SOME FISH AND SOME FISHING 



ing about on the surface of the ocean, feed- 

 ing, or rapidly travelhng seaward; then it 

 seems to be used as a rudder or guide, for 

 the fish open and close it as they drive and 

 jump along from wave to wave. 



"The chief motive and jumping power 

 of a fish is in its tail which as it hits the 

 water straightens out the curving body and 

 shoots it forward, allowing the pectoral and 

 ventral fins to strike flat with their full 

 power. The caudal, dorsal, and anal or 

 vertical fins have steering functions to per- 

 form, while the pectoral and ventral pairs 

 of fins are chiefly intended for balancing 

 purposes. 



Fish would be unable to navigate on an 

 even keel without these horizontal fins, for 

 the centre of gravity of most fish is toward 

 the head or dorsal side. 



To help matters a fish is supplied with 

 an air-sack which renders it bulk for bulk 

 about the same weight as the water it 

 displaces." 



[134] 



