ABSTRACT
A great deal of recent biological research has been concerned with elucidating the structure and functions of the nucleic acids, both the deoxyribonucleic acid (DNA) of the chromosomes and similar bodies and the ribonucleic acid which is believed to function as an intermediary between the DNA and the extra-nuclear protein-synthetic activities of the cell. 'Systematic serology' or 'immunodiagnostics' stands to the chemical study of protein structure in much the same relation as the Bolton-McCarthy DNA fibre-pairing technique stands to the structure of the DNA itself. The 'antibodies' produced in a vertebrate's blood in response to an injected alien protein are somewhat comparable to the 'complementary' fibres of DNA, and probably become attached to their complements in much the same way. Natural history in general knows of no techniques which provide infallible answers to the questions it asks, and DNA fibre pairing may well be the best single method available to us for measuring phylogenetic affinity between fairly distantly related organisms.
