1. Sagena ternaria, n. sp. (Pl. 108, fig. 8).

Network subregular, with equilateral triangular meshes, intermingled with single irregular meshes (fig. 8). Bars of the network smooth, its nodal points solid, not pierced.

Dimensions.—Diameter of the spherical shell 1.5 to 2.5, length of the bars 0.1 to 0.2, breadth 0.002 to 0.005.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, surface.

2. Sagena pertusa, n. sp.

Network subregular, with nearly equal triangular meshes. Bars of the network smooth, its nodal points pierced by a circular hole.

Dimensions.—Diameter of the shell 1.2 to 1.8, length of the bars 0.2 to 0.25, breadth 0.003.

Habitat.—Central Pacific, Stations 270 to 274, surface.

3. Sagena triangula, n. sp.

Network very regular, with equilateral triangular meshes. Bars of the network spinulate, like those of Sagoplegma spinulosa. (Pl. 108, fig. 14), its nodal points solid, not pierced.

Dimensions.—Diameter of the shell 2.2, length of the bars 0.25, breadth 0.004.

Habitat.—South Atlantic, Station 325, surface.

4. Sagena crucifera, n. sp.

Network more or less irregular, with unequal triangular meshes. Bars of the network studded with scattered, rectangular, minute crosses, arising perpendicularly, each cross composed of four small equal bars. Nodal points partly solid, partly pierced by a hole. Network very similar to that of Dictyosoma trigonizon, figured in my Monograph, Taf. xxvi. figs. 4, 5.

Dimensions.—Diameter of the shell 1.5, length of the bars 0.1 to 0.2, breadth 0.003.

Habitat.—Mediterranean, Atlantic, Canary Islands, Station 353, surface.

Genus 676. Sagosphæra,^[295] n. gen.

Definition.—Sagosphærida with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate, and bears on its nodal points radial spines.

The genus Sagosphæra differs from the preceding Sagena, its ancestral form, in the development of radial spines on the nodal points of the simple delicate lattice-sphere. It exhibits therefore the same relation to the latter as Aulosphæra bears to Aularia. The regular or subregular triangular meshes of the lattice-sphere are separated in Sagosphæra by solid, very thin threads, in the similar Aulosphæra, however, by thicker hollow tubes. The genus Sagosphæra may be divided into two subgenera:—Sagosphærella with a single radial spine at each nodal point of the network, and Sagosphæroma with a bunch of two to four or more divergent radial spines.

1. Sagosphæra trigonilla, n. sp.

Radial spines simple, straight, smooth, about as long as the smooth bars of the network, a single one at each nodal point. Meshes very regular, of equal size, equilateral triangular. (Similar to the common Aulosphæra trigonopa.)

Dimensions.—Diameter of the sphere 1.2 to 1.8, length of the bars 0.1 to 0.2, breadth 0.002 to 0.006.

Habitat.—Cosmopolitan; Mediterranean, Atlantic, Pacific, surface.

2. Sagosphæra penicilla, n. sp. (Pl. 108, fig. 10).

Radial spines straight, stout, a single one at each nodal point, twice as thick, but of the same length as the smooth bars of the network, armed at the distal end with a brush of numerous thin radial bristles. (Very similar to Sagenoscena penicillata, but without pyramidal elevations on the surface of the sphere.)

Dimensions.—Diameter of the sphere 1.0 to 1.5, length of the bars 0.1 to 0.15, breadth 0.002 to 0.004.

Habitat.—Antarctic Ocean, Station 154, surface.

3. Sagosphæra verticilla, n. sp.

Radial spines slender, slightly curved, a single one at each nodal point, armed with three to five cruciate verticils, each of which is composed of four crossed lateral branches with spinulate terminal knobs (similar to Sagmidium crucicorne, Pl. 108, fig. 9), but with a spherical shell, having a simply latticed, and not a spongy wall.

Dimensions.—Diameter of the sphere 2.0 to 2.5, length of the bars 0.1 to 0.2, breadth 0.002.

Habitat.—North Pacific, Station 256, surface

4. Sagosphæra furcilla, n. sp. (Pl. 108, figs. 11, 11a).

Radial spines short, spinulate, with a spiny terminal knob (fig. 11a), two or three arising from each nodal point of the network in divergent directions, only one-third or one-fourth as long as its smooth bars. Meshes more or less irregular, triangular.

