The application of cinemicrography to the dark-field ultramicroscopy of tex tile fibers permits repeated and close observation of the rapidly changing movements of colloidal inclusions energized by suitable swelling agents. Through this tech nique the permeable membranes of starch particles and natural fibers are made visible. The effects of osmotic pressure, such as the instantaneous eruption of col loidal masses from the ruptured envelope of starch grains and cotton fibers, have been recorded by the motion picture camera and thus made available for careful study.The inhomogeneity of wool scales and their capsule-like structure are recorded. The movement of colloidal particles within and through the outer walls of the swol len cotton fiber has been photographed and it can be analyzed at leisure by project ing the film.The fact that some of the material in this article has previously appeared in Kolloid Zeitschrift64,257 (1933), and Der Papier-Fabrikant 32,61 (1934), empha sizes its value, and for this reason it is now being presented in its present form in this journal.-Editor.