AbstractCompounds containing free amino, hydroxyl or carbonyl groups can be activated by reaction with polyphosphate ester. If the compounds contain a second functional group, polycondensations are possible; e.g. amino acids → polypeptides, carbohydrates → polysaccharides, nucleotides → polynucleotides. In the presence of polyadenylic acid, polymerization of uridylic acid is speeded up tenfold. This mutual effect of complementary nucleotide strands constitutes the experimental basis for a hypothesis concerning the terrestrial origin of systems capable of self‐repro