THE account of the actinia on the claws of a crab in your last number (p. 515) is of interest as raising the point as to what benefit the crab oerives from its friends. In the Annals of Natural History, many years ago, I wrote that, having for a long period kept Adamsia palliata with P. Prideauxii in confinement, I had no doubt but that the white tentacles of the anemone were a bait which attracted various small animals within reach of the crab's claws, though it did not, as Mobius seems to think, in any way aid the crab in capturing its prey.