(Pyrosoma).
This large planktonic organism is closely related to the chainjellies. In appearance it is like a rough leathery cylinder, brownish in colour and semitransparent, and up to about 10 in. in length, though tropical species as long as 4 ft have been reported. In reality a single Pyrosoma is not one individual but a colony of animals sharing a common alimentary canal. Its most interesting feature is its luminescence at night, particularly when disturbed, as, for instance, by the passage of a ship. One observer reports writing his name in letters of fire on the skin of a Pyrosoma, merely by tracing the letters with his finger.
by Richard Morrison Cassie, M.SC.(N.Z.), D.SC.(AUCK.), Senior Lecturer in Zoology, University of Auckland.