DIFFERENT WAYS OF SWIMMING 



hensile tails are clinging to a support. Sometimes, 

 one of them gets loose, and, gently, in its extraordinary 

 upright attitude, or leaning a little over, progresses 

 through the water with a sort of gliding motion. It 

 uses only its pectoral fins. Though small, thin, 

 transparent, in fact hardly visible, they are active and 

 effective, even if not very powerful. They are an 

 example of the least developed and perhaps rarest 

 method of swimming in this way. 



The methods of swimming, above described, namely 

 by means of the tail or the pectoral fins or both com- 

 bined, are the commonest. But there are others. 

 Sometimes the pectoral, the pelvic, and caudal fins are 

 altogether absent or so small that they are useless. 

 Then we find other machinery for swimming, other 

 methods which still further increase the extent of the 

 series of differences. 



Beside the skate, upon the bottom of the tank, we 

 find lying flat-fishes of a different kind, soles and 

 brill. Usually, like their neighbours, they stay there 

 without moving, stretched out, giving signs of life 

 only by the gleam in their eyes and the movements of 

 their breathing. But, occasionally, they move and 

 change position, either by swimming, or by gliding, 

 climbing over the bottom. Not, like the skate, able to 

 use their pectoral fins, which are too small and un- 

 suitably situated, or their tiny caudal fin, they employ 

 the body itself and their unpaired fins. The dorsal 

 and anal fins, surrounding almost the entire trunk 

 like a sort of collar, beat the water with a wavy motion 

 and so provide an impulse, which though not of any 

 great strength, still produces the desired effect. If 

 the body is heavy, as in the case of the brill and the 

 turbot, the fish swims slowly and only for a short 

 time; if it is more pointed, finer, as in the case of the 

 flounder, plaice, and dab, it gets along better. Finally, 

 if the fish is more pliable and longer, like the sole, the 

 body itself gives the required impulse. It bends over 

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