sliort time, generally expelled the air and water with considerable
force from the branchial apertures and mouth. It
could emit, at will, a certain portion of the water; and it
appears, therefore, probable, that this fluid is taken in partly
for the sake of regulating its specific gravity. This diodon
possessed several means of defence. It could give a severe
bite, and could eject water from its mouth to some distance,
at the same time it made a curious noise by the movement
of its jaws. By the inflation of its body, the papill®, with
which the skin is covered, became erect and pointed. But
the most curious circumstance was, that it emitted from
the skin of its belly, when handled, a most beautiful carmine
red and fibrous secretion, which stained ivory and paper
m so permanent a manner, that the tint is retained with all
Its brightness to the present day. I am quite ignorant of
the nature and use of this secretion.
M a r c h 1 8 t h .— We sailed from Bahia. A few days afterwards,
when not far distant from the Abrolhos islets, my
attention was called to a discoloured appearance in the sea.
The whole surface of the water, as it appeared under a weak
lens, seemed as if covered by chopped bits of hay, with
their ends jagged. One of the larger particles measured .03
of an inch in length, and .009 in breadth. Fxamined more
carefully, each is seen to consist of from twenty to sixty
cylindrical filaments, which have perfectly rounded extremities,
and are divided at regular intervals by transverse
septa, containing a brownish-green flocculent matter. The
filaments must be enveloped in some viscid fluid, for the
bundles adhered together without actual contact. I do not
know to what family these bodies properly belong, but they
have a close general resemblance in structure with the con-
fervifi which grow in every ditch. These simple vegetables,
thus constituted for floating in the open ocean, must in
certain places exist in countless numbers. The ship passed
through several bands of them, one of which was about ten
yards wide, and, judging from the mud-like colour of the
water, at least two and a half miles long. In almost every
long voyage some account is given of these confervoe. They
appear especially common in the sea near Australia. Off
Cape Leeuivin, I found some very similar to those above
described ; they differed chiefly in the bundles being rather
smaller, and being composed of fewer filaments. Captain
Cook, in his third voyage, remarks, that the sailors gave to
this appearance the name of sea-sawdust.
I may here mention that during two days preceding our
arrival at the Keeling Islands in the Indian Ocean, I saw in
many parts masses of flocculent matter, of a brownish-green
colour, floating in the sea. They varied in size, from half to
to three or four inches square ; and were quite irregular in
figure. In an opake vessel they could barely be distinguished,
but in a glass one they were clearly visible. Under
the microscope the flocculent matter was seen to consist of two
kinds of confervoe, between w’hich I am quite ignorant whether
there exists any connexion. Minute cylindrical bodies,
conical at each extremity, are involved in vast numbers, in
a mass of fine threads. These threads have a diameter of
about 3 o'o 0 of an inch ; they possess an internal lining, and
are divided at irregular and very wide inters’als by transverse
septa. Their length is so great, that I could never with certainty
ascertain the form of the uninjured extremity; they
are all curvilinear, and resemble in mass a handful of hair,
coiled up and squeezed together. In the midst of these
threads,^ and probably connected by some viscid fluid, the
other kind, or the cylindrical transparent bodies, float in
great numbers. These have their two extremities terminated
by cones, produced into the finest points : their diameter is
tolerably constant between .003 and .008 of an inch; liut
their length varies considerably from .04 to .06, and even
sometimes to .08. Near one extremity of the cylindrical
part, a green septum, formed of granular matter, and thickest
in the middle, may generally be seen. This, I believe, is
the bottom of a most delicate, colourless sack, composed of
a pulpy substance, which lines the exterior case, but does