Abstract
Two cell lines were established in vitro from a mouse ascites mammary carcinoma FM3A and they were similar to each other both in their in vitro growth rate and their morphological identity with in vivo tumor cells. Both A and B lines has 3 characteristic chromosomes and high transplantability, and the transplanted subcutaneous tumors showed the morphology of undif-ferentiated adenocarcinoma. The cloning of the present cell lines were made with the use of agar. The study of the nutritional requirement of the present lines showed that Bactopepton, pyruvate and serine were growth enhancing respectively and the combination of these additives were more effective than single addition. The glucose utilization of the lines in the course of the growth was enhanced at the growth stage of the lag phase and early logarithmic phase but decreased after the stage of late logarithmic phase. The capacity to grow in vitro without lag time could be maintained for a long time after transplantion to the host animal, but it fell gradually.