[The early development of the cranial segment of the müllerian duct in the rat].

In the rat the cranial part of the Muellerian duct (M-duct), i.e. the anlage of the uterine tube, is of dual origin. The different segments of the adult tube are already recognizable during embryogenesis and may be attributed to their original materials. The preampulla arises from the infundibular field of the coelomic epithelium (= MT). The isthmus is budding from the Wolffian duct (= MW). The middle segment of the tube, the ampulla, is organized by fusion of MT and MW. In the male rat embryo MW degenerates completely, whereas MT degenerates only partially. The remaining part of MT becomes to a solid structure close to the testis, namely the testicular appendage. In the rat testicular appendage is traceable until the first postnatal day.