Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria and Acantharia)

Chapter XI: Literature and History (3)

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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 {30}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 { Spicula simple, 7. _Thalassosphæra_.
nor without the {
central capsule. { Spicula branched, 8. _Thalassoxanthium_.

B. Numerous large alveoles }
within the central } Spicula simple, 9. _Physematium_.
capsule (not in the }
calymma). }

C. Numerous large alveoles { Spicula simple, 10. _Thalassoplancta_.
within the calymma (not {
in the central capsule). { 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. {31}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.

{32}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.

{33}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.

{34}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 {35}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.

{36}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.

{37}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 {38}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.

{39}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.

{40}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_, Doenitz, 1871, L. N. 60, p. 71.

{41}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, {42}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.

{43}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 coenobia 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 {44}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 coenobium, 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.

{45}_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.

{46}_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 {47}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 {48}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.)

_Dimensions._--Diameter of the central capsules 0.08 to 0.2, length of the simple spicula 0.1 to 0.15, of the geminate 0.08 to 0.16.

_Habitat._--South Pacific, west coast of Patagonia, Station 302, surface.

8. _Rhaphidozoum ascensionis_, n. sp.

Spicula mixed, of two different kinds, simple needles and geminate-triradiate; both kinds thin, smooth, without spinules. Simple needles somewhat curved, C- or S-shaped. Geminate spicula double-triradiate, composed of a simple, short, straight axial rod and three slender curved shanks on each end of it. Shanks two to four times longer than the middle rod. (Sometimes few simple hexaradiate and geminate tetraradiate spicula are mingled.)

_Dimensions._--Diameter of the central capsules 0.12 to 0.15, length of the simple spicula 0.1, of the double-triradiate 0.05 to 0.2.

_Habitat._--South Atlantic, off Ascension Island, Station 342, surface.

9. _Rhaphidozoum capense_, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, straight, pointed at both ends, the other kind geminate-quadriradiate, with a stout short middle rod and four longer bent shanks on each end of it. Both kinds smooth.

_Dimensions._--Diameter of the capsules 0.2 to 0.25, length of the simple needles 0.01 to 0.3, of the geminate spicula 0.05 to 0.15.

_Habitat._--Cape of Good Hope (Agulhas), Station 142, surface.

10. _Rhaphidozoum australe_, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, curved, thin; the other kind geminate, with a variable number of shanks on both ends of the shorter middle rod, often {49}different on the two poles of it. The prevalent number of rays on each end is three or four, often also two or five, rarely six. All spicula smooth, more or less bent.

_Dimensions._--Diameter of the capsules 0.1 to 0.2, length of the spicula 0.05 to 0.15.

_Habitat._--South West Pacific, Station 165, surface.

Subgenus 3. _Rhaphidonura_, Haeckel.

_Definition._--Spicula of three different kinds: one kind simple, needle-shaped; the second kind radiate, with three to six shanks radiating from a common central point; the third kind geminate-radiate, with rays on both poles of a middle rod.

11. _Rhaphidozoum polymorphum_, n. sp.

Spicula of three different kinds; simple needles, radiate, and geminate mixed. The simple needles straight and stout. The radiate spicula commonly with three or six, rarely four or five, rays. The geminate-radiate spicula prevalent, with three or four, rarely two or five, shanks on each end of the middle rod. Number very variable. All shanks straight and smooth.

_Dimensions._--Diameter of the capsule 0.1 to 0.2, length of the spicula 0.05 to 0.15.

_Habitat._--South Pacific, Station 295, surface.

12. _Rhaphidozoum pandora_, n. sp. (Pl. 4, fig. 6).

Spicula of three different kinds; simple needles, radiate and geminate mixed. The simple needles thin spindle-shaped, often curved. The radiate spicula commonly with three or four, rarely five or six, curved rays. The geminate-radiate spicula commonly with three or four, rarely two or five, shanks on each end, often different on the two ends of the middle rod. Number and form very variable. All or most of the shanks more or less bent and thorny.