Dimensions.—Diameter of the sphere 2.2, length of the bars 0.2 to 0.3, breadth 0.004.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

5. Sagosphæra coronilla, n. sp.

Radial spines slender, smooth, three to six arising from each nodal point of the network in divergent directions, about as long as its smooth bars, crowned at the distal end with a bunch of twenty to thirty radial terminal branches, and provided with a spinulate knob at the distal end (similar to Sagenoscena stellata, Pl. 108, fig. 3).

Dimensions.—Diameter of the sphere 3.0, length of the bars 0.1 to 0.2, breadth 0.002.

Habitat.—Central Pacific, Station 271, depth 2425 fathoms.

Genus 677. Sagoscena,^[296] n. gen.

Definition.—Sagosphærida with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate and covered with numerous pyramidal elevations; each pyramid bears on its top one or more radial spines, but has no axial rod in its radial axis.

The genus Sagoscena, and the following closely allied Sagenoscena (both very common and widely distributed), exhibit a peculiar and very remarkable structure of the delicate lattice-shell, similar to that which Auloscena represents among the Aulosphærida. The surface of the simple spherical lattice-shell is covered with numerous pyramidal or tent-shaped elevations. These elegant and delicate pyramids are, however, in Sagoscena usually not so regular as in the similar Auloscena; the edges of the pyramids are in the latter hollow cylindrical tubes, in the former thin solid threads. The top of each pyramid usually bears a bunch of apical spines.

1. Sagoscena castra, n. sp. (Pl. 108, fig. 1).

Pyramids subregular, of equal size and similar form, usually three-sided, crowned at the top with three divergent apical spines, which alternate with the three edges of the pyramids and bear a small spinulate terminal knob. (Some four-sided and single five-sided pyramids are often intermingled with the three-sided.)

Dimensions.—Diameter of the sphere 1.7 to 2.3, length of the bars 0.2 to 0.25, breadth 0.008.

Habitat.—South-Eastern Pacific, Stations 295, 296, surface.

2. Sagoscena tentorium, n. sp. (Pl. 108, fig. 6).

Pyramids subregular, of equal size and similar form, usually four-sided, crowned at the top with three divergent apical spines, which are trifurcate at the distal end. (Some three-sided and five-sided pyramids are often intermingled with the four-sided.)

Dimensions.—Diameter of the sphere 2.2, length of the bars 0.2 to 0.25, breadth 0.005.

Habitat.—South Pacific, Station 291, surface.

3. Sagoscena prætorium, n. sp. (Pl. 108, fig. 7).

Pyramids subregular, of equal size and similar form, usually four-sided, crowned at the distal top with three or four divergent apical spines, which bear some irregular verticils of lateral and terminal branches. (Some five-sided and some six-sided pyramids are often intermingled with the four-sided.)

Dimensions.—Diameter of the sphere 2.6, length of the bars 0.3, breadth 0.006.

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

4. Sagoscena pellorium, n. sp. (Pl. 108, fig. 5).

Pyramids subregular, of equal size and similar form, usually five-sided or six-sided, crowned at the distal end with three to six divergent apical spines, which bear an irregularly spinulate terminal knob. (The size and form of the apical spines is here very variable, as well as the number of the edges of the pyramids, which varies between three and six.)

Dimensions.—Diameter of the sphere 3.2, length of the bars 0.15 to 0.25, breadth 0.008.

Habitat.—Antarctic Ocean, Station 156, surface.

5. Sagoscena cruciarium, n. sp.

Pyramids subregular, usually six-sided (intermingled with single five-sided and seven-sided or eight-sided forms), crowned at the distal top with three divergent, slender, apical spines, each of which bears three to six regular cruciate verticils; the four crossed lateral branches of each verticil bearing a spinulate terminal knob. (Similar to Sagoplegma scenophora, Pl. 108, fig. 13.)

Dimensions.—Diameter of the shell 2.5, length of the bars 0.2 to 0.3, breadth 0.004.

Habitat.—North Pacific, Stations 240 to 244, surface.

6. Sagoscena debilis, n. sp.

Pyramids more or less irregular, with four, five, or six sides, of somewhat different form and unequal size; crowned at the top with one, two, or three slender apical spines, of variable length. These spines as well as the bars of the network bear scattered cruciate verticils, each usually composed of four crossed, small, lateral branches.

Dimensions.—Diameter of the shell 2 to 3.0, length of the bars 0.1 to 0.15, breadth 0.003.

