306 



ORDER TUBICOL^E; SERPULA, SPIRORBIS. 



FIG. 528 GKOUP OF SERPULA. 



most elegant fan-like appendages, which usually possess very 

 brilliant colours. At the base of each 

 series, there is a fleshy filament ; and 

 one of these, on the right or left side 

 indifferently, is prolonged and dilated at 

 its extremity into a flat disc, which fits 

 to the mouth of the shell, and serves to 

 close it when the animal is withdrawn 

 into the tube. The body of the animal 

 is composed of a great number of seg- 

 ments ; but these are for the most part 

 unprovided with any appendages. The 

 anterior segments, however, which are 

 much thicker than the rest, are furnished 

 on each side with bundles of stiff bristles. 

 The largest species of this, as of the 

 preceding groups, are found in tropical 

 regions, where they usually form their 



habitations in the midst of Corals, and lengthen their tubes as the 

 Coral is built up around them ; their length is sometimes as much 

 as three feet ; and their expanded gill-tufts are of extremely vivid 

 colours, strongly resembling the most brilliant Carnations in 

 general aspect. These are usually extended beyond the mouth 

 of the shell, in order to obtain the full influence of the water, 

 for the aeration of the circulating fluid ; but if they be touched, 

 they are immediately drawn in, and the mouth of the tube is 

 closed by the disc just mentioned. Numerous smaller species 

 are found on our own coasts ; and some of these are remarkable 

 for the brilliant hues of their expanded gills. A minute white 

 spiral shell may be frequently seen upon the flat fronds of sea- 

 weeds ; this is the Spirorbis, the animal of which is nearly allied 

 to that of the Serpula. The food of these Annelids probably 

 consists of Animalcules and small marine animals ; together, per- 

 haps, with particles of dead animal matter, which are brought 

 towards the mouth, by the currents created by the cilia on the 

 branchial tufts : their masticating apparatus is much less complete 

 than that of the Dorsibranchiata. 



841. Besides the Serpulae, we have to mention several other 