_Dimensions._--Diameter of the capsule 0.1 to 0.3, length of the spicula 0.05 to 0.2.

_Habitat._--South Atlantic (near Ascension Island), Station 343, surface.

----

Order II. SPHÆRELLARIA, Haeckel, 1881.

_Sphærellaria_, Haeckel, 1881, Prodromus, p. 421.
_Sphæridea_ vel _Peripylea_, Hertwig, 1879, Organismus der Radiol., p.
133.

_Definition._--SPUMELLARIA with latticed or spongy shell.

The order #Sphærellaria#, the second order of Radiolaria, comprises all those SPUMELLARIA in which the skeleton is a latticed or fenestrated, often more or less spongy, siliceous shell. Originally this shell is a simple extracapsular lattice-sphere, in which the central capsule is included; from this simple ancestral form an enormous {50}mass of different and often very complicated forms is derived; this order is by far the largest, and in morphological respects the most important and most interesting, of all Radiolaria. It contains not less than twenty-eight different families, three hundred and five genera, and more than sixteen hundred species.

In my Monograph (1862) seven families appertaining to this group are described--the Ethmosphærida, Cladococcida, Ommatida, Spongurida, Discida, Lithelida, and Collosphærida. The astonishing increase of this group by the detection of a large series of new and interesting forms, and particularly of important connecting forms between very different branches of it, now enables me to give a much better arrangement. I discern now four suborders or sections of #Sphærellaria#, according to the different geometrical form of the central capsule and of the latticed shell enveloping it. The first of these, and the common ancestral group of the whole order, is the #Sphæroidea#, with spherical capsule; in the #Prunoidea# it becomes ellipsoidal or cylindrical by prolongation of one axis; in the #Discoidea# lenticular or discoidal by shortening of one axis; in the #Larcoidea# lentelliptical, or triaxon-ellipsoid, by different growth of the capsule in three different "dimensive axes."

_Synopsis of the Four Suborders of_ #Sphærellaria#.

Central capsule { Shell a simple sphere or a
spherical. { system of concentric spheres, 1. #Sphæroidea#.

Central capsule { Shell a simple ellipsoid or a
ellipsoidal or { cylinder with annular
cylindrical. { transverse constrictions, 2. #Prunoidea#.

Central capsule
lenticular or { Shell a biconvex lens or a
discoidal. { flat disk, 3. #Discoidea#.

Central capsule
lentelliptical or { Shell a triaxon-ellipsoid, with
triaxon. { three different axes, 4. #Larcoidea#.

----

Suborder I. SPHÆROIDEA, Haeckel.

_Sphæroida_, _Sphæridea_, _Sphærida_, Haeckel, 1878, Protistenreich, p.
103.
_Sphæridea_, R. Hertwig, 1879, Organismus der Radiol., p. 39.

_Definition._--SPUMELLARIA with spherical central capsule (very rarely somewhat modified, or allomorphous); with spherical fenestrated siliceous shell (often an endospherical polyhedron, very rarely of more modified, subspherical form or allomorphous). Growth of the shell in the three dimensive axes equal.

The suborder #Sphæroidea#, the first and most important of the four of the #Sphærellaria#, comprises those SPUMELLARIA in which the original geometrical {51}spherical form is quite constantly preserved in the central capsule, and commonly also in the fenestrated shell enveloping the latter, although in many forms the sphere is more or less modified; very frequently it is an "endospherical polyhedron," _i.e._, a polyhedron all the angles (or the nodes of the network) of which lie upon the surface of a geometrical sphere; more rarely the spherical form is more or less modified and irregular. In the great majority of #Sphæroidea# there is no external indication of the three dimensive axes; but in many forms they are indicated by the regular position of certain external radial spines or internal radial beams. However, in no case are those three axes expressed in the form of the shell itself and of the enclosed spherical central capsule; this is the main character by which the #Sphæroidea# differ from the following sections:--#Prunoidea#, #Discoidea#, #Larcoidea#, all three of which arise from them.

