OBTUSENESS OF SENSE. 159 



aware of its habits that they commonly break all 

 Whelks containing Soldiers, in order to extract the 

 Nereis which they know is within. Dr. Johnston in 

 his description of N. hilineata (Ann. N. H. July, 1839) 

 has alluded to their occurrence together. 



Besides the interesting fact of this mutual friend- 

 ship, we learn somewhat from the above observation 

 of the rapacity and carnivorous habits of the genus 

 Nereis, already inferred from their anatomical struc- 

 ture. That the senses of this Worm are not very 

 acute I infer from the following experiment. I 

 dropped a piece of meat into the mouth of the Whelk- 

 shell that was tenanted only by a Nereis, and watched 

 the result. After a time the Worm protruded, not 

 apparently induced so to do by any expectation of 

 food, and though its head was often brought almost 

 into contact with the flesh, it was evidently uncon- 

 scious of the proximity ; for it took not the slightest 

 notice of it, and allowed it to remain untouched 

 all day. 



The gTaphic description of the Soldier going about 

 on the beach, turning over and examining shells, and 

 now and then trying how they would fit his body, — 

 has been so often quoted that we are apt to think it 

 is a common sight, and may be witnessed by any 

 stroller on a shelly beach. Yet I think the fact has 

 been very seldom seen ; and I judge so from my 

 never having seen any other than the one well-known 

 story, which, if I mistake not, was originally told by 

 old Du Tertre of some American species. I have had 

 the pleasure, however, of confirming its accui'acy, at 

 least in some points. 



