BRISTLES. 251 



side of which is attached hy a short footstalk the 

 beautiful pall-like leaflet, and on the under side a 

 similar smaller one, the tip of the foot projecting 

 between them. This point is perforated to give emis- 

 sion to the pencil of bristle-spears, which are arranged 

 like a fan, and are, at the will of the animal, projected 

 to a considerable length from the foot, or withdrawn 

 completely into its interior, as into a sheath. Each 

 individual bristle is composed of a very slender, long, 

 straight shaft, terminating in a knob somewhat resem- 

 bling the end of a limb-bone. This is slit in one 

 direction to receive the terminal lance-head, which is 

 fitted into it exactly as a knife-blade is fixed into its 

 handle. It is in fact a knife-blade having a thickened 

 back, and a very thin edge, which is notched with 

 teeth of the most delicate subtilty. The blade is 

 slightly curved, and drawn out to a long acute point ; 

 and the whole space is formed out of a substance that 

 rivals the purest glass. 



The full use of these most exquisitely contrived and 

 finished organs is, I think, yet to be discovered. They 

 are doubtless instruments of locomotion, being evi- 

 dently used to push the animal along, as a ferry-man 

 propels a boat with his pole ; and the saw-like teeth 

 may serve to catch the roughnesses of the surfaces 

 along which it is moving, It is possible also that 

 they may be weapons of defence ; for, being thrust out 

 at every laternal undulation of the segments, they 

 present formidable ehevaux de /rise to any small 

 enemy who may entertain malice prepense againt the 

 Annelid. Still the situation of these arms is hardly 

 such as we should expect, if this were their primary 



