AN UNEXPECTED GUEST. 157 



The association which often exists between animals 

 of diiFerent races and even of different classes, is always 

 a curious phenomenon ; and the motives which impel 

 to the companionship, no less than the mode in which 

 acquaintance is first formed, are most recondite. When 

 this species [Pagurus hernhardus) inhabits the shells 

 of the Whelk, it is quite common, though by no means 

 universal, to find the spire of the shell occupied as the 

 seat of that very fine Anemone, Act. ^jarasitica^ which 

 rears its tall and stout form like a thick pillar, sm*- 

 mounted by its dense fringe of tentacles that wave, 

 brush-like, with every vagrant movement of the Crab. 



But I find that this association is not the only one 

 that exists here. While I was feeding one of my 

 Soldiers, by giving him a fragment of cooked meat, 

 which he, having seized it with one claw, had trans- 

 ferred to the foot-jaws, and was munching, I saw pro- 

 trude from between the body of the Crab and the 

 Whelk-shell the head of a beautiful worm, Nereis 

 hilineata, which rapidly glided out round the Crab's 

 left cheek, and, passing between the upper and lower 

 foot-jaws, seized the morsel of food, and, retreating, 

 forcibly dragged it from the Crab's very mouth. I be- 

 held this with amazement, admiring that, though the 

 Crab sought to recover his hold, he manifested not the 

 least sign of anger at the actions of the Worm. I had 

 afterwards many opportunities of seeing this scene 

 enacted over again ; indeed, on every occasion that 

 I fed the Crab and watched its eating, the Worm ajD- 

 peared after a few moments, aware, probably by the 

 vibrations of its huge fellow-tenant's body, that feeding- 

 was going on, and not I think by any sense of smell, 



