ANNELIDA. 



Nothing can exceed the splendour of the colours which orna- 

 ment some of these fasciculi of hairs ; they yield, indeed, in no 

 respect to the most gorgeous tints of tropical birds or to the bril- 

 liant decorations of insects : green, yellow, and orange, blue, 

 purple, and scarlet, all the hues of Iris play upon them with the 

 changing light, and shine .with a metallic effulgence only com- 

 parable to that which adorns the breast of the humming-bird. 

 But it is not for their dazzling beauty merely that these setse are 

 remarkable ; they are not unfrequently important weapons of de- 



Fig. 88, 



fence, and exhibit a com- 

 plexity of structure far be- 

 yond anything to be met 

 with in the hair of higher 

 animals. In the Aphro- 

 dite hispida, for example, 

 (Jig. 88, A,) they are per- 

 fect harpoons ; the point 

 of each being provided 

 with a double series of 

 strong barbs, (fig- 88, B,) 

 so that when the creature 

 erects its bristles, much 

 more formidable than those 

 of the porcupine, the most 

 determined enemy would 

 scarcely venture to attack 

 it. 



But here we cannot help 

 observing an additional 

 provision, rendered neces- 

 sary by the construction of these lance-like spines. We have 

 before noticed that the bundles of setse are all retractile, and can 

 be drawn into the body by the muscular tube from which they 

 spring. It would be superfluous to point out to the reader the 

 danger which would accrue to the animal itself by the presence of 

 such instruments imbedded in its own flesh, as by every movement 

 of the body they would be inextricably forced into the surrounding 

 tissues. The contrivance to obviate such an accident is as beau- 

 tiful as it is simple. Every barbed spine is furnished with a 

 smooth, horny sheath, (fig. 88, a, 6,) composed of two blades, 

 between which it is lodged ; and these, closing upon the barbs when 



