Sfibella unispira. 



S&rpula contoTtuplifiUa. 



The gills, whose exquisitely graceful form and delicate colouring have always attracted 

 admiration, are affixed to the neck, as, if they were set at the opposite extremity of the 

 body or along the sides, they would not obtain sufficient air from the small amount of 

 water that could be contained in the tube. 



The beautiful scarlet stopper ought also to be mentioned. Each set of gills is furnished 

 with a tentacle-like appendage, one of which is small and thread-like, and the other 

 expanded at its extremity into a conical operculum or stopper, marked with a number 

 of ridges, which form a beautiful series of teeth around its circumference. The footstalk on 

 which this stopper is mounted is a little longer than the gills, so that when the animal 

 retreats into its tube the gills collapse and vanish, and the entrance of the tube is exactly 

 closed by the conical stopper. 



The Serpula is a lovely inhabitant of the aquarium, but has an inconvenient habit of 

 dying, sometimes coming out of the tube for that purpose, and sometimes retreating to its 

 furthest recesses, and there putrefying, to the great damage of the aquarium. There are 

 several kinds of Serpula, some of which are only attached by the lower part of the tube, 

 and hold the rest of that wonderful structure upright in the water ; some, like the present 

 species, intertwine their tubes very much like a handful of boiled macaroni ; while others, 

 such as the Serpula triquetra, form tubes which do not project at all, but are affixed 

 to their supports throughout their entire length. This species makes a triangular tube. 

 There are many interesting circumstances connected with the habits and structure of these 

 lovely worms, but our failing space will not admit of a longer description. 



We now come to another pretty tube-inhabiting annelid, which is called Sabella, 

 because it lives in the sand and forms its tube of that substance. Several species of Sabella 

 are found on the British coasts, the most common of which is the SHOKE SABELLLA (Sabella 

 alveolaria), a little creature seldom exceeding three-quarters of an inch in length. As is 

 the case with many of these worms, it has a thin tail-like appendage at the extremity of 

 its body, which is doubled up within the tube. The head is furnished with a great 

 number of little thread-like tentacles, which are very flexible, and under a good microscope 

 are seen to have a groove running along the centre, and a double row of teeth along the 

 edges, something like the snout of a saw-fish. 



