ITS HABITS. 147 



rally, however, it is found embracing some univalve 

 shell, which is tenanted by a Soldier Crab ; young 

 specimens on Turritella terehra, Trochus magus, 

 . T. siziphinus, &c., but adults, which are much more 

 frequently met with than the young, almost invariably 

 on the great Whelk {Buccinum undatum). The 

 dredge indeed often brings up shells invested by the 

 Actinia which are empty ; but I believe that in every 

 such case, the shell has recently been vacated by the 

 soldier, and that the Actinia never voluntarily selects 

 an empty shell for his base. 



The crab who sustains the honourable office of port- 

 er to this species is invariably Pagurus bernhardus, 

 as P. Prideauxii is favoured with the support of 

 Adamsia palliata. 



In the rude and blundering manner in which the 

 bearer performs his office, it cannot be but that the 

 poor Actinia gets many a hard knock, and many a 

 rough squeeze, among the rocks and stones over 

 which his servant travels; but he appears to bear 

 these mischances with great philosophy : I know of no 

 species which lives so constantly expanded. A rude 

 shook will indeed cause it to withdraw its tentacles, 

 and contract its disk into that button-like shape which 

 is common to the genus ; but this is only for a 

 moment : it instantly expands again and remains full 

 blown in spite of all its draggings about. Its skin 

 also is peculiarly tough and leathery; a provision, 

 doubtless, against the accidents to which its vagrant 

 life exposes it. 



We have no species which to such an extent as 

 this shoots forth those white filaments, which in this 



