With the purpose to elucidate the growth mechanism of cancer cells the structural arrangement of cancer cells and the newly developed vessels in cancer tissues have been studied morphologically on the reconstruction models obtained from the serial sections of the hepatoma induced experimentally in albino rats by feeding DAB, either in the original form or after irrigating it with India ink. The distribution of blood vessels in the hepatoma tissue is found to be poor and yet extremely irregular in pattern. India ink introduced through the artery or portal vein proved to be hard to reach the vessels of tumor tissues. This can be recognized both macroscopically and histologically as well. In pursuit of the mutual relationship between the development of cancer lobules and the blood vessels it has been revealed that in furthest the cancer cells are proliferating at the distance of 80 to 200μ away from the nearest vessel wall and as for the cell layer there are about 12 to 22 cancer cells, 15 cells on average, existing in between the furthest cell group and the vessel wall. However, in the area futher away from this distance the necrosis of the cells are found suggesting the cancer cells can not live there. The necrosis of the cell will be caused by the oxygen deficiency as it is supposed that any other anabolic or catabolic material is easier to be transferred by their higher diffusion constants than that of oxygen. From these morphologic observations and in view of theoretical consideraion on the oxygen tension in the cancer tissues it is deduced that the cancer cells require only an extremely small amount of oxygen but cannot live in complete absence of oxygen. Mitosis is seen frequently in the region surrounding the vessels and become rare in the parts apart from the vessels. On the basis of these observations the author discussed about the developing modes of cancer cells in the relation with the vessels, comparing his own experimental results with those presented by other investigators on the morphologic structure of blood vessels in various tumor tissues.