286 NOVEMBER. 



we are able to expose the' latter to view. We then see 

 that its length is by no means commensurate with the 

 length of its house, of which indeed it inhabits only the 

 last-made portion, having behind a roomy space into 

 which to retire in case of need. It is not more than an 

 inch or an inch and a quarter long, rather wide in propor- 

 tion, and flattened, with a well-marked distinction be- 

 tween the corslet and the abdomen. The former carries 

 on each side prominent foot-warts, which are vigorously 

 protrusile, and within which bundles of strong bristles 

 are thrust to and fro. On the upper part of each foot, 

 extending half across the back, is a row of microscopic 

 hooks, wielded by long thread-like tendons, which are 

 fixed, on mechanical principles, to the attached end of 

 each hook. By the aid of these, the Serpula so cleverly 

 withdraws with lightning-like rapidity on alarm. By 

 the action of muscles of indescribable delicacy, the 

 hooks are projected to some distance beyond the sur- 

 face of the body. These organs are formed on the 

 model of a hedger's bill-hook, only that the edge is cut 

 into long teeth. Carefully counting them I have found 

 that each Serpula carries about 1900 such hooks on its 

 corslet, and that each of these being cut into seven teeth, 

 there are between 13,000 and 14,000 teeth employed in 

 catching the lining membrane of the tube, and in draw- 

 ing the animal back. 



