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Abstract

In an attempt to solve some aspects of the long-standing controversy about the regenerative ability of appendages in vertebrate embryos, the tail bud of Xenopus laevis embryos has been amputated at stages ranging from St. 26 to St. 32 and its ability to regenerate during a culture period of 2–3 days has been studied. At amputation stages 26–28, the tail bud consisted only of undifferentiated mesoderm and ectoderm, but at stage 32 it had a fully differentiated neural tube, a vacuolated notochord and segmented somites. A total of 137 amputations at different stages gave consistent results: a tail formed in all the operated larvae and it had normal, well-developed axial tissues in most cases. The relatively few cases with abnormal tail structure were stunted, oedematous larvae with defects in the trunk region as well. It is concluded from these experiments that cells near the original tail bud are able to differentiate into tailbud tissue and to replace the amputated region, even at these late embryonic stages. The implications of these findings for comparative studies on regeneration in vertebrates are discussed.