DORSIBRANCHIATA. 367 



is left behind; thus resembling the brickwork of a 

 tunnel. 



It is not to such animals as these that we should 

 look for much splendour of colouring; and yet 

 there is a creature belonging to this Order, which 

 will vie with the most richly adorned bird or beetle. 

 It is the Sea-mouse (Halithea* Aculeata), whose 

 form is much shorter than that of most Annelidans, 

 approaching even to an oval. From the sides pro- 

 ject bunches of flexible spines or bristles, of a 

 splendid golden hue, on which play all the changing 

 tints of the rainbow : and which, as Cuvier observes, 

 f( are not inferior in beauty to the plumage of the 

 Humming-bird, or to the lustre of the richest gems." 

 Each of these bristles, moreover, is seen under the 

 microscope to be a barbed dart or harpoon, the ex- 

 tremity being cut into several teeth pointing back- 

 ward, affording truly formidable chevaux de frise, 

 for its protection against violence. But as these 

 spines, as usual in animals of this Class, are, when 

 not in use, drawn back, and sheathed as it were in 

 the body, an additional provision is necessary. It 

 is obvious that barbed spines, such as these, imbedded 

 in the flesh of the animal, would be exceedingly 

 painful, as every movement of the body would 

 force some of the points into the surrounding 

 parts, and laceration and injury would be the in- 

 fallible result. To prevent this, each individual 

 spine is provided with a smooth horny sheath, 



* "AXj, hals, the sea, and ^a, tfiea, a goddess. 



