In order to investigate the mechanism of early amphibian embryogenesis, the uncleaved eggs of Korean anuran Rana dybowskii were inverted at various times as well various duration after fertilization. However, developmental arrest at early gastrula stage always followed partial invagination of the dorsal lip. Nuclear transplantation was then employed to reveal the cause of death. Comparing the developmental capacity of the endodermal cells of inverted R. dybowskii and those of non-inverted normal control embryos, there was no difference between those two cases. It was concluded that the death of the inverted embryos was not attributed to the endodermal cells and the cause should be found elsewhere. Nuclear transplantations were also carried out to investigate the extent of development by newly injected nuclei from normal embryos. For that purpose nuclei from the cells at various developmental stages of blastula, gastrula, neurula an tail bud stages were injected into the eggs whose nuclei had been previously eliminated. It was revealed that as cells differentiated their nuclei progressively restricted in their ability to promote the development of enucleated eggs. The results are quite similar to those early observations by other investigators who used other amphibian species.