The constant association of a large group of animals like the Hermit-crabs with the appropriated empty houses of another group is sufficiently curious, but it does not stop there. In almost every case there are present one or more Sea-anemones growing on the outside of the shell, and each kind of Hermit-crab generally carries a special kind of Anemone. Thus at Plymouth, _Eupagurus bernhardus_ is generally symbiotic with _Sagartia parasitica_, or else with a colony of _Hydractinia echinata_, while _E. prideauxii_ is usually associated with _Adamsia palliata_. In the latter case the shell is frequently absorbed, so that the Anemone comes to envelop the crab like a blanket. Instead of Anemones carried turret-like and imposing aloft, or enveloping the inmate of the shell like a blanket, some of the Hermits have Sponges, an unexpected association; and it is a common sight at Naples to find the little red round Sponge, _Suberites_, running around animated by its Hermit within. It is held that Anemone and crab mutually assist one another, that the Anemone stings the crab’s enemies, and that the Hermit-crab carries the Anemone to new feeding-grounds. It is also said that when a crab grows too big for its shell, and is forced to seek another, it persuades the Anemone to loosen its attachment to the deserted shell and to be transplanted to the new one, and that there is something mesmeric in its power, because nobody else can pull an Anemone off a shell without either cutting it off at the base or tearing it to pieces. Other animals as well sometimes enter into this partnership. At Plymouth a Polychaet worm, _Nereis fucata_, frequently inhabits the Whelk’s shell, together with _Eupagurus bernhardus_, and puts out its head for a share of each meal; and at Naples the Amphipod _Lysianax punctatus_ is almost always present in the shells of _Eupagurus prideauxii_. [Illustration: FIG. 118.—_Pylocheles miersii_, × 1. =A=, End view of a piece of mangrove or bamboo, the opening of which is closed by the great chelae (_c_) of the Pagurid; =B=, the animal removed from its house. (After Alcock.) ] Besides the ordinary twisted Pagurids which inhabit Gasteropod shells, there are a few which preserve the symmetry of the body. The interesting _Pylocheles miersii_[143] (Fig. 118), taken by the _Investigator_ in the Andaman Sea at 185 fathoms, inhabits pieces of bamboo; it is perfectly symmetrical, with well-developed pleopods and symmetrical chelae, which, when the animal is withdrawn, completely shut up the entrance to its house (Fig. 118, A).