. A text-book of invertebrate morphology. Invertebrates. 554 INVERTEBRATE MORPHOLOGY. lime imbedded in the connective tissue, and bear upon their free extremity a number of radiating spines, which vary in the amount of movement of which they are capable in differ- ent species. The paxillae are frequently found in groups around the dermal branchiae, over which the spines may be bent so as to serve for protection. These dermal branchiae (Fig. 254, h) are pouchlike evagi- nations of the coelomic cavity with thin walls composed of ectoderm and a layer of ciliated cells continuous with the peritone
. A text-book of invertebrate morphology. Invertebrates. 554 INVERTEBRATE MORPHOLOGY. lime imbedded in the connective tissue, and bear upon their free extremity a number of radiating spines, which vary in the amount of movement of which they are capable in differ- ent species. The paxillae are frequently found in groups around the dermal branchiae, over which the spines may be bent so as to serve for protection. These dermal branchiae (Fig. 254, h) are pouchlike evagi- nations of the coelomic cavity with thin walls composed of ectoderm and a layer of ciliated cells continuous with the peritoneal lining of the coelom, between these two layers there being but a slight development of connectivetissue and. Fig. 254.—Transverse Section of Arm of a Starfish (modified from LUDWIG). A = ambulacral plate. I = schizocoelic sinus. am = ampulla. mn — muscular nervous system. an = aboral nerve. N = epithelial nervous system. 0 = ovum. p = peritoneal epithelium. pi = calcareous plate. rh = radial hydroooel-vessel. B = adambulacral plate. b = branchia. c = digestive caecum. ec = ectoderm. if = tube-foot. circular and longitudinal muscle-fibres. These pouches are scattered plentifully over the aboral surface, and in some forms occur upon the oral surface also. Their thin walls and the extent of surface they collectively represent leave little room for doubt but that they possess respiratory functions though they may also serve indirectly in excretion, since it has been asserted that the amoeboid cells of the coelomic hsemo. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original McMurrich, J. Playfair (James Playfair), 1859-1939. New York, H. Holt and Company
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1894
