The Center for Cancer Biology will attack the biological aspects of the cancer problem in the following ways: 1. Tumor Virology: The Viral Oncology group will concentrate its research on the relation of RNA tumor viruses to their host cells, particularly on enzymes elicited by virus infection and their role in reverse transcription and integration; and on the genetic control of the integration process. 2. Immunology: The Cancer Immunology group will develop the study of the abnormal immunoglobulins in mouse myeloma cells and the mechanism of rejection of some myelomas by immunological reaction to the foreign globulin. It will also initiate a long-term study on the differentiation of lymphocytes in organ cultures of the thymus gland. 3. Cell Biology: The Cell Biology group plans to concentrate mainly on the abnormalities of membranes in cancer cells, with physico-chemical, biochemical and immunochemical means. They will also plan to develop methods to ascribe malignancy to specific chromosomes of tumor cells through cell fusion and consequent elimination of chromosomes. 4. Developmental Biology: The Developmental Biology group will approach the pathogenesis of leukemia through a study of arrested or distorted development, with a view to understanding normal controls, their derangements in leukemia, and possible corrective measures.