SPONGES . The Sponges or Porifera See also:

• FORM (Lat. forma)

See also:

• CARTER, ELIZABETH (1717-1806)

Minchin's article in See also:

• SIR

35, g, fig. 36), which See also:

• LINE

In many cases the proper skeleton is more or less completely replaced by See also:

• SAND
• SAND, GEORGE (1804-1876)

Leucosolenia.—The genus Leucosolenia includes a number of calcareous sponges of very See also:

• SIMPLE

They probably serve to distribute See also:

• FOOD
• FOOD (like the verb " to feed," from a Teutonic root, whence O. Eng. foda; cf. " fodder "; connected with Gr. lrareicOae, to feed)

The monaxon spicules have one end embedded in the mesogloea while the other projects outwards and upwards and serves as a defence against See also:

• EXTERNAL

Just as in the Calcarea the most primitive " person " or individual is represented by the Olynthus type, so in the non-calcareous sponges we may recognize a primitive or (A ter See also:

• KELLER, ALBERT (1845- )
• KELLER, GOTTFRIED (1819-1890)
• KELLER, HELEN ADAMS (188o- )

In P. monolopha they are wide and See also:

• ILL

(After F. E. Schulze. From a coloured See also:

• PLATE

When the sponge is removed from the water the soft tissues rapidly decay and leave behind only the elastic " horny " skeleten, which is what we usually (After F. E. Schulze. From a plate in Zeitschrift fur Wissen. Zoologie, by permission of Wilhelm Engelmann.) Spicules, a—e, tetracts or calthrops; f—k, triacts or triradiates; i—t, diacts, showing how the monaxon form (I) may be derived from the primitive tetract (a) by suppression of actines.See also:

• CAR (Late Lat. carra)

E. Schulze.) Flo. 8.—Euspongia officinalis (bath sponge). See also:

• DIAGRAM

;). The canal-system (figs. 6, 8) is very complex and shows but little indication of its origin from a folded rhagon. The in- halant pores lead each into a See also:

• SHORT, FRANCIS JOB (1857– )

The exhalant canaliculi unite to-See also:

• MISSION

See also:

• STATIONERY

Slender branching forms are also not uncommon in shallow water, as seen in the common Chalina oculata of the See also:

• BRITISH

As a rule the colour is lost is spirit-preserved or dry specimens, but a noteworthy exception is found in the brilliant purple Suberites wilsoni of See also:

• PORT

This cavity must be regarded as the See also:

• ORIGINAL

See also:

• UTE
• UTE, or UTAH

See also:

• CHURCHILL (MISSINNIPPI or ENGLISH)
• CHURCHILL, CHARLES (1731-1764)
• CHURCHILL, LORD RANDOLPH HENRY SPENCER (1849-1895)

(After Polejaeff.) It is almost identical with one of the types commonly found in non-calcareous sponges (e.g. Plakina, fig. 4), but has of course been evolved independently. The various types of canal-system met with in the Calcarea are connected together by numerous intermediate forms, thus forming a very interesting evolutionary series, while both the Sylleibid and Leuconoid types appear to have been in-dependently evolved several times, thus affording excellent examples of the phenomenon of convergence, a phenomenon which is very frequently me,; with amongst sponges. (After Polejaeff.) In describing the anatomy of Plakina as a type of non-calcareous sponge, we have traced the development of a fairly complex canal-system from the so-called Rhagon form. We can, however, hardly regard the Rhagon as representing a fundamental type of canal-system common to all the Nen-calcarea, for in some of the Myxospongida, which are the most primitive of all, and again in the Hexactineliida, we find a type characterized by the presence of elongated sac-shaped flagellated chambers resembling those of the Syron type amongst the Calcarea, and these chambers are arranged radially around the exhalant canals (Halisarca, Hexactinellida). The first recognizable stage in the evolution of the canal-system of the Non-calcarea would thus appear to be a condition not unlike that of Sycon, with a number of elongated chambers arranged radially around a central gastrzl cavity and having their blind outer extremities covered over by a dermal membrane. This stage is very nearly reproduced in the young form of a Hexactinellid sponge, Lanuginella pupa. From some such form the Rhagon type may perhaps be derived by flattening out of the lower end of the sponge into a broad base of attachment, and by reduction in the size of the flagellated chambers, accompanied by a more irregular arrangement. Starting from the primitive Myxosponge ancestor, with large sac-shaped chambers, radially arranged, the Non-calcarea have apparently developed along four main lines, giving rise to the existing Myxospongida, the Hexactinellida (Triaxonida), the Tetraxonida "Sc. (After F. E.

