BONY FISHES 



250 BUIM fiStltb IX. 2- 



more likely; we can hardly imagine the fishes striving to make their 

 bladders bigger. But it must be remembered that only those that were 

 active swimmers, continually venturing into new waters, would be 

 able to make full use of the new organ. 



Fig. 151. Various fishes showing special conditions of the pectoral fins. 



A, eagle-ray (Myliobatis); B, dog-fish (Scyliorhimis); c, tunny (Thynmis) ; D, thread fin 



(Polynemus) ; e, sun-fish (Lepomis); f, mud-skipper (Periophtlialmus); c, scorpion fish 



(Pterois); n, cirrhitid fish (Paracirrhites); J, flying-fish (Exocoetus); K, catfish (Doras); 



L, gurnard (Trigla). (From Norman.) 



Many different fishes are able to jump out of the water, presumably 

 to escape enemies. Salmon and tarpon can jump to 8 or 9 ft above 

 the water. The flying-fishes have special structures to assist in such 

 jumps. In Exocoetus (Fig. 151) the enlarged pectoral fins serve for 

 gliding for distances up to 400 metres, but in the flying gurnards 

 (Dactylopterus) they are actually fluttered up and down, though the 

 flight is feeble. 



Several types of fish have the pectoral fin modified to allow 'walk- 

 ing'. The gurnards (Trigld) move in this way over the sea bottom 

 (Fig. 151), and the mud-skipper (Periophtlialmus) chases about catch- 



