The porifera and coelentera . araspect of each zooid is turned towards the stem, and therefore may becalled axial, the sulcar aspect is turned away from the stem and istherefore abaxial. When, as is the case in Pennatula and Pteroeides,several elongated zooids are fused together side by side to form leaflets orpinnae, these are always situate on the pararachides and are inserteddiagonally on those surfaces. Hence in each leaflet two surfaces may bedistinguished—an axial, turned towards tlie , and an abaxial. THE ANTHOZOA turned away from it. There are also three edges in each pinna—a ba
The porifera and coelentera . araspect of each zooid is turned towards the stem, and therefore may becalled axial, the sulcar aspect is turned away from the stem and istherefore abaxial. When, as is the case in Pennatula and Pteroeides,several elongated zooids are fused together side by side to form leaflets orpinnae, these are always situate on the pararachides and are inserteddiagonally on those surfaces. Hence in each leaflet two surfaces may bedistinguished—an axial, turned towards tlie , and an abaxial. THE ANTHOZOA turned away from it. There are also three edges in each pinna—a basal,attached to the rachis ; a lower, destitute of zooids ; and an upper, moreor less convex, bearing zooids. The axis of the Pennatulacea, whenpresent, is entirely enclosed within the tissues and is surrounded by anepithelium. There is not sufiBcient evidence to show from what layerthis epithelium is derived, but the evidence, as far as it goes, points toits being of endodermic origin. The development of Renilla has been. Fio. XVII. 1.—A young colony of i»nno/«/n pAospAorwiseen from the right side. P, the calyx of themother zooid ; Z, the tirst siphonozooid ; pi, thefirst lateral autozooid formed as a bud from P:T^, the third lateral autozooid. 2.—A somewhat older colony seen from theasulcar aspect, c, c-, lateral siphonozooidsformed at the bases of j>l, p3, the first andsecond lateral autozooids; p^p, successivelyformed lateral autozooids. 3.—Diagrammatic section through the ter-minal autozooid and siphonozooid of a youngcolony of Pen natula phofphorta. S, sulcar inter-mesenterial chamber ; .-Cs, asulcar chamber; st,stomodaeum of siphonozooid. 4.—A section of the same colony throughthe autozooid, in 2. :>, sulcar chamber of theaxial ziioid ; As, asulcar chamber; the two areseparated by the transverse partition, in whichtwo lateral canals (stem canals)are beingformed ;}A, pil, lateral autozooids. 5.—A .section somewhat lower down. Theaxis A is being fonue
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Keywords: ., bookcentury1900, bookdecade1900, booksubje, booksubjectctenophora
