THE SHORE SABELLA. 



699 



The gills, whose exquisitely graceful form and delicate coloring 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 fur- 

 nished 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 foot- 

 stalk 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 



Sabella unlsplra. 



Serpula contortupllcata. 



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, interwine 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 tri- 

 angular 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, be- 

 cause 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 SHORE 

 SABELLLA (Sabella alreolaria], 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 appen- 

 dage 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. 



