fact that Munro's experiments were carried out under less satisfactory conditions; he himself states that more than half the tadpoles died during the first week, and that from the original 250 eggs only 10 survived to metamorphosis. Our own animals were well fed on a high-protein diet and had a high survival rate. Munro, on the other hand, does not state that his animals were fed but only that ...

Well before the somites form, the paraxial mesoderm of vertebrate embryos is segmented into somitomeres. When newly formed, somitomeres are patterned arrays of mesenchymal cells, arranged into squat, bilaminar discs. The dorsal and ventral faces of these discs are composed of concentric rings of cells. Somitomeres are formed along the length of the embryo during gastrulation, and in the segment...