AbstractAn apparatus is described for the aeration of a series of tissue cultures at rates which may be varied independently for each vessel. The composition of the aerating gas can be adjusted to any desired percentages of CO2and O2. While designed particularly for study of the aeration requirements of submerged tissue growth, the equipment is equally adaptable for study of submerged growth of bacterial and other systems. The apparatus has been designed for future scale‐up and is adaptable to both the overlay and bubble‐through types of aeration. Flow rates necessary for producing mixtures of 5.0% CO2and 95.0% air or 5.6% CO2, 14.0% O2, and 80.4% nitrogen are given. The described system has been operated satisfactorily and has proved to be an inexpensive and useful research t