Summary Although 84 to 99% of seed virus was adsorbed to chorioallantoic membranes of chick embryos within 2 hr after infection, only 1% or less of the introduced virus was recoverable during the latent period. The length of this latent period was found to be at least 20 hr. The development of hemagglutinins and viral complement-fixing antigens in general paralleled that of infective virus and a rapid release of virus and these viral components form cells was in evidence. The development of soluble antigen, however, showed a more specific relationship to infective virus and release of this component from cells (if indeed it did originate from cells) was considerably delayed. The treatment of viral particles with anesthetic ether released internal S antigen; the quantity of released internal S antigen was related to the original concentration of the viral sample. The V antigen titers decreased 4- to 32-fold and hemagglutinin titers for chicken cells dropped 32-fold or more as the result of other treatment.