PERCH-LIKE EISHES 133 



chiefly at the breeding season, and probably serve as signals 

 for the assembling of the shoals. 



The sounds are produced through the agency of a special 

 muscle, which is attached either directly to the air-bladder 

 or close to it. The rapid expansion and contraction of this 

 muscle causes the walls of the bladder to vibrate, and, as the 

 latter has a complicated structure, it acts after the manner of 

 a resonatoi and amplifies the sound. An American investi- 

 gator, experimenting with living Croakers, found that if the 

 air-bladder was deflated or removed the sounds ceased 

 altogether, but that if an artificial rubber bladder was then 

 introduced the drumming started again. 



Another peculiarity of the Croakers is the large size of the 

 otoliths or ear-stones, which are usually finely sculptured and 

 provided with curious grooves and markings. These otoliths 

 are contained within the auditory organ on each side of the 

 head, and play an important part in preserving the equilibrium 

 of the fish. Small boys in America call the ear-stones of one 

 species " lucky-stones " as each otolith has the rough impression 

 of the letter " L " on its surface. In olden times the otoliths 

 of the Meagre were regarded as a sovereign specific for the 

 colic, and were worn suspended from the neck. 



There is little to be said about the breeding habits of the 

 Croakers. The numerous small, buoyant eggs are shed in the 

 open sea, and, as in the majority of Bony Fishes, after being 

 fertilized by the males, they are left to the mercy of the wind 

 and waves. In South Africa the Kabeljau spawns from 

 October to December, and the young fishes are abundant in 

 the bays and estuaries during the summer months. 



Nearly all the members of this family are valued as food, 

 and, although in some cases the flesh is coarse and somewhat 

 tasteless, in others it is of superior quality. The name " Weak- 

 fishes " given to some of the species refers to the tender flesh, 

 which is easily torn ; the word " Meagre " is a corruption of 

 the French " Maigre ", meaning " spare " or " lean " — an 

 allusion to the white and bloodless appearance of the flesh. 

 The air-bladders of some of the larger Croakers, particularly 

 in India and Malaya, provide a rough isinglass of some com- 

 mercial importance. The scales of certain American forms 

 are used in Florida in the manufacture of sprays of flowers 