Schulze. From Lankester's Treatise on Zoology.) specimen (spicules omitted). d.m, Dermal membrane. g.rrt, Gastral membrane. sd.tr, Subdermaltrabecularlayer. G.C, Gastral cavity. fl.c, Flagellated chamber. osc, Region of future osculum. sg.tr, Subgastral trabecular layer. and the Euceratosa. The Myxospongida have retained the large size of the chambers in certain forms (Halisarca, Bajalus), but have lost this primitive character in the more advanced members of the group (Oscarella). The Hexactinellida have retained the large size and radial arrangement of the flagellated chambers throughout their entire series. The chamber layer, however, tends to become more or less folded (fig. 19), and always lies between two layers of !Lc OR o t1 (After Schulze. From Lankester's Treatise on Zoology.) ex.c, Exhalant canals. sg.tr, Subgastral trabecular layer. d.m, Dermal membrane. g.m, Gastral membrane. sd.tr, Subdermaltrabecularlayer.

G.C, Gastral cavity. fl.c, Flagellated chambers. loose trabecular tissue in which the canals are represented by irregular spaces. The Tetraxonida appear to have suffered reduction in the size of the flagellated chambers at a very See also:

• EARLY
• EARLY, JUBAL ANDERSON (1816-1894)

In the majority of cases (e.g. (After Sollas.) Euspongia) the folding has become so complex that it is no longer recognizable as such, and the origin of the now well-defined inhalant and exhalant canals is completely disguised. in many cases the principal exhalant canals may be surrounded by a layer of tissue of considerable thickness in which there are no flagellated chambers at all, known as the endosome, so that the folded choanosome may be sandwiched in between ectosome' on the outside and endosome on the inside. The manner in which the flagellated chambers communicate with their respective branches of the inhalant and exhalant canal- (After Sollas.) system varies considerably in different forms, and the following types are recognizable, though by no means sharply distinguished from one another. In the more primitive forms (e.g. Hexactinellida, Aplysillidae, Spongeliidae) each chamber is provided with several prosopyles and receives its water supply See also:

• DIRECT

22). The progress from the eurypylous to the diplodal condition is accompanied by a corresponding increase in the development of the mesogloea, whereby the canals are greatly .Y restricted in diameter, and at the same time the mesogloea (After F. E. Schulze.) tends to lose its transparent FIG. 22.-Part of a section of gelatinous character and to Corticium See also:

• CANDELABRUM (from Lat. candela, a taper or candle)

The arrangement of the oscula and pores on the surface of the sponge varies greatly in different types, and sometimes gives rise to very striking modifications of the external form. The oscula or vents are usually relatively large openings situated on the more prominent parts of the sponge, often on special elevations. Occasionally they are replaced by See also:

• SIEVE (O.E. sife, older sibi, cf. Dutch zeef, Ger. Sieb; from the subst. comes O.E. siftan, to sift)

There appears to be little doubt that the Myxospongida are primitively devoid of skeleton, and in this respect they must becarefullydistinguishedfrom thegenusChondrosia, in which the skeleton has been secondarily suppressed, as well as from numerous and See also:

• DIVERS

The walls of the radial chambers are supported by a special " tubar " skeleton (cf. fig. 14), consisting exclusively of triradiates with their basal rays directed towards the distal end of each chamber. The oral rays are spread out at right angles to the length of the chamber, and as several spicules generally lie at the same level the tubar skeleton forms a series of more or less definite See also:

• JOINTS

Various aberrant types of skeleton are met with in the group. In the genus Lelapia we find a partly fibrous skeleton, in wjtich the fibres are composed of bundles of triradiates shaped like tuning-forks (fig. 24, o), and in Petrostoma the main skeleton is formed of calcareous spicules actually fused together. In Astrosclera (fig. 25) a very anomalous type of calcareous skeleton is found, consisting of spherical masses of arragonite, each originating in a special scleroblast and having a radiate structure, recalling that of a siliceous (After W. J. Sollas.) FfG. 26.—Typical Siliceous Megascleres. a, Diactinal monaxon (oxeate). g, b, See also:

• STYLE
• STYLE (from Gr. a-6'1ms, a column; a different word from that used in literature, see below)

f, Polyaxon desma. s (After E. A. Minchin. From Lankester's Treatise on Zoology.) same plane. Three chief varieties may be distinguished : (I) Regular (fig. 24, b), with all the rays and all the angles equal; (2) Sagittal (fig. 24, c, d, 1, &c.), with two of the rays or two of the angles forming a pair, differentiated in some respect from the remaining ray or See also:

