MANUAL OF NATURAL HISTOEY. 83 



One striking internal peculiarity of fishes must 

 here be noted, viz., the possession of a swimming- 

 bladder, or " sound/' as it is popularly termed. This 

 organ, which is generally situated in the abdomen, 

 laying close to the under surface of the back-bone, 

 is, from various anatomical and physiological char- 

 acters, which need not here be more than alluded to, 

 considered to represent the lungs of air-breathing 

 animals. It is found to exist in about three-fourths 

 of the total amount of species, and is believed to be 

 connected with their amount of buoyancy, as the 

 greater number of those which do not possess it are 

 ground fish. It is not found in the Sharks, as it 

 might interfere with their power of turning on their 

 side previously to seizing their prey. In a few it is 

 thought to be subservient to the production of sound. 



Among fishes remarkable for peculiar individual 

 properties, may be mentioned the Flying-Fishes, 

 which, by means of their extended pectoral fins are 

 enabled to take flights, or leaps out of the water ; and 

 which, while so engaged, form one of the strange 

 sights of tropical seas. The Pegasi, or Flying Sea- 

 Horses, also at times appear above the surface. There 

 are likewise wandering Fishes, which, imbued per- 

 haps, with a strong spirit of curiosity, like the 

 "Tree-Climber" (Anabas testudineus), set out on 

 their travels, leaving their native element, and pre- 

 senting the singular sight of "fish out of water/' 

 Some fishes, as the Gurnards, are known to utter 

 strange sounds. A species of Pogonias, named the 

 the " Organ/' or " Drum-fish/' mentioned in the 



