TEREDO. 1 1 



fig. 5). After this, the tube is carried on a httle further, 

 till it is separated into two smaller tubes, each ending in 

 an orifice, and the shelly tube will be found, if perfect, to 

 be divided correspondingly. These two openings are all 

 the means of communication possessed by the animal with 

 the world of waters around him ; for the larger end is quite 

 buried within the block into which he has found his way. 

 At this larger end is the body, which is round, and partly 

 covered by the bivalve shell. The shell opens in front, 

 and between its angular edges is seen a portion of fleshy 

 mantle, with a little hole, out of which protrudes the sucker, 

 or tongue-shaped foot. 



It is a difficult question, not yet satisfactorily determined, 

 how this creature manages to make its way into its hard 

 bed. The ancients felt no difficulty about this ; the thing 

 to them was perfectly clear. There was the bullet-headed 

 monster, and there w^as the pair of cutting teeth, and he had 

 nothing to do but to go head foremost, and eat his way in. 

 After a time however it became evident that the solution 

 was not so easy as supposed, for when the truth began to 

 appear, it was found that the valves could no more bite the 

 wood than the mollusc could eat it. Adanson, who made 

 great advances in a knowledge of the true character of this 



