Artificial neural induction in amphibia. I. Sandwich explants.

1. Embryonic tissues (ectoderm, neural plate) of Ambystoma mexicanum and Tritus were killed with hot water and implanted into ectoderm sandwiches. They induced the ectoderm to form neural tissue, lentoids and unspecialized epidermis. Neural tissue always showed retina character. Egg pigment was eliminated and gathered at the outer retinal surface or in the centre of rosettes. Neural crest cells like mesenchyme or melanophores were completely lacking, retinal pigment did not develop. 2. The thus induced living retina tissue was reimplanted into fresh ectoderm after 2 days. It continued histogenetic and morphogenetic differentiation and formed ocular vesicles with numerous eye cups. It induced the enveloping ectoderm to again form retina, lentoids and unspecialized epidermis without neural crest derivatives or RPE. 3. This inductive process can be reproduced several times.