Habitat.—Central Pacific, Stations 263 to 274, surface.

7. Sagoscena gracilis, Haeckel.

Pyramids more or less irregular, with five, six, or seven sides, often of somewhat different form and unequal size; crowned at the top with a single radial spine, which has the same size as the bars of the network, and bears in its distal half four cruciate verticils, each composed of four crossed and curved horizontal branches.

Dimensions.—Diameter of the sphere 1 to 2, length of the bars 0.08 to 0.09, breadth 0.002.

Habitat.—Mediterranean (Messina), surface.

8. Sagoscena fragilis, n. sp.

Pyramids very irregular, with four to eight sides, of different form and unequal size; crowned at the top with a single, slender, radial spine, of the same thickness as the slender bars of the network; the latter as well as the former are smooth, without lateral branches.

Dimensions.—Diameter of the sphere 1.0 to 2.0, length of the bars 0.1 to 0.2, breadth 0.001 to 0.002.

Habitat.—Cosmopolitan; Atlantic, Pacific, surface.

Genus 678. Sagenoscena,^[297] n. gen.

Definition.—Sagosphærida with a delicate spherical shell, the thin wall of which is composed of a simple lattice-plate and covered with numerous pyramidal elevations; each pyramid bears on its top one or more radial spines, and has an internal axial rod in its radial axis.

The genus Sagenoscena differs from the preceding closely allied Sagoscena in the possession of an internal radial axial rod, which arises in the centre of the base of each pyramid, and is prolonged usually over its apex into a free, radial, apical spine. The distal end of the latter is usually armed with a bunch of terminal teeth or bristles. In the similar Sagoscena the internal cavity of the pyramids is simple, without axial rod.

1. Sagenoscena stellata, n. sp. (Pl. 108, fig. 3).

Pyramids rather regular, usually six-sided (intermingled with single five-sided and four-sided forms); their axial rod and its prolongation, the radial apical spine, three to four times as thick as the slender edges of the pyramid. The distal end of the apical spine bears an elegant star of numerous radially divergent terminal branches, each of which is armed with a spinulate terminal knob.

Dimensions.—Diameter of the sphere 3.5 to 4.0, length of the net bars 0.3, breadth 0.003; length of the radial spines 0.2, breadth 0.012.

Habitat.—South Atlantic, Station 318, depth 2040 fathoms.

2. Sagenoscena ornata, n. sp. (Pl. 108, fig. 4).

Pyramids rather regular, usually six-sided (intermingled with single five-sided and seven-sided forms); their axial rod and apical spine spindle-shaped, two to four times as thick as the smooth bars of the network. The distal end of the radial spines bears an elegant, foliate, terminal knob, composed of four to six vertical pinnate leaves, lying in crossed meridional planes.

Dimensions.—Diameter of the sphere 2 to 3, length of the rods 0.1 to 0.2, breadth 0.003 to 0.01.

Habitat.—Antarctic Ocean, Station 156, depth 1975 fathoms.

3. Sagenoscena penicillata, n. sp. (Pl. 108, fig. 10).

Pyramids rather regular, usually six-sided (intermingled with single five-sided, seven-sided, and eight-sided forms); their axial rod and apical spine spindle-shaped, thicker than the smooth bars of the network. The distal end of the radial spines is penicillate and bears a brush of bristle-shaped, radial, terminal spinules (compare Sagosphæra penicilla, p. 1607).

Dimensions.—Diameter of the sphere 1 to 1.5, length of the bars 0.1 to 0.15, breadth 0.004 to 0.005.

Habitat.—Antarctic Ocean, Station 157, depth 1950 fathoms.

4. Sagenoscena coronata, n. sp.

Pyramids rather regular, usually four-sided (intermingled with single five-sided and six-sided forms); their axial rod and apical spines cylindrical, scarcely thicker than the smooth bars of the network. The distal end of the radial spines bears a corona of twenty to thirty curved terminal branches, which form a regular circle, and are armed with a spinulate terminal knob.

Dimensions.—Diameter of the sphere 2 to 3, length of the bars 0.12 to 0.18, breadth 0.004 to 0.008.

Habitat.—North Pacific, Station 256, surface.

5. Sagenoscena spathillata, n. sp.

Pyramids more or less irregular, of different sizes and various forms, each composed of four to eight convergent rods and a central axial rod. The latter is prolonged into a free apical spine, which bears at the distal end a spathilla of eight to twelve recurved teeth, and often beyond it a second similar verticil.

