Living Silver 



belonged to the bony type. The haddock and the plaice, the whit- 

 ing and the turbot, the catfish and the halibut, they were all bony 

 fish. Only the dogfish stood isolated. It swam in tides of its own 

 making, in evolutionary currents such as preceded the whole 

 existence of the bony fish. 



The sharks were the more ancient tribe. Even among them it 

 was possible to distinguish between the more primitive and the 

 less. The further back the biological history went, the more 

 marked were certain anatomical characteristics. The spines that 

 stuck out in front of every fin tended to stick out more obviously 

 and more numerously. The whole shape of the animal shifted into 

 a speedier outline. The innervation of the head grew more com- 

 plex. And yet, no matter how streamlined a shark might become, 

 it would never attain to the economic decorum of a bony fish : it 

 would never evolve, not even backwards, into a hake or a salmon. 



But then again there were some ways in which the sharks seemed 

 to be more highly developed than their marine inheritors. Among 

 all the bony fish that Jan met at sea there was only one that had 

 developed a similar power to protect its young - and that one was 

 the Norwegian haddock, Sebastes marinus. It bore its babies, as a 

 woman does, alive and kicking. The others simply spawned their 

 tiny numerous unprotected eggs, most of them to be eaten by the 

 first carnivores that came on the scene. But many of the sharks 

 had reached a like stage. They too gave birth. They did not spawTi. 

 Even the least protective of them built up an egg that was encased 

 in coverings as effective as the eggshell of a bird - a hard, tough, 

 horny structure, each with a filament of fibre that attached it to 

 the bottom of the sea, to a cranny or a ledge. Not many of these 

 eggs were laid. That would have been impossible. Each was so 

 complicated that it required months of construction within the 

 belly of the female. And it was therefore important that each of 

 these eggs should be fertilised. The sharks, therefore, copulated 

 as the bony fish did not and every male shark had an organ of intro- 

 mission, the claspers, which, though it could not be compared to 

 the mammalian penis in any other respects, was equally efficient 



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