7. {Amphidiscs present 8 {Amphidiscs absent 9 {Rooting spicules a well-defined wisp; four apertures lead into 8. { the gastric cavity _Hyalonema thomsoni_ {Rooting tuft diffuse; sponge oval; osculum single { _Pheronema carpenteri_ {Sponge tubular, dermal and gastral pinuli absent 9. { _Euplectella suberea_ {Sponge a widely open cup; dermal and gastral pinuli present { _Asconema setubalense_ {Tetractine spicule, a calthrop or triaene with short rhabdome; 10. { microsclere aspined microxea _Dercitus bucklandi_ {Triaenes with fully developed rhabdome 11 {222}[Illustration: 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. {Microscleres sigmata _Craniella cranium_ {Sigmata absent, asters present 12 {Microscleres include spirasters _Poecillastra compressa_ 12. {Microscleres include sterrasters 14 {Microscleres include euasters: spirasters and sterrasters absent 13 {Two kinds of euaster present _Stelletta_ 13. {Microscleres include a euaster and a sanidaster or amphiaster { _Stryphnus ponderosus_ 14. {Microscleres include microrhabdi _Pachymatisma johnstonia_ {Microscleres include many-rayed euasters _Cydonium milleri_ 15. {Some of the microscleres asters 16 {Microscleres absent, or not asters 17 {Skeleton radiate; asters of more than one kind _Tethya_ 16. {Sponge encrusting; asters of one kind only _Hymedesmia_ {Skeleton fibrous _Axinella spp._ {Megascleres all diactinal; chelae present _Desmacidon_ 17. {Megascleres all diactinal; chelae absent 18 {Some or all of the megascleres monactinal 19