Blood formation in a clonal cell line of mouse teratocarcinoma

Pluripotent cells of a teratocarcinoma clonal line differentiate into various tissues when they are cultivated in submerged cultures. We describe here the formation of endodermal vesicles and blood islands in organotypic cultures of such cells. These are the first macroscopically visible tissues to appear in organ culture and they give rise to megalocytes, the ultimate stage of blood cell evolution in the normal mouse embryo yolk-sac. As in the normal embryo yolk-sac, the formation of haemoglobin-containing cells stops after a while, but it is not replaced by adult haemopoiesis in culture.