Artificial neural induction in amphibia

Summary

• 1. Embryonic tissue of Triturus (ectoderm, neural plate) was killed with hot water and implanted into the blastocoel of young gastrulae. It induces the ventral ectoderm to form secondary neural plates with folds. Head-like protrusions develop with eyes, lenses, brain, ganglia, retinal pigment epithelium, balancers, mucous head epidermis, otic vesicles, olfactory organs, mesenchyme and melanophores.

• 2. Neural crest derivatives in these protrusions do not arise in the host's dorsal neural crests. When host neural folds are excised at early neural stages the host's body remains unpigmented, the induced protrusions, however, become pigmented and rich in head mesenchyme. Folds around the secondary neural plate must be the source for these cells.

• 3. Different results in explants (part I of this paper) and host embryos are discussed.

• a) Secondary neural folds arise in hosts only, not in explants. Their development depends on interactions between induced neural tissue, adjacent epidermis and/or ventral mesoderm.

• b) Ectomesenchyme derived from these folds influences development of the induced tissue. Unspecific induction by the implant results in neural (retina) tissue. All deviations from this line of development (segregation, transformation) are bound to the presence of mesenchyme.