Dimensions.—Diameter of the sphere 4.0, length of the bars 0.1 to 0.2, breadth 0.002.

Habitat.—Arctic Ocean, Greenland (Olrik).

6. Sagenoscena cruciata, n. sp.

Pyramids very irregular, of different sizes and various forms, each composed of six to nine convergent rods and a central axial rod. The latter is prolonged into a free apical spine, which bears three to five cruciate verticils, each composed of four perpendicularly crossed lateral branches which bear at the distal end a spinulate knob (similar to Sagmidium crucicorne, Pl. 108, fig. 9).

Dimensions.—Diameter of the sphere 1.0 to 1.2, length of the bars 0.06 to 0.09, breadth 0.001.

Habitat.—Central Pacific, Station 266, depth 2750 fathoms.

Subfamily 2. Sagmarida, Haeckel.

Definition.—Sagosphærida with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework.

Genus 679. Sagmarium,^[298] n. gen.

Definition.—Sagosphærida with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework, and exhibits a smooth surface, without radial spines and pyramidal elevations.

The genus Sagmarium, and the following two genera of Sagosphærida, represent together the subfamily Sagmarida, differing from the preceding Sagenida in the spongy structure of the shell-wall. Whilst in the latter the thin wall of the delicate spherical shell is composed of a simple lattice-plate with triangular meshes, in the former numerous branches diverge from the nodal points of these meshes, and produce by union an irregular and loose spongy framework. The surface of this spongy hollow sphere (similar to Plegmosphæra) is in Sagmarium smooth.

1. Sagmarium spongodictyum, n. sp. (Pl. 108, fig. 2).

Spongy wall of the hollow sphere about half as thick as the radius of its cavity. Bars of the spongy framework very thin and fragile, smooth, without thorns.

Dimensions.—Diameter of the sphere 2.0 to 2.4; length of the bars 0.1 to 0.2, breadth 0.001.

Habitat.—South Atlantic, Station 333, surface.

2. Sagmarium plegmosphærium, n. sp. (Pl. 108, fig. 14).

Spongy wall of the hollow sphere about one-fourth as thick as the radius of its cavity. Bars of the spongy framework rather stout, studded with numerous small spines, which arise perpendicularly from their surface.

Dimensions.—Diameter of the sphere 1.2 to 1.5, length of the bars 0.1 to 0.16, breadth 0.004.

Habitat.—Tropical Atlantic, Station 347, surface.

3. Sagmarium trigonizon, Haeckel.

Bars of the spongy framework thin, irregularly curved, bearing scattered small crosses, which are composed of four small rods arising perpendicularly from the bars. Nodal points of the framework partly pierced by a hole. The peculiar network of a complete specimen, observed by me at Portofino in 1880, was so similar to that of Spongodictyon trigonizon, described above (p. 91), and figured in 1862 in my Monograph, that I am doubtful if the two forms are not identical, the two medullary shells of the latter being accidentally entangled in the framework. (Compare p. 1602.)

Dimensions.—Diameter of the sphere 1.1 to 1.5, length of the bars 0.1 to 0.2, breadth 0.002.

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

Genus 680. Sagmidium,^[299] n. gen.

Definition.—Sagosphærida with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework, and bears on the nodal points of its surface radial spines.

The genus Sagmidium differs from the preceding Sagmarium in the development of radial spines on the surface of the spongy hollow sphere. It bears therefore the same relation to the latter as Sagosphæra does to Sagena, and may be derived either from Sagmarium by the formation of radial spines, or from Sagosphæra by development of the spongy envelope.

1. Sagmidium unicorne, n. sp.

Radial spines simple, straight, smooth, a single one at each nodal point of the surface of the spongy sphere, bearing on its distal end a spinulate knob, or a bunch of numerous radial bristles. (Similar to Sagenoscena penicillata, Pl. 108, fig. 10.) Bars of the spongy framework smooth.

Dimensions.—Diameter of the sphere 3.0 to 3.5, length of the bars 0.15 to 0.2, breadth 0.003 to 0.006.

Habitat.—Antarctic Ocean, Station 256, surface.

2. Sagmidium tricorne, n. sp.

Radial spines simple, smooth, usually three divergent united at each nodal point of the surface (sometimes two or four instead of three). Each spine bears on its distal end three short divergent conical teeth. (Similar to the terminal teeth of Sagoscena tentorium, Pl. 108, fig. 6.) Bars of the spongy framework smooth.

