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Precursor stages of large holotrichs in the mesenterial filaments of Corynactis californica and C.viridis have been visualised by simple methods using stained whole-mount preparations. Samples were taken from mesenterial filaments emitted during aggressive behaviour (which is reported for the first time in C. viridis). Results suggest that in natural conditions localised stimuli may provoke discharge along short stretches of mesenterial filament, followed by localised recruitment within these depleted areas.

Epizoic Kerona pediculus have been found on Hydra vulgaris and on Cristatella mucedo (Bryozoa) in the same habitat. On the basis of morphological characters (using Nomarski and Scanning Electron Microscopy) specimens from the two hosts are indistinguishable. Details revealed by SEM agree with previous results from silver staining, confirming the identity of K. pediculus. The taxonomic status of this species is briefly summarised. Host recognition, the inhibition of nematocyst discharge, and the possible role of host growth-promoting substances are not yet understood.