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a triangular figure. Tliat the true form of the filaments is triangular,
a careful microscopical examination will convince any
one. The filaments are generally more or less twisted, and
sometimes occur nearly pellucid and colourless : in such instances,
a solitary green line extends in a waving manner along
the filament. This line, upon examination, is found to he one
of the crenated angles, which being viewed through the body
of the filament, is rendered opake. The detachment of the
joints is exceedingly curious ; and I cannot exactly comprehend
in what manner it takes place, unless the internal structure of
the filament be more tenacious than the outer membrane. Before
the ultimate separation takes place at the articulation of
each joint, the outer membrane loses its continuity, and towards
the angles appears to collapse. In this state, the filament
may be said to he pimiatifid, for the joints are attached
only in the centre, as I conjecture by their internal substance.
A g a r d h has introduced this remarkable appearance
into the generic character ; hut I have been obliged to omit it,
as I have not observed it in the new species represented in the
subsequent plate.
Fig. 1. D. Swartzii, natural size. Figs. 2 , 2. Filaments presenting different
appearances. Fig. 3. Detached joints ; magnified.
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