. Elementary text-book of zoology. 158 ARCHICCELOMATA. really emerge from small holes between the ambulacral ossicles arranged in a row on each side. These ossicles form the walls of the grooves. At the edges of the grooves are rows of calcareous spines, and a few extra large ones, the oral spines, project inter-radially or towards the mouth. At the tip of each arm is a small eye-spot. If the upper surface be entirely removed the alimentary organs are brought into view. The mouth leads into a spacious cardiac part of the stomach which is radially lobed. A constriction leads into the pyloric po
. Elementary text-book of zoology. 158 ARCHICCELOMATA. really emerge from small holes between the ambulacral ossicles arranged in a row on each side. These ossicles form the walls of the grooves. At the edges of the grooves are rows of calcareous spines, and a few extra large ones, the oral spines, project inter-radially or towards the mouth. At the tip of each arm is a small eye-spot. If the upper surface be entirely removed the alimentary organs are brought into view. The mouth leads into a spacious cardiac part of the stomach which is radially lobed. A constriction leads into the pyloric portion which is pentagonal in shape, the angles pro- jecting radially. From each angle there runs a duct which Fig. 91.—Median Longitudinal Section through the Starfish in the plane of its Symmetry. SO Stone Canal. Ambulacral Ossicles. Water Vascular Vessel. Radial Nerve. Water Vascular Ring. {^{ exactly median the section would cut the median mesentery and not the gonad.) bifurcates into two long pyloric glands in each arm. The intestine is very short and has a pair of small branched anal glands. It will easily be seen that the pyloric glands are attached to the aboral wall by paired mesenteries, and that the cardiac part of the stomach is attached to the oral wall by retractor muscles. The cardiac portion is often protruded {, into oyster-shells) and prey is obtained in this way. The pyloric glands are said to be digestive in function and the anal glands mainly excretory. The coelom is spacious and is cut into during dissection. Vascular ^^ '^ divided into several separate parts. The most important is (i) the water-vascular system (or ambulacral system). This is a part of the coelom in which is concentrated the motor function found elsewhere. 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
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