366 ART1CULATA. ANNELIDA, 



ORDER II. DORSIBRANCHIATA.* 



THE branching gill-tufts are here placed on the 

 middle portion of the body, but in some they are 

 attached to every ring. A very few inhabit tubes, 

 but the greater number are free, and burrow in mud, 

 or swim in the ocean. For these purposes, each 

 ring is usually furnished with little packets of move- 

 able bristles, which act as feet or oars. 



One of the most common, as well as most useful 

 of the whole Class, is an animal of this Order, the 

 Sand-worm (Arenicola^ Piscatorum). It is exceed- 

 ingly abundant on sandy shores, and is eagerly 

 sought and used by the fishermen as bait. In Dor- 

 setshire it is called Lug. It is of a reddish colour ; 

 and the gill-tufts, which form a double row of little 

 bunches, down the middle part of the body, are of a 

 beautiful crimson hue, from the blood which abun- 

 dantly circulates in them. It bores rapidly in the 

 sand by means of its conical head, which can be 

 lengthened or shortened at pleasure ; and, as it moves 

 on, the sides of the treacherous passage are pre- 

 vented from closing up again, by a secretion from 

 the body of the animal, which unites the particles 

 of sand into a kind of wall, and which as it advances 



* Dorsum, the back, and brancliia, gills, 

 t Arena., sand, and cofo, to inhabit. 



