BORING LIFE 151 



therefore, tliey resemble all the wood borers with the 

 exception of the remarkably specialized Shipworm which 

 is unique amongst borers in its inability to make a new 

 burrow if removed from the one it originally constructed, 

 and its capacity to extract nourishment from the sub- 

 stance into which it bores. 



Besides being attacked by animals, rocks, surprisingly 

 enough, are also bored into by sea weeds. Here again 

 it is only limestone or other calcareous rocks which are 

 attacked, and the plants appear to prefer the harder 

 varieties which, by their action, are soon reduced to a 

 friable mass coloured blue or greenish owing to the weed 

 everywhere present in its substance. Their preference 

 for calcareous rocks is due to the fact that, like the Date- 

 mussel, they bore by chemical means, transforming the 

 hard carbonate of lime which composes the rock into the 

 soft, powdery, white bicarbonate. Besides rocks they 

 attack the shells of molluscs, doing great damage to the 

 oyster beds in the Bay of Sebastopol in the Black Sea 

 where they are especially common. They attack in the 

 same regions the shells of barnacles, the calcareous tubes 

 of worms and the external limy skeletons of other marine 

 creatures all of which are coloured by their presence. Their 

 prevalence in the Black Sea, where they are common in all 

 depths down to about 75 feet, is a serious economic problem 

 on account of the damage they do both to stone work and 

 animal life. 



Protection of Timber 



The problem of the protection of timber from the attacks 

 of marine borers has vexed mankind since the days of the 

 earliest wooden ships and harbour works. To-day, though 

 the advent of steel ships and concrete harbour works 

 has led to a great reduction in the use of timber in marine 



