an annular culture vessel for growing mammalian cells is constructed in a one piece integral and annular configuration with an open end which is closed by an endcap . the culture vessel is rotatable about a horizontal axis by use of conventional roller systems commonly used in culture laboratories . the end wall of the endcap has tapered access ports to frictionally and sealingly receive the ends of hypodermic syringes . the syringes permit the introduction of fresh nutrient and withdrawal of spent nutrients . the walls are made of conventional polymeric cell culture material and are subjected to neutron bombardment to form minute gas permeable perforations in the walls .