THE IMPENETRABLE SEA 



hard keeled scales, two dorsal fins, and other peculiar 

 characteristics, making it a grim, aggressive creature. 

 Some have long barbels on their chins, making them look 

 even more grotesque. 



The flying gurnards are less numerous than the flying 

 herrings (which are more closely allied to the gar-pike 

 than the herring, despite their name), there being only 

 three or four species of the former compared with nearly 

 sixty of the latter, which are found in numerous shoals — 

 often thousands in a shoal. 



Flying-fish cannot turn or guide themselves in their 

 flight, which is parabolic, like the flight of shells fired 

 from guns — appropriately enough, for they resemble pro- 

 jectiles more nearly than do the majority of fishes. It 

 would be wrong to think of them as jet-propelled. That 

 word can be more appropriately applied to animals 

 which propel themselves through the water by exhaling 

 jets. Of about 300 species of swift- travelling fish which 

 have been examined, 270 species possessed gill-clefts at the 

 right positions, potentially, for efficient jet-propulsion. 



All the fast-swimming types of fish in the ocean are 

 streamhned, and have full control of their water-ejection 

 systems, so that they can increase or decrease speed at 

 will and make efficient turns. Many fish have had an 

 ''induced stream-line system", using jet-propulsion in 

 highly eflficient ways. 



Although the flying-fish holds the record for the fastest 

 speed through the air of any creature normally living in the 

 sea, it is by no means the fastest fish in the sea. The sail-fish 

 has that distinction. Although it is not a true swordfish 

 it is closely related — it diflfers in having teeth, scales, 

 ventral fins of a few rays, and a very large dorsal fin. 

 The latter may give it the advantage in speed over the 

 true swordfish of a few miles an hour. 



The sword of a swordfish, although solid and as hard 

 as ivory, is not so strong that it could be forced through 

 the hulls of wooden ships unless the speed at the moment 



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