USE OF THE COMBS. 235 



the timidity induced by its novel circumstances, such 

 as the increased light, the slight depth of water, 

 the heightened temperature, &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 shew more of their bases. They thus separated 

 from each other, and each assumed the form of a 

 cuncave fan, or of a turkey'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 during my 

 absence from the room, and found it plunged to the 

 very bottom. Its mode of burrowing is as follows. 

 If the animal is not lying rightly, it turns 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 a Mollusk and 

 its shell), until the third of the circle inclosed 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 head 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, 



