mouth; and this is a curious circumstance, because, as it does not extend across the orifice, the animal assumes an annular form, the Crab inhabiting the shell, and protruding freely through the opening. On that side which is next the inner lip or column of the shell, and beneath the breast of the Crab, there opens a wide oblong mouth, in all essential particulars like that of an Actinia, surrounded by a delicate fringe of short white tentacles; which in general are freely exposed, seeking for prey; the animal being little alarmed by the rude treatment to which the peregrinations of its active companion expose it.
This form, at first sight, seems so very anomalous, that a naturalist of no small knowledge has recourse for its explanation, to the suggestion "that the old shell [of a Gasteropod Mollusk] with a young Crab in it may have been swallowed by the Actinia; that the Crab may have forced its way through the walls of the stomach and the integuments of the latter, and that the Actinia then secreting a peculiar membrane to defend its base, the Crab may have found itself provided with a habitation suited to its wants."[1] Yet it appears to me that the deviation from normal structure is more apparent than real. The Adamsia is evidently an Actinia of a long-oval form, capable of development in its long diameter into two lengthened wings. Its instinct invariably leads it to select as its support the inner lip of some univalve shell, having adhered to which, the lateral expansions creep along the shell, following its surface until they
- ↑ Coldstream, in Johnston's Brit. Zooph. i. 209.