• ANGLE (from the Lat. angulus, a corner, a diminutive, of which the primitive form, angus, does not occur in Latin; cognate are the Lat. angere, to compress into a bend or to strangle, and the Gr. ayKOS, a bend; both connected with the Aryan root ank-, to

The monaxon spicules (fig. 24, it, i, q, r, s) are straight or curved and the two ends are usually more or less sharply differentiated from one another. In all these spicules the form and arrangement of the rays is usually clearly correlated with their position in the sponge in such a manner that they are specially adapted for the work which they have to do. The arrangement of the spicules in the case of the genus Leucosolenia has been dealt with above, and we must pass on at once to the Calcarea Heterocoela. In this group the skeleton exhibits an evolutionary series no less remarkable than that of the canal-system. We may take as a convenient starting-point the genus Sycetta, a typical Syconoid form, with the flagellated chambers radiating independently from the central gastral cavity. The wall of the gastral cavity is supported by a gastral skeleton of triradiate or (After J. J. A See also:

• LISTER, JOSEPH LISTER
• LISTER, MARTIN (c. 1638-1712)

Sterraster (often regarded as a microsclere). h, Part of section of sterraster, showing two rays united by intervening silica. sterraster. These bodies become closely packed together over large areas, and give the sponge a stony hardness. Hexactinellida.—In this group the skeleton is composed of spicules of colloidal silica deposited in concentric lamellae around slender axes of an organic substance which in life occupies the " axial canal " of the spicule. Although varying greatly in detail and often exhibiting great complication or, it may be, reduction in structure, these spicules are all referable to the same fundamental triaxonid and hexactinellid type, characterized by the See also:

• POSSESSION
• POSSESSION (Lat. possessio, possidere, to possess)

E. Schulze.) a, See also:

• DAGGER

A hexaster (=rosette) is a perfectly symmetrical hexact whose actines branch out into secondary or terminal rays, in a See also:

• STAR

The distinction into large megascleres and small microscleres is perhaps less well marked in this group than in the Tetraxonida. Tetraxonida.—Here, again, the spicules are composed of colloidal silica deposited around organic axial threads. The starting _point in the evolution of the very complex series of tetraxonid spicules is the primitive tetract or calthrops, characteristic of the most primitive members of the group (e.g. Plakina). This fundamental ground-form (fig. 26, d) consists of four rays or actines of equal length, which all meet one another at equal angles in the centre of the spicule, while their apices would occupy the four angles of a regular See also:

• PYRAMID

15, Cladotylote. 26, Oxyaster. 3, Dchotriaene. 16, Acanthoxeate. 27, See also:

• ASTER (Gr. /MrTI P, a star)

30, Sigmata. monaxon. 20, Rhabdocrepid 31, Isochela. 9, Tetracrepid desma. (monocrepid) 32, Anisochela. to, Primitive diact. desma. 33, Diancistron. 11, Oxeate. 21, Aster. 34, Toxon. 12, Style. 22, Spheraster.

35, Labis (forcipi- 13, Tylostyle. 23, Sterraster. form). 14, Acanthotylostyle. 24, Spiraster. gated shaft, the angles all remaining approximately equal. If the angles between the cladi and shaft become approximately right angles we have an orthotriaene. If the cladi point forward, we have a protriaene (fig. 29, 6). If the cladi are turned backwards towards the shaft we have an anatriaene (fig. 29, 5). If the cladi branch each into two we have a dichotriaene (fig. 29, 3)• If the cladi are See also:

• EXPANDED

29, 4). The cladi may be reduced in size or even suppressed (fig. 29, 7, 8), leaving only the shaft, which may be either sharp at each end (oxeate) or sharp at the See also:

• APEX

29, 17), then if both ends become enlarged into knobs it is said to be tylote (fig. 29, i8). If one end only is rounded off, which apparently usually takes place by suppression of one ray, while the other remains sharp, the spicule is termed stylote (fig. 29, 12). It is now monactinellid as well as monaxonid. If the See also:

• BLUNT, JOHN HENRY (1823–1884)
• BLUNT, JOHN JAMES (1794–1855)
• BLUNT, WILFRID SCAWEN (184o— )

By enlargement of the spiny base of an acanthotylostyle and suppression of the shaft we get forms which simulate astrose microscleres and may be called pseudasters (fig. 29, 14a, 14b). Pseudasters may also be developed by shortening up of acanthoxeates, accompanied by enlargement of the spines (e.g. Spongillinae, fig. 29, 16a). The exotyle appears to have been formed by enlargement of the outer end of a radially placed oxeate at the surface of the sponge. By ramification of both ends of a diactinal megasclere we get the monocrepid desma (fig. 29, 20), characteristic of certain Lithistids and closely simulating the tetracrepid desma. By ramification of one end of a strongylote spicule we may get a cladostrongyle (fig. 29, 19). Diactinal Series of Microscleres.—The starting-point of this series is the primitive See also:

