Fig. 1. Successive stages in dermomyotome development at flank levels of the axis. (A-D) Phase contrast images. (A) T0. Epithelial somite stage with the prospective dermomyotome (DM) highlighted by broken lines. (B) T1. Initial formation of the DM following mesenchymalization of the sclerotome (Scl). At this stage the pioneer (P) myoblasts bend underneath the nascent DM. (C) T2. The DM of a fully dissociated somite in which the primary myotome (M) is well differentiated. Note the well defined medial and lateral edges (DML and VLL, respectively). (D) T3. The DM dissociates into dermis except for the DML and VLL, which still remain epithelial (demarcated by broken lines). See text for precise stages. DRG, dorsal root ganglion; NT, neural tube. Scale bar: 8 µm in A; 15 µm in B; 22 µm in C; 80 µm in D.