VERMETUS. 205 



The concliologist longs to become acquainted with the 

 habits and facilities for enjoyment that pertain to the above- 

 mentioned genera ; he discovers a difference in their shelly 

 habitations, and is naturally induced to conjecture that this 

 dissimilarity has some important beaming on the economy of 

 the indwelling mollusk. It may be that the one requires 

 to be continually in communication with his native element ; 

 that the other dwells alone in liis curiously divided chamber, 

 leading a kind of hermit life, and having little communi- 

 cation with the outward world. Be this as it may, it is 

 reasonable to conclude that in both, though probably sight- 

 less, the sense of feeling is not wanting ; that if the sense 

 of seeing or of hearing is withdrawn, the one of which we 

 speak is peculiarly acute ; and that, further, the approach of 

 any extraneous substances is readily discovered by the un- 

 dulations of the aqueous element which they inhabit. 



