94 SALT-WATER FISHES 



supple action, the marvellous speed, the lightning turns 

 and leaps and dives of these smaller sharks. They are less 

 often taken in shallow water farther up the Channel, and 

 more rarely still in the North Sea, for most of the examples 

 recorded from the east coast have been met with during 

 winter storms. One was, however, taken in the Firth of 

 Forth, July, 1898. Now and then one has been on view in 

 the tanks of the Brighton Aquarium, when the public is able 

 to contrast the graceful appearance and active movements 

 of these " ugly " sharks with those of the coarse-built cod, 

 as well as with the ungainly flat-fish with its twisted face and 

 sidelong motion. When a blue shark is firmly hooked so that 

 its teeth cannot cut through the line, it revolves in the water 

 with such force and swiftness as to wind the line about its 

 body in tight coils that threaten to score its rough, scaleless 

 skin, though whether this performance is the result of physical 

 pain, or whether the fish does it merely to recover its liberty, 

 we can only guess. 



Like most sharks, and indeed most sea-fish, the blue shark 

 is a migratory species, appearing on our coasts on the approach 

 of summer and retiring again some time during the autumn, 

 though it is sometimes cast ashore or, more rarely, taken in 

 the nets on the east coast during the coldest months of the 

 year. Although no study has been made, or at any rate 

 recorded, of its reproduction, it must almost certainly bring 

 forth living young, like its close relatives the hammerhead 

 and tope. 



The Hammerhead {Zygana malleus) shows extraordinary 

 specialisation, its hammer-like head contrasting with the shovel- 

 shaped snout in most sharks and notably in its nearest allies. 

 In colour it is dark brown or grey above, and lighter on the 

 lower parts. As above noted, the eyes have a nictitant mem- 

 brane, and are situated at the extremities of the hammer-like 

 development of the head. There are no breathing spiracles, 

 and in front of the head there is a curious groove, the object 



