250 M. R. IRWIN 



of species hybrids — that specific substance (cl-11) should be detectable in the 

 cells of livia. 



To date, reasonably extensive tests (unpublished) have not shown that the 

 cells of livia contain more than a trace of an antigenic substance related to the 

 d-11 of Pearlneck. Whatever the relationship of the genes in Pearlneck (as- 

 sociated with those on a chromosome effecting the d-11 specific substance) 

 and livia, respectively, which presumably by interaction with a gene or genes 

 from Ring dove in the two species hybrids effect a common fraction of the 

 two hybrid substances, they are not associated with genes which produce 

 similar antigenic patterns in the two species. On these grounds, it would seem 

 unlikely that the hybrid substances in these two kinds of species hybrids are 

 merely a different arrangement of a species specific antigen. 



The question is pertinent as to whether such reactivities in the cells of 

 these other species, as Senegal and Australian crested, are themselves an in- 

 dication of antigenic response to gene interaction within each species, or the 

 more direct product of a gene. This cannot be answered directly. But, as 

 given in Table 15.3, the fact that absorption of the reagent for the hybrid 

 substance by fractions dx-A, dx-B, or dx-C removes the antibodies for the 

 cells of Senegal indicates that there is some common constituent of these 

 three fractions related to, if not identical with, a reactive substance in Senegal 

 cells. However, only the dx-A fraction removes the antibodies for the cells of 

 the Australian crested dove. Further, absorption by the cells of the pigeon- 

 Ring dove hybrid also removes the antibodies from this reagent for the cells 

 of the Australian crested dove. 



The hypothetical explanations could be advanced, (1) that the antigenic 

 substances in Senegal and the Australian crested dove, themselves being dis- 

 tinct, but both related to the hybrid substance in Pearlneck-Ring dove 

 hybrids, are the result of a genie interaction. But there is no evidence for such 

 an assumption. Also, (2) the argument could be advanced that the relation- 

 ship between these substances in Senegal and Australian crested, and in the 

 respective species hybrids, is fortuitous, simulating the occurrence of the 

 Forssman antigen in many species of animals and plants, including bacteria 

 (Boyd, 1943). That is, the antigenic substances involved (related in some 

 manner to the hybrid substance) may be gene controlled in each of the re- 

 lated species, since indistinguishable substances to those of Senegal were 

 found in four other species of Streptopelia, capicola, dussumierl, humilis, and 

 orienlalis, and to those of the Australian crested dove in two species of an- 

 other genus, Phaps chalcoptera and Phaps elegans, but the antigenic similarity 

 to the hybrid substance is by virtue of some related antigenic component. 

 Various ramifications of these and other explanations would be purely 

 speculative. 



The hybrid substance, as it has been observed in the cells of various species 

 hybrids in birds, simulates for cellular antigens the expression of heterosis in 

 plants and animals. That is, it appears as the resultant of an interaction be- 



