Cell contacts between chorda-mesoderm and the overlaying neuroectoderm (presumptive central nervous system) during the period of primary embryonic induction in amphibians.

Using transmission and scanning electron microscopy we were able to show that during primary embryonic induction in amphibians (Triturus alpestris) the interspace between the inducing chorda-mesoderm and the reacting ectoderm (presumptive medullary plate) of mid-gastrula stages is traversed by cell projections starting from cells of both tissue layers. In addition intimate membrane contacts between the main bodies of the ectodermal and chorda-mesodermal cells could be observed. It could be ruled out that cytoplasmic bridges (anastomosis) exist between cells of inducing chorda-mesoderm and reacting ectoderm, which would allow a free transfer of inducing substances without passing through membranes, as Eakin and Lehmann [1] have postulated. The possible role of cell to cell contact for neural induction is emphasized.