TIGERS OF THE DEEP 



He had learned by experience how to avoid or deal 

 with most of the dangerous creatures of the lagoon 

 bottom, and was afraid only of sharks. For as he said 

 later, there is no infallible recipe for dealing with them. 

 The native's advice was effective on that occasion, but, 

 in Dr. Miner's own words, ''Another day they might not 

 be so accommodating." 



In his account of this incident Dr. Miner, an intrepid 

 and experienced explorer of the underseas, admits that 

 he felt fear as the sharks approached him, but does not 

 express an opinion one way or the other regarding this 

 very debatable question : whether sharks will attack men 

 except in self-defence. It is a problem which can only be 

 examined properly if the views of experienced fishmen 

 are compared, and this we shall do later in this chapter, 

 after learning something of the shark's structure and 

 habits. 



In view of their enormous diversity fishes have been 

 divided into numerous sub-classes and orders, but there 

 are only three main divisions. These are, the Cyclosto- 

 mata (fishes having pouched gills, the smallest of the 

 three classes, comprising lampreys and hag-fishes) ; the 

 Teleostei, which are the bony fishes; and the group 

 Selachii, which includes the sharks and their allies. 



The main difference between the Selachii and the other 

 two classes is that sharks, rays and skates have a skeleton 

 of cartilage or gristle, while the bony fishes have rigid, 

 bony skeletons. Other differences are that the skin of 

 a shark is covered by millions of tiny teeth. They actually 

 are teeth — each one has its coating of enamel and its 

 pulp cavity — so that they are rightly named ''dermal 

 denticles". They are microscopic compared with the 

 shark's true teeth, but are extremely sharp. Each one is a 

 scale with a sharp point projecting through the skin and 

 attached to a plate in the dermis. These placoid scales^ as 

 they are termed, neither overlap nor touch one another. 

 They are spaced in symmetrical rows with the utmost 



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