ANNELIDA. 277 



are placed on the head, where they form a circle of plumes or a tuft of 

 branched organs. The Serpulce, which form irregularly twisted cal- 

 careous tuhes, often grow together in large masses, generally attached 

 to shells and similar objects ; whilst those genera which, like Terebella, 

 build their residences of sand and stones, appear to prefer a life of 

 solitude. The curious little spiral shells often seen upon the fronds of 

 sea-weeds, are formed by an animal belonging to this family (Spirorbis). 



If, while the contained animals are alive, these be placed in a 

 vessel of sea- water, a very pleasing spectacle may soon be witnessed. 

 The mouth of the tube is first seen to 

 open, by the raising of an exquisitely 

 constructed door, and then the creature 

 cautiously protrudes the anterior part of 

 its body, spreading out at the same time 

 two beautiful fan-like expansions of a rich 

 purple or scarlet colour, which float ele- 

 gantly in the surrounding water, and serve 

 as branchial or breathing organs. The Ser- 

 pula, which fabricates these tubes, when 

 withdrawn from its residence (fig. 120), is 

 seen to have the lower part of its body 

 composed of a series of flattened rings, en- 

 tirely destitute of limbs or any other ap- 

 pendages. Its food is brought to its mouth 

 by the currents created by the cilia on the 

 branchial tufts. Many very beautiful speci- Tke Ser ? ulcl in its cal ous tule. 

 mens of this family may be seen alive in the tanks of the Zoological Society. 



Of the jErrantia, the highest of the order, we are unable to notice 

 more than one ; that of the family of Aphroditce, some species of 

 which are known as Sea-mice. In these worms the body is generally 

 broad, or ovate ; the head small, and furnished with very short tenta- 

 cles ; the feet large, with immense tufts of bristles and spines, often of 

 the most remarkable forms, and exhibiting the most brilliant metallic 

 colours. Each of these hairs is retractile within a horny sheath, 

 which serves to protect the soft parts of the animal from injury by its 

 own weapons. Their most remarkable peculiarity is, that the dorsal 

 surface is entirely or partially covered by a double series of large mem- 

 branous scales attached to the alternate segments, between which the 

 beautiful bristles of the feet make their appearance. These animals 

 generally inhabit deepish water; but numbers of them are often thrown 

 upon our coasts after a storm. 



