The European Pileworm, a Dangerous Marine Borer 7 



withdrawn when the animal extends its siphons to take in water for 

 food or oxygen. Let a worm or other enemy attempt to enter the 

 hole, and instantly the siphons are withdrawn and the pallets thrust 

 out, blocking- the entrance. 3 In onr native species, Bankia fimbriata, 

 the pallets are beautiful feather-like structures of purest white 

 (fig. 4). Anyone may determine, without the aid of a lens, whether 

 he is dealing with Teredo or Bankia, by examination of these pallets. 



Fig. 4. Posterior End of Bankia fimbriata, the Native Species 

 c, collar ; p, pallet ; s, non-pigmented siphons 



Bores with its Shell 



You may wonder why, since the animal lies completely within a 

 burrow, it has kept any shells at all. Here we see a strange instance 

 of how in nature a structure which originally is developed entirely for 

 protection, as it is in the clams and oysters, becomes by slight changes 

 adapted to quite different ends. For the shell of the pileworm is not 

 used as a protective covering but is the tool by means *of which it 

 bores. 



The shells of the hard clam, and those of most bivalves, are joined 

 together by a long hinge on the upper, or dorsal, side, and fit together 

 evenly all the way around. In the pileworm and its allies the shells 

 meet only at two narrow points ; in the hinge region, and directly op- 

 posite on the lower side, where each shell bears a rounded knob. On 

 account of the great development of these knobs the front and back 



3 Calman (1) notes that a species of annelid worm, Nereilepas fucata, has 

 been stated to prey on Teredo navalis, but there is no evidence that its attacks 

 lessen to any appreciable extent the destruction wrought by the pileworm. 



