1. Both Cellophane and velvet models have shown that packing barbs, attached to the inside of a fabric cylinder, in alternating whorls of three, generates a configuration of the fabric surface closely similar to that observed in the undischarged thread of the large holotrichous isorhizas of Corynactis viridis Allman.
2. When this assembly is caused to transform to the discharged configuration (a) there is no change in surface area and (b) there is no significant distortion of the fabric.
3. The model increases 3.08 times in length on transformation to the discharged configuration, as compared with an increase of 2.93 times measured on electron micrographs of median longitudinal sections.