Dimensions.—Diameter of the sphere 1.6 to 2.4, length of the bars 0.06 to 0.09, breadth 0.001 to 0.002.

Habitat.—Central Pacific, Stations 263 to 268, surface.

3. Sagmidium crucicorne, n. sp. (Pl. 108, fig. 9).

Radial spines slender, verticillate, three or four divergent arising from each nodal point of the surface. Each spine bears three to six cruciate verticils of lateral branches; each verticil being composed of four crossed small branches with a spinulate terminal knob. Bars of the spongy framework partly covered with similar verticils.

Dimensions.—Diameter of the sphere 2.0 to 3.0, length of the bars 0.2 to 0.3, breadth 0.002 to 0.003.

Habitat.—North Pacific, Stations 240 to 244, surface.

4. Sagmidium quadricorne, n. sp. (Pl. 108, fig. 12).

Radial spines stout, smooth, cylindrical, usually four divergent arising from each nodal point of the surface (sometimes three, five, or six, instead of four). Each spine bears on its distal end a club-shaped stellate knob. Bars of the spongy framework smooth.

Dimensions.—Diameter of the sphere 4.5, length of the bars 0.2 to 0.3, breadth 0.003 to 0.005.

Habitat.—South Pacific, Station 293, depth 2025 fathoms.

5. Sagmidium multicorne, n. sp.

Radial spines slender, more or less curved, verticillate, in variable number (three to six) divergent, arising from the nodal points of the surface. The spines as well as the bars of the spongy framework are partly simple, partly covered with irregularly scattered cruciate verticils, very similar to those of Sagmarium trigonizon (or Dictyosoma trigonizon), figured in my Monograph, pl. xxvi. figs. 4, 5.

Dimensions.—Diameter of the sphere 5.0, length of the bars 0.2 to 0.3, breadth 0.003.

Habitat.—Indian Ocean, Cocos Islands (Rabbe), surface.

Genus 681. Sagoplegma,^[300] n. gen.

Definition.—Sagosphærida with a spongy spherical shell, the thickened wall of which is composed of a loose spongy framework, and bears on its surface numerous pyramidal elevations.

The genus Sagoplegma differs from Sagmarium, its ancestral form, in the development of pyramidal or tent-shaped elevations on the surface of the spongy hollow sphere. It exhibits, therefore, the same relation to the latter as the similar Sagoscena bears to Sagena. The wall of the spherical shell is in the two latter genera a thin simple lattice-plate, in the former a thickened spongy framework.

1. Sagoplegma pyramidophora, n. sp.

Pyramids on the surface of the spongy sphere subregular, mostly tetrahedral, of nearly equal size and similar form. The three edges of each pyramid are prolonged over its top into three short, divergent, apical spines which are forked at the distal end. (Very similar to Sagoscena castra and Sagoscena tentorium, Pl. 108, figs. 1, 6, probably derived from them, but differing in the spongy structure of the thickened shell-wall, which is half as thick as the radius of its cavity.)

Dimensions.—Diameter of the sphere 2.0 to 2.5, length of the bars 0.15 to 0.2, breadth 0.002.

Habitat.—North Pacific, Stations 231 to 239, surface.

2. Sagoplegma scenophora n. sp. (Pl. 108, fig. 13).

Pyramids on the surface of the spongy sphere irregular, with three to six sides, unequal in size and different in form. The edges of each pyramid are prolonged over its top into three to six divergent apical spines, which bear three to six cruciate verticils, each composed of four small, crossed, lateral branches, armed with a spinulate knob at the distal end.

Dimensions.—Diameter of the sphere 3.0 to 3.5, length of the bars 0.25 to 0.35, breadth 0.003.

Habitat.—North Pacific, Stations 252, 253, surface.

Family LXXVI. Aulosphærida, Haeckel (Pls. 109-111).

Definition.—Phæodaria with a large spherical or subspherical (rarely spindle-shaped) articulated shell, which is composed of hollow tangential tubes. Nodal points of the loose network stellate, with a nodal cavity and astral septa. Meshes either triangular or polygonal. Hollow radial spines arise usually at the nodal points of the surface. No peculiar mouth in the shell. Central capsule tripylean, placed in the centre of the shell.

