rally, however, it is found embracing some univalve shell, which is tenanted by a Soldier Crab; young specimens on Turritella terebra, Trochus magus, T. ziziphinus, &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 porter 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 shock 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