• ANGULATE (Lat. angulus, an angle)

This has given rise to long See also:

• HAIR (a word common to Teutonic languages)

derived the diancistra (fig. 29, 33), shaped like See also:

• POCKET

In the sterraster (fig. 26, g, h), characteristic of the family Geodiidae, numerous slender rays become fused together side by side to form a solid See also:

• BALL (in Mid. Eng. bal; the word is probably cognate with " bale," Teutonic in origin, cf. also Lat. falls, and Gr. 7raXXa)
• BALL, JOHN (1585-1640)
• BALL, JOHN (1818-1889)
• BALL, JOHN (d. 1381)
• BALL, SIR ALEXANDER JOHN, BART
• BALL, THOMAS (1819- )

Sollas. ) initiated by the development of the triaenes. The cladi of these spicules are commonly extended in or beneath the ectosome and form a very efficient dermal skeleton, while the shafts are directed centripetally through the choanosome. In the genus Discodermia the discotriaenes form a continuous dermal See also:

• ARMOUR, PHILIP DANFORTH (1832-1901)

.0 b, Sigmata Toxon. Spiraster. Sanidaster. Amphiaster. Sigma. k, Isochelae. End of a chela, showing the teeth. skeleton which characterizes the majority of the so-called Monaxonellida. This is derived from the former by the See also:

• ESTABLISHMENT (0. Fr. establissement, Fr. etablissement, late Norm. Fr. establishement, from O. Fr. establir, Fr. etablir, Lat. stabilire, to make stable)

Modified from Lendenfeld's Horny Sponges, by permission of the Royal Society of London.) In the Sigmatomonaxonellida, derived from the Tetillidae, the reticulate type of skeleton is almost universal, and in this group an entirely new See also:

• ELEMENT (Lat. elementum)

Thus in the Geodiidae (ng. 23) the thick cortex is almost filled with densely packed sterrasters. In many forms there is a dense layer of small radially arranged monaxons at the surface of the sponge, whose projecting a, has: form an efficient protection. In the reticulate forms the ectosome is usually a thin dermal membrane supported by a reticulate dermal skeleton of slightly different structure from the " main " skeleton. In cases where a special stalk or a root-tuft is developed we also find a special and appropriate skeleton in connexion there-with. In the so-called Lithistida alone amongst the Tetraxonida do we find the spicules (desmas) united together by silica to form a coherent skeleton, sometimes of stony hardness, very different from the elastic, flexible skeleton resulting from the development of spongin, and analogous to the condition met with in the Dictyonine Hexactinellids. The microscleres usually play quite a subordinate part in the formation of the skeleton, being scattered irregularly throughout the mesogloea, though sometimes (Geodia, Tethya) the asters may form a definite cortical layer. Euceratosa.—In the true horny sponges, if we neglect for the moment the presence of foreign bodies, we may say that the skeleton consists from the first exclusively of spongin, secreted (by specialspongoblasts) in concentric layers to form very well defined fibres. In the most primitive forms (Aplysillidae) this horny skeleton is dendritic in arrangement (fig 33), composed of fibres which rise vertically upwards from the base of the sponge (where they may be expanded to form a horny basal cuticle which serves for attachment) and ramify towards the surface, where their apices push against the dermal membrane and cause it to project in the form of " conuli." No reticulation is formed in the simplest cases (A plysilla, Dendrilla), but in Megalopastas secondary connecting fibres are established (in relation, doubtless, to the increase in size and massive form of the sponge), and the skeleton thus simulates the pseudoceratose reticulate type of the Sigmatomonaxonellida. In Darwinella we have, in addition to the dendritic skeleton, isolated " spicules " of spongin scattered irregularly through the mesogloea. The presence of these spicules, which are sometimes, though by no means always, hexactinellid in form, has given rise to much See also:

• SPECULATION

The genus Megalopastas forms a natural transition to the Spongeliidae, in which the reticulation of the horny skeleton is an almost constant feature, and in which the tendency to supplement or replace the spongin by foreign bodies (sand. broken spicules) is very strongly marked. In extreme cases the skeleton is composed almost exclusively of sand (e.g. Psammopemma), and the whole sponge looks like a mass of sand See also:

• STUCK, FRANZ (1863— )