The section #Sphæroidea#, in the sense here restricted, was founded by me in my Protistenreich (1878, p. 103) and adopted by Hertwig (1879) in his Organismus der Radiolarien (p. 39). The different groups appertaining to this large section were characterised more accurately in my Prodromus (1881, pp. 448-456); there I gave the characters of six subfamilies with thirty tribes, containing ninety-three genera. Formerly, in my Monograph (1862), the #Sphæroidea# were disposed in five different families:--Ethmosphærida, Cladococcida, Ommatida, Spongosphærida, Collosphærida. At that time I could not separate them sufficiently from some ACANTHARIA and PHÆODARIA, which have a similar spherical lattice-shell.

As the number of different genera and species in the #Sphæroidea# is much greater than in all other sections of SPUMELLARIA, many forms were already described by former authors. In the oldest system of Ehrenberg (1847, _loc. cit._, p. 53) they represent one part of his Haliommatina (with four genera, _Haliomma_, _Chilomma_, _Stylosphæra_, _Spongosphæra_). Most species, however, of these genera are #Discoidea#. Also in the latest system of Ehrenberg (1875, _loc. cit._, p. 157) his Haliommatina are a confused conglomeration of different SPUMELLARIA (#Sphæroidea#, #Discoidea#, and #Prunoidea#).

The section #Sphæroidea# is the largest division of #Sphærellaria#, comprising not less than one hundred and seven genera and six hundred and fifty species. This enormous number (easily to be augmented by further investigations) requires a careful disposition in different families and subfamilies. For this disposition two different principles only can be employed: firstly, the number and disposition of the _radial spines_; secondly, the number of the _concentric latticed spheres_, which are connected by radial beams. I give here the preference to the first principle, whilst in my Prodromus (1881) I had preferred the second. The question, which of the two principles is more important for the classification of #Sphæroidea#, is very difficult to answer; probably in many cases the former, in many the latter is more important for their phylogeny.

{52}Regarding the number of the concentric shells which compose the latticed carapace of the #Sphæroidea#, we can distinguish six families, viz.:--

I. Monosphærida (with one single shell).
II. Dyosphærida (with two concentric shells).
III. Triosphærida (with three concentric shells).
IV. Tetrasphærida (with four concentric shells).
V. Polysphærida (with five or more concentric shells).
VI. Spongosphærida (with spongy shells).

On the other hand, regarding the number of the radial spines and their regular disposition on the shell-surface, we can distinguish five families, viz.:--

I. Liosphærida (without radial spines).
II. Stylosphærida (with two radial spines, opposite in one axis).
III. Staurosphærida (with four radial spines, opposite in pairs in two
axes, perpendicular one to another).
IV. Cubosphærida (with six radial spines, opposite in pairs in the
three dimensive axes).
V. Astrosphærida (with numerous--eight, twelve, twenty, or
more--radial spines, often more than a hundred).

All five latter groups contain representatives of all six former groups; therefore we get together not less than thirty different subfamilies of #Sphæroidea#, already enumerated in my Prodromus, 1881, p. 449. I repeat them here to give a better survey of the system there employed.

{53}The #Monosphærida# comprise all those #Sphæroidea# in which the carapace is represented only by one single lattice-shell. Originally this shell is probably everywhere an extracapsular or "cortical shell," which is developed on the outside of the jelly-veil enveloping the central capsule, and serves as a protective carapace for these soft enclosed parts. But with the progress of growth the central capsule becomes larger than the including shell, and sends out through its pores club-shaped prolongations or cæcal-sacs (Pl. 11, figs. 1, 5; Pl. 19, figs. 2, 3, 5; Pl. 20, fig. 1_a_; Pl. 27, fig. 3). These protruded sacs may fuse together again outside the shell and form a spherical bladder, now enveloping the smaller shell; the latter now becomes an intracapsular or "medullary shell."

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Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria and Acantharia)Chapter XI: Literature and History (3)

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