The family Aulosphærida comprises a great number of splendid and widely distributed Phæodaria, which have a special interest on account of the peculiarly complicated structure of their large lattice-shell, of the extraordinary beauty of their form and of their remarkable relations to the other Phæodaria. They differ from all the other Radiolaria in the peculiar articulate composition of the spherical skeleton of hollow tangential tubes, which are connected (and at the same time separated) by sutural or astral septa and filled up by jelly. The same peculiar structure recurs only in the closely allied Cannosphærida, which, however, differ in the possession of a second internal concentric shell, connected with the outer by radial beams. The similar Sagosphærida, which exhibit corresponding forms in various genera, differ from the Aulosphærida in the simpler structure of the delicate lattice-sphere, which is composed of very thin solid threads of silica, without astral septa. The Orosphærida, finally, also nearly related to the preceding families, differ from them in the coarse structure of the lattice-sphere, which is composed of very thick tangential, concentrically stratified rods, with an internal axial canal, but without astral septa at the nodal points.

One genus only, and two species, of Aulosphærida have been hitherto known, having been discovered by me in 1859 at Messina, and described in my Monograph in 1862 as Aulosphæra trigonopa and Aulosphæra elegantissima (loc. cit., p. 357, Taf. x. figs. 4, 5; Taf. ix. figs. 5, 6). The characteristic structure of their central capsule, as true Tripylea, was afterwards, in 1879, described more accurately by Richard Hertwig (Organism. d. Radiol., p. 90, Taf. x. figs. 2, 8, 14). The rich collection of the Challenger has demonstrated that the Aulosphærida belong to the most common and most widely distributed Phæodaria; many of them are distinguished by the admirable elegance and astonishing regularity of their large and delicate shell. Nine genera and fifty-six species of this great family are described in the following pages, which, however, may represent only a small part of the numerous forms which are found on the surface as well as in different depths of all oceans and in all zones.

The shell is in the great majority of Aulosphærida a regular sphere or an endospherical polyhedron. Two genera only, both rather rare, exhibit a different monaxonial form, one vertical main axis being developed either more or less than all the other ones of the sphere:—Aulatractus is spindle-shaped or ellipsoidal, with prolonged main axis; Aulophacus is lenticular or discoidal, with shortened main axis. The former may be compared to the Prunoidea, the latter to the Discoidea, in opposition to the common regular Sphæroidea. The size of the lattice-shell is very considerable in all Aulosphærida, its diameter varying usually between 1 and 3 mm., often it amounts to 4 or 5 mm.; very rarely the diameter is more than 5 or less than 1 mm. The largest form observed is the spindle-shaped Aulatractus, in which the vertical prolonged main axis attains 6 to 10 mm., the horizontal equatorial axis 3 to 5 mm.

The network of the lattice-shell exhibits in the Aulosphærida two different types, according to which we distinguish two different subfamilies: Aularida and Aulonida; the former are much more common and richer in remarkable forms than the latter. The meshes of the network are in the Aularida constantly triangular, regular or subregular, and very similar to those of the Sagosphærida; at each nodal point six tangential tubes are usually united, so that the network may be regarded also as composed of regular hexagonal meshes, each of which is divided into six smaller triangular meshes (Pl. 109, figs. 1, 3, 5). The second subfamily, the Aulonida, are much rarer than the former, and are distinguished by the polygonal meshes of the network; these are usually more or less irregular, pentagonal and hexagonal intermingled, more rarely tetragonal, heptagonal, or octagonal; usually three or four, rarely five or more tangential tubes are united at each nodal point (Pl. 111, figs. 1, 3). The size of the meshes is very considerable, and agrees with that of the Sagosphærida; their diameter being usually between 0.1 and 0.3, rarely less or more.

The hollow tubes which compose the loose network are usually cylindrical, straight or slightly curved, smooth (Pl. 111, fig. 2), more rarely somewhat spinulate (Pl. 109, fig. 5). Their length is usually between 0.1 and 0.2 mm., rarely less than 0.08, or more than 0.24 mm.; their diameter usually between 0.003 to 0.005, sometimes only 0.002 or less, at other times 0.006 or more. In several species the tangential tubes are thinner in the middle part, and thickened towards the two ends (Pl. 109, figs. 3, 4). Each tube consists of a thin cylindrical wall of silex, and of a jelly-mass filling up its cavity; in its axis runs a very thin, straight or slightly curved thread of silica, the axial filament.

