In fifty animals, measuring 9-12 cm in total length, the distal one half of the right maxillary barbls was amputated under anesthetization with 0.1 per cent solution of chloretone. By eighteen hours after amputation, the end of the barbel stump was sealed by a layer of stratified squamous epidermis which contained small accumulations of blood. And the cut end of a central blood vessel which occupied a core of the dermis of the barbel was plugged with a coagulated mass of blood. Five days after amputation, most of coagulated masses of blood found in the space beneath the sealing epidrmis and in the cut end of blood vessel were gradually absorved and replaced by cells which were mainly derived from the connective tissue near the wound area. These cells, may represent the initial formation of the regeneration blastema. Accordingly, the connective tissue may be primary source of the cells for blastema formation. At this time, mitotic figures were observed in this tissue near the wound area. Once the blastema has been formed, the barbel regeneration progresses satisfactorily. From the present observation it is probable that new endothelial cells contributing to the growth of the central blood vessel did not arise from their own kind, but from the blastema cells. This problem needs further investigation. The regeneration of the smooth muscle layer which encircles the central vessel seemed to take place by both the differentiation of the blastema cells and the proliferation of the former muscle of the stump.Terminal buds occurred in the epidermis of the regenerate within fifteen days after operation. By the twenty-fifth day the histological structure of the regenerate became almost undistinguishable from that of the stump, and the regenerate elongated at an average rate of 0.06 mm per day.