In almost
every long voyage some account is given of these confervae. They
appear especially common in the sea near Australia; and off Cape
Leeuwin I found an allied, but smaller and apparently different
species. Captain Cook, in his third voyage, remarks that the
sailors gave to this appearance the name of sea-sawdust.
Near Keeling Atoll, in the Indian Ocean, I observed many little
masses of confervae a few inches square, consisting of long
cylindrical threads of excessive thinness, so as to be barely
visible to the naked eye, mingled with other rather larger bodies,
finely conical at both ends. Two of these are shown in Plate 6
united together. They vary in length from .04 to .06, and even to
.08 of an inch in length; and in diameter from .006 to .008 of an
inch. 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 sac, composed of a pulpy substance, which
lines the exterior case, but does not extend within the extreme
conical points. In some specimens, small but perfect spheres of
brownish granular matter supplied the places of the septa; and I
observed the curious process by which they were produced.
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