Fig. 10. Notochord fails to form a cylindrical intermediate in embryos lacking both neural plate and muscle. (A) Late neurula stage. The lateral notochord arms have met at the posterior (compare with D and E in Fig. 9). (B) Late tailbud stage. Individual notochord cells have begun to swell as they do at later stages in control embryos, but the overall shape and organization of the notochord rudiment remains similar to that seen at late neurula stage.