FORM AND LOCOMOTION 



29 



The speed attained by fishes has always been the subject of 

 much speculation, but, unfortunately, very little accurate data 

 exists as to the relative speeds of different forms. The average 

 rate of progress of the Salmon [Salmo) has been estimated at 

 about seven miles per hour, and that of the Pike {Esox) as from 

 eight to ten miles per hour, but these come nowhere near the 

 speed attained by some of the large oceanic fishes. Remarking 

 that the speed of a Bonito might be reckoned by the aid of the 

 electrical contrivances by which the initial velocity of a pro- 

 jectile is calculated, Professor Goode adds: "The Bonitos in 

 our sounds to-day may have been passing Cape Colony or the 



Fig. II. — A FISH WHICH SWIMS UPSIDE DOWN. 



Cat-fish (Synodontis hatensoda), X |. 



Land of Fire the day before yesterday!" Of all fishes, the 

 Sword-fish {Xiphias) and its aUies (Fig. 6) are perhaps the most 

 rapid swimmers. A number of cases are on record in which 

 they have struck ships, and Professor Owen, who was once 

 called upon to testify in court as to the power of the Sword-fish, 

 stated that it "strikes with the accumulated force of fifteen 

 double-headed hammers; its velocity is equal to that of a 

 swivel-shot, and is as dangerous in its eflfects as an artillery 

 projectile." If the ship struck be a wooden one it is not un- 

 common for the sword to be driven in with such force that it 

 cannot be withdrawn, and the fish frees itself by breaking it 

 oflf short! How great must be the speed of these fishes to 

 produce such results ! 



Practically all fishes adopt a horizontal position when 



