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		Detailed protocol 1. The operation should be performed under aseptic conditions. All phases of the operation should be performed in Steinberg's solution to promote healing. After healing, however, embryos should be transferred to spring water or 10% amphibian ringers solution. 2. Dip the tip of the eyebrow knife in 90% alcohol and then passed through asmall beaker containing the operating medium. Make sure all instruments are sterile. 3. Transfer the Xenopus embryo to the agar dish containing operating medium. Removejelly coats and vitelline membrane, handle the denuded embryo CAREFULLY. 4. With a ball tipped glass needle or watchmakers forceps make a shallow depression in the agar in which the embryo can sit comfortably, dorsal side up. Using an eyebrow knife, carefully remove part of the dorsal lip. With a single motion, bottom to top, make a thin tear in the epidermis. Follow the first longitudinal cut with a second longitudinal cut. The subsequent two cuts are transverse cuts, to complete a rectangular area of dorsal lip tissue. 5. Life the entire rectangular area of tissue away from the embryo with the tip of the glass needle. 6. Prepare a small pocket in the ventral surface of the host embryo. Do not attempt to cut a rectangular section, all that is needed is a mere slit, or slight hole. The pocket can then be enlarged to receive the transplant by carefully removing some of the mesoderm cells.