The main object of our cytochemical studies at the Carlsberg Laboratory for some time has been the amoeba Chaos chaos (Pelomyxa carolinensis) . This organism has certain properties that make it a good object for cytochemical experimentation. It is closely related, both morphologically and physiologically, to the well-known Amoeba proteus , but differs from the latter in that it is multinuclear and correspondingly larger. Its average size is about 0⋅03 μ 1., which is the right order of magnitude for work with the quantitative enzymatic micromethods at our disposal. Another important property is the ease with which the cytoplasmic components can be separated by centrifugation of the living cell. Floating in a density gradient of gum-arabic solution and in centrifugal fields of about 1000 to 2000 g a stratification of the cellular contents takes place (figure 1). When the amoeba is removed from the centrifuge, remixing of the strata by cytoplasmic currents begins immediately, and if the amoeba is kept at room temperature, after 30 to 60 min it will appear perfectly normal, not only with regard to microscopical appearance but also in motility, oxygen consumption, etc. In other words the stratification brought about by a centrifugal force of 1000 to 2000 g is perfectly reversible by all the criteria that we have been able to apply. This indicates that the separation of cytoplasmic constituents by centrifugal stratification of the living cell must be a rather mild procedure. If the remixing is retarded, e. g. by chilling the amoeba, one can separate by means of microneedles cell fragments which contain concentrates of the various cytoplasmic constituents, isolated from each other by this mild and essentially reversible procedure.