Briggs and King describe a method for transplanting nuclei from blastula cells into enucleated frog eggs, demonstrating that living nuclei can be transplanted and that the resulting embryos develop normally. The study shows that the nuclei are not significantly damaged and that the technique can be used to test nuclei from various differentiated parts of the amphibian embryo. The method involves transferring the nucleus of a blastula cell into an enucleated egg, which then cleaves and develops into a normal embryo. When the nucleus is from a different species, the enucleated egg forms a blastula that is arrested and subsequently dies, similar to the normally produced hybrids between the two species. This indicates that the blastula cell nucleus can be transplanted in undamaged condition, suggesting that the technique of nuclear transplantation is now sufficiently well developed to study nuclear differentiation and possibly other nuclear functions. The study also shows that the method allows for the detection of irreversible changes in nuclei that may limit differentiation. The results of the experiments provide evidence that the technique is successful and that the transplanted nuclei can be used to study nuclear differentiation. The method involves transferring the cytoplasm as well as the nucleus of the blastula cell into the enucleated egg, but the cytoplasm is not significantly diluted. The study also discusses the potential applications of the technique, including testing whether nuclei treated in various ways still retain their capacity for mitosis. The method is described as a valuable tool for studying nuclear differentiation and may have other uses in the future. The study is supported by a research grant from the National Cancer Institute and an institutional grant from the American Cancer Society.Briggs and King describe a method for transplanting nuclei from blastula cells into enucleated frog eggs, demonstrating that living nuclei can be transplanted and that the resulting embryos develop normally. The study shows that the nuclei are not significantly damaged and that the technique can be used to test nuclei from various differentiated parts of the amphibian embryo. The method involves transferring the nucleus of a blastula cell into an enucleated egg, which then cleaves and develops into a normal embryo. When the nucleus is from a different species, the enucleated egg forms a blastula that is arrested and subsequently dies, similar to the normally produced hybrids between the two species. This indicates that the blastula cell nucleus can be transplanted in undamaged condition, suggesting that the technique of nuclear transplantation is now sufficiently well developed to study nuclear differentiation and possibly other nuclear functions. The study also shows that the method allows for the detection of irreversible changes in nuclei that may limit differentiation. The results of the experiments provide evidence that the technique is successful and that the transplanted nuclei can be used to study nuclear differentiation. The method involves transferring the cytoplasm as well as the nucleus of the blastula cell into the enucleated egg, but the cytoplasm is not significantly diluted. The study also discusses the potential applications of the technique, including testing whether nuclei treated in various ways still retain their capacity for mitosis. The method is described as a valuable tool for studying nuclear differentiation and may have other uses in the future. The study is supported by a research grant from the National Cancer Institute and an institutional grant from the American Cancer Society.