The latter lines practically the whole of the primitive gastral cavity in the Calcarea Homocoela, but in all higher types becomes restricted to well- defined " flagellated chambers." A gelatinous " mesogloea;" which must be regarded primarily as an intercellular substance, appears between the primitive outer and inner layers of the sponge-wall. This contains primitive amoeboid wandering cells (archaeocytes), 2 (After Dendy. From Quart fourn. Micro. See also:

• SCIENCE (Lat. scientia, from scire; to learn, know)

They may be glandular and may secrete a definite cuticle (as in many Euceratosa). They may also be highly contractile. Porocytes.—In certain Calcareous sponges (Leucosolenia) it has been shown (by E. A. Minchin) that the primitive inhalant pores (prosopyles) are formed as perforations in certain of the pavement epithelium cells, which acquire a tubular form and extend through the mesogloea from the dermal to the gastral surface. The outer portion of each porocyte forms a contractile diaphragm which doubtless regulates the See also:

• ADMISSION

d, Desmacyte, from Deegmastra normani. e, Myocytes and collencytes, from Cinachyra barbata. f, Thesocyte, from Thenea muricata. g, Collared cell (choanocyte), from Sycon raphanus. See also:

• HEN

35, a) embedded in it; (b) Sarcenchyme, in which the quantity of intercellular matrix is greatly reduced and the connective-tissue cells are closely packed together; (c) Cystenchyme (fig. 7, Coll , fig. 35, c), consisting of close-packed, oval, vesicular cells with fluid contents and strands of See also:

• PROTOPLASM

They sometimes aid in the See also:

• NUTRITION

In many cases the collars of adjacent choanocytes have been observed to be connected by a definite membrane which stretches from one to the other at the level of their margins. This is known as Sollas's membrane, but it is apparently not a permanent structure, and the circumstances under which it appears require elucidation. In the Hexactinellida the form of the collared cells appears to be somewhat unusual (fig. 36). Archaeocytes.—The term " archaeocytes " has been applied to certain undifferentiated amoeboid cells which make their See also:

• APPEARANCE (from Lat. apparere, to appear)

34, 6) are formed from amoehocytes, which grow to a large size and finally withdraw their pseudopodia and acquire a rounded form. They have large nuclei with a very distinct nuclear membrane and commonly a conspicuous nucleolus. The spermatozoa (fig. 37) closely resemble those of higher animals, consisting each of a small " See also:

• HEAD (in 0. Eng. heafad; the word is common to Teutonic languages; cf. Dutch hoofd, Ger. Haupt, generally taken to be in origin connected with Lat. caput, Gr. KerbOvi7)
• HEAD, SIR EDMUND WALKER, BART
• HEAD, SIR FRANCIS BOND, BART

Each gemmule consists of an See also:

• AGGREGATION (from the Lat. ad, to, gregare, to collect together)

One of the best-known cases is that of the calcareous genus Sycon (fig. 38). The fertilized ova develop into ciliated larvae within the parent sponge, embedded in the walls of the radial chambers, in their endothelial capsules. Each divides first into two, then into four, and then into eight equal and similar blastomeres by successive vertical clefts. The eight-celled stage (fig. 38, b, c,) has the form of a somewhat flattened cushion, with an axial cavity which is the beginning of the blastocoel or segmentation cavity. A See also:

• HORIZONTAL

The large granula (dermal) cells now become invaginated, but this f, Invagination of flagellated cells. g, Gastrula attached by oral See also:

• FACE (from Lat. fades, derived either from facere, to make, or from a root fa-, meaning " appear "; cf. Gr. cbatvstv)

b, c, Embryo with 8 blastomeres (b, top view, c, side view). d, Blastosphere (blastula). e, Larva at time of See also:

• ESCAPE (in mid. Eng. eschape or escape, from the O. Fr. eschapper, modern echapper, and escaper, low Lat. escapium, from ex, out of, and cappa, cape, cloak; cf. for the sense development the Gr. iichueoOat, literally to put off one's clothes, hence to sli

It is now in the Olynthus condition (fig. 38, h) and is exactly comparable to a simple Leucosolenia individual. As it grows older radial flagellated chambers are budded out around the central gastral cavity and the collared cells lining the latter are replaced by pavement-epithelium derived from the dermal layer. An interesting account of the development of Leucosolenia (Clathrina) blanca has been given by E. A. Minchin. Segmentation is regular and complete, resulting in the formation of a hollow, ciliated, oval blastula (fig. 39, A), with a large blastocoel and a wall composed of a single layer of columnar flagellated cells and a pair of very large granular cells at the posterior pole. The latter are primitive archaeocytes and are destined to give rise to the amoebocytes and germ-cells of the adult. The flagellated cells will give rise to all the other cells of the adult, both dermal and gastral. The larva becomes free-swimming in this condition. Here and there individual flagellated cells (destined to form the cells of the dermal layer) lose their flagella and, becoming amoeboid, migrate into the blastocoel, which presently becomes completely filled with such cells.

