THE SONG OF FISHES. 
341 
or less distended with a gas to which impulse would have been 
transmitted by the vibration of the diaphragm, had now been 
opened. 
So much for M. Moreau. The rest of this article must perforce he 
devoted to the admirable researches of M. Dufosse, whose obser- 
vations and experiments have been so numerous, so carefully 
conducted, and so productive of valuable results, that this 
savant is at length enabled to reduce to system and classify — 
an all-important step in any branch of science — the various 
acoustic phenomena which he has observed among fishes.* 
Such phenomena may he divided into two primordial groups or 
“ categories .’ 5 Under the first of these may be placed the 
various sounds which fishes produce when taken off the hook and 
line, and are pitched into a basket or some other receptacle. Such 
sounds are accidental, temporary, for the most part evidently 
involuntary; often convulsive, being produced sometimes by 
one part of the organism, at another time by another part. 
Such sounds are subservient to the exercise of a function which 
cannot he expressed, and cannot he brought into relation with 
any intention on the part of the animal. Among such noises 
are those produced by unusual movements of the bony elements 
of the jaw or gill-coverings (“ opercula”), e.g. in the barbel, 
loach, carp, gurnard, and others. In the short-snouted variety 
of the sea-horse ( Hippocampus ) a peculiar sharp sound is 
made by a little chevron-shaped bone, loosely articulated with 
two of the bony ( pveopevculav ) elements of the gill-covering, 
resembling that produced by the sudden return of a displaced 
foot tendon into its bony groove. The tench, carp, loach, and 
other thick-lipped fish, make a peculiar noise if they be com- 
pelled suddenly to open the mouth. This in the tench is so often 
repeated as to be in a degree comparable with the croaking of a 
frog. To such sounds M. Dufosse gives the name of “pheno- 
menes accoustiques irreguliers.” 
With regard to the sounds of the second category, which 
“better merit the attention of the physiologist,” these are 
voluntary, constant, and are always produced by the same organ. 
They are, moreover, always reproduced under analogous circum- 
stances, are evidently intentional, and can even serve to charac- 
terise a species. Such are the 66 phenomenes acoustiques 
reguliers.” The phenomena of this category are further divided 
by M. Dufosse into groups or sections. The first of these com- 
prises “ expressive noises, or incommensurable expressive 
sounds.” As the noises are not all engendered by the same 
* Recherches sur les bruits et les sons expressifs que font entendre les 
poissons d’Europe. u Annales des Sciences Naturelles,” 5 1 !™? serie, Zoologie,, 
tome xx. 1874. 
