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Show 14 BAHIA-BRAZIL. Feb. 1832. short 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 t~is fluid .is taken .in ~artly for the sake of regulating its specific gravity. This dwdon possessed several means of defe!'J.Ce. 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 papillre, 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 in 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. MARC II 18TH.-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 chopperl bits of hay, with their ends jagged. One of the larger particles measured .03 of an inch in length, and .009 in breadth. Examined 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 confervre 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 Mar. 1832. PELAGIC CONFERV£, 15 water, at least two and a half miles long. In almost every long voyage ~orne account is. given of these confervre. They appear especially common m the sea near Australia. ·Off Cape Leeuwin, I found some very similar to those above described; they differed chiefly in the bundles being rather smalle~, a~d b~ing composed of fewer filaments. Captain Cook, m h1s third voyage, remarks, that the sailors gave to this appearance the name of sea-sawdust. ~ may here mention that during two days preceding our arrival at the Keeling Islands in the Indian Ocean, I saw in many parts ~as~es of flocculent matter, of a brownish-green colour, floatmg m the sea. They varied in size, from half to to three or four inches square; and were quite irregular in fig~re. In ~n opake vessel they could barely be distingmsh~ d, but m a glass one they were clearly visible. Under the miCroscope the flocculent matter was seen to consist of two kinds of confervre, between which I am quite ignorant whethe~ there exists any connexion. Minute cylindrical bodies, comcal at each extremity, are involved in vast numbers, in a mass of fine threads. These threads have a diameter of abou~ ~ o2o o o~ an inch; they possess an internal lining, and are diVIded at Irregular and very wide intervals by transverse septa. Their length is so great, that I could never with certainty ascer~~in the form of the uninjured extremity; they are all cUTVIlmear, and resemble in mass a handful of hair coiled up and squeezed together. In the midst of thes~ threads, and probably connected by some viscid fluid the other kind, or the cylindrical transparent bodies, flo~t in great numbers. These have their two extremities terminated by cones, produced into the finest points : their diameter is tolerably constant between .005 and .008 of an inch . but their ~ength 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 m the middle, may generally be seen. ".rhis, I believe, is the bottom of a most delicate, colourless sack, composed of a pulpy substance, which lines the exterior case, but does |