general reference to the life of the coral reef.

A third species, rare in a certain sense only, is of a most retiring, not
to say secretive, disposition. For several years I sought in vain a
living specimen of a flattened elongated bivalve (VALSELLA),
buff-coloured externally, very lustrous within, with a hinge the centre
of which resembles a split pearl. The blacks could offer no information
beyond that which was delightfully indefinite. "That fella plenty alonga
reef. You look out. B'mbi might you catch 'em!" "Tom," who never
wilfully parades his ignorance, boldly asserted that they favoured rocks,
but he had no name for them, and no living specimen was ever forthcoming
to substantiate confident opinions.

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