An inexpensive but versatile and reliable fermentor of novel design is described which may be used for cultivating a wide range of microorganisms and tissue cells in batch, continuous (single and multistage), and phased (synchronous) culture. It can be used advantageously for growing material sensitive to the shearing effects of circulation pumps or impellers of other fermentors. The conditions of aeration are comparable with those observed in conventional fermentors.