CHAPTER III: THE SHIP WORM 



Family TEREoiDy^ 



Genus TEREDO, Linn. 



Shell bivalve, globular, small; valves three-lobed, gaping, 

 with interior spoon-shaped processes from the hinge; animal 

 worm- like, in shelly burrow, with two long siphons, united almost 

 to the ends, tipped with shelly pallets ; orifices fringed. 



The Ship Worm (7. navalis, Linn.) has long been known 

 and dreaded as the treacherous destroyer of ships and wharves, 

 which damages shipping in European and American ports contin- 

 uously. Modern scientific researches have uncovered the methods 

 of this mollusk, and devised a preventive of depredations from it. 



The life history is most interesting. There is a brief, free 

 swimming period, during which the infant borer has eyes, which 

 disappear in later life. When the size of a pin head, the young 

 settle on the surface of submerged timbers. They begin to bur- 

 row inside, cutting oflF fine chips with the foot, possibly also by 

 scraping with the valves. The burrow gradually grows in diameter 

 and length, the siphon tips always at the small exit, the shells at 

 the extreme end of the excavation. The burrow follows the grain 

 where convenient, avoiding knots by changing direction, and 

 turning aside usually for the burrows of others, though any bur- 

 rowed wood specimen shows numerous exceptions to this rule. 



The fine chips are swallowed and thrown out of the excurrent 

 siphon, but this does not prove that they yield any sustenance to 

 the mollusk. The large incurrent siphon, ciliated at the mouth, 

 admits a steady stream of water charged with fresh air to bathe 

 the gills; the lashing cilia drive in also minute organisms like 

 infusorians which are passed into the stomach. This supply of 

 food is quite sufficient. Moreover, the wood particles ejected 

 seem only compressed, in no sense changed in composition or 

 structure by digestive processes. 



The Teredo breeds in spring. Millions of eggs are said to 



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