[Hypothesis on the mechanism of cnidocyst discharge (author's transl)]

The geometic aspects of the cnidocystic filament before invagination, during invagination and after the process of evagination are shown. Experiments are described that allow an approach to study the mechanism of discharge. It is suggested here that the filament is an elastic tube which, when it is intracapsular, is folded and spiraled and thus, under a constraining action. Evagination then consists simply in the release of the constraining force and reversion of the filament to the primitive cylindric shape. The presence of water seems indispensable to the process to take place; however this does not necessarily imply that a hydratation take place in the filament wall. It also seems obvious that if expansion is a normal tendency of the constrained filament, eversion is a result of the continuity between the wall of the filament and that of the capsule. In conclusion, the invagination of the tube during cnidogenesis may be interpreted as a mean of storing energy for the evagination.