218 NATURE'S TEACHINGS. 



waters can cement together, while under water, the various 

 materials of which its tubular house is formed. The different 

 Sticklebacks perform similar feats, no matter whether they 

 inhabit fresh or salt water. 



All those who take an interest in the productions of the sea- 

 shore will have noticed upon our coasts the flexible tube of thf> 

 Terebella, with its curiously fringed ends. This tube, as any 

 one may see at a glance, is composed of grains of sand and 

 similar materials, fastened strongly together by a kind of 

 cement exuded from the worm, and possessing the property of 

 hardening under water. As on some of our coasts fragments 

 of shell are used for the tube, the worm goes by the popular 

 name of Shell-binder. 



If one of these worms be taken out of its tube, placed in 

 a vessel with sea-water and a quantity of sand, broken shells, 

 and little pebbles, the mode of building will soon be seen. At 

 the extremity of the head are a number of extremely mobile 

 tentacles, and these are stretched about in all directions, seizing 

 upon the particles of sand and shell, seeming to balance them 

 as if to decide whether they are suitable for the tube, and then 

 fixing them one by one with the cement which has already 

 been mentioned. 



Generally speaking, the Terebella works only in the evening, 

 but, if it be hastily deprived of its tube, it cannot help itself, 

 and is perforce obliged to work while it can. It is worthy of 

 remark that the Terebella, although, as a rule, it lives in a tube 

 all its life, is capable of swimming with the usual serpentine 

 motion of marine worms, and, when taken out of its tube, 

 rushes about violently, and soon exhausts itself by its efforts. 



Along most of our rocky seashores may be seen vast quan- 

 tities of a sort of hardened sand, penetrated with small tubes. 

 On a closer examination this sand-mass is resolved into a 

 congeries of tubes, matted and twisted together, and each being 

 the habitation of a marine worm called the Sabella. This name 

 is derived from a Latin word signifying sand, and is given to 

 the worm in allusion to the material of which it makes its 

 habitation. 



Like the Terebella, the Sabella uses its tentacles for the 

 purpose of building the tubes, which are much stiffer than 

 those of the Terebella. They are strong enough, indeed, to 



