218 BONY FISHES vii. 16- 



16. Sound production in fishes 



A surprisingly large number of fishes can produce sounds audible 

 to ourselves, and these noises are used by the fishes either for shoaling, 

 or to bring the sexes together, or to warn or startle enemies. Some fish 

 may use the sounds they produce for echo-location. Among the loudest 

 of the sounds is that produced by the drum-fish (Pogonias) of the 

 Eastern Atlantic. The 'whistling' and other noises of the 'maigre' 

 (Sciaend) are supposed to be the origin of the song of the Sirens, since 

 they can easily be heard above the water. In both these fishes the 

 sounds are made mostly if not wholly in the breeding season. In 

 others, such as siluroids and Diodon, the noise is associated with the 

 presence of spines and may be a warning. In Congiopodas the nerves 

 that innervate the muscles of sound production also supply muscles 

 that raise the spines (Packard). 



The mechanism for sound production is very varied, involving 

 either stridulation by the vertebrae (some siluroids), operculum 

 (Cottus, the bull-head), pectoral girdle (trigger-fishes), teeth (some 

 mackerel and sun-fish), or phonation by the air bladder. The latter 

 may be involved either by its use for 'breathing' sounds in physosto- 

 matous forms (p. 261) or as a resonator. Noise production is common 

 in some families (Triglidae, Sciaenidae, Siluridae) but almost absent 

 from others. The advantages to be obtained from sound production 

 underwater have led to parallel evolution of similar mechanisms in 

 several different groups. 



17. The lateral line organs of fishes 



The lateral line organs occur partly as rows of distinct pits, partly 

 in canals that communicate with the surface through pores in the 

 scales. Besides the main canal running down the body and served 

 by the lateral line branch of the tenth cranial nerve, there are also 

 lines following a definite pattern on the head, namely, supra- and 

 sub-orbital lines, a line on the lower jaw, and a temporal line across 

 the back of the skull. The canals on the head are innervated mainly 

 from the seventh, partly from the ninth cranial nerve. The nerve- 

 fibres enter the very large acoustico-lateral centres of the medulla and 

 valvula cerebelli. 



Fishes possess the capacity to react to an object moving some dis- 

 tance away in the water ('distant touch sense') and this is reduced or 

 absent after section of the lateral line nerve. Presumably the moving 

 object sets up currents in the water, which move the fluid (or mucus) 

 in the canals. It has also been suggested that the canals serve to record 



