Preparatory work for this monograph started in 1988 and 1989. The motive was provided by certain incongruities in the illustra- tion of descensus testis for the chapter "Entwicklung der Genital- organe" in the book Humanembryologie. The evoked discussion was reason enough for our own re- search on the phenomenon and uncertainties of testicular des- cent in human. The basis ofthese investigations was the collection of human embryos founded by Prof. Hinrichsen in 1970 at the Department of Anatomy and Embryology, Ruhr-University Bo- chum. The preparation of the material used in this paper has...