Circumstances:
The aircraft was being flown for the purpose of endorsing the pilot-under-training. The upper Airwork had been completed and a flapless approach and touch and go landing was to be the final circuit sequence. On the downwind leg the instructor pilot called out the pre-landing checklist, which was apparently complied with by the pilot-under training. At about this time the pilot-under-training was also involved with obtaining an onwards airways clearance through Flight Service. The aircraft was flared normally but settled onto the runway with the landing gear retracted. The landing gear selector was found to have been in the up position. The pilot-in-command said the landing gear warning horn was not heard prior to touchdown.
