Nuclei of large oocytes of Fringilla coelebs were isolated in the Steinberg medium with thin needles under binocular lens. Oocytes of 1-2 mm in diameters have the nuclei of 150-300 mcm. By phase contrast microscopy, it was possible to follow the conspicuous steps of fusion of intranucler protein bodies during the karyosphere formation. To obtain remnant structures (components of nuclear structures), the nuclei and karyospheres isolated from large nuclei were treated with 2 M NaCI, 1% Triton X-100 and RNase. No changes in the appearance and dimensions of unfixed nuclei, protein bodies and karyospheres were observed during such a treatment. Pronase digested the remnant structures (nuclei and isolated karyospheres) completely. On ultrathin sections of the remnant nuclei untreated with RNase the following elements of nuclear matrix were revealed: 1) the fibrous layer of nuclear envelope (dense lamina) with remnant pore complexes; 2) remnant intranuclear fibrillar bodies; 3) numerous clumps of fibrous material probably representing fragments of nuclear bodies; 4) fibrillar-granular inner net (nucleonema). The structural continuity of nucleonema with other components of remnant nucleus is demonstrated on the ultrathin sections of matrixes. It is suggested that intranuclear fibrillar bodies on lampbrush chromosomes in oocytes of birds, participating in karyosphere formation, appear to be formed by nuclear matrix proteins.