An exceptionally low tide revealed several hitherto cautiously preserved secrets of the reef, among them the location of a species of sponge, dark brown, some semi-spherical, some turreted in fantastic fashion. Embedded upright in the sponges, like almonds in plum-puddings, so that merely the extremities of the valves were visible as narrow slits, were the long-sought-for molluscs. Judging by the extreme care of the species for its own protection--for it is ill-fitted in model and texture for a rough-and-tumble struggle for existence--one is inclined to the opinion that it must have many enemies. The valves are frail and brittle, and only when they gape are they revealed, and the gape is self consciously polite. The sponge embraces the slender mollusc so maternally that rude yawning is forbidden. It may lisp only and in smooth phrases, such as "prunes" and "prisms"; and, moreover, the host further insures it against molestation by the diffusion of an exceptionally powerful odour, which, though to my sense of smell resembles phosphorus, is, I am informed on indubitable authority, derivable from the active form of oxygen known as ozone. Experimentally I have placed these molluscs in fresh water, to find it quickly dyed to a rich amber colour while acquiring quite remarkable pungency. Even after the third change the water was impregnated. Interest in the mollusc became secondary upon the discovery of the host and in consideration of the part it plays in the production of one of the special effects of coral reefs; but the mollusc serves another and timely purpose--purely personal and yet not to be disregarded. It indicates a dilemma with which the wilful amateur in the first-hand study of conchology is confronted. Although, as I have said, no local knowledge of identity was available, reference to a well-disposed expert secured the information that its title in science is VULSELLA LINGULATA; that some twenty species are known; that they all associate with sponges, and that possibly different species inhabit different kinds of sponges. It may seem unpardonably gratuitous on the part of one professedly ignorant to offer general observations upon natural phenomena; but as I find myself among the great majority who do not know and who may be more or less interested and anxious to learn, I claim justification in describing that which to me is novel and rare. In this splendid isolation I cannot hope to illuminate primary investigations with the searching light in which science basks unblinkingly, for the nearest library of text-books is close on a thousand miles away. Nor can I keep all my observations to myself. There are some which, like murder, "will out," conscious though I am of meriting the censure of the learned.