Fig. 5. Time-window of requirement for FGFR activity in neural induction. Developmental stages are shown from fertilization (F) to stage 35, in register with time (in hours) elapsed at 23°C. Embryos were cultured in the presence of 80 µM SU5402 during the periods indicated with bars, and phenotypes were analysed at stage 35. Results are represented as the number of embryos of each class out of the total number of treated embryos. Starting 5.5 hours treatment at MBT, but not later, completely suppressed neural development.