128 



SEA-SHORE LIFE 



of wood, excepting palmetto logs or teak. The ship-worm begins 

 to burrow into the wood by movements of its foot and shell, when 

 only as large as a pin's head, so that the opening to the burrow 

 is small. For a short distance from the entrance inward the bur- 

 row is apt to be perpendicular to the surface, but it soon turns 

 and runs more or less in the direction of the grain of the wood, 

 although usually quite twisted. The burrow is lined with shelly 

 material secreted by the teredo, and it is interesting to observe that 

 no matter how numerous the teredos infesting a piece of wood, their 

 tubes remain separate one from another and never intersect. The 

 shelly material lining the tube is not the true shell of the teredo. 

 The true sliell is found at the head-end of the body which is farthest 

 in from the opening to the burrow. Its two valves are small, 

 white and delicately sculptured. The long, worm-shaped body is yel- 

 lowish-white and tapers gradually to the posterior end which is 

 near the opening of the burrow. The two long, extensible siphons 

 are found here; and on both sides near their base are a pair of 



Fig. 88; SHIP-WORM with SIPHONS PHOTKUDING. From living specimens infesting 



wood in the New York Aquarium. 



shelly llappers which serve to close the opening of the burrow 

 when the siphons are withdrawn. A thick muscular collar at the 

 base of the flapper also assists in closing the opening. 



The teredo does not eat the wood into which it bores and is, 

 therefore, but little affected by poisoning the timber. The most 

 efficient protection is copper sheating. Species of teredo are widely 

 distributed and do enormous damage to submerged timber. Tere- 



