50 



SPONGES 



Family 3. tCHONELASMATiD^;. Flat or beaker-shaped ; straight 

 funnel-shaped canals perforating the wall perpendicularly and 

 opeuinf laterally on each side. Example : Chonelasma, Schulze. 



FamFly 4. tVoLVULiNiD^s. Tubular, goblet-shaped, or massive ; 

 crooked canals more or less irregular in their course. Examples : 

 Volmdina, Schulze ; Fieldingia, S. Kent. 



Family 5. SCLEROTHAMNIMS. Arborescent body ; perforated at 

 the ends and sides by round narrow radiating canals. Example : 

 Sclerothamnus, Marshall. 



Sub-order 2. INERMIA. 



Dictyonina without uncinati, clavulse, or scopulariae. 



Family 1. tMYLiusiDa:. Depressed cup -shaped; a complex 

 folding of the wall produces lateral excurrent tubes. Example : 

 Myliusia, Gray. 



Family 2. tDACTYLOCALYClD*;. Goblet -shaped or pateriiorm, 

 with a thick wall consisting of numerous parallel anastomosing 

 tubes, of uniform breadth, which terminate at the same level 

 within and without. Examples : Dactylocalyx, Gray ; Scleroplegma, 

 O.S. ; MargarUella, O.S. 



Family 3. tEuRYPLEGMATiD.*. Goblet-shaped or resembling 

 ear-shaped saucers ; the wall deeply folded longitudinally so as to 

 produce a number of dichotomously branched canals or covered-in 

 grooves. Example : Euryplegma, Schulze. 



Family 4. tAuLOCYSTiD^E. Of massive rounded form, with an 

 axial cavity ; wall consisting of a system of obscurely radiating 

 anastomosing tubes and intervening inter-canals ; both inter-canals 

 and the external terminations of the tubes are covered by a thin 

 membrane, which is perforated by slit -like openings over the 

 lumina of the tubes, and thus assumes a sieve -like character. 

 Examples : Aulocystis, Schulze ; Cystispongia, Roemer. 



This arrangement of the Hexactinellida is taken from the latest 

 work on the subject, Schulze's Preliminary Report on the "Challen- 

 ger " Hexactinellida. The reference of fossil forms to the families 

 here instituted is rendered difficult by the disappearance of the 

 requisite "guiding" spicules in the process of mineralization. A 

 revision of the fossil families to bring them into harmony with the 

 recent has certainly been rendered necessary, but this is too large 

 a task to undertake in this place. 



Sub-class II. DEMOSPONGI.E. 

 Tribe a. MONAXONIDA. 

 Order 1. MONAXONA. 



Family 1. TETHYID.E. Skeleton consisting of radiately arranged 

 strongyloxeas (except in the genus Chondrilla, which is without 

 megascleres) and large spherasters. The ectosome is a thick fibrous 

 cortex. Example: Tethya, Lmk. ; Chondrilla, O.S. 



Family 2. POLYMASTIM. Skeleton consisting of styles radiately 

 arranged and cortical tylostyles. The oscules in many cases open 

 at the ends of long papillae. Examples : Polymastia, Bwk. ; Theca- 

 phora, O.S. ; Trichostemma, Sars. 



Family 3. SUBERITID.E. Skeleton consisting of strongylate or 

 tylotate styles, arranged to form a felt. The flesh spicules when 

 present are usually microrabds or spirasters. Examples : Suberites, 

 Nardo ; Cliona, Grant ; Poterion, Schlegel. 



Family 4. DESMACIDONID-E. The flesh spicules are cymbas. 



Examples : Esperella, Vosm. ; Desmacidon, Bwk. ; Cladorhiza, Sars. 



Family 5. tHALiCHONDRlM. The flesh spicules when present 



are never cymbas. Examples : Halickondria, Fl. ; Rcniera, O.S. ; 



Chalina, Bwk. ; * Pharetrospongia, Soil. 



Family 6. ECTYONID.E. The skeleton consists of fibres echinated 

 by projecting spicules. Examples : Plocamia, 0. S. ; Ectyon, Gray ; 

 Clathria, O.S. 



Family 7. tSpONGiLLiD*. Halichondridas which are reproduced 

 both sexually and by statoblasts. Habitat freshwater. Examples : 

 Spongilla, Lmk. ; Ephydatia, Lmk. ; Parmula, Crtr. ; Potamolepis, 

 Marshall. 1 



The foregoing classification is purely provisional ; the group re- 

 quires a complete revision. 



Order 2. CERATOSA. 



Family 1. DARWINELLID.SI. Canal system of the eurypylons 

 Rhagon type. Flagellated chambers, pouch-shaped, large ; the sur- 

 rounding collenchyme not granular. Horny fibres with a thick 

 core. Examples : Darwinella, Fritz Miiller ; Aplysilla, F.E.S. ; 

 lanthella, Gray. 



Family 2.. SPONGELID^E. Canal system as in the Darwincllidse, 

 but the flagellated chambers more or less spherical. Horny fibres 

 with a thin core, and usually containing foreign enclosures. 

 Examples : Velinea, Vosm. ; Spongelia, Nardo ; Psammoclema, 

 Marshall ; Psammopemma, Marshall. 



Family 3. SPOXGID.E. Canal system aphodal. Chambers small 

 and spherical ; surrounding collenchyme granular. Fibres with a 

 thin core. Examples : Euspongia, Bronn ; Coscinodcrma, Crtr. ; 

 Phyllospongia, Ehlers. 



