Mollusca. 



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localities, as is Taranto at the present day, for the culture of the 

 Oyster. At the present time Oysters are cultivated in Lake 

 Fusaro near Naples, where they grow to a considerable size. The 

 Oysters in Lake Lucrino are imported from Taranto . In the Mare 

 Morto, too, near Capo Miseno, Oysters have been reared for some 

 years past. 



The Edible Mussel, Mytilus galloprovincialis (fig. 24), has the 

 well known, almost triangular, blue-black shell. The animal has 

 a so-called byssus-gland with which it produces long horny threads, 

 which fasten it to rocks and woodwork. If it wants to leave its 

 home, it produces a new byssus with its finger-like foot and then 

 it tears the old byssus away; by repeatedly doing this it moves 

 very slowly onwards. As in the seas of northern Europe, the Mussel 

 is extensively cultivated in the Gulf of Naples, and especially 

 at Taranto ("Cozzeche di Taranto") and Spezia; stakes of wood 

 are let down into the water and from time to time drawn up, and 

 the adhering Mussels removed. 



Pinna (fig. 127) is a large, thin-walled, club-shaped shell, which 

 is fixed in the mud by its narrow end. It also possesses a byssus 

 which, however, is much longer and composed of finer threads 

 than that of the Mussel. These silken threads were formerly 

 used for the manufacture of gloves, stockings and even entire 

 garments; in the i8th century there existed at Naples and Sicily 

 large works for spinning them. The shells of Pinna also yield 

 occasionally pearls, but these are of very little value. The fable 

 of the crab. Pinnotheres, acting as watchman to its host, the 

 Pinna, has been believed from the most ancient times up to the 

 present day; similar crabs are known to frequent some other 

 Mollusks, Ascidians and Sponges. It is doubtful whether in any 

 case the host derives benefit from its lodger. 



Avicula (fig. 126) is remarkable as a very near relation of 

 Meleagrina margaritifera, the Pearl-oyster, which produces the 

 finest pearls. These are nothing more than secretions of carbonate 

 of lime with which the animal covers up extraneous bodies — 

 whether parasitic worms or not has lately been questioned. Each 

 pearl, however, contains as its centre some foreign object and 

 in this way man can cause the production of pearls, a fact of which 

 the Chinese have taken advantage to make pearls of various forms. 



A shell of interesting habits is Lithodomus (fig. 26), which is 

 always found in holes in rocks or coral reefs. The animal is a 

 favorite dehcacy and often appears in the markets. It is not yet 

 understood how it works its way into the stone; its shell is per- 

 fectly smooth and so it cannot file its way in, as the Piddock, 

 Pholas (fig. 27), does with its rough shell armed with hard ridges. 

 Probably Lithodomus secretes a fluid which acts upon the lime- 

 stone and dissolves it. The holes they make are quite smooth 

 inside. The Temple of Serapis at Pozzuoli has made these shells 



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