keep our owne." We
do not, however, mean to assert that there are not sponges of some
species (though not the sponge of commerce) which exist at a depth as
great as that which he mentions, for Forbes dredged a living specimen of
one small kind from 185 fathoms in the Gulf of Macri.

The sponge of commerce (_Spongia officinalis_) was divided by Aristotle
into three kinds--namely, the loose and porous, the thick and close, and
the fine and compact. These last, which are rare, were called the
sponges of Achilles, and were placed by the ancients in the interior of
their helmets and boots, as protections from pressure and abrasion.

The same naturalist states that those sponges are best which are found
on coasts where the water becomes suddenly deep, and attributes this
superiority to the greater equality of temperature obtained in such
waters--observations which have been corroborated by Professor E.
Forbes.

Fifty-six species of sponges have been enumerated, ten or eleven of
which are found in the British isles. A portion of these inhabit fresh
water, among which we may mention the river sponge (_S. fluviatilis_),
which abounds in the Thames. Among the British sponges, too, is the
stinging or crumb-of-bread sponge (_S. urens_), a widely-diffused
species, which, when taken out of the sea is of a bright orange color,
and which will, if rubbed on the hand raise blisters. This stinging
quality is highly increased by drying the sponge; a process which also
gives it the color and appearance of crumbs of bread, whence its popular
name.

Sponges, as may be imagined from the mode of their growth, are most
sportive in their forms: some a tubular, others mushroom-like, a few
almost globular, and still others branched or hand-shaped; in the warmer
seas they hang in fantastic and gorgeous fans from the roofs of
submarine caverns, or decorate the sides with vases of classic elegance,
though of nature's handiwork. Nor are their colors less various: some
are of the most brilliant scarlet or the brightest yellow, others green,
brown, blackish, or shining white; while Peron mentions one procured by
him in the South Sea which was of a beautiful purple, and from which a
liquor of the same color was extracted by the slightest pressure; with
this liquor he stained several different substances, and found that the
color was not affected by the action of the air, and that it would bear
several washings.

The value of the sponge in surgery i