BRISTLES. 245 



produced on each side into a little conical wart-like 

 foot, on the upper side of which is attached, by 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 emission to the pencil of bristle-spears, which 

 are aiTanged 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 foot, or withdrawn completely into its interior, as into 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 resembling 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 

 evidently 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 sur- 

 faces along which it is moving. It is possible also 

 that they may be weapons of defence ; for, being 

 thrust out at every lateral undulation of the segments, 

 they present formidable chevaux de frise to any small 

 enemy who may entertain malice prepense against the 



