iii. vi. I have
heard of sounds produced under water at Baltimore, and supposed to be
produced by the "cat-fish;" and at Swan River in Australia, where they
are ascribed to the "trumpeter." A similar noise heard in the Tagus is
attributed by the Lisbon fishermen to the "_Corvina_"--but what fish is
meant by that name, I am unable to tell.]

Organs of hearing have been clearly ascertained to exist, mot only in
fishes[1], but in mollusca. In the oyster the presence of an acoustic
apparatus of the simplest possible construction has been established by
the discoveries of Siebold[2], and from our knowledge of the reciprocal
relations existing between the faculties of hearing and of producing
sounds, the ascertained existence of the one affords legitimate grounds
for inferring the coexistence of the other in animals of the same
class.[3]

[Footnote 1: AGASSIZ, _Comparative Physiology_, sec. ii. 158.]

[Footnote 2: It consists of two round vesicles containing fluid, and
crystalline or elliptical calcareous particles or otolites, remarkable
for their oscillatory action in the living or recently killed animal.
OWEN'S _Lectures on the Comparative Anatomy and Physiology of the
Invertebrate Animals_, 1855, p. 511-552.]

[Footnote 3: I am informed that Professor MUeLLER read a paper on
"Musical fishes" before the Academy of Berlin, in 1856. It will probably
be found in the volume of MUeLLER'S _Archiv. fuer Physiologie_ for that
year; but I have not had an opportunity of reading it.]

Besides, it has been clearly established, that one at least of the
gasteropoda is furnished with the power of producing sounds. Dr. Grant,
in 1826, communicated to the Edinburgh Philosophical Society the fact,
that on placing some specimens of the _Tritonia arborescens_ in a glass
vessel filled with sea water, his attention was attracted by a noise
which he ascertained to proceed from these mollusca. It resembled the
"clink" of a steel wire on the side of the jar, one stroke only being
given at a time, and repeated at short intervals.[1]

[Footnote 1: _Edinburgh Philosophical Journ_., vol. xiv. p. 188. See
also the Appendix to this chapter.]

The affinity of structure between the _Tritonia_ and the mollusca
inhabiting the shells brought to me at Batticaloa, might justify the
belief of the natives of Ceylon, that the latter are the authors of the
sounds I heard; and the description of those emitted by the former as
given by Dr. Grant, so nearly