1. The mechanical properties of the mesogloea of the sea anemone Metridium senile were investigated. An amorphous polymer network in the matrix was found to play a major role in determining the mechanical properties of the tissue.
2. The matrix network provides an elastic mechanism based on ‘rubber elasticity’ of the folded matrix molecules. The properties of the matrix network alone account for the extensibility and elasticity of mesogloea.
3. The collagen acts as a reinforcing filler providing short-term rigidity to the flimsy polymer network.
4. The collagen fibres are not directly cross-linked to one another but are tied together through the amorphous matrix.
5. The extensibility and elasticity of the tissue appear to be dependent on a very low degree of cross-linking in the mesogloeal system. Inorganic ions mask ionized groups on the collagen and matrix polymer chains and block electrostatic interactions which could cross-link the system.