o-Dianisidine staining of whole embryos and erythroid cells. (A) Stage-35 whole embryo; the arrow points to the blood island that is stained orange-brown. (B) pcDNA3–BMP-4 (200 pg)– injected embryos; the ventralized embryos have diffuse orange-brown staining of the mesoderm. The arrow points to the enlarged blood island of a partially ventralized embryo. (C, D)o-dianisidine–positive cells from a dispersed stage-33 tadpole VBI. The cells in (C) were photographed at 10× original magnification, whereas the cells in (D) were photographed at 20× original magnification.