The larva is thus converted into a solid " parenchymula," in which the archaeocytes remain unchanged in their original position at the posterior extremity. It now fixes itself and flattens out upon the substratum in the pupal condition. During the metamorphosis Which now ensues the majority of the cells of the inner mass (dermal cells) pass out to the exterior again between the flagellated cells(gastral cells), over which they spread themselves in the form of a dermal layer of flattened epithelium. Some of the dermal cells, however, remain in the inner mass as porocytes; the primitive archaeocytes have divided up into amoebocytes; and porocytes, amoebocytes and the cells of the gastral layer are all crowded together in the interior of the pupa. The pupa now elongates vertically. A gastral cavity appears in the interior. The cells of the gastral layer arrange themselves around this cavity and develop their collars and flagella. At first, however, the gastral cavity is lined by the porocytes, which presently separate and migrate out-wards.' Scleroblasts migrate inwards from the dermal layer and secrete spicules. An osculum and prosopyles are formed as in Sycon and the Olynthus stage is reached. The development of sponges in general appears to be characterized by a remarkable want of uniformity in the arrangement of the different kinds of cells of which the larva is composed. Two, or possibly three, primary groups of cells are universally present; the flagellated cells, which will give rise to the collared cells of the adult, the non-flagellated (granular) cells, which will give rise to the dermal layer and its derivatives, and possibly the primitive archaeocytes (perhaps to be regarded as undifferentiated blastomeres). It may be considered as doubtful, however, whether the primitive archaeocytes can in all cases be distinguished from the primitive dermal cells.

The latter are in some cases (amphiblastula type) grouped at the posterior pole of the larva (Sycon), while in other cases (pa.renchymula type) they may pass inwards and completely fill the interior, blocking up the blastocoel and perhaps also freely projecting at the hinder end (fig. 39, F). At the time of the metamorphosis the dermal cells pass to the outside and come to completely enclose the gastral cells, so that the two layers acquire their proper relative positions. The sponge larva in many respects closely resembles the Coelenterate " planula," with its ectoderm and endoderm, but it is very doubtful how far this comparison is valid, and in the present See also:

• STATE
• STATE, GREAT OFFICERS OF

34, 2) or, in the case of some prosopyles, by the contractility of the porocytes themselves. The ingestion of the food particles is no doubt effected in large measure by the collared cells, which seem to feed much in the same manner as independent collared monads (Choanoflagellata). It seems not improbable that Sollas's membrane may be a temporary structure which assists in arresting food particles as they pass through the flagellate chambers. There is reason to believe also that amoebocytes (in this case therefore phagocytes) may See also:

• CAPTURE (from Lat. capere, to take; Fr. prise maritime; Ger. Wegnahme)

C, Young larva of Leucosolenia (or pseudogastrula stage of Sycon). D, See also:

• LATE

The vast majority of sponges are marine, only a single sub-family, the Spongillinae, having acquired the habit of living in fresh water. The Spongillinae are, however, very widely distributed, being found in lakes and See also:

• RIVERS
• RIVERS, ANTHONY WOODVILLE, or WYDEVILLE, 2ND EARL (c. 1442—1483)
• RIVERS, EARL
• RIVERS, RICHARD SAVAGE, 4TH EARL (c. 1660—1712)

Classification. The classification of the Phylum Porifera, the characters of which have already been given, is as follows: Sub-phylum and Class Calcarea.—Sponges with a skeleton composed of carbonate of lime, commonly in the form of isolated spicules whose most usual shape is triradiate. Order z. Honiocoela.—Calcarea in which the gastral cavity and its outgrowths are lined throughout by collared cells. This order is sometimes divided into two families, Clathrinidae and Leucosoleniidae, but it is doubtful if this distinction can be maintained, and by some writers only a single genus .(Leucosolenia) is recognized. Order 2. Heterocoela.—Calcarea in which the original lining of the gastral cavity is partly replaced by pavement epithelium, so that the collared cells are confined to separate flagellated chambers. This order includes the living families Leucascidae, Sycettidae, Grantidae, Heteropidae, Amphoriscidae and Pharetronidae (with only two living representatives but numerous fossil forms). The relationships of the anomalous Astrosclera (fig. 25), for which the family Astroscleridae has been proposed by J. J. Lister, must still be regarded as problematical.

