A device for developing electrostatic images includes a toner supply chamber for holding a supply of dry toner and a feed member located generally at the bottom of the supply chamber. To break up agglomeration of toner in the supply chamber an agitator, for example an elongated polypropylene fiber brush, is placed on top of the feed member and is supported totally at its periphery by the feed member and associated walls of the supply chamber. As the feed member rotates, the agitator is rotated to maintain the toner in particulate form.