Fig. 2. DiI labeling of the P. sinensis mesoderm and origin of the CR. (A-C) DiI was injected focally into the ventrolateral part of the dermomyotome at stages 11-11⁺. Arrowheads indicate the ventral limit of the CR or the junction of the lateral body wall. (A) Just after labeling. Note that the DiI labeling is restricted to the dermomyotome, and no part of the lateral plate is labeled. (B) Transverse sections of another embryo treated as in A and incubated for 5 days. Some somite-derived cells are migrating into the body wall, representing the hypaxial muscle precursor. (C) Higher magnification of the box in B. Mesenchymal labeling is restricted to the CR, except for a few labeled cells in the lateral body wall. (D-G) Labeling of the lateral plate (somatic) mesoderm. (D) A transverse section of the embryo just after labeling. Labeling is restricted to the most medial part of the lateral plate mesoderm, and no labeling occurs in the dermomyotome. (E-G) Five days after labeling. Transverse sections of an embryo treated as in D. Labeled mesenchyme is found only in the dermis of the lateral body wall. (F,G) Higher magnifications of boxes in E and F, respectively, showing the absence of labeled mesenchyme in the CR. In many embryos with the same labeling, a part of the CR-covering epidermis is labeled. (G) The CR does not contain any labeled mesenchymal cells. Scale bars: 100 µm for A,D; 200 µm for B,E; 50 µm for C,F,G. cr, carapacial ridge; dm, dermomyotome; hd, lateral body wall; hm, hypaxial muscle precursor; n, notochord; nt, neural tube; r, rib primordium; sc, sclerotome; sm, somatic mesoderm.