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BIOCHEMICAL SYSTEMATICS 



birds are considerably more complex than those obtained from 

 seed proteins (Fig. 6-4). It would be interesting to compare the results 

 of this approach with the serological data obtained by Boyden and 

 others (Chapter 4). There is, however, some danger of circular reason- 

 ing whenever one engages in apriori deductive speculations concerning 

 the systematic value of a character which is studied only superficially. 

 This statement, which is not intended as a condemnation of Sibley's 

 methods, needs some clarification. Sibley points out that the proteins 

 are of particular significance since they are more or less direct gene 

 products. While no one would dispute the general principle, the fact 

 remains that electrophoretic data yield only patterns. They are 

 accordingly a cumulative expression of the protein complement and 

 do not provide evidence as to the particular structure of particular 

 proteins. Therefore, it seems that the force of the argument is lost, 

 and it is a mistake to assume that the electrophoretic patterns 

 are more incisive indicators of phyletic affinity than the morpho- 

 logical pattern also evoked by those same agents (the genes) perhaps 

 more indirectly. It is unnecessary to reaffirm the conviction that 

 intimate knowledge of protein molecular structure is of profound 

 phylogenetic importance and the statements above are not intended 

 to refute this hypothesis. 



