RECENTLY1,2 we described “residual complexes” from calf thymus chromatin which consist of DNA and protein. We concluded from the strong binding forces that the complexes represent native substructures of the chromosomes. The proteins, although often designated as non-histones, proved to be chiefly histones which become insoluble in acids because of their strong association with DNA. We failed to find more than 3 per cent of non-basic or acidic proteins in the core of chromatin. Our findings are confirmed by the results of Fredericq and Houssier3.