quantity of culture liquid 44 and they then isolate it from the rest of the culture liquid 16 gas exchanges can thereby take place at the level of the surface 16 s of the culture liquid and at the level of the surface 44 s of the quantity of withdrawn liquid 44 temporarily stored in each container 36 the total exchange surface area is therefore increased when the body 12 tilts to the opposite position from that represented in fig5 it is inclined with respect to its resting position the first containers 36 a extend above the culture liquid 16 and some e g as represented at 46 of the quantity of withdrawn liquid 44 pours out of the first containers 36 a into the rest of the culture liquid 16 the quantity 46 which pours out of the containers makes it possible to increase the total surface area of the culture liquid owing to its own surface area when the body 12 returns to the position in which the first containers 36 a are immersed the quantity of withdrawn culture liquid 44 is re introduced and mixes in with the rest of the culture liquid 16 combined with the stirring or agitating of the culture liquid 16 the action of the containers 36 makes it possible to increase the gas exchange surface area of the culture liquid 16 according to a variant not shown of the invention the body 12 can include a plurality of series or rows of containers 36 which are arranged at different distances from the bottom 24 so that at least some of the containers 36 are effective regardless of the depth of the culture liquid 16 contained in the body 12 thus plural containers can be provided.