Fig. 109.—Microscleres of Demospongiae. a, b, Sigmaspires viewed in different directions; c, d, bipocilli viewed in different directions; e, toxaspire; f, f', spiraster; g, sanidaster; h, amphiaster; i, sigma; j, diaucistra; k, isochela; l, m, anisochelae viewed in different directions; n, cladotyle; o, toxa; p, forceps; q, oxyaster; r, spheraster; s, oxyaster with 6 actines; t, another with 4 actines; u, another with rays reduced to two (centrotylote microxea); v, tylote microrhabdus; w, trichodragmata; x, oxeate microrhabdus or microxea.
| 11. | (a) | Microscleres sigmata | Craniella cranium |
| (b) | Sigmata absent, asters present | [12] | |
| 12. | (a) | Microscleres include spirasters | Poecillastra compressa |
| (b) | Microscleres include sterrasters | [14] | |
| (c) | Microscleres include euasters: spirasters and sterrasters absent | [13] | |
| 13. | (a) | Two kinds of euaster present | Stelletta |
| (b) | Microscleres include a euaster and a sanidaster or amphiaster | Stryphnus ponderosus | |
| 14. | (a) | Microscleres include microrhabdi | Pachymatisma johnstonia |
| (b) | Microscleres include many-rayed euasters | Cydonium milleri | |
| 15. | (a) | Some of the microscleres asters | [16] |
| (b) | Microscleres absent, or not asters | [17] | |
| 16. | (a) | Skeleton radiate; asters of more than one kind | Tethya |
| (b) | Sponge encrusting; asters of one kind only | Hymedesmia | |
| (c) | Skeleton fibrous | Axinella spp. | |
| 17. | (a) | Megascleres all diactinal; chelae present | Desmacidon |
| (b) | Megascleres all diactinal; chelae absent | [18] | |
| (c) | Some or all of the megascleres monactinal | [19] | |
| 18. | (a) | Habitat fresh water | [56] |
| (b) | Habitat marine | [22] | |
| 19. | (a) | Megascleres include cladotyles | Acarnus |
| (b) | Megascleres include dumb-bell or sausage-shaped spicules forming the main reticulum | Plocamia | |
| (c) | Microscleres include bipocilli | [20] | |
| (d) | Microscleres include diancistra | Hamacantha | |
| (e) | Megascleres include forceps | Forcepia | |
| (f) | Skeleton formed of isolated monactines vertically placed | Hymeraphia | |
| (g) | None of the above peculiarities present | [21] | |
| 20. | (a) | Skeleton fibre not echinated | Iophon |
| (b) | Skeleton fibre echinated | Pocillon | |
| 21. | (a) | Skeleton with echinating spicules | [28] |
| (b) | Skeleton without echinating spicules | [30] | |
| 22. | (a) | Spongin abundant | [23] |
| (b) | Spongin scanty | [25] | |
| 23. | (a) | Fibre not echinated | [24] |
| (b) | Fibre echinated | Diplodemia | |
| 24. | (a) | Fibre with a single axial series of spicules | Chalina |
| (b) | Fibres with numerous spicules arranged polyserially | Pachychalina | |
| 25. | (a) | Microscleres absent | [26] |
| (b) | Microscleres sigmata and/or toxa | [27] | |
| 26. | (a) | Skeleton confused | Halichondria |
| (b) | Skeleton reticulate | Reniera | |
| 27. | (a) | Rind and fistulous appendages present; microscleres sigmata | Oceanapia |
| (b) | No rind; skeleton reticulate; microscleres sigmata and/or toxa | Gellius | |
| 28. | (a) | Skeleton confused or formed of bundles of spicules with echinating spined styles | [29] |
| (b) | Skeleton fibrous or reticulate, or formed of short columns | [45] | |
| (c) | Skeleton formed of a dense central axis, and columns radiating from it to the surface | [52] | |
| 29. | (a) | Spicules of the ectosome styles | Pytheas |
| (b) | Spicules of the ectosome oxeas or absent | Clathrissa | |
| (c) | Main skeleton confused. Special ectosomal skeleton absent | Spanioplon | |
| 30. | (a) | Megascleres of the choanosome not differing from those of the ectosome | [31] |
| (b) | Megascleres of the choanosome differing from those of the ectosome | [32] | |
| 31. | (a) | Chelae absent. | [33] |
| (b) | Chelae present | [44] | |
| 32. | (a) | Trichodragmata present | Tedania |
| (b) | Trichodragmata absent | [42] |
Fig. 110.—Megascleres. a-l and q-s, Modifications of monaxon type. a, Strongyle; b, tylote; c, oxea; d, tylotoxea; e, tylostyle; f, style; g, spined tylostyle; h, sagittal triod (a triaxon form derived from monaxon); j, oxytylote; k, anatriaene; l, protriaene; m, sterraster (polyaxon); n, radial section through the outer part of m, showing two actines soldered together by intervening silica; o, desma of an Anomocladine Lithistid (polyaxon); q, crepidial strongyle, basis of rhabdocrepid Lithistid desma; r, young form of rhabdocrepid desma, showing crepidial strongyle coated with successive layers of silica; s, rhabdocrepid desma.
