The development of the attachment between the lamina propria and epithelium of the dorsal surface of the tongues of mice were studied. With the days after birth gone by, the papillae of lamina propria increase in their length and width. The cytoplasmic processes of the epithelial basal cells begin to elongate by the 25th day after birth, and the serrated structure of the lower surface of the epithelial basal cells becomes prominent by the 75th day after birth. The processes of reticular fibers protrude into the epithelium by the 25th day after birth. The development of these processes almost complete about 75 days after birth, and are formed completely by 125 days after birth.