[Footnote 1: The Cuckoo Gurnard (_Triglia cuculus_) and the maigre (_Sciæna aquila_) utter sounds when taken out of the water (YARRELL, vol. i. p. 44, 107); and herrings when the net has just been drawn have been observed to do the same. This effect has been attributed to the escape of air from the air bladder, but no air bladder has been found in the _Cottus_, which makes a similar noise.] [Footnote 2: The fishermen assert that a fish about five inches in length, found in the lake at Colombo, and called by them "_magoora_," makes a grunt when disturbed under water. PALLEGOIX, in his account of Siam, speaks of a fish resembling a sole, but of brilliant colouring with black spots, which the natives call the "dog's tongue," that attaches itself to the bottom of a boat, "et fait entendre un bruit très-sonore et même harmonieux."--Tom. i. p. 194. A _Silurus_, found in the Rio Parana, and called the "armado," is remarkable for making a harsh grating noise when caught by hook or line, which can be distinctly heard when the fish is beneath the water. DARWIN, _Nat. Journ._ ch. vii. Aristotle and Ælian were aware of the existence of this faculty in some of the fishes of the Mediterranean. ARISTOTLE, _De Anim_., lib. iv. ch. ix.; ÆLIAN, _De Nat. Anim._, lib. x. ch. xi.; see also PLINY, lib. ix. ch. vii.. lib. xi. ch. cxiii.; ATHENÆUS, lib. vii. ch. 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 MÜLLER read a paper on "Musical fishes" before the Academy of Berlin, in 1856. It will probably be found in the volume of MÜLLER'S _Archiv. für Physiologie_ for that year; but I have not had an opportunity of reading it.]