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tear it loose. When it wishes to change its place , it spins new 

 byssus-threads , and tears the old ones. By repeating this ope- 

 ration it slowly moves forward. The mussel thrives best in 

 north European seas, where it is in fact the object of exten- 

 sive culture. So-called mussel-logs are sunk into the sea for 

 the mussels to settle upon, and are then drawn up from time 

 to time covered thickly with the animals in all stages of de- 

 velopment. In the market at Kiel about 800 tons of mussel are 

 sold annually, each ton containing on an average 4200 animals, 

 so that altogether 3,360,000 mussels are taken in one winter. 



Very interesting in its habits is the Stone-mussel (Litho- 

 domus lithophagus). It is always found in holes made by 

 itself in the rocks or in corals. The smooth oval shell is 

 brown and shining, the animal a favourite food, and therefore 

 often in the market. How these creatures bore into the rocks 

 is still undetermined. Their shells being perfectly smooth, they 

 cannot make holes by. filing, as is the case with the Phola* 

 or boring-mussel. It is probable that the effect is produced by 

 the dissolving power of some animal secretion. Internally the 

 holes made by the Lithodomus are perfectly smooth and regu- 

 lar. These mussels have become celebrated through the Temple 

 of Sempis at Pozzuoli, on the columns of which is seen a sharply 

 limited belt, six feet wide, of holes made by the Lithodomus. 

 The temple at some period sank below the level of the sea 

 with a subsidence of the land , and was raised again subse- 

 quently. 



The Pinna are large thin-shelled club shaped mollusks, which 

 stick the pointed ends of their shells into the soft bottom of 

 the sea. They also possess a byssus gland, which , however , 

 is much larger and finer than that of the common mussel, and 

 the threads produced were once manufactured into all kinds of 

 fabrics. As late as last century factories might be found in 

 Taranto, Naples and Sicily, occupied solely in manufacturing 

 a sort of silk from mussel-threads: the shining green bundle 

 of threads was washed twice in soap and water and thrice in 

 pure water , then immediately hatchelled , and spun on the 

 distaff into a yarn of three threads, from which gloves , sto- 

 ckings and even whole dresses were made. 



Now and then pearls are found in the Pinna, but they are 

 of no value. The ancient fable of the mussel-guard (Pinnotheres), 

 which warned its host of approaching danger, and received a 

 lodging in recompense, was founded on the fact that in almost 

 all mussels is found a small crab, such as is also seen in the 



