A treatise on zoology . erradius, one on either side of the base of the Polianvesicle, but in the interradius containing the stone-canal there isonly a single Tiedemanns body. The presence of a blood-vascular system in Asteroids is not yetdetermined, the organs described as such belonging to the Pseud-haemal System (cf. pp. 22, 26). The main organ in this systemis the axial sinus, which is a rather thick vertical tube sur-rounding the stone-canal. It communicates below with a ring (thecircumoesophageal pseudhaemal ring), which surrounds the mouthand gives off five radial branches, which pass o
A treatise on zoology . erradius, one on either side of the base of the Polianvesicle, but in the interradius containing the stone-canal there isonly a single Tiedemanns body. The presence of a blood-vascular system in Asteroids is not yetdetermined, the organs described as such belonging to the Pseud-haemal System (cf. pp. 22, 26). The main organ in this systemis the axial sinus, which is a rather thick vertical tube sur-rounding the stone-canal. It communicates below with a ring (thecircumoesophageal pseudhaemal ring), which surrounds the mouthand gives off five radial branches, which pass one along the upperside of each ray. At its upper end the axial sinus communicateswith the genital ring; attached to this ring are five pairs of shortprocesses, while an additional pair passes beside a prolongation ofthe axial sinus leading to the madreporite. Some of the pores ofthe madreporite open to the axial sinus, and there is no knowndirect communication between the latter and the stone-canal. 244 THE STELLEROIDEA. Km. coronuta. Alwictiiial siirfnco. The Nervous System consists of three (Hsconnectcci sots ofnerves. The niost important set is composed of a circumoral THE STELLEROIDEA 245 ring, from wliicli ;i brunch runs up cacli i;iy between the rows oftube-feet, and exteinul to tlie })seu(lhiienial radial vessel. Eachbranch gives oil nerves to the tube feet and ectodeim of its second set of nerves consists of l)ands lying internal to theradial branches of the first set; they lie along the i)erihaenial canal,which surrounds the i)seudhaenial vessel ; the branches from thesenerves supply the muscles of the and)ulacral ossicles. The thirdgroup of nerves is abactinal in position ; there is a ring roundthe aims, giving off a branch along the upper side of each ray, andinnervating the nuiscles of the body wall. The Genital Organs of Astevias consist of ten branched glands,
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
