74 BIOCHEMICAL SYSTEMATICS 



Systematic applications of serology require more insight into the 

 molecular basis of the phenomenon than now exists, yet there is no 

 clear indication that this facet of the problem is being aggressively 

 explored except by biochemists. No vigorous analytical treatment of 

 the problem of the qualitative aspects of the reaction appears from 

 the literature of systematic serology. The critical question of precisely 

 what is being measured has not been faced. For example, what are the 

 relative contributions of structural proteins, storage proteins, enzy- 

 matic proteins and non-proteins to the total reaction? Most proteins 

 which have been tested are antigenic, but their effectiveness varies. 

 What bearing, for example, does the disclosure that one may convert 

 gelatin from a weak antigen into a potent antigen by the attachment 

 of tyrosine, tryptophan or phenylalanine peptides (Sela and Arnon, 

 1960) have upon the question? 



Granted that it is perhaps not required that systematic 

 serologists establish, themselves, the precise molecular dynamics of 

 the reaction, there remains nevertheless an obligation to attempt to 

 establish some parameters with respect to the presumptive validity 

 of the method through experimentation. Several possibilities are 

 apparent. For example, it should not be difficult to obtain genetic 

 stocks of different highly homozygous lines of intensively investigated 

 species, such as maize. Hybrids could then be produced and back- 

 crossed, in successive generations, to each parental type. By this 

 method one could obtain, empirically, a graded series of genetic types 

 from one parental extreme to the other. If a parental "standard" is 

 utilized to prepare an antiserum, then the remaining lines would, if 

 the technique is valid, be predicted to yield heterologous reactions of 

 decreasing amount. Should a linear trend in the serological results 

 appear, it would provide convincing corroboration of the method. 

 Unfortunately, this type of experiment has not apparently been done. 

 In hybrid populations, where morphological hybrid indices (and even 

 biochemical indices in the case of Baptisia) are available, the serolog- 

 ical data could be correlated with data of these other types. Unless 

 experiments of these types are conducted, one cannot accept the 

 taxonomic implications of serological data without considerable reser- 

 vations. Actually, Moritz has undertaken a number of serological in- 

 vestigations of hybrids (for example, Moritz and von Berg, 1931), in 

 which pre-adsorption with appropriate parental serum was utilized, 

 among other devices, in establishing the hybrid nature of a putative 

 hybrid. That is, if a putative hybrid is used to produce an antiserum, 

 and following pre-adsorption with a serum from one and then the 

 other parent, no reaction occurs with the homologous serum, it is 

 concluded that the hybrid has no antigens not present in one or the 



