Early limb development of Xenopus laevis

This investigation has used histological techniques and the scanning electron microscope to establish the presence of an apical ectodermal ridge in the developing limbs of Xenopus laevis . The ridge appeared at stage 50, reached its maximal size at stage 51, and subsequently disappeared by stage 53. The course of the ridge was consistently related to a marginal sinus in the underlying mesenchyme. The other features of limb morphogenesis, such as the formation of a paddle and the sequence of condensation of skeletal rudiments in the mesenchyme, corresponded closely to those seen in other vertebrates. It remains to be seen whether the ridge we have demonstrated in Xenopus exercises a similar function to that claimed for its counterpart in the chick.