First molar tooth germs consisting of dental organ, dental papilla and dental follicle were dissected from one-day old mice and transplanted subcutaneously into young adult animals of the same strain. Three to four weeks after implantation the host animals were sacrificed and the transplants harvested. The transplants were prepared for either routine histological examination or for electron microscopy. Forty tooth germs continued development with the formation of a periodontium consisting of cement, periodontal ligament and bone. Electron microscopical examination of this material demonstrated the presence of lymphocytes in association with the subcutaneous bone and thereby suggested the origin of the bone from donor tissue.