; the central capsule or the internal part with the nucleus, and the external part or extracapsulum with the calymma; propagation by flagellated spores produced in the central capsule; the sarcode or the protoplasm of both parts communicates by fine pores, piercing the separating membrane, which is called the capsule-membrane.

The Central Capsule or the inner part of the Radiolarian body is constantly composed of three essential parts, viz.:—

1. The Central Nucleus (a true cell-nucleus).

2. The Intracapsular Sarcode (endosarc) or surrounding internal protoplasm.

3. The Capsule Membrane or enveloping porous membrane.

Besides these constant and essential elements, the central capsule contains very commonly (but not constantly) some other enclosed structures, viz.:—

4. An internal or intracapsular skeleton.

5. Intracapsular vacuoles or alveoli.

6. Fat-granules or oil-globules.

7. Crystals of different composition.

8. Pigment-granules.

The Extracapsulum, or the outer part of the Radiolarian body is also constantly composed of three essential elements,—

1. The Calymma, or the thick extracapsular jelly-veil, completely enveloping the whole central capsule.

2. The Matrix, or the maternal tissue of the external protoplasm, enveloping immediately the capsule-membrane as a thin continuous layer of extracapsular sarcode (ectosarc).

3. The Pseudopodia, or the very numerous thread-like filaments of protoplasm, which radiate from the matrix; whilst their inner part is enclosed in the calymma, their outer part floats freely in the sea-water.

Besides these three constant and essential elements, the extracapsulum contains very commonly (but not constantly) some other enclosed structures, viz.:—

4. An external or extracapsular skeleton.

5. Extracapsular vacuoles or alveoli.

6. Fat-granules or oil-globules.

7. Pigment-granules or a peculiar large body of dark extracapsular pigment, the "phæodium."

8. "Xanthellæ" or "zooxanthellæ," peculiar yellow cells, which contain starch and are unicellular yellow Algæ, living as "Symbiontes" in true Symbiosis with a great many Radiolaria.

The Nucleus of the Radiolaria is a large true simple cell-nucleus, originally a solid spherical, roundish or longish body of nuclein. It is placed either in the centre of the capsule (in most Peripylea) or excentrically (in most other Radiolaria). Originally solid, the nucleus is commonly differentiated later into an outer dense nuclear-membrane and an inner softer or fluid content; either with one single nucleolus or with a variable number of nucleoli. Originally always simple, the nucleus becomes afterwards constantly divided into numerous small nuclei, each of which, together with a part of the surrounding protoplasm, forms a vibratile-spore or "flagellate-spore." This division in the Acantharia and in the social (or colonial) Peripylea begins very early, in all other Radiolaria much later, immediately before propagation.

The Endoplasm or "endosarc," or "intracapsular protoplasm" or "inner sarcode," in all Radiolaria originally fills that space within the capsule, which is not taken up by the nucleus. It seems to be employed mainly for the purpose of propagation, becoming divided earlier or later into numerous small particles, each of which surrounds a small particle of the nucleus and forms together with it a flagellate-spore. Besides this the endoplasm of the Radiolaria seems to have a great significance for the nutrition, mainly for the interchange of materials. It becomes very often vacuolate or alveolate, filled with smaller or larger spherical drops of fluid; it produces very commonly smaller fat-granules or larger oil-globules, and further pigment-granules of different colours, more rarely crystals and other peculiar enclosed parts.

The Membrane or "capsule-membrane" is the most typical and characteristic part of the body of a Radiolarian, sufficient of itself to separate this class from all other Rhizopoda. At the same time, by its different shape it presents the best means for the systematic distinction of the four subclasses or "legions" of the class. The membrane is composed of a special organic matter (probably nearly related to chitin) and combines density with elasticity to a high degree. Observed with a high power of the microscope its margin (or section) appears commonly simple-edged, but often in larger forms distinctly double-edged.

The legion Phæodaria is distinguished by a double membrane (the thinner inner and thicker outer membranes being separated by an interval); in the three other legions it is simple. The membrane completely separates the intracapsular from the extracapsular body, both communicating only by certain pores or openings in the membrane. With reference to this important communication, the whole class can be divided into two subclasses, Holotrypasta and Merotrypasta: the Holotrypasta contain the Peripylea and Actipylea, in which the membrane is pierced by innumerable very small pores; the Merotrypasta consist of the Monopylea and the Cannopylea, in which the membrane exhibits only one large main opening, distinguished in the former by a peculiar "porous area," in the latter by an "osculum" or a prolonged tubule.

The Calymma or "jelly-veil" is the most characteristic part of the extracapsular body in all Radiolaria; in the majority of the class it is the most voluminous part of the whole body, being much more voluminous than all the other parts taken together. The calymma is a structureless, clear, and transparent jelly-envelope which always includes the whole central capsule and often also the whole extracapsular skeleton. Owing to the high degree of its consistence, this jelly-veil takes a very important part in the formation of the extracapsular skeleton, furnishing the matrix for the deposition of its tangential parts.

The Matrix or the "maternal tissue of the pseudopodia" is formed in all Radiolaria by the thin layer of exoplasm or of extracapsular sarcode, which immediately envelops the central capsule and is itself enclosed by the calymma. This continuous sarcode-cover of the capsule communicates by its pores or openings with the endoplasm or the intracapsular sarcode; whilst from its outer surface arise the pseudopodia. The morphological signification of the matrix is very small, but the physiological importance is very great, for it seems to be the chief organ of many vital functions.

