CHAPTER IV. 



SOME CURIOUS TUBE-BUILDERS. 



MANY of the worms that are dwellers in the sea 

 are most expert builders, constructing remark- 

 able tubular dwellings out of particles of sand, frag- 

 ments of shell, and even fine mud, in which to live. 

 These marine worms are all much handsomer arid 

 more complex animals than their humbler land rela- 

 tions the earth worms, and possess special organs for 

 collecting the materials out of which they construct 

 their tubes. 



A familiar object, often to be found at the bottom 

 of a rock pool on the seashore, is an old whelk shell, 

 upon the back of which may be seen a number of long 

 shelly tubes, more or less bent into curves, and firmly 

 attached by their sides to the whelk shell. Small and 

 closed at one end, they increase in diameter towards 

 the mouth or open end, and are considerably longer 

 than the worms which formed and inhabit them, and 

 are marked at irregular intervals with encircling ridges, 

 each ridge representing a period of growth. The 

 worm which forms this tube is called the Serpula, and 

 is a most interesting and handsome little creature. 

 The tube is built for the protection of the soft body 

 from hungry foes, as well as for a dwelling-place, and 



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