Mesoderm induction by the mesoderm of Xenopus neurulae.

Combinations were made between explants of mesoderm from the archenteron roof of early Xenopus neurulae and explants of ectoderm from mid-blastulae. In each combination one component was labeled with the fluorescent lineage label RDA (rhodamine-dextran-amine). Frequent and large mesoderm inductions, consisting mainly of muscle, were found where the presomite plate was used as the inducer. Less frequent and smaller mesoderm inductions were found when notochord was used as the inducer. We conclude that induced mesoderm can itself be active as a mesoderm inducing tissue. If this capability is acquired in the blastula then it follows that mesoderm induction must propagate from cell to cell and its spread be antagonized by some other factor.