The influence of N-ethyl urethane on the early development and nucleic acid metabolism in the embryos ofMicrohyla ornata.

1. The effects of N-ethyl urethane on the development ofMicrohyla ornata have been studied. 2. The embryos treated at early gastrula stage showed a disorganization and lack of differentiation of various organs. A range of abnormalities includes oedema, dwarfism, bent trunk or tail, brain and eye defects. 3. However, when urethane (0.4%) treated embryos received a subsequent thymidine treatment (6×10-4 M) they showed a remarkable improvement in the development of various organs. 4. The possible mode of action of urethane and its relationship with nucleic acid metabolism has been discussed.