. The physiology of the Invertebrata. of the circulatory apparatus in the Echinodermata,but since the time of Cuvier and Tiedemann the presenceor absence of a blood-vascular system in the Asteridea hasbeen alternately asserted and denied. The investigations ofGreef,* Hoffmann,f and Teuscher| are in favour of the * Marhurg Sitxungsherichte, Niederlandisches Archiv, vol. Jenaische ZeiUclirift, vol. 10. i86 PHYSIOLOGY OF THE INVERTEBRATA. existence of the anal ring, and of an extensively ramifiedsystem of canals, connected with it and with the nenralcanals. But according to Prof. Hux
. The physiology of the Invertebrata. of the circulatory apparatus in the Echinodermata,but since the time of Cuvier and Tiedemann the presenceor absence of a blood-vascular system in the Asteridea hasbeen alternately asserted and denied. The investigations ofGreef,* Hoffmann,f and Teuscher| are in favour of the * Marhurg Sitxungsherichte, Niederlandisches Archiv, vol. Jenaische ZeiUclirift, vol. 10. i86 PHYSIOLOGY OF THE INVERTEBRATA. existence of the anal ring, and of an extensively ramifiedsystem of canals, connected with it and with the nenralcanals. But according to Prof. Huxley, the facts, as theyare now known, do not appear to justify the assumption thatthese canals constitute a distinct system of Huxley doubts the special circulatory function of theneural canals, and he does not consider that the sinus whichaccompanies the madreporic canal is in reality a heart. Hestates that this sinus and canals are mere sub-divisions of-the interval between the parietes of the body and those of. Fig. 36,—Circulation in Echinodermata (Sea-urchin). the alimentary canal, arising from the disposition of vessels and that of the walls of the peritonealcavity; both of which, as their development shows, are theresult of the metamorphosis of saccular diverticula of thealimentary canal, which have encroached upon, and largelydiminished, the primitive perivisceral cavity which exists inthe embryo. The peritoneal cavity of the body and rays isfilled with a watery corpusculated fluid (blood); a similarfluid is found in the ambulacral vessels, and probably fills allthe canals. rig. 36 represents the circulatory system in Echinus. PHYSIOLOGY OF THE INVERTEBRATA. 187 The Trichoscolices. In the Turbdlaria, Trematoda, and Cestoidea, the lacunteof the mesoderm and the interstitial fluid of its tissues arethe only representatives of a blood-vascular system. It isprobable that these communicate directly with the terminalramifications of the wa
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectinverte, bookyear1892
