Evidence was presented in a previous paper' that a hybrid substance, encountered after an antigenic character (ch4) of Streptopelia chinensis was transferred to S. risoria, resulted from the interaction of nonallelic genes. Specifically, the cha4 cellular antigen from chinensis showed no hybrid substance when present in backcross individuals that were homozygous for an independently inherited character of chinensis (ch-8/ch-8). In contrast, all backcross individuals with ch-4 invariably showed the hybrid substance in the presence of the ri-8 antigen of risoria, ri-8 being a contrasting character of risoria to ch-8 of chinensis.'In this paper, evidence is given of the dependence of the antigenic specificities of the hybrid substance upon whether the gene for the group4 antigen, following transfer to risoria from each of the four species [ch-4 from chinensis, hu4 from humilis (also called tranquebarica), or4 from orientalis, or se4 from senegalensis] interacts with the gene(s) for ri-8 of risoria, or with that for hu-8 of humilis, or-8 of orientalis, or se-8 of senegalensis. (The genes effecting these five members of the group-8 antigen seemingly form a multiple allelic series.5) The data show that se-4, which behaves genetically as a single character in senegalensis,2' 3 hu4, and or4 within the respective species contain demonstrable antigenic specificities that actually are interaction products.Explanation.-The technical procedures employed in transferring to risoria the respective antigenic characters of both group-4 and group-8 from chinensis, humilis, orientalis, and senegalensis were described or cited in a previous report.' In brief, backcross hybrids, which are distinguishable from risoria birds only in that they possess the ch-4 antigen of chinensis, carry antigenic factors (defghi) in addition to factors abc that characterize ch-4 in chinensis.". 3 Further, the backeross birds carrying only hu-4, or-4, or se-4 to differentiate them from risoria individuals also possess these six specificities.' Thus, the four kinds of backcross birds are indistinguishable in their content of factors of the group-4 antigen.