The arrangement of the tangential tubes, which originally, in the simplest Aulosphærida, lie tangentially in the spherical face of a simple lattice-sphere, exhibits various secondary modifications, leading to various interesting generic forms. Two genera only, Aularia (with triangular meshes, Pl. 111, fig. 2) and Aulonia (with polygonal meshes, Pl. 111, fig. 1) possess a smooth, perfectly simple lattice-sphere, and may therefore be regarded as the ancestral genera of the two subfamilies. Two other corresponding genera, the common Aulosphæra (Pl. 109) and the rarer Aulastrum (Pl. 111, fig. 3), differ from the former in the development of radial spines at the nodal points of the simple lattice-sphere. Aulophacus may be developed from Aulosphæra by shortening, Aulatractus, however, by prolongation of the vertical main axis (Pl. 111, figs. 6, 7). In two genera, Auloplegma and Aulodictyum, the latticed wall of the spherical shell becomes thickened and spongy, an irregular framework being formed by tubes connected in different directions (Pl. 111, fig. 8). The most remarkable and the most elegant form, however, of the whole family is represented by Auloscena (Pl. 110). The entire surface of the spherical lattice-shell is here covered with numerous regular or subregular pyramids, or tent-shaped elevations. Usually each pyramid is six-sided, and surrounded by six other six-sided pyramids, their bases being separated by six triangular meshes, which lie in the spherical face. A similar elegant form is developed among the Sagosphærida in the genera Sagoscena, Sagenoscena and Sagoplegma (Pl. 108, fig. 1). The structure of Auloscena, however, is usually more regular, and in the top of each pyramid a radial tube arises.

The junction of the cylindrical tubes at the nodal points of the network is very remarkable. Aularia, the simplest form of the family, exhibits at each nodal point the union of six tangential tubes (Pl. 111, fig. 2); their ends are so pointed and truncated that they are connected in the form of a regular six-radiate star; the conical end of each tube is separated from, and at the same time closely connected with, the adjacent conical ends of the two neighbouring tubes by a thin septum, the astral or sutural septum. The six astral septa compose together a six-radiate star, and in the centre of this star the six axial filaments of the tubes are united. Their central union is surrounded by a small, double-contoured circle, and this circle seems to be the perimeter of a small and flat cavity on the inside of the star, which we call shortly the "nodal cavity" ("die kleine Vertiefung" according to Hertwig, loc. cit., p. 90). The nodal cavity of Aularia probably possesses a central opening on its inside and six small surrounding pores, which lead into the six connected tangential tubes. In Aulosphæra and Auloscena, where a radial spine arises at each nodal point, its axial filament arises from the centre of the star, and is usually prolonged on the inside into a free centripetal beam (Pl. 109, figs. 6, 7; Pl. 110, figs. 4, 6). This centripetal beam is a slender, very thin, conical tube (often with a six-sided pyramidal base) and perhaps of great morphological interest as a rudiment, being homologous to the hollow radial beams which connect the two concentric spheres of the Cannosphærida. Possibly the Aulosphærida have been derived from the latter by loss of the inner shell and reduction of the radial beams; the centripetal beams which are found in many (but not in all) Aulosphærida, may be the last remnant of those radial beams. They contain also an axial filament, as a direct internal prolongation of that of the external radial spine. The axial filaments of the radial spines are usually connected with their thin wall by a variable number of scattered transverse threads, or sometimes even by thin transverse septa (Pl. 110, figs. 4-7, &c.). This structure corresponds to the similar axial filaments and their thin filiform transverse branches which we have found in other Phæodaria, e.g., in the Tuscarorida and Circoporida.

The Aulonida (with polygonal meshes) exhibit in general the same structure as the Aularida (with triangular meshes). But whilst in the latter usually six tangential tubes are united at each nodal point, in the former only three or four tubes become united. Therefore also the number of the small sutural partitions or astral septa, which radiate from the central openings of the nodal cavity, is six in the latter, three or four in the former. Correspondingly three or four small pores lead from the nodal cavity into the surrounding tangential tubes.