1 Freshwater sponges without statoblasts are excluded from this family, and 

 left for distribution amongst allied marine genera. 



Family 4. APLYSINID.E. Canal system diplodal ; collenchyme 

 surrounding the flagellated chambers densely granular. Fibres 

 with a thick core. Examples : Luffaria, Duch. and Mich. ; Verrni- 

 gia, Bwk. ; Aplysina, Nardo. 



The species of sponge in common use are three, Euspongia 

 offic.ina.lis (Linn.), the tine Turkey or Levant sponge ; E. zimocca 

 'O.S.), the hard Zimocca sponge ; and Hippospongia equina (O.S.), 

 the horse sponge or common bath sponge. The genus Euspongia. 

 is distinguished by the regular development of the skeletal network 

 throughout the body, its narrow meshes, scarcely or not at all 

 visible to the naked eye, and the regular radiate arrangement of 

 its chief fibres. Hippospongia is distinguished by the thinness of 

 its fibres and the labyrinthic character of the choanosome beneath 

 the skin. As a consequence its chief fibres have no regular radiate 

 arrangement. The species of Euspongia are distinguished as fol- 

 lows. In E. officinalis the chief fibres are of different thicknesses, 

 irregularly swollen at intervals, without exception cored by sand 

 grains ; in E. zimocca they are thinner, more regular, and almost 

 A-ee from sand. In E. officinalis, again, the uniting fibres are soft, 

 thin, and elastic ; whilst in E. zimocca they are denser and thicker, 

 to which difference the latter sponge owes its characteristic hard- 

 ness. Finally, the skeleton of E. officinalis is of a lighter colour than 

 that of E. zimocca. The common bath sponge (Hippospongia, 

 equina) has almost always a thick cake-like form ; but its specific 

 characters are not yet further defined. 



Tribe b. TETKACTINELLIDA. 



Order 1. CHORISTIDA. 

 Sub-order 1. SIGMATOPHORA. 



The microsclere is a sigmaspire. 



Family 1. TETILLID^E. The characteristic megasclere is a pro- 

 triaene. Canal system in the lower forms eurypylous, in the higher 

 aphodal. The ectosome in the simpler forms is a dermal membrane, 

 in the higher a highly differentiated cortex. Examples : Tetilla, 

 O.S.; Craniclla, O.S. (fig. 2.1 h, I). 



Family 2. SAMID^E. The characteristic megasclere is an amphi- 

 trisene. Example : Samus, Gray. 



Sub-order 2. ASTEROPHORA. 



The microsclere is an aster. 



Group 1. SPIRASTROSA. A spiraster is usually present. 



Family 1. THENEID.E, Carter. The flesh spicule is a spiraster. 

 Canal system eurypylous. Ectosome not differentiated to form a 

 cortex. Examples : Thenea, Gray (fig. 21 a, /) ; Paxillastra (Nor- 

 mania), Bwk. 



Family 2. tPACHASTRELL!D,E. Canal system eurypylous in the 

 lower, aphodal in the higher forms. Examples : Plakortis, F.E.S.; 

 Dercitus, Gray. 



Group 2. EtTASTROSA. Spirasters are absent. 



Family 1. tSTELLETTiD*. Canal system aphodal, but approach- 

 ing the eurypylous in the lower forms. The cortex chiefly consists 

 of collenchyme in the lower forms ; in the higher it is highly differ- 

 entiated. Example: Stelletta, O.S. (fig. 11); Ancorina, O.S. ; 

 Myriastra, Soil. 



Family 2. TETHYID/E. Although this family has been placed 

 in the Monaxonida, this seems to be its more natural position. 



Group 3. STERRASTROSA. A sterraster is present, usually in 

 addition to a simple aster. 



Family 1. tGEODlNiD^E. The megascleres are partly trisenes. 

 Canal system always aphodal. Cortex highly differentiated. Ex- 

 amples : Gcodia, Lmk. (fig. 21 n) ; Pachymatisma, Bwk. (fig. 21 c) ; 

 Cydonium, Miiller (fig. 10) ; Erylus, Gray. 



Family 2. PLACOSPONGIM. The megasclere is a tylostyle. 

 Triffines are absent. Example : Placospongia, Gray. 

 Sub-order 3. MICROSCLEROPHORA. 



Microscleres only are present. 



Family 1. PLAKINID.E, Schulze. Canal system very simple, 

 belonging to eurypylous Rhagon type. Characteristic spicules 

 candelabra. Examples: Plakina., F.E.S. (fig. 26). 



Family 2. CORTICIM;. Canal system aphodal or diplodal. 

 Mesoderm a collenchyme crowded with oval granular cells ; the 

 spicules either candelabra, amphitrisenes, or triaenes irregularly 

 dispersed in it. Example : Corticium, O.S. (figs. 9, 21 b). 



Family 3. THROMBID^G. Canal system diplodal. Spicules tricho- 

 triaenes. Example : Thrombus, Soil. 



The Pacliastrettidx or the Corticidx are probably the families 

 from which the Tetracladine Lithistids have been derived. In the 

 Tetillidie the characteristic microsclere may occasionally fail, but 

 there is never any difficulty in identifying the sponge in this case, 

 as the trisenes are of a very characteristic form : the arms of the 

 protrifenes are slender, simple, and directed very much forwards, 

 making a very large angle with the shaft. Microscleres, having the 

 form of little'globules, are sometimes present with the sigmaspires. 



Order 2. LITHISTIDA, O.S. 

 Sub-order 1. TETRACLADINA, Zittel. 

 The desmas are modified calthrops spicules. 



