SPECIFICITY OF GENE EFFECTS 245 



somes of Pearlneck produce effects on cellular antigens which differentiate 

 Pearlneck from Ring dove. Although the cellular substances particular to 

 Ring dove, in contrast to Pearlneck, have not been obtained as units, the 

 available evidence indicates strongly that a gene or genes on nine or ten 

 chromosomes of Ring dove produce antigenic effects which differentiate that 

 species from Pearlneck. 



The question may well be raised as to what this recital of antigenic char- 

 acters in man and doves, which in general illustrates gene specificity in the 

 production of cellular antigens, has to do with the general topic of heterosis. 

 The so-called hybrid substance has one word (hybrid) in common with the 

 term hybrid vigor, and suggests a possible relationship of the two terms. 



The hybrid substance seemingly represents a departure from the hypoth- 

 esized direct action of a gene on the antigenic substance, in that it appears 

 to result from the interaction of two or more genes in the species hybrids to 

 produce some antigenic substance different from any detectable in either 

 parent. With but one exception proposed by Thomsen (1936) in chickens, and 

 for which another explanation will be considered shortly, a hybrid substance 

 has thus far been found only in species hybrids. 



Mention should be made of the technics required for the detection of the 

 hybrid substance. Briefly, if an antiserum prepared against the cells of an 

 individual, whether a species hybrid or not, would be absorbed by the cells of 

 both its parents and would then react with the cells of the individual, but not 

 with the cells of either parent, there would be evidence of a different anti- 

 genic substance in the homologous cells — those used in the immunization. 

 (If an antigen were recessive, it would be present in the heterozygote, and 

 presumably could absorb its specific antibody.) 



Domestic Fowl Hybrids 



As stated above, Thomsen (1936) reported that within each of two families 

 of chickens there was a different antigenic substance present than was found 

 in the parents. Attempts in our laboratory by Mrs. Ruth Briles to duplicate 

 this finding were without success, but a very interesting and quite unex- 

 pected observation was made which may be the explanation of Thomsen 's 

 finding. If an antigenic substance were present in an individual different from 

 that possessed by either parent, immunization of either parent (as #1) with 

 the cells of this individual might engender antibodies against the new sub- 

 stance. Absorption of such an antiserum by the cells of the other parent (as 

 #2) should remove all antibodies except those formed against the new or 

 hybrid substance, and such a reagent should be reactive only with the cells 

 containing the new substance. This was the procedure followed by Thomsen, 

 except that his tables do not show that the cells of the two parents were used 

 as negative controls in the tests made after the various absorptions. 



Immunizations of each of the parents of a family of chickens against the 



