The chiton"s nervous system is simple. The circumesophageal ring has four longitudinal cords, two of which control the foot. Aside from the circumesophageal ring the chiton has only one other sense organ. Aesthetes are light receptors that are located in the valve plates.

             Gonoducts exit the gonad and send gametes to the genital openings in the mantle groove. Fertilization occurs externally and chiton zygotes develop into planktonic trochophore larvae.

             --Cephalopoda--.

             The cephalopods, head-footed, are marine animals that have eight arms, some having eight arms and two tentacles, extending from their head.

             All cephalopods live in marine habitats. The nautilus lives in the tropical Pacific ocean. Squids live in the deep waters of the North Atlantic. Octopi habit the bottom of the ocean.

             Cephalopods are the most active of the phylum Mollusca. Using their siphon as a jet propulsion system, cephalopods expel water from it causing them to thrust themselves through the water. The water is expelled by strong muscles in the mantle and direction can be controlled by adjusting the siphon backward or forward. Fins on the side of the squid act as stabilizers for swimming. The species Loligo is the fastest invertebrate and can swim in bursts of up to 43 KPH.

             Unlike any other mollusc, cephalopods actively pursue prey. Usually feeding on fish or crustaceans, the cephalopod will use jet propulsion to hunt the prey and its suction-cupped arms to capture it. After the prey has been captured the cephalopod will use its chitinous beak to tear at its dinner"s flesh. Sometimes the food is showered with digestive enzymes before being ingested. The radula conveys food to the gut where it then digested. Strong muscles also move food by peristalsis. Digestion and nutrient absorption begins in the stomach and then is completed in the cecum. The digestive glands, sometimes called the liver and pancreas, sends digestive enzymes to the stomach and cecum.