Cover. Micrograph of isolated nematocysts, explosive organelles with high internal pressure which are used for prey capture in Hydra and other Cnidaria. The major components of the nematocyst wall are 'minicollagens', small collagens with only 14 Gly-X-Y repeats. A switch from intra- to intermolecular disulfide bonds in flanking cysteine-rich domains creates an oligomeric structure with high tensile strength and elasticity. Ulrike Engel is a Graduate Student in the group of Thomas W.Holstein at the Darmstadt University of Technology, Germany. The group's research concerns the molecular evolution of the nervous system and structure--function relationships in nematocyte exocytosis. For further details, see Engel et al., pages 3063--3073.