Fig. 1. (A) Convergent extension occurs in both dorsal mesodermal and posterior neural tissues. Axial mesoderm (red) involutes and undergoes convergent extension in parallel to convergent extension of overlying posterior neural ectoderm (blue). AR, archenteron; BC, blastocoel. (B-D) Cell behaviors during convergent extension. (B) Dorsal mesoderm (Shih and Keller, 1992a); (C) neural-over-mesoderm (Elul and Keller, 2000); (D) isolated posterior neural ectoderm (Elul et al., 1997). Red, mesoderm; Blue, posterior neural. In C, light blue indicates notoplate.