76 HALF AN HOUR WITH SEA-WORMS. 



Coal Measures, where it is seen attached to old fossil 

 tree trunks, &c. Many people mistake the long 

 white tubes, which may be seen ramifying through 

 pieces of old wreck that have been cast ashore, for 

 sea-worms. This, however, is a mistake, although 

 the popular name of " ship-worms " (Teredo navalis) 

 is always given to them. They are in reality a 

 species of bivalve mollusc, which bore into and take 

 up their lodgment in the wood, leaving the excava- 

 tions lined with carbonate of lime for the sea-water 

 to communicate with them and bring them their 

 food. 



Those of our readers who have visited the Crystal 

 Palace Aquarium a capital place for a young 

 naturalist will have noticed in one of the tanks 

 a group of large-tubed sea-worms, with large 

 feathery branchiae. These are the Sabella, of which 

 we have three or four species living in the deeper 

 rock-pools along our coasts. Like the serpula, they 

 are usually found in clusters, but not always so, and 

 never so numerous as the former. They differ from 

 them also in two or three very important parti- 

 culars. First, they do not possess the operculum or 

 plug, which is such a a marked feature in the living 

 serpula. Second, their tubes are not .composed of 

 carbonate of lime. Instead of this, they secrete a 

 kind of mucus, and this hardens, after having been 

 strengthened by the adherence of grains of sand, &c. 

 These tubes not unfrequently extend to several feet 

 in length. The animals inhabiting them do not 