Sub-phylum Non-Calcarea.—Sponges without any calcareous skeleton. Class and Order MYxosroNGIDA.—Sponges with no skeleton; with simple canal system and usually large flagellate chambers. (The absence of skeleton is primitive and not due to degeneration.) This class is sometimes divided into two families—Halisarcidae, with elongated, sac-shaped chambers, and Oscarellidae, with more or less spherical chambers. Class TRIAXONIDA (=HEXACTINELLIDA).—Sponges with a skeleton composed of siliceous spicules, either isolated or cemented together by silica, and either triaxonid and hexactinellid in form or derivable from the triaxonid and hexactinellid type. The canal system is simple and the flagellated chambers are large and sac-shaped, and more or less radially arranged in a network of trabecular tissue. Spongin is never formed. Order z. Amphidiscophora.—Triaxonida with characteristic amphidisc spictles, but no hexasters, and with a root-tuft of anchoring spicules. The family Hyalonematidae, including the well-known glass-rope sponges of the genus Hyalonema, is the only family recognized in this order. Order 2. Hexasterophora.—Triaxonida whose most characteristic spicules are hexasters. To this order belong the living families Euplectellidae, Asconematidae, Rossellidae, Euretidae, Melittionidae, Coscinoporidae, Tretodictyidae and Maeandrospongidae, and a number of See also:

• EXTINCT

Class TETRAXONIDA.—Sponges with a skeleton composed of siliceous spicules, either isolated or cemented together (by silica or by spongin), and either tetraxonid and tetractinellid in form or derivable from the tetraxonid and tetractinellid type. The canal system is usually complex, with small, more or less spherical flagellated chambers. Grade TETRACTINELLIDA.—Tetraxonida in which some, at any rate, of the megasclergs retain the primitive tetractinellid form. No desmas are developed. Order z. Homosclerophora.--Tetractinellida in which microscleres and megascleres are not yet sharply differentiated from one another and no triaenes are developed. The canal system is comparatively simple. This order includes the family Plakinidae (see Plakina, ante) which forms the starting-point of the evolution of the class. Order 2. Astrophora.—Tetractinellida with triaenes and with astrose microscleres, without sigmata. This order includes the families Pachastrellidae, Theneidae, Stellettidae, Geodiidae. Order 3.

Sigrnatophora.—Tetractinellida with triaenes, with sigmata for microscleres (when present), without asters. This order includes the families Tetillidae and Samidae. Grade (? order) LrrulsrIDA.—Tetraxonida in which the megascleres form desmas, typically united with each other by siliceous cement to form a continuous skeleton, often of stony hardness. This group includes both tetractinellid and monaxonellid forms and may possibly be of polyphy'.etic origin. The Lithistida bear the same relation to the other Tetraxonida that the dictyonine Hexactinellids bear to the lyssacine forms, but in the present state of See also:

• BUR, or BURR (apparently the same word as Danish borre, burdock, cf. Swed. kard-boore)

Families.—Epipolasidae, Tethyidae, Spirastrellidae (including Placospongiidae), Clionidae (the boring sponges), Suberitidae, Chondrosiidae. (In Chondrosia the skeleton is entirely suppressed, so that it simulates the Myxospongida.) Order 2. Sigmatomonaxonellida --Monaxonellida in which tht typical microscleres are sigmata, or other diactinal forms. Normal astrose microscleres are absent (though secondary pseudasters are occasionally present). The members of this order are to be regarded as descended from sigma-bearing tetractinellid ancestors. Families.—Haploscleridae (chief sub-families: Gelliinae, Renierina Chalininae, Spongillinae), Desmacidonidae (chief sub-families: Esperellinae, Ectyoninae), Axinellidae. Class and Order EUCERATOSA.—Non-calcareous sponges without siliceous spicules, but with a skeleton composed of horny fibres developed independently, i.e. not in relation to any pre-existing spicular skeleton. The skeleton is often supplemented, or even largely replaced, by foreign bodies. This group includes the bath-sponges and their very numerous relations. Families.—Aplysillidae, Spongeliidae, Spongiidae. There are two groups of palaeozoic fossil siliceous sponges which apparently do not See also:

• FIT

Hinde. The former, represented by the genus Astraeospongin, have cctactinal megascleres. The latter, represented by the genera Tholiasterella and Asteractinella, have poly-axon megascleres with an indefinite number of rays. These may indicate the former existence of two distinct classes of siliceous sponge: A .8 (After G. J. Hinds.) which are, so far as we know, totally unrepresented at the present day. C (After G. J. Hinde.) A, Typical polyactine. B, Rosette-like form. C, D, E, See also:

