A STUDY OF SERIAL PASSAGE IN THE ALLANTOIC SAC OF AGENTS THAT COMBINE THE ANTIGENS OF Two DISTINCT INFLUENZA A STRAINS* BY

I n the accompanying paper of this series (1), some experiments are presented in which the simultaneous inoculation of two distinct strains of influenza A virus into the allantoic sac resulted in the appearance of a new kind of virus containing some of the antigens from both strains. The present communication deals with the cultivation of this new form in the allantoic sac and tells of the recognition during serial passages of three varieties of it. One of these varieties was isolated in what appears to be pure culture and it is, so far as we are aware, the first instance in which antigens from two differing animal viruses have been combined in one stable unit. t