Abstract
Acquisition by pneumococcal variants of M protein and of capsular polysaccharide different from those present in the parent strain has been effected in vitro by means of transforming reactions with extracts of heterologous encapsulated pneumococci. Similar transformations have been accomplished in vivo with heat-killed vaccines as the transforming agents. Independent variation of pneumococcal capsular polysaccharide and M protein observed in nature can be brought about also in the laboratory. By means of transforming reactions, it has been demonstrated that inheritable characters of three distinct pneumococcal strains can be combined within a single strain. It is suggested that acquisition of M protein through transformation reactions occurs in cells deficient in that character.