• NAIL (O. Eng. naegal, cf. Dutch, Ger., Swed. nagel; the word is also related to Lat. unguis, Gr. ovu, Sans. nakhas)

The most recent views as to the evolution and inter-relationships of the principal groups of sponges above enumerated may be conveni- 4° ently expressed by the accompanying phylogenetic See also:

• TREE (0. Eng. treo, treow, cf. Dan. tree, Swed. Odd, tree, trd, timber; allied forms are found in Russ. drevo, Gr. opus, oak, and 36pv, spear, Welsh derw, Irish darog, oak, and Skr. dare, wood)
• TREE, SIR HERBERT BEERBOHM (1853- )

29). In many of the more advanced Tetraxonida, especially in the Chalininae, the development of spongin cement also appears as a new See also:

• FACTOR (from Lat. facere, to make or do)

This has taken place independently in the Calcarea (Petrostoma), the Dictyonine Hexactinellida and the Lithistid Tetraxonida. Affinities of the Porif era. Three main views have been put forward with regard to the position of the Sponges in the animal kingdom: (I) that they are colonies of Protozoa; (2) that they form a subdivision of the Coelenterata; (3) that they are not Protozoa but have originated from Protozoon ancestors quite independently from other Metazoa (Enterozoa). The first of these views, associated especiai'.y with the names of See also:

• JAMES
• JAMES (Gr. 'IlrKw,l3or, the Heb. Ya`akob or Jacob)
• JAMES (JAMES FRANCIS EDWARD STUART) (1688-1766)
• JAMES, 2ND EARL OF DOUGLAS AND MAR(c. 1358–1388)
• JAMES, DAVID (1839-1893)
• JAMES, EPISTLE OF
• JAMES, GEORGE PAYNE RAINSFOP
• JAMES, HENRY (1843— )
• JAMES, JOHN ANGELL (1785-1859)
• JAMES, THOMAS (c. 1573–1629)
• JAMES, WILLIAM (1842–1910)
• JAMES, WILLIAM (d. 1827)

Theel. It would, in short, , be difficult to See also:

• FRAME

J. Sollas, who invented the term " Parazoa " for the group. In support of this view it may be pointed out that the tendency to form hollow, spherical colonies, resembling the blastosphere stage in the development of Enterozoa, is met with in very distinct groups of Protozoa (e.g. Volvox, Sphaerozoum). This form of colony is obviously polyphyletic in origin. The fact that the segmentation of the ovum leads to such a form in both Sponges and Enterozoa is therefore by no means conclusive See also:

• EVIDENCE (Lat. evidentia, evideri, to appear clearly)

The sponges of See also:

• COMMERCE
• COMMERCE (Lat. commercium, from, cum, together, and rnerx, merchandise)

As far back as 1862 Oscar See also:

• SCHMIDT, H
• SCHMIDT, HEINRICH JULIAN (1818-1886)
• SCHMIDT, KARL VON (1817-1875)
• SCHMIDT, WILHELM ADOLF (1812-1887)

The eggs of the bath sponge, like those of other sponges, develop into free-swimming ciliated larvae, and these might be made to attach themselves, like See also:

• OYSTER

1892) ; (4) A. Dendy, ' Monograph of Victorian Sponges," pt. i., Trans. Royal Soc., Victoria III. (1891) ; (5) idem, " Studies on the Comparative Anatomy of Sponges," pts. See also:

• LEVI, HERMANN (1839-1900)
• LEVI, LEONE (1821-1888)

See also:

• HYATT, ALPHEUS (1838–1902)

(1898), vol. xl.; (13) idem, " Sponges," in Lankester's Zoology, pt. ii. (1900); (14) N. Polejaeff, " Calcarea," " Challenger " Reports, ' Zoology" (1883), vol. viii.; (15) S. 0. Ridley and A. Dendy, " Monaxonida," " Challenger" Reports, " Zoology " (1888) vol. xx.; (16) F. E. Schulze, " Untersuchungen abet- den Bau and die Entwicklung der Spongien," Zeitschrift fur wiss. Zoologie (1875–1881) ; (17) idem, " Hexactinellida" (" Challenger " Reports, "Zoology," vol. xxi.); (IS) idem, Amerikanische Hexactinelliden (Gustav See also:

• FISCHER
• FISCHER, EMIL (1852– )
• FISCHER, ERNST KUNO BERTHOLD (1824–1907)

J. Sollas, " Tetractinellida " (" Challenger" Reports, " Zoology,"' vol. See also:

• XXV

See also:

• VOSMAER, CAREL (1826-1888)