The porifera and coelentera . producedinto spouts (Spinipora) or cups (Stylaster) for the same pores may be scattered, or may be arranged in definite systems,in which the dactylozooids are in lines parallel to, and on eachside of, a line of gastrozooids (Distichopora), or in circles roundthe gastrozooids (Stylaster), Fig. 43, h and c. A circular system 36 THE HYDROMEDUSAE {cydosystem) may be protected by a calcareous flange (Cryptohelia);in some cases calcareous laminae between the dactylozooids of acyclosystem simulate the arrangement of septa in an Anthozoantheca (Allopora). In b
The porifera and coelentera . producedinto spouts (Spinipora) or cups (Stylaster) for the same pores may be scattered, or may be arranged in definite systems,in which the dactylozooids are in lines parallel to, and on eachside of, a line of gastrozooids (Distichopora), or in circles roundthe gastrozooids (Stylaster), Fig. 43, h and c. A circular system 36 THE HYDROMEDUSAE {cydosystem) may be protected by a calcareous flange (Cryptohelia);in some cases calcareous laminae between the dactylozooids of acyclosystem simulate the arrangement of septa in an Anthozoantheca (Allopora). In branching forms the whole thickness of thebranch is often permeated by coenosarcal tubes; in massive formsthe living tissues are confined to the circumference, and by secretingplates of coenenchyme behind them as they grow peripherallyoutwards, give rise to ialulae below the zooids. Calcareous brush-like styles rise in some instances from the tabplae of both gastro-pores and dactylopores (Stylaster), or in the gastropores only. 42.—Portion of the calcareous corallnm of MilU-pnm ncilo^^n, showinR the cyclical airaii(;e-meiit of the pores occupieil by the hydroiils. Twice the natural size. (Froui Mdseley.) 43.—Enlarged view of the surfaceof a living Millepora, showing live liactylozooids surrouml-iug a central gastrozooid. (From Moseley.) (Distichopora). Special pits for the reception of the gonophoresmay occur in the coenenchyme, and are termed amjniUac. The coenosarc is covered by a superficial sheet of ectodermwhich is provided with very large nematocysts. This sheet, whichis perhaps composed of two layers, rests partly on spines of theskeleton, partly on the blind ends of the coenosarcal tubes, and inretraction is continued downwards as a lining to the pores; hereit }>ecomes continuous with the ectoderm of the zooids, and form a circular operculum over them when retracted than in this sheet, ectoderm, mesogloea, and endodermbear to one an
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Keywords: ., bookcentury1900, bookdecade1900, booksubje, booksubjectctenophora
