Fig. 1.

Dorsal blastopore lip tissue of the early gastrula displays organizing activity. Excision of dorsal blastopore lip tissue from the pigmented newt Triturus taeniatus and transplantation in the region of presumptive ventral epidermis in a non-pigmented Triturus cristatus early gastrula. The donor tissue induces a secondary invagination in the host embryo and exerts organizing activity to surrounding host tissues. A secondary embryo forms where the donor tissue contributes mainly to notochord and prechordal mesoderm structures and re-organizes the normally ventral surrounding host tissues, which are dorsalized into neural tube and mesoderm (adapted from Gilbert, Developmental Biology)