The accident occurred during an instructional flight while practicing landings. The flight instructor reported that he became distracted while teaching his student and forgot to ensure that the landing gear was extended before landing. He stated that the landing gear warning horn was sounding before touchdown, but he did not realize that the landing gear was not configured until it was too late. Post accident inspection revealed that several fuselage structural components were damaged during the gear-up landing. The flight instructor reported that there were no preimpact mechanical malfunctions or failures that would have precluded normal operation of the airplane.