[Researches on Mullerian duct morphogenesis in birds : I. Descriptive study].

A descriptive study of the Mullerian duct morphogenesis was made in the chick embryo, using methods of photonic and electronic microscopy.The ambiguity of the relations between the wolffian and mullerian ducts proceeds from the tight topographic disposition of the distal end of the growing mullerian anlage and the wolffian epithelium. This distal end, the terminal mullerian strip, exhibits some peculiar cytological characteristics (undifferentiated cells, high nucleocytoplasmic ratio, big network-nucleolus), suggesting that this anlage does not proceed from the wolffian duct, as the old theories said. It would be responsible, both in Birds and Reptiles, for the caudad extension of the inner epithelium of the young mullerian duct.The conjunctive coat of the mullerian duct is formed "in situ" from the mullerian strip, the differentiated mesothelium of which is transformed into concentric mesenchymal layers, along the wolffian duct.The modalities of the mullerian duct morphogenesis in Birds are compared with those of the organ formation in other vertebrates.