[Ultrastructural study of the differentiation of the mesonephrogenic blastema cultivated in vitro in the presence of the primary ureter in the frog, Rana dalmatina Bon].

The culture of undifferentiated mesonephric blastema with the pronephric duct shows a beginning of differentiation of the blastema. This latter is formed by a cluster of mesonephretic cells with pseudopods towards the ureter. The increasing of cytoplasm and the multiplication of the organelles characterise these cells. The differentiation of blastema stops before the tubulogenesis.