The Pseudopodia or the very fine, long, thread-like filaments of exoplasm arise in all Radiolaria in very great numbers from the surface of the matrix, and exhibit in general the same characteristic shape as in the other Rhizopoda. Their inner or proximal part is enclosed within the jelly-veil or calymma, whilst their outer or distal part floats freely in the sea-water. Their special motions and modifications exhibit considerable variations in different groups, their tendency to ramify, anastomose, and form networks being in some cases very small, in others very great. Also the characteristic motion of granules in the pseudopodia is very different. In general those most important exoplasmatic filaments serve as organs both for the vegetative functions of nutrition, and for the animal functions of motion and sensation.

The class Radiolaria can be divided according to its varying structure into four different legions or subclasses, the characters of which are the following:—

I. PERIPYLEA or SPUMELLARIA.

Membrane of the central capsule simple, perforated by innumerable very fine pores. Fundamental form originally homaxon or spherical. Skeleton wanting or siliceous. No phæodium in the extracapsular calymma. The Peripylea comprise two orders:—

A. Collodaria (without lattice-shell).
B. Sphærellaria (with lattice-shell).

II. ACTIPYLEA or ACANTHARIA.

Membrane of the central capsule simple, perforated by innumerable fine pores. Fundamental form originally homaxon or spherical. Skeleton acanthinic (not siliceous). No phæodium in the extracapsular calymma. The Actipylea consist of two orders:—

A. Acanthometra (without complete lattice-shell).
B. Acanthophracta (with complete lattice-shell).

III. MONOPYLEA or NASSELLARIA.

Membrane of the central capsule simple, perforated by a porous-area, or by one single large opening, divided into numerous very fine pores. Fundamental form originally monaxon or egg-shaped. Skeleton siliceous. No phæodium in the extracapsular calymma. The Monopylea comprise two orders:—

A. Plectellaria (without complete lattice-shell).
B. Cyrtellaria (with complete lattice-shell).

IV. CANNOPYLEA or PHÆODARIA.

Membrane of the central capsule double, perforated by one simple main-opening, prolonged into a tubulus, and besides this commonly by one or two (rarely more) small accessory openings. Fundamental form originally monaxon or egg-shaped. Skeleton siliceous. Constantly a peculiar dark pigment-body or "phæodium" in the extracapsular calymma. The Cannopylea comprise two orders:—

A. Phæocystina (without lattice-shell).
B. Phæocoscina (with lattice-shell).

Synopsis of the four Subclasses or Legions of Radiolaria.

A. HOLOTRYPASTA.		B. MEROTRYPASTA.
Central capsule everywhere perforated by innumerable small pores.		Central capsule with one large main-opening (with or without small accessory openings).
Fundamental form originally homaxon (spherical or derived from a sphere).		Fundamental form originally monaxon (egg-shaped or perhaps dipleural).
I.	II.	III.	IV.
Spumellaria.	Acantharia.	Nassellaria.	Phæodaria.
(Peripylea.)	(Actipylea.)	(Monopylea.)	(Cannopylea.)
Wall-pores of the capsule equally disposed.	Wall-pores of the capsule symmetrically disposed.	Main-opening of the capsule with a porous operculum.	Main-opening of the capsule with a short tubule.
Skeleton siliceous or wanting.	Skeleton acanthinic (organic).	Skeleton siliceous (rarely wanting).	Skeleton siliceous (rarely wanting).
Calymma without phæodium.	Calymma without phæodium.	Calymma without phæodium.	Calymma constantly with a phæodium.

Legion I. SPUMELLARIA,

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

Spumellaria (exclusis Spyridinis), Ehrenberg, 1875.
Peripylea (inclusis Thalassicollis et Sphærozois), Hertwig, 1879.
Peripylaria (inclusis Collodariis et Polycyttariis), Haeckel, 1881.

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.^[1] 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.^[2]

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.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	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.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \\\ \\\ \ \end{matrix}}\right.}$	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.

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Order I. COLLODARIA, Haeckel, 1881.

Collodaria, Haeckel, Prodromus, 1881, p. 469.
Collida et Sphærozoida, Haeckel, 1862, Monogr. d. Radiol., pp. 246, 522.

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.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	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.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Solitary cells, living as isolated individuals (Beloidea monozoa),	3. Thalassosphærida.
		Associated cells, living in colonies or cœnobia (Beloidea polyzoa),	4. Sphærozoida.

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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.

Thalassicollida, Haeckel, 1862, Monogr. d. Radiol., p. 246.
Thalassicollida, Haeckel, 1881, Prodromus, p. 469.

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.^[3] 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.^[4] A very accurate histological description of these forms was given in 1876 by Richard Hertwig.^[5] 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.^[6]

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.	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Nucleus spherical (sometimes ellipsoidal), not branched,	1. Actissa.
B. Numerous large alveoli within the central capsule (not in the calymma).	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	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.	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Nucleus spherical,	4. Thalassicolla.
		Nucleus branched or covered with radial sacs,	5. Thalassophysa.

Genus 1. Actissa,^[7] 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,^[8] 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,^[9] 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,^[10] 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,^[11] 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,^[12] 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.

1. Sitzungsb. med.-nat. Gesellsch. Jena, February 16, 1883.
2. Loc. cit.
3. Abhandl. d. k. Akad. d. Wiss. Berlin, 1858, p. 28.
4. Monogr. d. Radiol., 1862, Taf. ii. p. 253.
5. Histologie der Radiolarien, pp. 43-73, Taf. iii.-v.
6. Sitzungsb. med.-nat. Gesellsch. Jena, February 16, 1883.
7. Actissa = Radiant, ἀκτίς.
8. Thalassolampe = Sea-scum; θάλασσα and λάμπη.
9. Thalassopila = Sea-ball; θάλασσα, πίλα.
10. Thalassicolla = Sea-jelly, θάλασσα, κόλλα.
11. Thalassophysa = Sea-bladder; θάλασσα, φῦσα.
12. Collozoum = Jelly-animal; κόλλα, ζῶον.