In the roller-tube Bashford's carcinoma tissue culture the author succeeded in culturing five successive generations for as long as three consecutive months, and obtaiued the following results. 1. Judging from the change in the increasing number of nuclei in long successive culture, when 30×104 cells are transplanted in one culture field, it is necessary to replace the medium every four days with fresh one and the tissue must be replanted every once in 15-20 days. 2. Those cancer cells cultured successively for a long period of time are more slender and have formed meshworks as compared with those at early stage of culter. In the observation under the phasecontrast microscope the thickening of nuclear membrane, a decreased number of mitochondria, and the enlargment of Golgi's apparatus can be recognized, but they still maintain specific characteristics of tumor cells. 3. In retransplanting the cancer cells cultured successively for a long time back to mice on 15th, 20th, and 50th days of culture, it has been possible to produce tumors exactly identical with the original ones in each retransplantation.