THE IMPENETRABLE SEA 



like grunts ! For gurnards do emit such sounds, and boat- 

 men who have heard them out at sea have often described 

 them as not merely hog-like but uncannily human. Some 

 authorities say that the grunts are emitted only when the 

 fish are handled, and that they are caused by air escaping 

 from the air-bladders. But there is some evidence that 

 the gurnard often makes the noise when swimming. 



One authority suggests that the sudden little bellow, 

 which sounds alarming even to human ears, has some 

 purpose in enabling the gurnard to frighten away its 

 foes. This theory implies that many creatures of the sea 

 have hearing — an idea which was once thought unten- 

 able, but is now gaining a measure of acceptance. The 

 noises made by one species of gurnard has gained it, 

 locally, the name of ''piper". 



The flying squid is another extraordinary creature 

 among those which shoot themselves into the air, or leap 

 upward from the waves. Its body is long, cylindrical, 

 and pointed towards the rear end, and it has two 

 triangular fins which it uses to project itself from the 

 water — sometimes to such a height that it will fall to a 

 ship's deck, a circumstance which has given the fish the 

 name among sailors of "sea-arrow". The flying squid is 

 one species of a genus of decapod (ten-legged) cephalo- 

 pods. Like other cephalopods it swims by ejecting water 

 forcibly from its mantle or gill cavities — jet-propulsion 

 again. 



Flying squid are included among those cephalopods 

 which, have the cornea of the eye open, so that sea water 

 is in contact with the lens. The internal shell, or ''pen", 

 of the flying squid is a very interesting structure. It has 

 three diverging rays and a hollow conical appendage. 

 The species vary in length from one to four feet, yet to 

 this family belong the giant squids which inhabit the 

 arctic and sub-arctic seas, and are occasionally stranded 

 on the shores of Norway and Greenland. All the species 

 are fish- eaters. 



44 



