Fig. 3. Ventricular and atrial endocardial progenitors are intermingled at 40% epiboly. The fate map of endocardial chamber progenitors is depicted as described for the myocardial fate map (Fig. 2B). In this map, bar colors correspond to the endocardial contribution of labeled cells: red, contribution to ventricular endocardium; yellow, contribution to atrial endocardium; cyan, contribution to both ventricular and atrial endocardium; black, no endocardial progeny. All data from Table 2, except for the experiment labeling five blastomeres, are included. Endocardial progenitors are found 55-140° from dorsal in all four tiers.