The sexual reproductive process of Achlya ambisexualis, a heterothallic form belonging to a well known and widely distributed genus of saprophytic aquatic fungi, is initiated and coordinated by means of specific substances (Raper, 1939, a). Four of these substances have been demonstrated (Raper, 1939, b, 1940) in the r&es of initiators and coordinators of the various stages in the sexual proces...
