Abstract
As described in the first report, both the HVJ virus and the influenza (A) PR8 virus were made to multiply simultaneously by mixed inoculation of them into the CAC of a developing embryonated egg, and examined by two different methods, one taking advantage of the heat fragility of the Z virus and the other adopting as a means the determination of the hemagglutinating inhibition titers (HI titers). The result was that the ratios of the two strains in simultaneous growth, when obtained by each of these two different methods, were found to disagree and that there were some variable clones with such inhibitory effect as could never be found in the control experiment in which only the two strains were mixed artificially. This was probably because both the thermofragility and antigenicity was subjected to change, and the variable clones thus produced might possibly be considered to be some recombinants of the two strains. But since most of these variable clones were found to revert to the pure Z virus or PR8 virus in its original form in the course of limiting dilution passages, it is impossible to say definitely that their peculiar characters are entirely attributable to their gene.
Both the change of thermo-fragility and that of antigenicity can be considered to be phenotypic. As a different type of progeny is sometimes produced even by variable clones of the same phenotype, the cause for it may be that virus particles of different types mixed in the clones are put together and thus manifest a single type. In an attempt to inquire further into the characters of these clones, the author analysed the characters of the progeny produced by them in the course of serial passages in order to find the constituents of the parent strain, and parallel with it, made a statistical observation of the characters of those descendants emerging from each variable strain.
