Transformation of the rete ovarii into a rete testis and of the epoophoron into an epididymis after experimental sex reversal in Gallus domesticus is described. After castration of female chicks, the medulla of the left ovary and/or the right gonadal rudiment develop into a testoid or an ovotestis. From general view, this is observed as sex reversal. In case of formation of a testoid, the epoophoron develops into an epididymis and the rete ovarii develops into a rete testis which consists of intra- and extratesticular and intracapsular parts. Thus, a luminated duct system is developed which allows the transport of semen. In case of formation of an ovotestis, the discontinuously side-by-side located parts of the rete ovarii and of the epoophoron are maintained.