CELLULAR INHERITANCE AND TRANSFORMATION

1. The article summarizes the empirical evidence relating to the production of inherited character differences between cells that generate cell lineages by asexual fission.
2. The modes of cellular transformation are classified under three headings: adaptive transformations , including antibody formation and some forms of bacterial adaptation; infective transformations , including those secured by viruses, some cellular transformations of micro-organisms, and a colour transformation of mammalian skin; and inductive transformations , mainly exemplified by carcinogenesis and embryonic evocation.
3. Selective transformations of populations of cells are considered only as they may qualify the interpretation of the other types.
4. Adaptive transformations are defined as initially reversible and progressively induced particulate changes in cellular heredity that are functionally dependent in degree and kind upon the nature of the transforming stimulus.
5. Infective transformations are defined as heritable and serially propagable cellular transformations, not normally reversible and not progressively induced, in which the continued presence of the transforming agent or a replica of it is a necessary condition for the maintenance of the transformed state.
6. Inductive transformations are defined as heritable cellular transformations, normally irreversible, not serially propagable, and not progressively induced, in which the maintenance of the transformed state after its initiation does not depend on the continued presence of the inductive stimulus.
7. The inherited character differences between cells are particulate and combinatorial in nature, and there is ground for supposing that they are mediated by cytoplasmic entities that behave as discrete self-reproducing particles.