The large cardiac portion of the stomach which has 5 pouches, one per arm. The cardiac stomach everts through the mouth at the time of feeding, and after digestive enzymes have acted upon the food, the stomach contents are retracted into the body by means of special retractor muscles a pair of which extend into each arm. Aborally the cardiac portion of the stomach leads into the smaller, thin- walled and flattened pyloric portion of the stomach. The pyloric stomach receives the common ducts from five pairs of hepatic caeca . From the middle of the upper portion of the pyloric stomach a short rectum extends to the anus which is located on the aboral surface.
Gonads are conspicuous in specimens captured during or just prior to the reproductive season.
Examine the water system in an arm. A radial canal runs the entire length of each arm. An individual tube foot consists of a closed cylinder with a sucker at the distal end and at its proximal end, a bulb-like ampulla lying within the body. Examine the following classes of Echinoderms.