In all the cases mentioned, the advantages of the partnership seem to be all on one side, but there are numerous instances in which both partners seem to reap some benefit. A species of Hermit Crab very common in moderately deep water on many parts of the British coasts, _Eupagurus prideauxi_, is always found to have a Sea-anemone (_Adamsia palliata_) attached to the shell which it carries. The Anemone has a broad base which is wrapped round the shell, the mouth, surrounded by the tentacles, being on the under-side next the opening of the shell. There seems no reason to doubt that the presence of the Anemone does afford some degree of protection to the Hermit, and that, on the other hand, the Anemone benefits by being carried about, and shares in the crumbs from the Hermit's meals. It is stated that, when the Hermit removes to a new shell, it detaches the Anemone from the old shell with its pincers and places it in position on the new one. It appears, however, that it is not always necessary for the Hermit to remove to a larger shell as it grows, for the enveloping Anemone, as it increases in size, extends beyond the mouth of the shell, and so enlarges the shelter. Further, the Anemone in course of time dissolves the shell almost entirely away, and the Hermit is enveloped only by the soft fleshy mantle which it forms. In a similar way the deep-sea Hermit Crab _Parapagurus pilosimanus_ (see Plate XVI.) is always found lodged in a fleshy mass formed by a colony of Sea-anemones (_Epizoanthus_), within which, when it is cut open, may be found the remains of the shell which the Hermit first inhabited. A further development of the same habit is given by _Paguropsis typica_, found in deep water in Indian seas, which does not inhabit a shell at any time, but carries a fleshy blanket formed by a colony of Anemones. In dredging off the British coasts, we often find smooth rounded lumps of a Sponge (_Suberites ficus_), generally yellowish-grey in colour, having a round opening in which the claws of a small Hermit Crab (_Eupagurus cuanensis_) may be seen. On cutting open the Sponge, the body of the Hermit is seen to be lodged in a spiral cavity, and at the apex may be found the remains of a shell that has been corroded away by the Sponge which settled on and replaced it. Other species of Hermit Crabs constantly have their shells covered with a horny crust formed by Hydroid zoophytes (_Hydractinia_, etc.), and in this case also the extension of the Hydroid colony beyond the lip of the shell relieves the Hermit from the necessity of so frequently changing to a larger shell as it grows.