The true nature of the nodal points, and the intimate structure of the different parts here united, is a matter which it is very difficult to explain. It is a certain fact, well established by hundreds of observations, that in the complete and well-preserved skeletons which are perfectly purified by fire, or by hot mineral acids, and afterwards dried, all the tubes of the skeleton, the tangential as well as the radial cylinders, become filled up by air. Each tube contains usually one large cylindrical air-bubble, with two hemispherical ends. But the air-bubbles of the neighbouring tubes are completely separated one from another by the thin astral or sutural septa, and the air-bubble of the radial tubes is also separated from the former. The central cavity of each nodal point is therefore surrounded in the Aularida by six, in the Aulonida by three or four separate cylinders of air. This fact seems to be explained only on the supposition that each single tube has two terminal pores or fissures, which open into the two nodal cavities on its two ends. The radial tubes must also possess at least one small opening, probably on their base, and probably they have another on their distal apex. In no other way can it be explained, that in all complete, well-preserved and purified skeletons, each single tube constantly becomes easily filled by an air-bubble after drying.

In the living Aulosphærida the cavities of all tubes are filled up by a jelly-substance, which may be stained by carmine and is probably identical with the jelly of the calymma. The latter is probably in direct connection with the former by the central pore of the nodal cavity, which is placed on its inside and surrounded by the astral septa; these separate the tangential tubes, radiating from one nodal point, completely, and are thin and simple, but very solid lamellæ of silica. Therefore the nodal stars of broken shells usually remain united, whilst the single radiating tubes composing them are broken off (Pl. 110, figs. 3, 8, 10). But it happens only rarely (and only in certain individual species) that complete single tubes separate; usually the fragments of the connected neighbouring tubes remain on their ends. The two small terminal openings of each tangential tube, which lead from its cavity into the nodal cavity, and are surrounded on each end by the truncated ends of two neighbouring astral septa, are very difficult to observe (Pl. 110, figs. 8-10).

The wonderful elegance and the high complication of these regular skeletons of the Aulosphærida, produced by a single cell, becomes increased by the graceful and manifold appendages and apophyses which are usually developed on the radial tubes. In only a few species these are simple, as in the common and cosmopolitan Aulosphæra trigonopa. Usually lateral or terminal appendages are developed in great variety, a selection of which is figured in Pls. 109-111. The lateral branches are either irregularly scattered spines (Pl. 110, figs. 3-7) or regular verticils of cruciate or radiate spines; each verticil is usually composed of four perpendicularly crossed horizontal branches (Pl. 109, figs. 3, 4, 7, 10, &c.), more rarely of a greater number of radiating transverse branches.

The terminal appendages of the radial spines exhibit a striking similarity with those of the Aulacanthida (Pls. 102-105). They are either forks with two or three divergent branches (Pl. 111, figs. 3, 4), or regular crosses with four branches opposite in pairs (Pl. 109, figs. 2, 6, 7, 10), or elegant crowns or verticils, composed of numerous radiating branches (Pl. 110, figs. 1-6). The distal ends of the terminal as well as of the lateral branches are either simple, pointed, or armed with a spinulate knob, or with a terminal spathilla. The variety and elegance of these terminal ornaments, the function of which is that of capturing tentacles, is in the Aulosphærida not less admirable than in the Aulacanthida and Cœlodendrida.

The central capsule of the Aulosphærida (Pl. 111, fig. 2) was first figured in my Monograph (1862, Taf. xi. fig. 5) of Aulosphæra elegantissima, as a sphere of 0.2 to 0.3 mm. in diameter. I described there the large nucleus (of half that size) as a spherical "Binnenblase," and the numerous pseudopodia which arise from the capsule and radiate through the meshes of the lattice-shell. But I had not observed at that time the three typical openings of the capsule, which were first discovered and accurately described by R. Hertwig (1879, loc. cit., p. 94, Taf. x. figs. 2, 4, 5, 8, 14). The large astropyle with its radiate operculum and proboscis, and the two smaller lateral parapylæ, provided with a smaller tubule, have in general the same shape as in the closely allied Sagosphærida and Orosphærida, and agree in their strong development with that of the Aulacanthida. The collection of the Challenger contains numerous well-preserved preparations of Aulosphærida, which were stained by carmine immediately after being captured, and in which the central capsule and its nucleus exhibit the same intimate structure already accurately described by R. Hertwig. The diameter of the capsule is usually between 0.2 and 0.3, rarely less than 0.15 or more than 0.35 mm., the nucleus has half that size. The phæodium has usually about the same volume (Pl. 109, fig. 1), but seems to be in many Aulosphærida less developed than in the other Phæodaria.

Synopsis of the Genera of Aulosphærida.

Subfamily 1. Aularida, Haeckel.

Definition.—Network of the shell with triangular, regular or subregular meshes; six tangential tubes being united at each nodal point.