Fig. 1. Neural crest induction in vitro. (A) Non-neural ectoderm (open blue rectangle) and intermediate neural plate (solid blue line) were dissected from 8- to 12-somite chicken embryos (cross section of dissection shown in A'). (B) After 24 hours in culture, neural crest induction occurs only when neural plate and non-neural ectoderm are cultured in contact with one another (Dickinson et al., 1995; Selleck and Bronner-Fraser, 1995). (C) RT-PCR for the neural crest marker slug.