. Elementary text-book of zoology. i6o ARCHICCELOMA TA. {, Arenicola) as a general feature of the whole coelom. It Consists mainly of a ring-canal round the mouth, five radial vessels just below the heads of the ambulacral ossicles, and a single inter-radial stone-canal running in the median mesentery to the madreporite, through which it communi- cates with the exterior. Each radial canal gives off paired Fig- 93.—Diagram of the Water-Vascular System OF the Common Starfish. (Altered from Gegenbaur.) Stone Canal,. .Madreporite. Radial Canal. Ring Canal. lateral canals which lead to the roun
. Elementary text-book of zoology. i6o ARCHICCELOMA TA. {, Arenicola) as a general feature of the whole coelom. It Consists mainly of a ring-canal round the mouth, five radial vessels just below the heads of the ambulacral ossicles, and a single inter-radial stone-canal running in the median mesentery to the madreporite, through which it communi- cates with the exterior. Each radial canal gives off paired Fig- 93.—Diagram of the Water-Vascular System OF the Common Starfish. (Altered from Gegenbaur.) Stone Canal,. .Madreporite. Radial Canal. Ring Canal. lateral canals which lead to the round vesicles or ampullcB seen as a double row on the inside of the ambulacral ossicles. These ampullae communicate with the tube-feet, which, as noticed before, protrude into the ambulacral groove, between the ambulacral ossicles. The walls of this system are mus- cular, and it works as a hydraulic system by means of the tube-feet. The rest of the ccelom is formed by (2) a large and spacious cavity, the hypogastric cavity, surrounding the lower part of the stomach, produced into the arms and forming a median mesentery in the madreporic inter-radius. {3) Aboral to this, lying on the stomach and produced into each arm along the aboral surface of the pyloric glands, is the epigastric cavity. Its walls form, with those of the hypogastric cavity, the two mesenteries along each hepatic csecum. The hypo- gastric cavity is produced along the oral surface of each arm, inside the radial nerve, to form a pair of perihasmal cavities. The inner walls of these cavities form a median mesentery, in which is contained the radial. 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 Masterman, Arthur Thomas. Edinburgh, E. & S. Livingstone
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