- according to Hottinger (2006):
CHAMBER LUMEN - (=chamberlet lumen); a shell cavity filled with protoplasm (usually of an endoplasmic nature except in newly formed chambers), coated by an organic lining, the primary cell envelope. By definition, chamber lumina communicate exclusively through intercameral foramina and/or multiple stolon systems. The term "chamber lumen" is used in particular to distinguish between the "inside" and "outside" of a shell, i.e. between intra- and interlocular spaces. The latter are never papered with an organic lining. Within the boundaries of intraspecific variability the volume of chamber lumina may depend on the seasonal availability of food and be independent of wall thickness which in lamellar foraminifera is dependent on water turbulence.
Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744