| 33. | (a) | Skeleton reticulate or fibrous | [34] |
| (b) | Skeleton radiate or diffuse | [37] | |
| (c) | Skeleton with radiating fibres forming a reticulum with others crossing them at right angles | Quasillina | |
| 34. | (a) | No microscleres | [35] |
| (b) | Microscleres sigmata and/or toxa with or without trichodragmata | Desmacella | |
| 35. | (a) | Sponge fan- or funnel-shaped | [36] |
| (b) | Sponge not fan- or funnel-shaped | Hymeniacidon | |
| 36. | (a) | Megascleres slender and twisted | Phakellia |
| (b) | Megascleres somewhat stout, not twisted | Tragosia | |
| 37. | (a) | Sigmata present, skeleton diffuse | Biemma |
| (b) | Sigmata absent | [38] | |
| 38. | (a) | Skeleton more or less radiate | [39] |
| (b) | Skeleton diffuse; sponge boring | Cliona | |
| 39. | (a) | Sponge discoid with marginal fringe | Halicnemia |
| (b) | Sponge massive or stipitate without marginal fringe | [40] | |
| 40. | (a) | Sponge body prolonged into mammiform projections | Polymastia |
| (b) | Sponge body without mammiform projections | [41] | |
| 41. | (a) | No microscleres. Megascleres tylostyles with or without styles | Suberites |
| (b) | Microscleres centrotylote. Megascleres styles or tylostyles | Ficulina | |
| 42. | (a) | Choanosomal megascleres smooth | [43] |
| (b) | Choanosomal megascleres spined | Dendoryx | |
| 43. | (a) | Microscleres chelae and sigmata of about the same size | Lissodendoryx |
| (b) | Chelae, if present, smaller than the sigmata | Yvesia | |
| 44. | (a) | Isochelae | Esperiopsis |
| (b) | Anisochelae | Esperella | |
| 45. | (a) | Fibres or columns plumose | [46] |
| (b) | Fibres or columns ectyonine | [47] | |
| 46. | (a) | Microscleres toxa | Ophlitaspongia |
| (b) | Microscleres absent | Axinella | |
| 47. | (a) | Skeleton reticulate | [48] |
| (b) | Skeleton not reticulate | [49] | |
| 48. | (a) | Microscleres present. Spicules of the fibre core spined | Myxilla |
| (b) | Microscleres absent. Spicules of the fibre core smooth | Lissomyxilla | |
| 49. | (a) | Main skeleton formed of plume-like columns | [50] |
| (b) | Main skeleton formed of horny fibres (ectyonine). Special dermal skeleton wanting | Clathria | |
| 50. | (a) | Dermal skeleton contains styles only | Microciona |
| (b) | Dermal skeleton contains diactine spicules with or without styli | [51] | |
| 51. | (a) | Main skeleton columns with a core of smooth oxeas | Plumohalichondria |
| (b) | Main skeleton columns with a core of spined styles | Stylostichon | |
| 52. | (a) | Central axis contains much spongin. Echinating spined styli present | Raspailia |
| (b) | Central axis with little or no spongin. Spined styles absent. Pillars radiating from the axis support dermal skeleton | Ciocalypta | |
| 53. | (a) | Ground substance between chambers clear; chambers pear-shaped or oval; eurypylous | Spongelia |
| (b) | Ground substance granular. Chambers spherical with aphodi | [54] | |
| 54. | (a) | Fibres not pithed; sponge fan-shaped | Leiosella |
| (b) | Fibres pithed; sponge massive | Aplysina | |
| 55. | (a) | Chambers long, tubular, branched | Halisarca |
| (b) | Chambers not much longer than broad; not branched | Oscarella | |
| 56. | (a) | Amphidiscs present | Ephydatia |
| (b) | Amphidiscs absent | Spongilla |
CHAPTER IX
PORIFERA (CONTINUED): REPRODUCTION, SEXUAL AND ASEXUAL—PHYSIOLOGY—DISTRIBUTION—FLINTS
The reproductive processes of Sponges are of such great importance in leading us to a true conception of the nature of a sponge that we propose to treat them here in a special section. Both sexual and asexual methods are common; the multiplication of oscula we do not regard as an act of reproduction (p. [174]).
Fig. 111.—A, amphiblastula larva of Sycon raphanus; B, later stage, showing invagination of the flagellated cells. c.s, Segmentation cavity; ec, ectoderm; en, endoderm. (After F. E. Schulze, from Balfour.)