Summary.  The development of the so‐called uterus masculinus is described from sections of 19‐to 32‐day post‐coitum embryos.  It was found that the structure is formed from the joining of the swollen bases of the Wolffian canals and is connected to the urethra by a short projection from the dorsal wall of the sinus. Since it is formed predominantly from Wolffian tissue it is renamed vesicula seminalis as suggested by Jost (1943, 1947), who first described the role of the Wolffian and sinus tissues in the formation of the vesicula seminalis.