USE OF THE COMBS. 229 



tlie timidity induced by its novel circumstances, sucli 

 as the increased light, the slight depth of water, the 

 heightened temperatm-e, &c., it was interesting to 

 watch its proceedings, especially at night with a 

 candle ; as then it was more active. I had put it into 

 a vase of water with two inches of fine siliceous sand 

 for a bottom, on which the tube lay along. After a 

 few tentative essays, it grew bold enough to thrust 

 out its cork-like head, projecting the combs as it did 

 so, so as to show more of their bases. They thus 

 separated from each other, and each assumed the form 

 of a concave fan, or of a tm'key's tail were the shafts 

 of the feathers stripped of the vanes. 



Their use was now apparent. The animal is a 

 burrower in sand ; I repeatedly lost it dm'ing my 

 absence from the room, and found it plunged to the 

 very bottom. Its mode of bmTowing is as follows : — 

 If the animal is not lying rightly, it tui'ns on its axis 

 within the tube (which it can do with perfect facility, 

 as there is no organic connexion between its body 

 and its dwelling, as there is between the Mollusk and 

 its shell), until the third of the circle enclosed by the 

 angle of the combs is next the surface. These organs 

 are now thrust outwards and downwards, so that their 

 points enter the soil like shovels ; then, by muscular 

 movements of the liead, they are lifted upwards and 

 backwards, carrying in their concavity their load of 

 sand, which they throw over the upper margin of the 

 tube, behind the head. The combs, or, as I may now 

 call them, digging-forks, immediately make another 

 plunge, and deliver their spadeful of sand in like 

 manner. A considerable hollow is presently formed, 



