Determination of Neural Ectoderm by Induction

Earlier you know that the dorsal mesoderm induces the ectoderm to differentiate into neural tissue. Spemann and his co-workers conducted their experiments in newts, a group of amphibians. Two types of species of newts whose cells differed in pigmentation were chosen for the experiments. These involved the non-pigmented Triturus cristatus and the pigmented Triturus taeniatus. After that he exchanged pieces of presumptive epidermal and neural ectoderms among early embryos of the two species and followed the development of grafted tissue in the respective hosts with pigment as the marker.

While a piece of prospective neural ectoderm from an early gastrula stage donor embryo was grafted into a region of the host embryo in which belly skin should develop, the graft developed into belly ectoderm. Similarly, when the prospective epidermal ectoderm was grafted into a region in which a neural plate should develop, it developed into a neural plate. Such type of exchange of embryonic tissues made in early gastrula stages resulted in the development of structures as per to their new surroundings. These results clearly displayed that the fate of neither the prospective epidermal nor of neural ectoderm are not determined at the early gastrula stage embryos of the two species of newts on which the experiments were made.