This latter movement is effected solely by the aid of
the pectoral fins; the tail being collapsed and not used. From the
body being buoyed up with so much air, the branchial openings are
out of water, but a stream drawn in by the mouth constantly flows
through them.
The fish, having remained in this distended state for a 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 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 making a curious noise by the
movement of its jaws. By the inflation of its body, the papillae,
with which the skin is covered, become erect and pointed. But the
most curious circumstance is, that it secretes from the skin of its
belly, when handled, a most beautiful carmine-red fibrous matter,
which stains 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.
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